# Patent

## Title
Methods of screening for agonists and antagonists of patched-2

## Abstract

The present invention relates to nucleotide sequences, including expressed sequence tags (ESTs), oligonucleotide probes, polypeptides, antibodies, vectors and host cells expressing, immunoadhesins, agonists and antagonists to patched-2.

## Background
RELATED APPLICATIONS
This application is a continuation of U.S. Ser. No. 09/990,046, filed Nov. 20, 2001, which is a continuation of U.S. Ser. No. 09/293,505, filed Apr. 15, 1999, now U.S. Pat. No. 6,348,575, which claims the benefit under 35 §119 of U.S. Ser. No. 60/081,884, filed Apr. 15, 1998, now expired, the contents all of which are incorporated herein by reference.


FIELD OF THE INVENTION
The present invention relates generally to signaling molecules, specifically to signaling and mediator molecules in the hedgehog (Hh) cascade which are involved in cell proliferation and differentiation.
BACKGROUND OF THE INVENTION
Development of multicellular organisms depends, at least in part, on mechanisms which specify, direct or maintain positional information to pattern cells, tissues, or organs. Various secreted signaling molecules, such as members of the transforming growth factor-beta (TGF-β), Wnt, fibroblast growth factors and hedgehog families have been associated with patterning activity of different cells and structures in Drosophila as well as in vertebrates. Perrimon, Cell: 80: 517-520 (1995).
Segment polarity genes were first discovered in Drosophila, which when mutated caused a change in the pattern of structures of the body segments. These changes affected the pattern along the head to tail axis. Hedgehog (Hh) was first identified as a segment-polarity gene by a genetic screen in Drosophila melanogaster, Nusslein-Volhard et al., Roux. Arch. Dev. Biol. 193: 267-282 (1984), that plays a wide variety of developmental functions. Perrimon, supra. Although only one Drosophila Hh gene has been identified, three mammalian Hh homologues have been isolated: Sonic Hh (Shh), Desert Hh (Dhh) and Indian Hh (Ihh), Echelard et al., Cell 75: 1417-30 (1993); Riddle et al., Cell 75: 1401-16 (1993). Shh is expressed at high level in the notochord and floor plate of developing vertebrate embryos, and acts to establish cell fate in the developing limb, somites and neural tube. In vitro explant assays as well as ectopic expression of Shh in transgenic animals show that SHh plays a key role in neural tube patterning, Echelard et al. (1993), supra.; Ericson et al., Cell 81: 747-56 (1995); Marti et al., Nature 375: 322-5 (1995); Roelink et al. (1995), supra; Hynes et al., Neuron 19: 15-26 (1997). Hh also plays a role in the development of limbs (Krauss et al., Cell 75: 1431-44 (1993); Laufer et al., Cell 79, 993-1003 (1994)), somites (Fan and Tessier-Lavigne, Cell 79, 1175-86 (1994); Johnson et al., Cell 79: 1165-73. (1994)), lungs (Bellusci et al., Develop. 124: 53-63 (1997) and skin (Oro et al., Science 276: 817-21 (1997). Likewise, Ihh and Dhh are involved in bone, gut and germinal cell development, Apelqvist et al., Curr. Biol. 7: 801-4 (1997); Bellusci et al., Dev. Suppl. 124: 53-63 (1997); Bitgood et al., Curr. Biol. 6: 298-304 (1996); Roberts et al., Development 121: 3163-74 (1995). Specifically, Ihh has been implicated in chondrocyte development [Vortkamp, A. et al., Science 273: 613-22 (1996)] while Dhh plays a key role in testis development. Bitgood et al., supra. With the exception of the gut, in which both Ihh and Shh are expressed, the expression patterns of the hedgehog family members do not overlap. Bitgood et al., supra.
At the cell surface, Hh function appears to be mediated by a multicomponent receptor complex involving patched (e.g., Ptch) and Smoothened (e.g., Smo), two multi-transmembrane proteins initially identified as segment polarity genes in Drosophila and later characterized in vertebrates. Nakano et al., Nature 341: 508-513 (1989); Goodrich et al., Genes Dev. 10: 301-312 (1996); Marigo et al., Develop. 122: 1225-1233 (1996); van den Heuvel, M. & Ingham, P. W., Nature 382: 547-551 (1996); Alcedo, J. et al., Cell 86: 221-232 (1996); Stone, D. M. et al., Nature 384: 129-34 (1996). Upon binding of Hh to Patched, the normal inhibitory effect of Patched on Smo is relieved, allowing Smo to transduce the Hh signal across the plasma membrane. It remains to be established if the Patched/Smo receptor complex mediates the action of all 3 mammalian hedgehogs or if specific components exist. Interestingly, a second murine Patched gene, Patched-2 was recently isolated [Motoyama, J. et al., Nature Genetics 18: 104-106 (1998)], but its function as a Hh receptor has not been established. In order to characterize Patched-2 and compare it to Patched with respect to the biological function of the various Hh family members, Applicants have isolated the human Patched-2 gene. Biochemical analysis of Patched and Patched-2 show that both bind to all members of the Hh family with similar affinity and that both molecules can form a complex with Smo. However, the expression patterns of Patched-2 and Patched do not overlap. While Patched is expressed throughout the mouse embryo, Patched-2 is found mainly in spermatocytes which require Desert Hedgehog (Dhh) for proper development suggesting that Patched-2 mediates Dhh's activity in the testis. Chromosomal localization of Patched-2 places it on chromosome 1p33-34, a region deleted in some germ cell tumors, raising the possibility that Patched-2 may be a tumor suppressor in Dhh target cells.
SUMMARY OF THE INVENTION
In one embodiment, the invention provides an isolated nucleic acid molecule having at least about 80% sequence identity to (a) a DNA molecule encoding a patched-2 polypeptide comprising the sequence of amino acids 1 to 1203 of FIG. 1 (SEQ ID NO:2), or (b) the complement of the DNA molecule of (a); and encoding a polypeptide having patched-2 biological activity. The sequence identity preferably is >91%, more preferably about 92%, most preferably about 95%. In one aspect, the isolated nucleic acid has at least >91%, preferably at least about 92%, and even more preferably at least about 95% sequence identity with a polypeptide having amino acid residues 1 to about 1203 of FIG. 1 (SEQ ID NO:2). In a further aspect, the isolated nucleic acid molecule comprises DNA encoding a human patched-2 polypeptide having amino acid residues 1 to about 1203 of FIG. 1. In yet another aspect, the invention provides for an isolated nucleic acid comprising DNA having at least a 95% sequence identity to (a) a DNA molecule encoding the same mature polypeptide encoded by the cDNA in ATCC Deposit No. 209778 (designation: pRK7.hptc2.Flag-1405), alternatively the coding sequence of clone pRK7.hptc2.Flag-1405, deposited under accession number ATCC 209778. In a still further aspect, the invention provides for a nucleic acid comprising human patched-2 encoding sequence of the cDNA in ATCC Deposit No. 209778 (designation: pRK7.hptc2.Flag-1405) or a sequence which hybridizes thereto under stringent conditions.
In another embodiment, the invention provides a vector comprising DNA encoding a human patched-2 polypeptide. A host cell comprising such a vector is also provided. By way of example, the host cells may be mammalian cells, (e.g. CHO cells), prokaryotic cells (e.g., E. coli) or yeast cells (e.g., Saccharomyces cerevisiae). A process for producing patched-2 polypeptides is further provided and comprises culturing host cells under conditions suitable for expression of patched-2 and recovering the same from the cell culture.
In yet another embodiment, the invention provides an isolated patched-2 polypeptide. In particular, the invention provides isolated native sequence patched-2 polypeptide, which in one embodiment is a human patched-2 including an amino acid sequence comprising residues 1 to about 1203 of FIG. 1 (SEQ ID NO:2). Human patched-2 polypeptides with or without the initiating methionine are specifically included. Alternatively, the invention provides a human patched-2 polypeptide encoded by the nucleic acid deposited under accession number ATCC 209778.
In yet another embodiment, the invention provides chimeric molecules comprising a patched-2 polypeptide fused to a heterologous polypeptide or amino acid sequence. An example of such a chimeric molecule comprises a patched-2 polypeptide fused to an epitope tag sequence or a constant region of an immunoglobulin.
In yet another embodiment, the invention provides expressed sequence tag (EST) comprising the nucleotide sequences identified in FIG. 2A (905531) and FIG. 2B (1326258).
In yet another embodiment, the invention provides for alternatively spliced variants of human patched-2 having patched-2 biological activity.
In yet another embodiment, the invention provides for method of using patched-2 for the treatment of disorders which are mediated at least in part by Hedgehog (Hh), especially Desert hedgehog (Dhh). In particular, testicular cancer. In yet another embodiment, the invention provides a method of using antagonists or agonists of patched-2 for treating disorders or creating a desirable physiological condition effected by blocking Hh signaling, especially Dhh signaling. (E.g, contraception).



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A-1E shows the nucleotide (SEQ ID NO:1) and derived amino acid (SEQ ID NO:2) sequence of a native sequence of human Ptch-2 polypeptide.
FIG. 2A shows EST 905531 (SEQ ID NO:3) and FIG. 2B shows EST 1326258 (SEQ ID NO:5) in alignment with human Ptch (SEQ ID NO:18). These ESTs were used in the cloning of human full-length Ptch-2 (SEQ ID NO:1).
FIGS. 3A-3D show a comparison between human Ptch (SEQ ID NO:33) and Ptch-2 (SEQ ID NO:2). Gaps introduced for optimal alignment are indicated by dashes. Identical amino acids are boxed. The 12 transmembrane domains are indicated by the gray boxes, all of which are conserved between the two sequences. Alignment results between the two sequences indicate 53% identity. The most significant difference is a shorter C-terminal intracellular domain in human Ptch-2 (SEQ ID NO:2) in comparison with human Ptch (SEQ ID NO:33).
FIG. 4 shows a northern blot of Ptch-2 which indicates expression is limited to the testis. Multiple human fetal and adult tissue northern blots were probe fragments corresponding to the 3′-untranslated region of murine Ptch-2.
FIG. 5 shows a chromosomal localization of two BAC clones which were isolated by PCR screening with human patched-2 derived probes. Both probes were mapped by FISH to human chromosome 1p33-34.
FIGS. 6A-F is an in situ hybridization comparing Ptch, Ptch-2 and Fused (FuRK). High magnification of mouse testis showing expression of (A) Ptch, Ptch-2 (B) and FuRK (C). Low magnification of testis section hybridized with Ptch-2 sense (D) and anti-sense probe (E) respectively. FIG. 6(F) shows low magnification of testis section hybridized with FuRK. Scale bar: A, B, C, 0.05 mm; D, E, F: 0.33 mm.
FIG. 7A is logarithmic plot comparing the binding Ptch-2 to Dhh and Shh. Competitive binding of recombinant murine 125I-Shh to 293 cells overexpressing hPtch or hPtch-2. There was no detectable binding to mock transfected cells (data not shown). FIG. 7B is a western blot illustrating co-immunoprecipitation of epitope tagged Ptch or Ptch-2 with epitope tagged Smo. Immunoprecipitation was performed with antibodies to the Flag tagged Ptch and analyzed on a 6% acrylamide gel with antibodies to the Myc tagged Smo. Protein complexes can be detected for both Ptch and Ptch-2 with Smo. Ptch and Ptch-2 express at similar levels as shown by immunoprecipitation using antibodies to the Flag-tag and western blot using the same anti-Flag antibody.
FIGS. 8A-8D is a sequence comparison between human Ptch-2 (SEQ ID NO:2) and murine Ptch 2 (SEQ ID NO:7), which indicates that there is about 91% identity between the two sequences.
FIG. 9 is an in situ hybridization which demonstrates the accumulation of Ptch and Ptch-2 mRNA detected by in situ hybridization in basal cells of E18 transgenic mice overexpressing SMO-M2 (Xie et al., Nature 391: 90-92 (1998)).
FIGS. 10A-10E depict a partial sequence representing clone 3A (SEQ ID NO:8), a partial patched-2 fragment which was initially isolated from a fetal brain library.
FIGS. 11A-C depict a partial sequence representing clone 16.1 (SEQ ID NO:9), a partial patched-2 fragment which was isolated from a testis library.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. Definitions
The terms “patched-2” and “patched-2 polypeptide” when used herein encompass native sequence patched-2 and patched-2 variants (which are further defined herein) having patched-2 biological activity. Patched-2 may be isolated from a variety of sources, such as from testes tissue types or from another source, or prepared by recombinant or synthetic methods.
A “native sequence patched-2” comprises a polypeptide having the same amino acid sequence as a human patched-2 derived from nature. Such native sequence patched-2 can be isolated from nature or can be produced by recombinant and/or synthetic means. The term “native sequence vertebrate patched-2” specifically encompasses naturally occurring truncated forms of human patched-2, naturally occurring variant forms (e.g., alternatively spliced forms) and naturally-occurring allelic variants of human patched-2. Thus, one embodiment of the invention, the native sequence patched-2 is a mature or full-length native patched-2 comprising amino acids 1 to 1203 of FIG. 1 (SEQ ID NO:2) with or without the initiating methionine at position 1.
“Patched-2 variant” means an active human patched-2 as defined below having at least >91% amino acid sequence identity to (a) a DNA molecule encoding a patched-2 polypeptide, or (b) the complement of the DNA molecule of (a). In a particular embodiment, the patched-2 variant has at least >91% amino acid sequence homology with the human Ptch-2 having the deduced amino acid sequence shown in FIG. 1 for a full-length native sequence human patched-2. Such patched-2 variants include, without limitation, patched-2 polypeptides wherein one or more amino acid residues are added, or deleted, at the N- or C-terminus of the sequence of FIG. 1 (SEQ ID NO:2). Preferably, the nucleic acid or amino acid sequence identity is at least about 92%, more preferably at least about 93%, and even more preferably at least about 95%.
The term “Ptch” or “Ptch-2” refer to the particular species of molecules isolated and characterized in the application, while the terms “patched” and patched-2” refer to the more generalized description as defined above.
“Percent (%) amino acid sequence identity” with respect to the patched-2 sequences identified herein is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the patched-2 sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST-2 software that are set to their default parameters. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. Alternatively, % identity can be determined by Align-2, authored by Genentech, Inc., which was filed with user documentation in the United States Copyright Office, Washington, D.C. 20559, on Dec. 10, 1991, and is registered under U.S. Copyright Registration No. TXU 510087.
“Percent (%) nucleic acid sequence identity” with respect to the patched-2 sequences identified herein is defined as the percentage of nucleotides in a candidate sequence that are identical with the nucleotides in the patched-2 sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity. Alignment for purposes of determining percent nucleic acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST-2 software that are set to their default parameters. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. Alternatively, % identity can be determined by Align-2, authored by Genentech, Inc., which was filed with user documentation in the United States Copyright Office, Washington, D.C. 20559, on Dec. 10, 1991, and is registered under U.S. Copyright Registration No. TXU 510087.
The term “epitope tagged” when used herein refers to a chimeric polypeptide comprising patched-2 polypeptide, or a portion thereof, patched-2 to a “tag polypeptide”. The tag polypeptide has enough residues to provide an epitope against which an antibody can be made, yet is short enough such that it does not interfere with activity of the patched-2 polypeptide. The tag polypeptide preferably also is fairly unique so that the antibody does not substantially cross-react with other epitopes. Suitable tag polypeptides generally have at least six amino acid residues and usually between about 8 to about 50 amino acid residues (preferably, between about 10 to about 20 residues).
As used herein, the term “immunoadhesin” designates antibody-like molecules which combine the binding specificity of a heterologous protein (an “adhesin”) with the effector functions of immunoglobulin constant domains. Structurally, the immunoadhesin comprise a fusion of an amino acid sequence with the desired binding specificity which is other than the antigen recognition and binding site of an antibody (i.e., is “heterologous”), and an immunoglobulin constant domain sequence. The adhesin part of an immunoadhesin molecule typically is a contiguous amino acid sequence comprising at least the binding site of a receptor or a ligand. The immunoglobulin constant domain sequence in the immunoadhesins may be obtained from any immunoglobulin, such as IgG-1, IgG-2, IgG-3 or IgG-4 subtypes, IgA (including IgA-1 and IgA-2, IgE, IgD or IgM. Immunoadhesion reported in the literature include fusions of the T cell receptor* [Gascoigne et al., Proc. Natl. Acad. Sci. USA 84: 2936-2940 (1987)]; CD4* [Capron et al., Nature 337: 525-531 (1989); Traunecker et al., Nature 339: 68-70 (1989); Zettmeissl et al., DNA Cell Biol. USA 9: 347-353 (1990); Byrn et al., Nature 344, 667-670 (1990)]; L-selectin (homing receptor) [Watson et al., J. Cell. Biol. 110, 2221-2229 (1990); Watson et al, Nature 349, 164-167 (1991)]; CD44* [Aruffo et al., Cell 61, 1303-1313 (1990)]; CD28* and B7* [Linsley et al., J. Exp. Med. 173, 721-730 (1991)]; CTLA-4* [Lisley et al., J. Exp. Med. 174, 561-569 (1991)]; CD22* [Stamenkovic et al., Cell 66. 1133-1144 (1991)]; TNF receptor [Ashkenazi et al., Proc. Natl. Acad. Sci. USA 88, 10535-10539 (1991); Lesslauer et al., Eur. J. Immunol. 27, 2883-2886 (1991); Peppel et al., J. Exp. Med. 174 1483-1489 (1991)]; NP receptors [Bennett et al., J. Biol. Chem. 266, 23060-23067 (1991)]; IgE receptor α-chain* [Ridgway and Gorman, J. Cell. Biol. 115, abstr. 1448 (1991)]; HGF receptor [Mark, M. R. et al., J. Biol. Chem., 267(36): 26166-26171 (1992)], where the asterisk (*) indicates that the receptor is a member of the immunoglobulin superfamily.
“Stringency” of hybridization reactions is readily determinable by one of ordinary skill in the art, and generally is an empirical calculation dependent upon probe length, washing temperature, and salt concentration. In general, longer probes require higher temperatures for proper annealing, while shorter probes need lower temperatures. Hybridization generally depends upon the ability of denatured DNA to reanneal when complementary strands are present in an environment near but below their Tm (melting temperature). The higher the degree of desired homology between the probe and hybridizable sequence, the higher the relative temperature which can be used. As a result, it follows that higher relative temperatures would tend to make the reaction conditions more stringent, while lower temperatures less so. Moreover, stringency is also inversely proportional to salt concentrations. For additional details and explanation of stringency of hybridization reactions, see Ausubel et al., Current Protocols in Molecular Biology (1995).
“Stringent conditions,” as defined herein may be identified by those that: (1) employ low ionic strength and high temperature for washing, for example 0.015 M sodium chloride/0.0015 M sodium citrate/0.1% sodium dodecyl sulfate at 50° C.; (2) employ during hybridization a denaturing agent, such as formamide, for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin/1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM sodium chloride, 75 mM sodium citrate at 42° C.; (3) employ 50% formamide, 5×SSC (0.75 M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1% sodium pyrophosphate, 5×Denhardt's solution, sonicated salmon sperm DNA (50 μg/ml), 0.1% SDS, and 10% dextran sulfate at 42° C., with washes at 42° C. in 0.2×SSC (sodium chloride/sodium citrate) and 50% formamide at 55° C., followed by a high-stringency wash consisting of 0.1×SSC containing EDTA at 55° C.
“Isolated,” when used to describe the various polypeptides disclosed herein, means polypeptide that has been identified and separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials that would typically interfere with diagnostic or therapeutic uses for the polypeptide, and may include enzymes, hormones, and other proteinaceous or non-proteinaceous solutes. In preferred embodiments, the polypeptide will be purified (1) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator, or (2) to homogeneity by SDS-PAGE under non-reducing or reducing conditions using Coomassie blue or, preferably, silver stain. Isolated polypeptide includes polypeptide in situ within recombinant cells, since at least one component of the vertebrate patched-2 natural environment will not be present. Ordinarily, however, isolated polypeptide will be prepared by at least one purification step.
An “isolated” patched-2 nucleic acid molecule is a nucleic acid molecule that is identified and separated from at least one contaminant nucleic acid molecule with which it is ordinarily associated in the natural source of the patched-2 nucleic acid. An isolated patched-2 nucleic acid molecule is other than in the form or setting in which it is found in nature. Isolated patched-2 nucleic acid molecules therefore are distinguished from the corresponding native patched-2 nucleic acid molecule as it exists in natural cells.
The term “control sequences” refers to DNA sequences necessary for the expression of an operably linked coding sequence in a particular host organism. The control sequences that are suitable for prokaryotes, for example, include a promoter, optionally an operator sequence, and a ribosome binding site. Eukaryotic cells are known to utilize promoters, polyadenylation signals, and enhancers.
Nucleic acid is “operably linked” when it is placed into a functional relationship with another nucleic acid sequence. For example, DNA for a presequence or secretory leader is operably linked to DNA for a polypeptide if it is expressed as a preprotein that participates in the secretion of the polypeptide; a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation. Generally, “operably linked” means that the DNA sequences being linked are contiguous, and, in the case of a secretory leader, contiguous and in reading frame. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exist, the synthetic oligonucleotide adaptors or linkers are used in accordance with conventional practice.
The term “antibody” is used in the broadest sense and specifically covers single monoclonal antibodies (including agonist and antagonist antibodies), antibody compositions with polyepitopic specificity, as well as antibody fragments (e.g., Fab, F(ab′)2 and Fv), so long as they exhibit the desired biological activity.
The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to conventional (polyclonal) antibody preparations that typically include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they are synthesized by the hybridoma culture, uncontaminated by other immunoglobulins. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybridoma method first described by Kohler & Milstein, Nature 256:495 (1975), or may be made by recombinant DNA methods [see, e.g. U.S. Pat. No. 4,816,567 (Cabilly et al.)].
The monoclonal antibodies herein specifically include “chimeric” antibodies (immunoglobulins) in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity [U.S. Pat. No. 4,816,567; Cabilly et al.; Morrison et al., Proc. Natl. Acad. Sci. USA 81, 6851-6855 (1984)].
“Humanized” forms of non-human (e.g. murine) antibodies are chimeric immunoglobulins, immunoglobulin chains or fragments thereof (such as Fv, Fab, Fab′, F(ab′)2 or other antigen-binding subsequences of antibodies) which contain minimal sequence derived from non-human immunoglobulin. For the most part, humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat or rabbit having the desired specificity, affinity and capacity. In some instances, corresponding non-human residues replace Fv framework residues of the human immunoglobulin. Furthermore, humanized antibody may comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. These modifications are made to further refine and optimize antibody performance. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. For further details see: Jones et al., Nature 321, 522-525 (1986); Reichmann et al., Nature 332, 323-329 (1988); Presta, Curr. Op. Struct. Biol. 2 593-596 (1992) and U.S. Pat. No. 5,225,539 (Winter) issued Jul. 6, 1993.
“Active” or “activity” for the purposes herein refers to form(s) of patched-2 which retain the biologic and/or immunologic activities of native or naturally occurring patched-2. A preferred activity is the ability to bind to and affect, e.g., block or otherwise modulate, hedgehog, especially Desert hedgehog signaling. For example, the regulation of the pathogenesis of testicular cancer, male spermatocyte formation and basal cell carcinoma.
The term “antagonist” is used herein in the broadest sense to include any molecule which blocks, prevents, inhibits, neutralizes the normal functioning of patched-2 in the Hh signaling pathway. One particular form of antagonist includes a molecule that interferes with the interaction between Dhh and Ptch-2. Alternatively, an antagonist could also be a molecule which increases the levels of patched-2. In a similar manner, the term “agonist” is used herein to include any molecule which promotes, enhances or stimulates the binding of a Hh to patched-2 in the Hh signaling pathway (e.g., blocking binding of Ptch-2 to Smo). Suitable molecules that affect the protein-protein interaction of Hh and Ptch-2 and its binding proteins include fragments of the latter or small bioorganic molecules, e.g., peptidomimetics, which will prevent or enhance, as the case may be, the binding of Hh to Ptch-2. Non-limiting examples include proteins, peptides, glycoproteins, glycopeptides, glycolipids, polysaccharides, oligosaccharides, nucleic acids, bioorganic molecules, peptidomimetics, pharmacological agents and their metabolites, transcriptional and translation control sequences, and the like. Another preferred form of antagonist includes antisense oligonucleotides that inhibit proper transcription of wild type patched-2.
The term “modulation” or “modulating” means upregulation or downregulation of a signaling pathway. Cellular processes under the control of signal transduction may include, but are not limited to, transcription of specific genes; normal cellular functions, such as metabolism, proliferation, differentiation, adhesion, apoptosis and survival, as well as abnormal processes, such as transformation, blocking of differentiation and metastasis.
The techniques of “polymerase chain reaction,” or “PCR”, as used herein generally refers to a procedure wherein minute amounts of a specific piece of nucleic acid, RNA and/or DNA are amplified as described in U.S. Pat. No. 4,683,195 issued 28 Jul. 1987. Generally, sequence information from the ends of the region of interest or beyond needs to be available, such that oligonucleotide primers can be designed; these primers will be identical or similar in sequence to opposite strands of the template to be amplified. The 5′ terminal nucleotides of the two primers may coincide with the ends of the amplified material. PCR sequences form total genomic DNA, and cDNA transcribed from total cellular RNA, bacteriophage, or plasmid sequences, etc. See generally Mullis et al., Cold Spring Harbor Symp. Quant. Biol. 51: 263 (1987); Erlich, Ed., PCR Technology, (Stockton Press, NY, 1989). As used herein, PCR is considered to be one, but not the only, example of a nucleic acid test sample comprising the use of a known nucleic acid as a primer and a nucleic acid polymerase to amplify or generate a specific piece of nucleic acid.
II. Compositions and Methods of the Invention
A. Full-Length Patched-2
The present invention provides newly identified and isolated nucleotide sequences encoding polypeptides referred to in the present application as patched-2. In particular, Applicants have identified and isolated cDNA encoding a human patched-2 polypeptide, as disclosed in further detail in the Examples below. Using BLAST, BLAST-2 and FastA sequence alignment computer programs (set to the default parameters), Applicants found that a full-length native sequence human Ptch-2 (SEQ ID NO:2) (shown in FIG. 3) has 53% amino acid sequence identity with human patched (SEQ ID NO:33). Moreover human full-length patched-2 (SEQ ID NO:2) has about a 91% sequence identity with murine Ptch-2 (SEQ ID NO:7) (FIG. 8). Accordingly, it is presently believed that the human patched-2 (SEQ ID NO:2) disclosed in the present application is a newly identified member of the mammalian hedgehog signaling cascade, specifically Desert hedgehog.
The full-length native sequence of human patched-2 gene, or portions thereof, may be used as hybridization probes for a cDNA library to isolate the full-length gene or to isolate still other vertebrate homolog genes (for instance, those encoding naturally-occurring variants of patched-2 or patched-2 from other species) which have a desired sequence identity to the human patched-2 sequence disclosed in FIG. 1 (SEQ ID NO:2). Optionally, the length of the probes will be about 20 to about 50 bases. The hybridization probes may be derived from the nucleotide sequence of FIG. 1 (SEQ ID NO:1) or from genomic sequences including promoters, enhancer elements and introns of native sequence vertebrate patched-2. By way of example, a screening method will comprise isolating the coding region of the vertebrate patched-2 gene using the known DNA sequence to synthesize a selected probe of about 40 bases. Hybridization probes may be labeled by a variety of labels, including radionucleotides such as 32P or 35S, or enzymatic labels such as alkaline phosphatase coupled to the probe via avidin/biotin coupling systems. Labeled probes having a sequence complementary to that of the vertebrate patched-2 gene of the present invention can be used to screen libraries of human cDNA, genomic DNA or mRNA to determine which members of such libraries the probe hybridizes to.
B. Patched-2 Variants
In addition to the full-length native sequence patched-2 described herein, it is contemplated that patched-2 variants can be prepared. Patched-2 variants can be prepared by introducing appropriate nucleotide changes into a known patched-2 DNA, or by synthesis of the desired patched-2 polypeptides. Those skilled in the art will appreciate that amino acid changes may alter post-translational processes of patched-2.
Variations in the native full-length sequence patched-2 or in various domains of the patched-2 described herein, can be made, for example, using any of the techniques and guidelines for conservative and non-conservative mutations set forth, for instance, in U.S. Pat. No. 5,364,934. Variations may be a substitution, deletion or insertion of one or more codons encoding the patched-2 that results in a change in the amino acid sequence of patched-2 as compared with the native sequence patched-2. Optionally, the variation is by substitution of at least one amino acid with any other amino acid in one or more of the domains of patched-2. Guidance in determining which amino acid residue may be inserted, substituted or deleted without adversely affecting the desired activity may be found by comparing the sequence of the patched-2 with that of homologous known protein molecules and minimizing the number of amino acid sequence changes made in regions of high homology. Amino acid substitutions can be the result of replacing one amino acid with another amino acid having similar structural and/or chemical properties, such as the replacement of a leucine with a serine, i.e., conservative amino acid replacements. Insertions or deletions may optionally be in the range of 1 to 5 amino acids. The variation allowed may be determined by systematically making insertions, deletions or substitutions of amino acids in the sequence and testing the resulting variants for activity in the in vitro assay described in the Examples below.
The variations can be made using methods known in the art such as oligonucleotide-mediated (site-directed) mutagenesis, alanine scanning, and PCR mutagenesis. Site-directed mutagenesis [Carter et al., Nucl. Acids Res., 13:4331 (1986); Zoller et al., Nucl Acids Res., 10: 6487 (1987)], cassette mutagenesis [Wells et al., Gene, 34:315 (1985)], restriction selection mutagenesis [Wells et al., Philos. Trans. R. Soc. London SerA, 317:415 (1986)] or other known techniques can be performed on the cloned DNA to produce the vertebrate patched-2 variant DNA.
Scanning amino acid analysis can also be employed to identify one or more amino acids along a contiguous sequence. Among the preferred scanning amino acids are relatively small, neutral amino acids. Such amino acids include alanine, glycine, serine, and cysteine. Alanine is typically a preferred scanning amino acid among this group because it eliminates the side-chain beyond the beta-carbon and is less likely to alter the main-chain conformation of the variant. Alanine is also typically preferred because it is the most common amino acid. Further, it is frequently found in both buried and exposed positions [Creighton, The Proteins, (W.H. Freeman & Co., N.Y.); Chothia, J. Mol. Biol., 150:1 (1976)]. If alanine substitution does not yield adequate amounts of variant, an isoteric amino acid can be used.
In the comparison between human Ptch (SEQ ID NO:33) and Ptch-2 (SEQ ID NO:2) sequences depicted in FIG. 3, the 12 transmembrane domains are identified in gray, while identical residues are boxed. Gaps are indicated by dashes (−) and are inserted to maximize the total identity score between the two sequences.
C. Modifications of Patched-2
Covalent modifications of patched-2 are included within the scope of this invention. One type of covalent modification includes reacting targeted amino acid residues of patched-2 with an organic derivatizing agent that is capable of reacting with selected side chains or the N- or C-terminal residues of the vertebrate patched-2. Derivatization with bifunctional agents is useful, for instance, for crosslinking patched-2 to a water-insoluble support matrix or surface for use in the method for purifying anti-patched-2 antibodies, and vice-versa. Commonly used crosslinking agents include, e.g., 1,1-bis(diazo-acetyl)-2-phenylethane, glutaraldehyde, N-hydroxy-succinimide esters, for example, esters with 4-azido-salicylic acid, homobifunctional imidoesters, including disuccinimidyl esters such as 3,3′-dithiobis-(succinimidyl-propionate), bifunctional maleimides such as bis-N-maleimido-1,8-octane and agents such as methyl-3-[(p-azidophenyl)-dithio]proprioimidate.
Other modifications include deamidation of glutaminyl and asparaginyl residues to the corresponding glutamyl and aspartyl residues, respectively, hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the a-amino groups of lysine, arginine, and histidine side chains [T. E. Creighton, Proteins: Structure and Molecular Properties, W.H. Freeman & Co., San Francisco, pp. 79-86 (1983)], acetylation of the N-terminal amine, and amidation of any C-terminal carboxyl group.
Another type of covalent modification of patched-2 comprises linking the patched-2 polypeptide to one of a variety of nonproteinaceous polymers, e.g., polyethylene glycol, polypropylene glycol, or polyoxyalkylenes, in the manner set forth in U.S. Pat. No. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or 4,179,337. Such modifications would be expected in increase the half-life of the molecules in circulation in a mammalian system; Extended half-life of patched-2 molecules might be useful under certain circumstances, such as where the patched-2 variant is administered as a therapeutic agent.
The patched-2 of the present invention may also be modified in a way to form a chimeric molecule comprising patched-2 bonded to another, heterologous polypeptide or amino acid sequence. In one embodiment, such a chimeric molecule comprises a fusion of patched-2 with a tag polypeptide, which provides an epitope to which an anti-tag antibody can selectively bind. The epitope tag is generally placed at the amino- or carboxyl-terminus of the patched-2. The presence of such epitope-tagged forms of the patched-2 can be detected using an antibody against the tag polypeptide. Also, provision of the epitope tag enables the patched-2 to be readily purified by affinity purification using an anti-tag antibody or another type of affinity matrix that binds to the epitope tag. In an alternative embodiment, the chimeric molecule may comprise a fusion of the patched-2 with an immunoglobulin or a particular region of an immunoglobulin. For a bivalent form of the chimeric molecule, such a fusion could be to the Fc region of an IgG molecule. Ordinarily, the C-terminus of a contiguous amino acid sequence of a patched-2 receptor is fused to the N-terminus of a contiguous amino acid sequence of an immunoglobulin constant region, in place of the variable region(s), however N-terminal fusions are also possible.
Typically, such fusions retain at least functionally active hinge, CH2 and CH3 domains of the constant region of an immunoglobulin heavy chain. Fusions are also made to the C-terminus of the Fc portion of a constant domain, or immediately N-terminal to the CH1 of the heavy chain or the corresponding region of the light chain. This ordinarily is accomplished by constructing the appropriate DNA sequence and expressing it in recombinant cell culture. Alternatively, immunoadhesins may be synthesized according to known methods.
The precise site at which the fusion is made is not critical; particular sites are well known and may be selected in order to optimize the biological activity, secretion or binding characteristics of the immunoadhesins.
In a preferred embodiment, the C-terminus of a contiguous amino acid sequence which comprises the binding site(s) of patched-2, at the N-terminal end, to the C-terminal portion of an antibody (in particular the Fc domain), containing the effector functions of an immunoglobulin, e.g., immunoglobulin G1 (IgG-1). As herein above mentioned, it is possible to fuse the entire heavy chain constant region to the sequence containing the binding site(s). However, more preferably, a sequence beginning in the hinge region just upstream of the papain cleavage site (which defines IgG Fc chemically; residue 216, taking the first residue of heavy chain constant region to be 114 [Kobat et al., supra], or analogous sites of other immunoglobulins) is used in the fusion. Although it was earlier thought that in immunoadhesins the immunoglobulin light chain would be required for efficient secretion of the heterologous protein-heavy chain fusion proteins, it has been found that even the immunoadhesins containing the whole IgG1 heavy chain are efficiently secreted in the absence of light chain. Since the light chain is unnecessary, the immunoglobulin heavy chain constant domain sequence used in the construction of the immunoadhesins of the present invention may be devoid of a light chain binding site. This can be achieved by removing or sufficiently altering immunoglobulin heavy chain sequence elements to which the light chain is ordinarily linked so that such binding is no longer possible. Thus, the CH1 domain can be entirely removed in certain embodiments of the patched-2/immunoglobulin chimeras.
In a particularly preferred embodiment, the amino acid sequence containing the extracellular domain(s) of patched-2 is fused to the hinge region and CH2, CH3; or CH1, hinge, CH2 and CH3 domains of an IgG-1, IgG-2, IgG-3, or IgG-4 heavy chain.
In some embodiments, the patched-2/immunoglobulin molecules (immunoadhesins) are assembled as monomers, dimers or multimers, and particularly as dimers or tetramers. Generally, these assembled immunoadhesins will have known unit structures similar to those of the corresponding immunoglobulins. A basic four chain structural unit (a dimer of two immunoglobulin heavy chain-light chain pairs) is the form in which IgG, IgA and IgE exist. A four chain unit is repeated in the high molecular weight immunoglobulins; IgM generally exists as a pentamer of basic four-chain units held together by disulfide bonds. IgA globulin, and occasionally IgG globulin, may also exist in a multimeric form in serum. In the case of multimers, each four chain unit may be the same or different.
It is not necessary that the entire immunoglobulin portion of the patched-2/immunoglobulin chimeras be from the same immunoglobulin. Various portions of different immunoglobulins may be combined, and variants and derivatives of native immunoglobulins can be made as herein above described with respect to patched-2, in order to optimize the properties of the immunoadhesin molecules. For example, immunoadhesin constructs in which the hinge of IgG-1 was replaced with that of IgG-3 were found to be functional and showed pharmacokinetics comparable to those of immunoadhesins comprising the entire IgG-1 heavy chain.
Various tag polypeptides and their respective antibodies are well known in the art. Examples include poly-histidine (poly-his) or poly-histidine-glycine (poly-his-gly) tags; the flu HA tag polypeptide and its antibody 12CA5 [Field et al., Mol. Cell. Biol., 8: 2159-2165 (1988)]; the c-myc tag and the 8F9, 3C7, 6E10, G4, B7 and 9E10 antibodies thereto [Evan et al., Molecular and Cellular Biology, 5:3610-3616 (1985)]; and the Herpes Simplex virus glycoprotein D (gD) tag and its antibody [Paborsky et al., Protein Engineering, 3(6):547-553 (1990)]. Other tag polypeptides include the Flag-peptide [Hopp et al., BioTechnology, 6:1204-1210 (1988)]; the KT3 epitope peptide [Martin et al., Science, 255:192-194 (1992)]; an α-tubulin epitope peptide [Skinner et al., J. Biol. Chem., 266:15163-15166 (1991)]; and the T7 gene 10 protein peptide tag [Lutz-Freyermuth et al., Proc. Natl. Acad. Sci. USA, 87:6393-6397 (1990)]. A preferred tag is the influenza HA tag.
D. Preparation of Patched-2
The description below relates primarily to production of a particular patched-2 by culturing cells transformed or transfected with a vector containing patched-2 nucleic acid. It is, of course, contemplated that alternative methods, which are well known in the art, may be employed to prepare patched-2. For instance, the patched-2 sequence, or portions thereof, may be produced by direct peptide synthesis using solid-phase techniques [see, e.g., Stewart et al., Solid-Phase Peptide Synthesis, W.H. Freeman Co., San Francisco, Calif. (1969); Merrifield, J. Am. Chem. Soc., 85:2149-2154 (1963)]. In vitro protein synthesis may be performed using manual techniques or by automation. Automated synthesis may be accomplished, for instance, using an Applied Biosystems Peptide Synthesizer (Foster City, Calif.) using manufacturer's instructions. Various portions of the vertebrate patched-2 may be chemically synthesized separately and combined using chemical or enzymatic methods to produce the full-length patched-2.
1. Isolation of DNA Encoding Vertebrate Patched-2
DNA encoding patched-2 may be obtained from a cDNA library prepared from tissue believed to possess the patched-2 mRNA and to express it at a detectable level. Accordingly, human patched-2 DNA can be conveniently obtained from a cDNA library prepared from human tissue, such as described in the Examples. The vertebrate patched-2-encoding gene may also be obtained from a genomic library or by oligonucleotide synthesis.
Libraries can be screened with probes (such as antibodies to the patched-2 or oligonucleotides of at least about 20-80 bases) designed to identify the gene of interest or the protein encoded by it. Screening the cDNA or genomic library with the selected probe may be conducted using standard procedures, such as described in Sambrook et al., Molecular Cloning: A Laboratory Manual (New York: Cold Spring Harbor Laboratory Press, 1989). An alternative means to isolate the gene encoding vertebrate patched-2 is to use PCR methodology [Sambrook et al., supra; Dieffenbach et al., PCR Primer: A Laboratory Manual (Cold Spring Harbor Laboratory Press, 1995)].
The Examples below describe techniques for screening a cDNA library. The oligonucleotide sequences selected as probes should be of sufficient length and sufficiently unambiguous that false positives are minimized. The oligonucleotide is preferably labeled such that it can be detected upon hybridization to DNA in the library being screened. Methods of labeling are well known in the art, and include the use of radiolabels like 32P-labeled ATP, biotinylation or enzyme labeling. Hybridization conditions, including moderate stringency and high stringency, are provided in Sambrook et al., supra.
Sequences identified in such library screening methods can be compared and aligned to other known sequences deposited and available in public databases such as GenBank or other private sequence databases. Sequence identity (at either the amino acid or nucleotide level) within defined regions of the molecule or across the full-length sequence can be determined through sequence alignment using computer software programs such as BLAST, BLAST-2, ALIGN, DNAstar, and INHERIT which employ various algorithms to measure homology.
Nucleic acid having protein coding sequence may be obtained by screening selected cDNA or genomic libraries using the deduced amino acid sequence disclosed herein for the first time, and, if necessary, using conventional primer extension procedures as described in Sambrook et al., supra, to detect precursors and processing intermediates of mRNA that may not have been reverse-transcribed into cDNA.
2. Selection and Transformation of Host Cells
Host cells are transfected or transformed with expression or cloning vectors described herein for patched-2 production and cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences. The culture conditions, such as media, temperature, pH and the like, can be selected by the skilled artisan without undue experimentation. In general, principles, protocols, and practical techniques for maximizing the productivity of cell cultures can be found in Mammalian Cell Biotechnology: A Practical Approach, M. Butler, ed. (IRL Press, 1991) and Sambrook et al., supra.
Methods of transfection are known to the ordinarily skilled artisan, for example, CaPO4 and electroporation. Depending on the host cell used, transformation is performed using standard techniques appropriate to such cells. The calcium treatment employing calcium chloride, as described in Sambrook et al., supra, or electroporation is generally used for prokaryotes or other cells that contain substantial cell-wall barriers. Infection with Agrobacterium tumefaciens is used for transformation of certain plant cells, as described by Shaw et al., Gene, 23:315 (1983) and WO 89/05859 published 29 Jun. 1989. For mammalian cells without such cell walls, the calcium phosphate precipitation method of Graham and van der Eb, Virology 52:456-457 (1978) can be employed. General aspects of mammalian cell host system transformations have been described in U.S. Pat. No. 4,399,216. Transformations into yeast are typically carried out according to the method of Van Solingen et al., J. Bact., 130:946 (1977) and Hsiao et al., Proc. Natl. Acad. Sci. (USA), 76:3829 (1979). However, other methods for introducing DNA into cells, such as by nuclear microinjection, electroporation, bacterial protoplast fusion with intact cells, or polycations, e.g., polybrene, polyornithine, may also be used. For various techniques for transforming mammalian cells, see Keown et al., Methods in Enzymology, 185:527-537 (1990) and Mansour et al., Nature, 336:348-352 (1988).
Suitable host cells for cloning or expressing the DNA in the vectors herein include prokaryote, yeast, or higher eukaryote cells. Suitable prokaryotes include but are not limited to eubacteria, such as Gram-negative or Gram-positive organisms, for example, Enterobacteriae such as E. coli. Various E. coli strains are publicly available, such as E. coli K12 strain MM294 (ATCC 31,446); E. coli X1776 (ATCC 31,537); E. coli strain W3110 (ATCC 27,325) and K5 772 (ATCC 53,635).
In addition to prokaryotes, eukaryotic microbes such as filamentous fungi or yeast are suitable cloning or expression hosts for vertebrate patched-2-encoding vectors. Saccharomyces cerevisiae is a commonly used lower eukaryotic host microorganism.
Suitable host cells for the expression of vertebrate patched-2 are derived from multicellular organisms. Examples of invertebrate cells include insect cells such as Drosophila S2 and Spodoptera Sf9, as well as plant cells. Examples of useful mammalian host cell lines include Chinese hamster ovary (CHO) and COS cells. More specific examples include monkey kidney CV1 line transformed by SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line (293 or 293 cells subcloned for growth in suspension culture, Graham et al., J. Gen Virol., 36:59 (1977)); Chinese hamster ovary cells/-DHFR(CHO, Urlaub and Chasin, Proc. Natl. Acad. Sci. USA, 77:4216 (1980)); mouse sertoli cells (TM4, Mather, Biol. Reprod. 23:243-251 (1980)); human lung cells (W138, ATCC CCL 75); human liver cells (Hep G2, HB 8065); and mouse mammary tumor (MMT 060562, ATCC CCL51). The selection of the appropriate host cell is deemed to be within the skill in the art.
3. Selection and Use of a Replicable Vector
The nucleic acid (e.g., cDNA or genomic DNA) encoding patched-2 may be inserted into a replicable vector for cloning (amplification of the DNA) or for expression. Various vectors are publicly available. The vector may, for example, be in the form of a plasmid, cosmid, viral particle, or phage. The appropriate nucleic acid sequence may be inserted into the vector by a variety of procedures. In general, DNA is inserted into an appropriate restriction endonuclease site(s) using techniques known in the art. Vector components generally include, but are not limited to, one or more of a signal sequence, an origin of replication, one or more marker genes, an enhancer element, a promoter, and a transcription termination sequence. Construction of suitable vectors containing one or more of these components employs standard ligation techniques, which are known to the skilled artisan.
Both expression and cloning vectors contain a nucleic acid sequence that enables the vector to replicate in one or more selected host cells. Such sequences are well known for a variety of bacteria, yeast, and viruses. The origin of replication from the plasmid pBR322 is suitable for most Gram-negative bacteria, the 2μ plasmid origin is suitable for yeast, and various viral origins (SV40, polyoma, adenovirus, VSV or BPV) are useful for cloning vectors in mammalian cells. A preferred replicable expression vector is the plasmid is pRK5. Holmes et al., Science, 253:1278-1280 (1991).
Expression and cloning vectors will typically contain a selection gene, also termed a selectable marker. Typical selection genes encode proteins that (a) confer resistance to antibiotics or other toxins, e.g., ampicillin, neomycin, methotrexate, or tetracycline, (b) complement auxotrophic deficiencies, or (c) supply critical nutrients not available from complex media, e.g., the gene encoding D-alanine racemase for Bacilli. 
An example of suitable selectable markers for mammalian cells are those that enable the identification of cells competent to take up the patched-2 nucleic acid, such as DHFR or thymidine kinase. An appropriate host cell when wild-type DHFR is employed is the CHO cell line deficient in DHFR activity, prepared and propagated as described by Urlaub et al., Proc. Natl. Acad. Sci. USA, 77:4216 (1980). A suitable selection gene for use in yeast is the trp1 gene present in the yeast plasmid YRp7 [Stinchcomb et al., Nature, 282:39 (1979); Kingsman et al., Gene, 7:141 (1979); Tschemper et al., Gene, 10:157 (1980)]. The trp1 gene provides a selection marker for a mutant strain of yeast lacking the ability to grow in tryptophan, for example, ATCC No. 44076 or PEP4-1 [Jones, Genetics, 85:12 (1977)].
Expression and cloning vectors usually contain a promoter operably linked to the patched-2 nucleic acid sequence to direct mRNA synthesis. Promoters recognized by a variety of potential host cells are well known. Promoters suitable for use with prokaryotic hosts include the β-lactamase and lactose promoter systems [Chang et al., Nature, 275:615 (1978); Goeddel et al., Nature, 281:544 (1979)], alkaline phosphatase, a tryptophan (trp) promoter system [Goeddel, Nucleic Acids Res., 8:4057 (1980); EP 36,776], and hybrid promoters such as the tac promoter [deBoer et al., Proc. Natl. Acad. Sci. USA, 80:21-25 (1983)]. Promoters for use in bacterial systems also will contain a Shine-Dalgarno (S.D.) sequence operably linked to the DNA encoding patched-2.
Examples of suitable promoting sequences for use with yeast hosts include the promoters for 3-phosphoglycerate kinase [Hitzeman et al., J. Biol. Chem., 255:2073 (1980)] or other glycolytic enzymes [Hess et al., J. Adv. Enzyme Reg., 7:149 (1968); Holland, Biochemistry, 17:4900 (1978)], such as enolase, glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phospho-fructokinase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase, and glucokinase.
Other yeast promoters, which are inducible promoters having the additional advantage of transcription controlled by growth conditions, are the promoter regions for alcohol dehydrogenase 2, isocytochrome C, acid phosphatase, degradative enzymes associated with nitrogen metabolism, metallothionein, glyceraldehyde-3-phosphate dehydrogenase, and enzymes responsible for maltose and galactose utilization. Suitable vectors and promoters for use in yeast expression are further described in EP 73,657.
Patched-2 transcription from vectors in mammalian host cells is controlled, for example, by promoters obtained from the genomes of viruses such as polyoma virus, fowlpox virus (UK 2,211,504 published 5 Jul. 1989), adenovirus (such as Adenovirus 2), bovine papilloma virus, avian sarcoma virus, cytomegalovirus, a retrovirus, hepatitis-B virus and Simian Virus 40 (SV40), from heterologous mammalian promoters, e.g., the actin promoter or an immunoglobulin promoter, and from heat-shock promoters, provided such promoters are compatible with the host cell systems.
Inserting an enhancer sequence into the vector may increase transcription of a DNA encoding the vertebrate patched-2 by higher eukaryotes. Enhancers are cis-acting elements of DNA, usually about from 10 to 300 bp, that act on a promoter to increase its transcription. Many enhancer sequences are now known from mammalian genes (globin, elastase, albumin, α-fetoprotein, and insulin). Typically, however, one will use an enhancer from a eukaryotic cell virus. Examples include the SV40 enhancer on the late side of the replication origin (bp 100-270), the cytomegalovirus early promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers. The enhancer may be spliced into the vector at a position 5′ or 3′ to the patched-2 coding sequence, but is preferably located at a site 5′ from the promoter.
Expression vectors used in eukaryotic host cells (yeast, fungi, insect, plant, animal, human, or nucleated cells from other multicellular organisms) will also contain sequences necessary for the termination of transcription and for stabilizing the mRNA. Such sequences are commonly available from the 5′ and, occasionally 3′, untranslated regions of eukaryotic or viral DNAs or cDNAs. These regions contain nucleotide segments transcribed as polyadenylated fragments in the untranslated portion of the mRNA encoding patched-2.
Still other methods, vectors, and host cells suitable for adaptation to the synthesis of patched-2 in recombinant vertebrate cell culture are described in Gething et al., Nature, 293:620-625 (1981); Mantei et al., Nature, 281:40-46 (1979); EP 117,060; and EP 117,058.
4. Detecting Gene Amplification/Expression
Gene amplification and/or expression may be measured in a sample directly, for example, by conventional Southern blotting, Northern blotting to quantitate the transcription of mRNA [Thomas, Proc. Natl. Acad. Sci. USA, 77:5201-5205 (1980)], dot blotting (DNA analysis), or in situ hybridization, using an appropriately labeled probe, based on the sequences provided herein. Alternatively, antibodies may be employed that can recognize specific duplexes, including DNA duplexes, RNA duplexes, and DNA-RNA hybrid duplexes or DNA-protein duplexes. The antibodies in turn may be labeled and the assay may be carried out where the duplex is bound to a surface, so that upon the formation of duplex on the surface, the presence of antibody bound to the duplex can be detected.
Gene expression, alternatively, may be measured by immunological methods, such as immunohistochemical staining of cells or tissue sections and assay of cell culture or body fluids, to quantitate directly the expression of gene product. Antibodies useful for immunohistochemical staining and/or assay of sample fluids may be either monoclonal or polyclonal, and may be prepared in any mammal. Conveniently, the antibodies may be prepared against a native sequence patched-2 polypeptide or against a synthetic peptide based on the DNA sequences provided herein or against exogenous sequence patched-2 to patched-2 DNA and encoding a specific antibody epitope.
5. Purification of Polypeptide
Forms of patched-2 may be recovered from host cell lysates. Since patched-2 is membrane-bound, it can be released from the membrane using a suitable detergent solution (e.g. Triton-X 100) or by enzymatic cleavage. Cells employed in expression of patched-2 can be disrupted by various physical or chemical means, such as freeze-thaw cycling, sonication, mechanical disruption, or cell lysing agents.
It may be desired to purify patched-2 from recombinant cell proteins or polypeptides. The following procedures are exemplary of suitable purification procedures: by fractionation on an ion-exchange column; ethanol precipitation; reverse phase HPLC; chromatography on silica or on a cation-exchange resin such as DEAE; chromatofocusing; SDS-PAGE; ammonium sulfate precipitation; gel filtration using, for example, Sephadex G-75; protein A Sepharose columns to remove contaminants such as IgG; and metal chelating columns to bind epitope-tagged forms of the patched-2. Various methods of protein purification may be employed and such methods are known in the art and described for example in Deutscher, Methods in Enzymology, 182 (1990); Scopes, Protein Purification: Principles and Practice, Springer-Verlag, New York (1982). The purification step(s) selected will depend, for example, on the nature of the production process used and the particular patched-2 produced.
E. Uses for Patched-2
(1) Patched-2 is a Specific Receptor for Dhh
The hedgehog signaling pathway has been implicated in the formation of embryonic structures in mammals and invertebrates. The multi-pass transmembrane receptor Ptch, is a negative regulator of the hedgehog pathway, repressing the serpentine signaling molecule Smoothened (Smo). Data have shown that loss of Ptch leads to deregulation of the hedgehog pathway leading to formation of aberrant structures in the embryos and carcinoma in the adult.
Applicants' newly identified second human patched gene, termed patched-2, has a similar 12 transmembrane domain topology as does patched, and can bind to all the members of the Hh family and can complex with Smo. However, the expression patterns of Ptch-2 and Ptch do not overlap. Ptch-2 is expressed mainly in the developing spermatocytes, which are supported directly by the Dhh producing Sertoli cells, which suggests that Ptch-2 is a receptor for Desert hedgehog.
In the adult tubule, Sertoli cells, which are unusually large secretory cells, traverse the seminiferous tubule from the basal lamina to the luminal aspect, sending out cytoplasmic protrusions that engulf the germ cells. These contacts are particularly close during spermiogenesis, in which the haploid round spermatids undergo differentiation to produce the highly specialized, motile sperm. Tight junctions between adjacent Sertoli cells compartmentalize the tubule into a basal region, which contains mitotic spermatogonia and early spermtocytes, and an adluminal compartment, which contains meiotic spermatocytes and maturing spermatids. In fact, a Sertoli-derived cell line supports the meiotic progression of germ cells in culture, consistent with the view that factors derived from Sertoli cells contribute to germ cell maturation, Rassoulzadegan, M., et al., Cell 1993, 75: 997-1006. Loss of Dhh activity results in a recessive, sex-specific phentotype. Female mice homozygous for the mutation were fully viable and fertile, whereas male mice were viable but infertile. A gross examination indicated that, as early as 18.5 dpc, the testes of mutant males were noticeably smaller than those of heterozygous littermates. Bitgood et al., Curr. Biol., 1996 6(3): 298-304. Thus, Sertoli cells likely independently regulate mitotic and meiotic stages of germ cell development during postnatal development. Therefore, since patched-2 appears to be the receptor for Dhh, molecules which modulate the binding of Dhh to Ptch-2 would affect the activation of Dhh signaling, and thereby would have utility in the treatment of conditions which are modulated by Dhh. (For example, testicular cancer). Alternatively, it is also provided that antagonists or agonists of patched-2 may be used for treating disorders or creating a desirable physiological condition effected by blocking Dhh signaling. (E.g, contraception, infertility treatment).
(2) General Uses for Patched-2
Nucleotide sequences (or their complement) encoding patched-2 have various applications in the art of molecular biology, including uses as hybridization probes, in chromosome and gene mapping and in the generation of anti-sense RNA and DNA. Patched-2 nucleic acid will also be useful for the preparation of patched-2 polypeptides by the recombinant techniques described herein.
The full-length native sequence patched-2 gene, or portions thereof, may be used as hybridization probes for a cDNA library to isolate the full-length gene or to isolate still other genes (for instance, those encoding naturally-occurring variants of patched-2) which have a desired sequence identity to the patched-2 sequence disclosed in FIG. 1 (SEQ ID NO:1). Optionally, the length of the probes will be about 20 to about 50 bases. The hybridization probes may be derived from the nucleotide sequence of FIG. 1 (SEQ ID NO:1) or from genomic sequences including promoters, enhancer elements and introns of native sequence patched-2. By way of example, a screening method will comprise isolating the coding region of the patched-2 gene using the known DNA sequence to synthesize a selected probe of about 40 bases. Hybridization probes may be labeled by a variety of labels, including radionucleotides such as 32P or 35S, or enzymatic labels such as alkaline phosphatase coupled to the probe via avidin/biotin coupling systems. Labeled probes having a sequence complementary to that of the patched-2 gene of the present invention can be used to screen libraries of human cDNA, genomic DNA or mRNA to determine to which members of such libraries the probe hybridizes. Hybridization techniques are described in further detail in the Examples below.
The probes may also be employed in PCR techniques to generate a pool of sequences for identification of closely related patched-2 sequences.
Nucleotide sequences encoding patched-2 can also be used to construct hybridization probes for mapping the gene, which encodes patched-2 and for the genetic analysis of individuals with genetic disorders. The nucleotide sequences provided herein may be mapped to a chromosome and specific regions of a chromosome using known techniques, such as in situ hybridization, linkage analysis against known chromosomal markers, and hybridization screening with libraries.
Patched-2 polypeptides can be used in assays to identify the other proteins or molecules involved in complexing with patched-2 which ultimately results in the modulation of hedgehog signaling. Alternatively, these molecules can modulate the binding of patched-2 to Dhh. By such methods, inhibitors of the binding interaction can be identified. Proteins involved in such binding interactions can also be used to screen for peptide or small molecule inhibitors or agonists of the binding interaction. Also, the substrate of patched-2 can be used to isolate correlative complexing proteins. Screening assays can be designed to find lead compounds that mimic the biological activity of a native patched-2 or to find those that act as a substrate for patched-2. Such screening assays will include assays amenable to high-throughput screening of chemical libraries, making them particularly suitable for identifying small molecule drug candidates. Such small molecule inhibitors could block the enzymatic action of patched-2, and thereby inhibit hedgehog signaling. Small molecules contemplated include synthetic organic or inorganic compounds. The assays can be performed in a variety of formats, including protein-protein binding assays, biochemical screening assays, immunoassays and cell based assays, which are well characterized in the art.
Nucleic acids which encode patched-2 or its modified forms can also be used to generate either transgenic animals or “knock out” animals which, in turn, are useful in the development and screening of therapeutically useful reagents. A transgenic animal (e.g., a mouse or rat) is an animal having cells that contain a transgene, was introduced into the animal or an ancestor of the animal at a prenatal, e.g., an embryonic stage. A transgene is a DNA sequence that is integrated into the genome of a cell from which a transgenic animal develops. In one embodiment, cDNA encoding patched-2 can be used to clone genomic DNA encoding patched-2 in accordance with established techniques and the genomic sequences used to generate transgenic animals that contain cells which express DNA encoding patched-2. Methods for generating transgenic animals, particularly animals such as mice or rats, have become conventional in the art and are described, for example, in U.S. Pat. Nos. 4,736,866 and 4,870,009. Typically, particular cells would be targeted for patched-2 transgene incorporation with tissue-specific enhancers. Transgenic animals that include a copy of a transgene encoding patched-2 introduced into the germ line of the animal at an embryonic stage can be used to examine the effect of increased expression of DNA encoding patched-2. Such animals can be used as tester animals for reagents thought to confer protection from, for example, pathological conditions associated with its overexpression.
Non-human homologues of vertebrate patched-2 can be used to construct a patched-2 “knock out” animal which has a defective or altered gene encoding patched-2 as a result of homologous recombination between the endogenous gene encoding patched-2 and altered genomic DNA encoding patched-2 introduced into an embryonic cell of the animal. For example, cDNA encoding patched-2 can be used to clone genomic DNA encoding patched-2 in accordance with established techniques. A portion of the genomic DNA encoding patched-2 can be deleted or replaced with another gene, such as a gene encoding a selectable marker that can be used to monitor integration. Typically, several kilobases of unaltered flanking DNA (both at the 5′ and 3′ ends) are included in the vector [see e.g., Thomas and Capecchi, Cell, 51:503 (1987) for a description of homologous recombination vectors]. The vector is introduced into an embryonic stem cell line (e.g., by electroporation) and cells in which the introduced DNA has homologously recombined with the endogenous DNA are selected [see e.g., Li et al., Cell, 69:915 (1992)]. The selected cells are then injected into a blastocyst of an animal (e.g., a mouse or rat) to form aggregation chimeras [see e.g., Bradley, in Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, E. J. Robertson, ed. (IRL, Oxford, 1987), pp. 113-152]. A chimeric embryo can then be implanted into a suitable pseudopregnant female foster animal and the embryo brought to term to create a “knock out” animal. Progeny harboring the homologously recombined DNA in their germ cells can be identified by standard techniques and used to breed animals in which all cells of the animal contain the homologously recombined DNA. Knockout animals can be characterized for instance, for their ability to defend against certain pathological conditions and for their development of pathological conditions due to absence of the patched-2 polypeptide.
Suppression or inhibition (antagonism) of Dhh signaling is also an objective of therapeutic strategies. Since patched-2 can combine with all members of the hedgehog family (i.e., Shh, Dhh, Ihh), antagonist molecules which prevent the binding of hedgehog molecules to Ptch-2 have therapeutic utility. For example, SHh signaling is known to be activated in Basal Cell Carcinoma; Dhh is known to be involved in the regulation of spermatogenesis. Inhibitor or antagonist of Hh signaling would be effective therapeutics in the treatment of Basal Cell Carcinoma or male contraception, respectively.
The stimulation of Dhh signaling (agonism) is also an objective of therapeutic strategies. Since Ptch-2 also binds to the other members of the Hh family, Ihh and Shh, activating Dhh signaling would be useful in disease states or disorders characterized by inactive or insufficient Hh signaling. For example, degenerative disorders of the nervous system, e.g., Parkinson's disease, memory deficits, Alzheimer's disease, Lou Gehrig's disease, Huntington's disease, schizophrenia, stroke and drug addiction. Additionally, patched-2 agonists could be used to treat gut diseases, bone diseases, skin diseases, diseases of the testis (including infertility), ulcers, lung diseases, diseases of the pancreas, diabetes, osteoporosis.
F. Anti-Patched-2 Antibodies
The present invention further provides anti-vertebrate patched-2 antibodies. Exemplary antibodies include polyclonal, monoclonal, humanized, bispecific, and heteroconjugate antibodies.
1. Polyclonal Antibodies
The anti-patched-2 antibodies may comprise polyclonal antibodies. Methods of preparing polyclonal antibodies are known to the skilled artisan. Polyclonal antibodies can be raised in a mammal, for example, by one or more injections of an immunizing agent and, if desired, an adjuvant. Typically, the immunizing agent and/or adjuvant will be injected in the mammal by multiple subcutaneous or intraperitoneal injections. The immunizing agent may include the patched-2 polypeptide or a fusion protein thereof. It may be useful to conjugate the immunizing agent to a protein known to be immunogenic in the mammal being immunized. Examples of such immunogenic proteins include but are not limited to keyhole limpet hemocyanin, serum albumin, bovine thyroglobulin, and soybean trypsin inhibitor. Examples of adjuvants that may be employed include Freund's complete adjuvant and MPL-TDM adjuvant (monophosphoryl Lipid A, synthetic trehalose dicorynomycolate). The immunization protocol may be selected by one skilled in the art without undue experimentation.
2. Monoclonal Antibodies
The anti-patched-2 antibodies may, alternatively, be monoclonal antibodies. Monoclonal antibodies may be prepared using hybridoma methods, such as those described by Kohler and Milstein, Nature, 256:495 (1975). In a hybridoma method, a mouse, hamster, or other appropriate host animal, is typically immunized with an immunizing agent to elicit lymphocytes that produce or are capable of producing antibodies that will specifically bind to the immunizing agent. Alternatively, the lymphocytes may be immunized in vitro.
The immunizing agent will typically include the patched-2 polypeptide or a fusion protein thereof. Generally, either peripheral blood lymphocytes (“PBLs”) are used if cells of human origin are desired, or spleen cells or lymph node cells are used if non-human mammalian sources are desired. The lymphocytes are then fused with an immortalized cell line using a suitable fusing agent, such as polyethylene glycol, to form a hybridoma cell [Goding, Monoclonal Antibodies: Principles and Practice, Academic Press, (1986) pp. 59-103]. Immortalized cell lines are usually transformed mammalian cells, particularly myeloma cells of rodent, bovine and human origin. Usually, rat or mouse myeloma cell lines are employed. The hybridoma cells may be cultured in a suitable culture medium that preferably contains one or more substances that inhibit the growth or survival of the unfused immortalized cells. For example, if the parental cells lack the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT or HPRT), the culture medium for the hybridomas typically will include hypoxanthine, aminopterin, and thymidine (“HAT medium”), which substances prevent the growth of HGPRT-deficient cells.
Preferred immortalized cell lines are those that fuse efficiently, support stable high level expression of antibody by the selected antibody-producing cells, and are sensitive to a medium such as HAT medium. More preferred immortalized cell lines are murine myeloma lines, which can be obtained, for instance, from the Salk Institute Cell Distribution Center, San Diego, Calif. and the American Type Culture Collection, Rockville, Md. Human myeloma and mouse-human heteromyeloma cell lines also have been described for the production of human monoclonal antibodies [Kozbor, J. Immunol., 133:3001 (1984); Brodeur et al., Monoclonal Antibody Production Techniques and Applications, Marcel Dekker, Inc., New York, (1987) pp. 51-63].
The culture medium in which the hybridoma cells are cultured can then be assayed for the presence of monoclonal antibodies directed against patched-2. Preferably, the binding specificity of monoclonal antibodies produced by the hybridoma cells is determined by immunoprecipitation or by an in vitro binding assay, such as radioimmunoassay (RIA) or enzyme-linked immunoabsorbent assay (ELISA). Such techniques and assays are known in the art. The binding affinity of the monoclonal antibody can, for example, be determined by the Scatchard analysis of Munson and Pollard, Anal. Biochem., 107:220 (1980).
After the desired hybridoma cells are identified, the clones may be subcloned by limiting dilution procedures and grown by standard methods [Goding, supra]. Suitable culture media for this purpose include, for example, Dulbecco's Modified Eagle's Medium and RPMI-1640 medium. Alternatively, the hybridoma cells may be grown in vivo as ascites in a mammal.
The monoclonal antibodies secreted by the subclones may be isolated or purified from the culture medium or ascites fluid by conventional immunoglobulin purification procedures such as, for example, protein A-Sepharose, hydroxylapatite chromatography, gel electrophoresis, dialysis, or affinity chromatography.
The monoclonal antibodies may also be made by recombinant DNA methods, such as those described in U.S. Pat. No. 4,816,567. DNA encoding the monoclonal antibodies of the invention can be readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of murine antibodies). The hybridoma cells of the invention serve as a preferred source of such DNA. Once isolated, the DNA may be placed into expression vectors, which are then transfected into host cells such as simian COS cells, Chinese hamster ovary (CHO) cells, or myeloma cells that do not otherwise produce immunoglobulin protein, to obtain the synthesis of monoclonal antibodies in the recombinant host cells. The DNA also may be modified, for example, by substituting the coding sequence for human heavy and light chain constant domains in place of the homologous murine sequences [U.S. Pat. No. 4,816,567; Morrison et al., supra] or by covalently joining to the immunoglobulin coding sequence all or part of the coding sequence for a non-immunoglobulin polypeptide. Such a non-immunoglobulin polypeptide can be substituted for the constant domains of an antibody of the invention, or can be substituted for the variable domains of one antigen-combining site of an antibody of the invention to create a chimeric bivalent antibody.
The antibodies may be monovalent antibodies. Methods for preparing monovalent antibodies are well known in the art. For example, one method involves recombinant expression of immunoglobulin light chain and modified heavy chain. The heavy chain is truncated generally at any point in the Fc region so as to prevent heavy chain crosslinking. Alternatively, the relevant cysteine residues are substituted with another amino acid residue or are deleted so as to prevent crosslinking.
In vitro methods are also suitable for preparing monovalent antibodies. Digestion of antibodies to produce fragments thereof, particularly, Fab fragments, can be accomplished using routine techniques known in the art.
3. Humanized Antibodies
The anti-patched-2 antibodies of the invention may further comprise humanized antibodies or human antibodies. Humanized forms of non-human (e.g., murine) antibodies are chimeric immunoglobulins, immunoglobulin chains or fragments thereof (such as Fv, Fab, Fab′, F(ab′)2 or other antigen-binding subsequences of antibodies) which contain minimal sequence derived from non-human immunoglobulin. Humanized antibodies include human immunoglobulins (recipient antibody) in which residues from a complementary determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat or rabbit having the desired specificity, affinity and capacity. In some instances, Fv framework residues of the human immunoglobulin are replaced by corresponding non-human residues. Humanized antibodies may also comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin [Jones et al., Nature, 321:522-525 (1986); Riechmann et al., Nature, 332:323-329 (1988); and Presta, Curr. Op. Struct Biol., 2:593-596 (1992)].
Methods for humanizing non-human antibodies are well known in the art. Generally, a humanized antibody has one or more amino acid residues introduced into it from a source that is non-human. These non-human amino acid residues are often referred to as “import” residues, which are typically taken from an “import” variable domain. Humanization can be essentially performed following the method of Winter and co-workers [Jones et al., Nature, 321:522-525 (1986); Riechmann et al., Nature, 332:323-327 (1988); Verhoeyen et al., Science, 239:1534-1536 (1988)], by substituting rodent CDRs or CDR sequences for the corresponding sequences of a human antibody. Accordingly, such “humanized” antibodies are chimeric antibodies (U.S. Pat. No. 4,816,567), wherein substantially less than an intact human variable domain has been substituted by the corresponding sequence from a non-human species. In practice, humanized antibodies are typically human antibodies in which some CDR residues and possibly some FR residues are substituted by residues from analogous sites in rodent antibodies.
Human antibodies can also be produced using various techniques known in the art, including phage display libraries [Hoogenboom and Winter, J. Mol. Biol., 227:381 (1991); Marks et al., J. Mol. Biol., 222:581 (1991)]. The techniques of Cole et al. and Boerner et al. are also available for the preparation of human monoclonal antibodies [Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985) and Boerner et al., J. Immunol., 147(1):86-95 (1991)].
4. Bispecific Antibodies
Bispecific antibodies are monoclonal, preferably human or humanized, antibodies that have binding specificities for at least two different antigens. In the present case, one of the binding specificities is for the vertebrate patched-2, the other one is for any other antigen, and preferably for a cell-surface protein or receptor or receptor subunit.
Methods for making bispecific antibodies are known in the art. Traditionally, the recombinant production of bispecific antibodies is based on the co-expression of two immunoglobulin heavy-chain/light-chain pairs, where the two heavy chains have different specificities [Milstein and Cuello, Nature, 305:537-539 (1983)]. Because of the random assortment of immunoglobulin heavy and light chains, these hybridomas (quadromas) produce a potential mixture of ten different antibody molecules, of which only one has the correct bispecific structure. The purification of the correct molecule is usually accomplished by affinity chromatography steps. Similar procedures are disclosed in WO 93/08829, published 13 May 1993, and in Traunecker et al., EMBO J., 10:3655-3659 (1991).
Antibody variable domains with the desired binding specificities (antibody-antigen combining sites) can be fused to immunoglobulin constant domain sequences. The fusion preferably is with an immunoglobulin heavy-chain constant domain, comprising at least part of the hinge, CH2, and CH3 regions. It is preferred to have the first heavy-chain constant region (CH1) containing the site necessary for light-chain binding present in at least one of the fusions. DNAs encoding the immunoglobulin heavy-chain fusions and, if desired, the immunoglobulin light chain, are inserted into separate expression vectors, and are co-transfected into a suitable host organism. For further details of generating bispecific antibodies see, for example, Suresh et al., Methods in Enzymology, 121:210 (1986).
5. Heteroconjugate Antibodies
Heteroconjugate antibodies are also within the scope of the present invention. Heteroconjugate antibodies are composed of two covalently joined antibodies. Such antibodies have, for example, been proposed to target immune system cells to unwanted cells [U.S. Pat. No. 4,676,980], and for treatment of HIV infection [WO 91/00360; WO 92/200373; EP 03089]. It is contemplated that the antibodies may be prepared in vitro using known methods in synthetic protein chemistry, including those involving crosslinking agents. For example, immunotoxins may be constructed using a disulfide exchange reaction or by forming a thioether bond. Examples of suitable reagents for this purpose include iminothiolate and methyl-4-mercaptobutyrimidate and those disclosed, for example, in U.S. Pat. No. 4,676,980.
G. Uses for Anti-Patched-2 Antibodies
The anti-patched-2 antibodies of the invention have various utilities. For example, anti-patched-2 antibodies may be used in diagnostic assays for patched-2, e.g., detecting its expression in specific cells, tissues, or serum. Various diagnostic assay techniques known in the art may be used, such as competitive binding assays, direct or indirect sandwich assays and immunoprecipitation assays conducted in either heterogeneous or homogeneous phases [Zola, Monoclonal Antibodies: A Manual of Techniques, CRC Press, Inc. (1987) pp. 147-158]. The antibodies used in the diagnostic assays can be labeled with a detectable moiety. The detectable moiety should be capable of producing, either directly or indirectly, a detectable signal. For example, the detectable moiety may be a radioisotope, such as 3H, 14C, 32P, 35S, or 125I, a fluorescent or chemiluminescent compound, such as fluorescein isothiocyanate, rhodamine, or luciferin, or an enzyme, such as alkaline phosphatase, beta-galactosidase or horseradish peroxidase. Any method known in the art for conjugating the antibody to the detectable moiety may be employed, including those methods described by Hunter et al., Nature, 144: 945 (1962); David et al., Biochemistry, 13:1014 (1974); Pain et al., J. Immunol Meth., 40:219 (1981); and Nygren, J. Histochem. and Cytochem., 30:407 (1982).
Anti-patched-2 antibodies also are useful for the affinity purification of patched-2 from recombinant cell culture or natural sources. In this process, the antibodies against patched-2 are immobilized on a suitable support, such a Sephadex resin or filter paper, using methods well known in the art. The immobilized antibody then is contacted with a sample containing the patched-2 to be purified, and thereafter the support is washed with a suitable solvent that will remove substantially all the material in the sample except the patched-2, which is bound to the immobilized antibody. Finally, the support is washed with another suitable solvent that will release the patched-2 from the antibody.
Basal cell carcinoma (BCC) is the most common human cancer. The Hh signaling pathway was found to activated in all BCCs. Loss of Ptch function is thought to lead to unregulated Smo activity and is responsible for about half of all BCCs. Ptch being a target of the Hh pathway itself, increases in Ptch mRNA levels have been detected in BCC [Galiani, et al., Nature Genet. 14: 78-81 (1996)] as well as in animal models of BCC. Oro et al., Science 276: 817-821 (1997); Xie et al., Nature 391: 90-92 (1998). Abnormal activation of Sh signaling, such as that which occurs in BCC, was examined to confirm whether Ptch-2 expression was increased. As shown in FIG. 9, an in situ hybridization for Ptch (SEQ ID NO:4) and Ptch-2 in Smo-M2 transgenic mice (Xie et al., supra), while lower than Ptch, was still high in tumor cells. This suggests that therapeutic antibodies directed toward Ptch-2 may be useful for the treatment of BCC.
Anti-patched-2 antibodies also have utilities similar to those articulated for under the previous section “E. Uses of Patched-2”. Depending on whether anti-patched-2 antibodies will bind patched-2 receptors so as to either inhibit Hh signaling (antagonist) or inhibit patched-2 complexing with Smo and thereby remove the normal inhibitory effect of Smo on Hh signaling (agonist) the antibody will have utilities corresponding to those articulated previously for patched-2.
H. Patched-2 Antagonists
Several approaches may be suitably employed to create the patched-2 antagonist and agonist compounds of the present invention. Any approach where the antagonist molecule can be targeted to the interior of the cell, which interferes or prevents wild type patched-2 from normal operation is suitable. For example, competitive inhibitors, including mutant patched-2 receptors which prevent wild type patched-2 from properly binding with other proteins necessary for Dhh and Hh signaling. Additional properties of such antagonist or agonist molecules are readily determinable by one of ordinary skill, such as size, charge and hydrophobicity suitable for transmembrane transport.
Where mimics or other mammalian homologues of patched-2 are to be identified or evaluated, the cells are exposed to the test compound and compared to positive controls which are exposed only to human patched-2, and to negative controls which were not exposed to either the compound or the natural ligand. Where antagonists or agonists of patched-2 signal modulation are to be identified or evaluated, the cells are exposed to the compound of the invention in the presence of the natural ligand and compared to controls which are not exposed to the test compound.
Detection assays may by employed as a primary screen to evaluate the Hh signaling inhibition/enhancing activity of the antagonist/agonist compounds of the invention. The assays may also be used to assess the relative potency of a compound by testing a range of concentrations, in a range from 100 mM to 1 pM, for example, and computing the concentration at which the amount of phosphorylation or signal transduction is reduced or increased by 50% (IC50) compared to controls.
Assays can be performed to identify compounds that affect Hh signaling of patched-2 substrates. Specifically, assays can be performed to identify compounds that increase the phosphorylation activity of patched-2 or assays can be performed to identify compounds that decrease the Hh signaling of patched-2 substrates. These assays can be performed either on whole cells themselves or on cell extracts. The assays can be performed in a variety of formats, including protein-protein binding assays, biochemical screening assays, immunoassays, cell based assays, etc. Such assay formats are well known in the art.
The screening assays of the present invention are amenable to high-throughput screening of chemical libraries, and are particularly suitable for identifying small molecule drug candidates.
(1) Antagonist and Agonist Molecules
To screen for antagonists and/or agonists of patched-2 signaling, the assay mixture is incubated under conditions whereby, but for the presence of the candidate pharmacological agent, patched-2 induces hedgehog signaling with a reference activity. The mixture components can be added in any order that provides for the requisite hedgehog activity. Incubation may be performed at any temperature that facilitates optimal binding, typically between about 4° and 40° C., more commonly between about 15° and 40° C. Incubation periods are likewise selected for optimal binding but also minimized to facilitate rapid, high-throughput screening, and are typically between about 0.1 and 10 hours, preferably less than 5 hours, more preferably less than 2 hours. After incubation, the effect of the candidate pharmacological agent on the patched-2 signaling is determined in any convenient way. For cell-free binding-type assays, a separation step is often used to separate bound and unbound components. Separation may, for example, be effected by precipitation (e.g. TCA precipitation, immunoprecipitation, etc.), immobilization (e.g. on a solid substrate), followed by washing. The bound protein is conveniently detected by taking advantage of a detectable label attached to it, e.g. by measuring radioactive emission, optical or electron density, or by indirect detection using, e.g. antibody conjugates.
For example, a method of screening for suitable patched-2 antagonists and/or agonists could involve the application of Dhh and other hedgehog ligands. Such a screening assay could compare in situ hybridization in the presence and absence of the candidate antagonist and/or agonist in a patched-2 expressing tissue as well as confirmation or absence of patched-2 modulated cellular development. Typically these methods involve exposing an immobilized patched-2 to a molecule suspected of binding thereto and determining the level of ligand binding downstream activation of reporter constructs and/or evaluating whether or not the molecule activates (or blocks activation of) patched-2. In order to identify such patched-2 binding ligands, patched-2 can be expressed on the surface of a cell and used to screen libraries of synthetic candidate compounds or naturally-occurring compounds (e.g., from endogenous sources such as serum or cells).
Suitable molecules that affect the protein-protein interaction of patched-2 and its binding proteins include fragments of the latter or small molecules, e.g., peptidomimetics, which will inhibit ligand-receptor interaction. Such small molecules, which are usually less than 10 K molecular weight, are preferable as therapeutics since they are more likely to be permeable to cells, are less susceptible to degradation by various cellular mechanisms, and are not as apt to elicit an immune response as proteins. Small molecules include but are not limited to synthetic organic or inorganic compounds. Many pharmaceutical companies have extensive libraries of such molecules, which can be conveniently screened by using the assays of the present invention. Non-limiting examples include proteins, peptides, glycoproteins, glycopeptides, glycolipids, polysaccharides, oligosacchardies, nucleic acids, bioorganic molecules, peptidomimetics, pharmacological agents and their metabolites, transcriptional and translation control sequences, and the like.
A preferred technique for identifying molecules which bind to patched-2 utilizes a chimeric substrate (e.g., epitope-tagged patched-2 or patched-2 immunoadhesin) attached to a solid phase, such as the well of an assay plate. The binding of the candidate molecules, which are optionally labeled (e.g., radiolabeled), to the immobilized receptor can be measured. Alternatively, competition for various Hh pathways, especially Dhh (SEQ ID NO:13) can be measured. In screening for antagonists and/or agonists, patched-2 can be exposed to a patched-2 substrate followed by the putative antagonist and/or agonist, or the patched-2 binding protein and antagonist and/or agonist can be added simultaneously, and the ability of the antagonist and/or agonist to block patched-2 activation can be evaluated.
(2) Detection Assays
The patched-2 polypeptides are useful in assays for identifying lead compounds for therapeutically active agents that modulate patched-2 receptor/ligand hedgehog signaling. Specifically, lead compounds that either prevent the formation of patched-2 signaling complexes or prevent or attenuate patched-2 modulated hedgehog signaling (e.g, binding to patched-2) can be conveniently identified.
Various procedures known in the art may be used for identifying, evaluating or assaying the inhibition of activity of the patched-2 proteins of the invention. As patched-2 is believed to be a receptor for Dhh, but also binds Shh and Ihh, techniques known for use with identifying ligand/receptor modulators may also be employed with the present invention. In general, such assays involve exposing target cells in culture to the compounds and a) biochemically analyzing cell lysates to assess the level and/or identity of binding; or (b) scoring phenotypic or functional changes in treated cells as compared to control cells that were not exposed to the test substance. Such screening assays are described in U.S. Pat. No. 5,602,171, U.S. Pat. No. 5,710,173, WO 96/35124 and WO 96/40276.
(a) Biochemical Detection Techniques
Biochemical analysis can be evaluated by a variety of techniques. One typical assay mixture which can be used with the present invention contains patched-2 and a ligand protein with which patched-2 is normally associated (e.g., Dhh) usually in an isolated, partially pure or pure form. One or both of these components may be patched-2 to another peptide or polypeptide, which may, for example, provide or enhance protein-protein binding, improve stability under assay conditions, etc. In addition, one of the components usually comprises or is coupled to a detectable label. The label may provide for direct detection by measuring radioactivity, luminescence, optical or electron density, etc., or indirect detection such as an epitope tag, an enzyme, etc. The assay mixture can additionally comprise a candidate pharmacological agent, and optionally a variety of other components, such as salts, buffers, carrier proteins, e.g. albumin, detergents, protease inhibitors, nuclease inhibitors, antimicrobial agents, etc., which facilitate binding, increase stability, reduce non-specific or background interactions, or otherwise improve the efficiency or sensitivity of the assay.
The following detection methods may also be used in a cell-free system wherein cell lysate containing the signal transducing substrate molecule and patched-2 is mixed with a compound of the invention. To assess the activity of the compound, the reaction mixture may be analyzed by the SDS-PAGE technique or it may be added to substrate-specific anchoring antibody bound to a solid support, and a detection procedure as described above is performed on the separated or captured substrate to assess the presence or absence of a patched-2 binding ligand. The results are compared to those obtained with reaction mixtures to which the compound is not added. The cell-free system does not require the natural ligand or knowledge of its identity. For example, Posner et al. (U.S. Pat. No. 5,155,031 describes the use of insulin receptor as a substrate and rat adipocytes as target cells to demonstrate the ability of pervanadate to inhibit PTP activity. Another example, Burke et al., Biochem. Biophys. Res. Comm. 204: 129-134 (1994) describes the use of autophosphorylated insulin receptor and recombinant PTP1B in assessing the inhibitory activity of a phosphotyrosyl mimetic.
(i) Whole Cell Detection
A common technique involves incubating cells with patched-2 and radiolabeled ligand, lysing the cells, separating cellular protein components of the lysate using an SDS-polyacrylamide gel (SDS-PAGE) technique, in either one or two dimensions, and detecting the presence of labeled proteins by exposing X-ray film. Detection can also be effected without using radioactive labeling. In such a technique, the protein components (e.g., separated by SDS-PAGE) are transferred to a nitrocellulose membrane where the presence of patched-ligand complexes is detected using an anti-ligand antibody.
Alternatively, the anti-patched-2 ligand antibody can be conjugated with an enzyme, such as horseradish peroxidase, and detected by subsequent addition of a colorimetric substrate for the enzyme. A further alternative involves detecting the anti-patched-2 ligand by reacting with a second antibody that recognizes anti-patched-2 ligand, this second antibody being labeled with either a radioactive moiety or an enzyme as previously described. Examples of these and similar techniques are described in Hansen et al., Electrophoresis 14: 112-126 (1993); Campbell et al., J. Biol. Chem. 268: 7427-7434 (1993); Donato et al., Cell Growth Diff. 3: 258-268 (1992); Katagiri et al., J. Immunol 150: 585-593 (1993). Additionally, the anti-patched-2 ligand can be detected by labeling it with a radioactive substance, followed by scanning the labeled nitrocellulose to detect radioactivity or exposure of X-ray film.
Further detection methods may be developed which are preferred to those described above. Especially for use in connection with high-throughput screening, it is expected that such methods would exhibit good sensitivity and specificity, extended linear range, low background signal, minimal fluctuation, compatibility with other reagents, and compatibility with automated handling systems.
The in vivo efficacy of the treatment of the present invention can be studied against chemically induced tumors in various rodent models. Tumor cell lines propagated in in vitro cell cultures can be introduced in experimental rodents, e.g. mice by injection, for example by the subcutaneous route. Techniques for chemical inducement of tumors in experimental animals are well known in the art.
(ii) Kinase Assays
Because patched-2 is a negative regulator of Hh signaling, which when activated by Hh releases the normal inhibitory effect on Smo, the inhibition of patched-2 binding to Smo can be measured by activation of various kinase substrate associated with Hh signaling. When the screening methods of the present invention for patched-2 antagonists/agonists are carried out as an ex vivo assay, the target kinase (e.g. fused) can be a substantially purified polypeptide. The kinase substrate (e.g., MBP, Gli) is a substantially purified substrate, which in the assay is phosphorylated in a reaction with a substantially purified phosphate source that is catalyzed by the kinase. The extent of phosphorylation is determined by measuring the amount of substrate phosphorylated in the reaction. A variety of possible substrates may be used, including the kinase itself in which instance the phosphorylation reaction measured in the assay is autophosphorylation. Exogenous substrates may also be used, including standard protein substrates such as myelin basic protein (MBP); yeast protein substrates; synthetic peptide substrates, and polymer substrates. Of these, MBP and other standard protein substrates may be regarded as preferred. Other substrates may be identified, however, which are superior by way of affinity for the kinase, minimal perturbation of reaction kinetics, possession of single or homogenous reaction sites, ease of handling and post-reaction recover, potential for strong signal generation, and resistance or inertness to test compounds.
Measurement of the amount of substrate phosphorylated in the ex vivo assay of the invention may be carried out by means of immunoassay, radioassay or other well-known methods. In an immunoassay measurement, an antibody (such as a goat or mouse anti-phosphoserine/threonine antibody) may be used which is specific for phosphorylated moieties formed during the reaction. Using well-known ELISA techniques, the phosphoserine/threonine antibody complex would itself be detected by a further antibody linked to a label capable of developing a measurable signal (as for example a fluorescent or radioactive label). Additionally, ELISA-type assays in microtitre plates may be used to test purified substrates. Peraldi et al., J. Biochem. 285: 71-78 (1992); Schraag et al., Anal. Biochem. 211: 233-239 (1993); Cleavland, Anal. Biochem. 190: 249-253 (1990); Farley, Anal. Biochem. 203: 151-157 (1992) and Lozaro, Anal. Biochem. 192: 257-261 (1991).
For example, detection schemes can measure substrate depletion during the kinase reaction. Initially, the phosphate source may be radiolabeled with an isotope such as 32P or 33P, and the amount of substrate phosphorylation may be measured by determining the amount of radiolabel incorporated into the substrate during the reaction. Detection may be accomplished by: (a) commercially available scintillant-containing plates and beads using a beta-counter, after adsorption to a filter or a microtitre well surface, or (b) photometric means after binding to a scintillation proximity assay bead or scintillant plate. Weernink and Kijken, J. Biochem. Biophs. Methods 31: 49, 1996; Braunwalder et al., Anal. Biochem. 234: 23 (1996); Kentrup et al., J. Biol. Chem. 271: 3488 (1996) and Rusken et al., Meth. Enzymol. 200: 98 (1991).
Preferably, the substrate is attached to a solid support surface by means of non-specific or, preferably, specific binding. Such attachment permits separation of the phosphorylated substrate from unincorporated, labeled phosphate source (such as adenosine triphosphate prior to signal detection. In one embodiment, the substrate may be physically immobilized prior to reaction, as through the use of NuncTM high protein binding plate (Hanke et al., J. Biol. Chem. 271: 695 (1996)) or Wallac ScintiStripTM plates (Braunwalder et al., Anal. Biochem. 234: 23 (1996). Substrate may also be immobilized after reaction by capture on, for example, P81 phophocellulose (for basic peptides), PEI/acidic molybdate resin or DEAE, or TCA precipitation onto WhatmanTM 3MM paper, Tiganis et al., Arch. Biochem. Biophys. 325: 289 (1996); Morawetz et al., Mol. Gen. Genet. 250; 17 (1996); Budde et al., Int J. Pharmacognosy 33: 27 (1995) and Casnellie, Meth. Enz. 200: 115 (1991). Yet another possibility is the attachment of the substrate to the support surface, as by conjugation with binding partners such as glutathione and streptavidin (in the case of GST and biotin), respectively) which have been attached to the support, or via antibodies specific for the tags which are likewise attached to the support.
Further detection methods may be developed which are preferred to those described above. Especially for use in connection with high-throughput screening, it is expected that such methods would exhibit good sensitivity and specificity, extended linear range, low background signal, minimal fluctuation, compatibility with other reagents, and compatibility with automated handling systems.
The in vivo efficacy of the treatment of the present invention can be studied against chemically induced tumors in various rodent models. Tumor cell lines propagated in in vitro cell cultures can be introduced in experimental rodents, e.g. mice by injection, for example by the subcutaneous route. Techniques for chemical inducement of tumors in experimental animals are well known in the art.
(b) Biological Detection Techniques:
The ability of the antagonist/agonist compounds of the invention to modulate the activity of patched-2, which itself modulates hedgehog signaling, may also be measured by scoring for morphological or functional changes associated with ligand binding. Any qualitative or quantitative technique known in the art may be applied for observing and measuring cellular processes which comes under the control of patched-2. The activity of the compounds of the invention can also be assessed in animals using experimental models of disorders caused by or related to dysfunctional hedgehog signaling. For example, ineffective Dhh hedgehog signaling in mice leads to viable but sterile mice. Additionally, proper Shh signaling is critical to murine embryonic development at the notochord and floor plate, neural tube, distal limb structures, spinal column and ribs. Improper Shh signaling, is also correlative with cyclopia. Any of these phenotypic properties could be evaluated and quantified in a screening assay for patched-2 antagonists and/or agonist. Disease states associated with overexpression of hedgehog is associated with basal cell carcinoma while inactive Shh signaling leads to improper neural development.
The data obtained from these cell culture assays and animal studies can be used in formulating a range of dosages for use in humans. The dosage of the compounds of the invention should lie within a range of circulating concentrations with little or no toxicity. The dosage may vary within this range depending on the dosage form employed and the route of administration.
(2) Antisense Oligonucleotides
Another preferred class of antagonists involves the use of gene therapy techniques, including the administration of antisense oligonucleotides. Applicable gene therapy techniques include single or multiple administrations of therapeutically effective DNA or mRNA. Antisense RNAs and DNAs can be used as therapeutic agents for blocking the expression of certain genes in vivo. Reference short antisense oligonucleotides can be imported into cells where they act as inhibitors, despite their low intracellular concentrations caused by restricted uptake by the cell membrane, Zamecnik et al., Proc. Natl. Acad. Sci. USA 83: 4143-4146 (1986). The anti-sense oligonucleotides can be modified to enhance their uptake, e.g., by substituting their negatively charged phophodiester groups by uncharged groups.
There are a variety of techniques known for introducing nucleic acids into viable cells. The techniques vary depending upon whether the nucleic acid is transferred into cultured cells in vitro, ex vivo, or in vivo in the cells of the intended host. Techniques suitable for the transfer of nucleic acid into mammalian cells in vitro include the use of liposomes, electroporation, microinjection, cell fusion, DEAE-dextran, the calcium phosphate precipitation method, etc. The currently preferred in vivo gene transfer techniques include transfection with viral (typically retroviral) vectors and viral coat protein-liposome mediated transfection, Dzau et al., Trends Biotech. 11: 205-210 (1993). In some situations it is desirable to provide the nucleic acid source with an agent that targets the cells, such as an antibody specific for a cell surface membrane protein associated with endocytosis may be used for targeting and/or to facilitate uptake, e.g., capsid proteins or fragments thereof tropic for a particular cell type, antibodies for proteins which undergo internalization in cycling, and proteins that target intracellular localization and enhance intracellular half-life. The technique of receptor-mediated endocytosis is described, for example, by Wu et al., J. Biol. Chem. 262: 4429-4432 (1987); Wagner et al., Proc. Natl. Acad. Sci. USA 87: 3410-3414 (1990). For a review of known gene targeting and gene therapy protocols, see Anderson et al., Science 256: 808-813 (1992).
In one embodiment of the invention, patched-2 expression may be reduced by providing patched-2-expressing cells with an amount of patched-2 antisense RNA or DNA effective to reduce expression of the patched-2 protein.
I. Diagnostic Uses
Another use of the compounds of the invention (e.g., patched-2, patched-2 variant and anti-patched-2 antibodies) described herein is to help diagnose whether a disorder is driven, to some extent, by patched-2 or hedgehog signaling. For example, basal cell carcinoma cells are associated with active hedgehog signaling, spermatocyte formation is associated with Dhh signaling, and defective Ptch and Ptch-2 suppression may be associated with testicular carcinomas.
A diagnostic assay to determine whether a particular disorder is driven by Ptch-2 modulated hedgehog signaling, can be carried out using the following steps: (1) culturing test cells or tissues; (2) administering a compound which can prevent Ptch-2 binding with Smo, thereby activating the Hh signaling pathway; and (3) measuring the amount of Hh signaling. The steps can be carried out using standard techniques in light of the present disclosure. For example, standard techniques can be used to isolate cells or tissues and culturing or in vivo.
Compounds of varying degree of selectivity are useful for diagnosing the role of patched-2. For example, compounds which inhibit patched-2 in addition to another form of kinase can be used as an initial test compound to determine if one of several signaling ligands drive the disorder. The selective compounds can then be used to further eliminate the possible role of the other ligands in driving the disorder. Test compounds should be more potent in inhibiting ligand-patched-2 binding activity than in exerting a cytotoxic effect (e.g., an IC50/LD50 of greater than one). The IC50 and LD50 can be measured by standard techniques, such as an MTT assay, or by measuring the amount of LDH released. The degree of IC50/LD50 of a compound should be taken into account in evaluating the diagnostic assay. For example, the larger the IC50/LD50 ratio the more relative the information. Appropriate controls take into account the possible cytotoxic effect of a compound of a compound, such as treating cells not associated with a cell proliferative disorder (e.g., control cells) with a test compound, can also be used as part of the diagnostic assay. The diagnostic methods of the invention involve the screening for agents that modulate the effects of patched-2 upon hedgehog signaling. Exemplary detection techniques include radioactive labeling and immunoprecipitating (U.S. Pat. No. 5,385,915).
J. Pharmaceutical Compositions and Dosages
Therapeutic formulations of the compositions of the invention are prepared for storage as lyophilized formulations or aqueous solutions by mixing the patched-2 molecule, agonist and/or antagonist having the desired degree of purity with optional “pharmaceutically-acceptable” or “physiologically-acceptable” carriers, excipients or stabilizers typically employed in the art (all of which are termed “excipients”). For example, buffering agents, stabilizing agents, preservatives, isotonifiers, non-ionic detergents, antioxidants and other miscellaneous additives. (See Remington's Pharmaceutical Sciences, 16th Ed., A. Osol, Ed. (1980)). Such additives must be nontoxic to the recipients at the dosages and concentrations employed.
Buffering agents help to maintain the pH in the range which approximates physiological conditions. They are preferably present at concentration ranging from about 2 mM to about 50 mM. Suitable buffering agents for use with the present invention include both organic and inorganic acids and salts thereof such as citrate buffers (e.g., monosodium citrate-disodium citrate mixture, citric acid-trisodium citrate mixture, citric acid-monosodium citrate mixture, etc.), succinate buffers (e.g., succinic acid-monosodium succinate mixture, succinic acid-sodium hydroxide mixture, succinic acid-disodium succinate mixture, etc.), tartrate buffers (e.g., tartaric acid-sodium tartrate mixture, tartaric acid-potassium tartrate mixture, tartaric acid-sodium hydroxide mixture, etc.), fumarate buffers (e.g., fumaric acid-monosodium fumarate mixture, etc.), fumarate buffers (e.g., fumaric acid-monosodium fumarate mixture, fumaric acid-disodium fumarate mixture, monosodium fumarate-disodium fumarate mixture, etc.), gluconate buffers (e.g., gluconic acid-sodium glyconate mixture, gluconic acid-sodium hydroxide mixture, gluconic acid-potassium glyconate mixture, etc.), oxalate buffer (e.g., oxalic acid-sodium oxalate mixture, oxalic acid-sodium hydroxide mixture, oxalic acid-potassium oxalate mixture, etc.), lactate buffers (e.g., lactic acid-sodium lactate mixture, lactic acid-sodium hydroxide mixture, lactic acid-potassium lactate mixture, etc.) and acetate buffers (e.g., acetic acid-sodium acetate mixture, acetic acid-sodium hydroxide mixture, etc.). Additionally, there may be mentioned phosphate buffers, histidine buffers and trimethylamine salts such as Tris.
Preservatives are added to retard microbial growth, and are added in amounts ranging from 0.2%-1% (w/v). Suitable preservatives for use with the present invention include phenol, benzyl alcohol, meta-cresol, methyl paraben, propyl paraben, octadecyldimethylbenzyl ammonium chloride, benzalconium halides (e.g., chloride, bromide, iodide), hexamethonium chloride, alkyl parabens such as methyl or propyl paraben, catechol, resorcinol, cyclohexanol, and 3-pentanol.
Isotonifiers sometimes known as “stabilizers” are present to ensure isotonicity of liquid compositions of the present invention and include polyhydric sugar alcohols, preferably trihydric or higher sugar alcohols, such as glycerin, erythritol, arabitol, xylitol, sorbitol and mannitol. Polyhydric alcohols can be present in an amount between 0.1% to 25% by weight, preferably 1% to 5% taking into account the relative amounts of the other ingredients.
Stabilizers refer to a broad category of excipients which can range in function from a bulking agent to an additive which solubilizes the therapeutic agent or helps to prevent denaturation or adherence to the container wall. Typical stabilizers can be polyhydric sugar alcohols (enumerated above); amino acids such as arginine, lysine, glycine, glutamine, asparagine, histidine, alanine, ornithine, L-leucine, 2-phenylalanine, glutamic acid, threonine, etc., organic sugars or sugar alcohols, such as lactose, trehalose, stachyose, mannitol, sorbitol, xylitol, ribitol, myoinisitol, galactitol, glycerol and the like, including cyclitols such as inositol; polyethylene glycol; amino acid polymers; sulfur containing reducing agents, such as urea, glutathione, thiocitic acid, sodium thioglycolate, thioglycerol, α-monothioglycerol and sodium thio sulfate; low molecular weight polypeptides (i.e. <10 residues); proteins such as human serum albumin, bovine serum albumin, gelatin or immunoglobulins; hydrophilic polymers, such as polyvinylpyrrolidone monosaccharides, such as xylose, mannose, fructose, glucose; disaccharides such as lactose, maltose, sucrose and trisaccacharides such as raffinose; polysaccharides such as dextran. Stabilizers can be present in the range from 0.1 to 10,000 weights per part of weight active protein.
Non-ionic surfactants or detergents (also known as “wetting agents”) are present to help solubilize the therapeutic agent as well as to protect the therapeutic protein against agitation-induced aggregation, which also permits the formulation to be exposed to shear surface stressed without causing denaturation of the protein. Suitable non-ionic surfactants include polysorbates (20, 80, etc.), polyoxamers (184, 188 etc.), Pluronic® polyols, polyoxyethylene sorbitan monoethers (Tween®-20, Tween®-80, etc.). Non-ionic surfactants are present in a range of about 0.05 mg/ml to about 1.0 mg/ml, preferably about 0.07 mg/ml to about 0.2 mg/ml.
Additional miscellaneous excipients include bulking agents, (e.g. starch), chelating agents (e.g. EDTA), antioxidants (e.g., ascorbic acid, methionine, vitamin E), and cosolvents.
The formulation herein may also contain more than one active compound as necessary for the particular indication being treated, preferably those with complementary activities that do not adversely affect each other. For example, it may be desirable to further provide an immunosuppressive agent. Such molecules are suitably present in combination in amounts that are effective for the purpose intended.
The active ingredients may also be entrapped in microcapsule prepared, for example, by coascervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-microcapsule and poly-(methylmethacylate) microcapsule, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences, 16th edition, A. Osal, Ed. (1980).
The formulations to be used for in vivo administration must be sterile. This is readily accomplished, for example, by filtration through sterile filtration membranes.
Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semi-permeable matrices of solid hydrophobic polymers containing the compounds of the invention, which matrices are in the form of shaped articles, e.g., films, or microcapsules. Examples of sustained-release matrices include polyesters, hydrogels (for example, poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides (U.S. Pat. No. 3,773,919), copolymers of L-glutamic acid and ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradable lactic acid-glycolic acid copolymers such as the LUPRON DEPOTTM (injectable microspheres composed of lactic acid-glycolic acid copolymer and leuprolide acetate), and poly-D-(−)-3-hydroxybutyric acid. While polymers such as ethylene-vinyl acetate and lactic acid-glycolic acid enable release of molecules for over 100 days, certain hydrogels release proteins for shorter time periods. When encapsulated compounds of the invention remain in the body for a long time, they may denature or aggregate as a result of exposure to moisture at 37° C., resulting in a loss of biological activity and possible changes in immunogenicity. Rational strategies can be devised for stabilization depending on the mechanism involved. For example, if the aggregation mechanism is discovered to be intermolecular S—S bond formation through thio-disulfide interchange, stabilization may be achieved by modifying sulfhydryl residues, lyophilizing from acidic solutions, controlling moisture content, using appropriate additives, and developing specific polymer matrix compositions.
The amount of therapeutic polypeptide, antibody or fragment thereof which will be effective in the treatment of a particular disorder or condition will depend on the nature of the disorder or condition, and can be determined by standard clinical techniques. Where possible, it is desirable to determine the dose-response curve and the pharmaceutical compositions of the invention first in vitro, and then in useful animal model systems prior to testing in humans. However, based on common knowledge of the art, a pharmaceutical composition effective in modulating Dhh and Hh signaling may provide a local patched-2 protein concentration of between about 10 and 1000 ng/ml, preferably between 100 and 800 ng/ml and most preferably between about 200 ng/ml and 600 ng/ml of Ptch-2.
In a preferred embodiment, an aqueous solution of therapeutic polypeptide, antibody or fragment thereof is administered by subcutaneous injection. Each dose may range from about 0.5 μg to about 50 μg per kilogram of body weight, or more preferably, from about 3 μg to about 30 μg per kilogram body weight.
The dosing schedule for subcutaneous administration may vary from once a week to daily depending on a number of clinical factors, including the type of disease, severity of disease, and the subject's sensitivity to the therapeutic agent.
Patched-2 polypeptide may comprise an amino acid sequence or subsequence thereof as indicated in FIG. 1 (SEQ ID NO:2), active amino acid sequence derived therefrom, or functionally equivalent sequence as this subsequence is believed to comprise the functional portion of the patched-2 polypeptide.
If the subject manifests undesired side effects such as temperature elevation, cold or flu-like symptoms, fatigue, etc., it may be desirable to administer a lower dose at more frequent intervals. One or more additional drugs may be administered in combination with patched-2 to alleviate such undesired side effects, for example, an anti-pyretic, anti-inflammatory or analgesic agent.
The following examples are offered for illustrative purposes only, and are not intended to limit the scope of the present invention in any way.
All patent and literature references cited in the present specification are hereby incorporated by reference in their entirety.
EXAMPLES
Commercially available reagents referred to in the examples were used according to manufacturer's instructions unless otherwise indicated. The source of those cells identified in the following examples, and throughout the specification, by ATCC accession numbers is the American Type Culture Collection, Rockville, Md.
Example 1
Introduction
At the cell surface, Hh function appears to be mediated by a multicomponent receptor complex involving Ptch and Smo, two multi-transmembrane proteins initially identified as segment polarity genes in Drosophila and later characterized in vertebrates. Nakano, Y. et al., Nature 341: 508-513 (1989); Goodrich et al., Gene Dev. 10: 301-312 (1996); Marigo et al., Develop. 122: 1225-1233 (1996); van den Heuvel et al., Nature 382: 547-551 (1996); Alcedo et al., Cell 86: 221-232 (1996); Stone et al. Nature 384: 129-34 (1996). Both genetic and biochemical evidence support the existence of a receptor complex where Ptch (SEQ ID NO:4) is the ligand binding subunit, and where Smo, a G-protein coupled receptor like molecule, is the signaling component. Stone et al., Nature 384: 129-134 (1996), Marigo et al., Nature 384: 176-79 (1996), Chen et al., Cell 87: 553-63 (1996). Upon binding of Hh to Ptch, the normal inhibitory effect of Ptch on Smo is relieved, allowing Smo to transduce the Hh signal across the plasma membrane.

Results:

It remains to be established if the patched-Smoothened receptor complex mediates the action of all 3 mammalian Hhs or if specific components exist. Recently, a second murine patched gene, Ptch-2 was recently isolated [Motoyama et al., Nature Genet. 18: 104-106 (1998)] but its function as a Hh receptor has not been established. In order to characterize Ptch-2 and compare it to Ptch with respect to the biological function of the various Hh family members, we have screened EST databases with the Ptch protein and identified 2 EST candidates for a novel human patched gene. A full length cDNA encoding human Ptch-2 was cloned from a testis library. The initiation ATG defines a 3612 nucleotide open reading frame encoding a 1204 amino acid long protein with a predicted molecular weight of approximately 131 kDa. The overall identity between human Ptch (SEQ ID NO:33) and Ptch-2 (SEQ ID NO:2) is 54% (FIG. 1), while the identity between human Ptch-2 (SEQ ID NO:2) and the recently described mouse Ptch 2 (SEQ ID NO:7) is 90%. (FIG. 8). The most obvious structural difference between the two human Ptch proteins is a truncated C-terminal cytoplasmic domain in Ptch-2. In addition, only one of the two glycosylation sites present in Ptch is conserved in Ptch-2.
To determine if Ptch-2 is a Hh receptor and if the two patched molecules are capable of discriminating between the various Hh ligands through specific binding, Applicants transfected human 293 embryonic kidney cells with Ptch or Ptch-2 expression constructs and analyzed the cells for binding of Shh, Dhh and Ihh. As shown on FIG. 7A, binding of 125I-Shh can be competed with an excess of Shh, Dhh or Ihh. Scatchard analysis of the displacement curves indicates that all Hhs have similar affinity for Ptch (Shh, 1.0 nM; Dhh, 2.6 nM; Ihh, 1.0 nM) and Ptch-2 (Shh, 1.8 nM; Dhh, 0.6 nM; Ihh, 0.4 nM) indicating that both Ptch and Ptch-2 can serve as physiological receptors for the 3 mammalian Hh proteins.
Applicants next determined whether, like Ptch, Ptch-2 forms a physical complex with Smo. Expression constructs for Flag-tagged Ptch or Ptch-2 were transiently co-transfected in 293 cells with Myc-tagged Smo. As described previously [Stone et al., Nature 384: 129-34 (1996)], in cells expressing Ptch and Smo, Ptch can be immunoprecipitated with antibodies against the epitope-tagged Smo (FIG. 7B). Similarly, Ptch-2 can be immunoprecipitated with antibodies against the epitope-tagged Smo when the two proteins are co-expressed in 293 cells. Together, these results suggest a model where Ptch-2 forms a multicomponent Hh receptor complex with Smo similar to the one described for patched (Stone et al., supra). Interestingly, these results also demonstrate that the long C-terminal tail which is missing in Ptch-2 is not required for the interaction with Smo as was already suggested by the analysis of truncated patched (Stone et al., supra). However, it remains possible that the absence of a C-terminal domain affects the capacity of Ptch-2 to block signaling by Smo or leads to difference in signaling by patched compared to patched-2.
To further investigate whether patched-2 could mediate the action of a specific Hh molecule based on its expression profile, Applicants have compared the expression pattern of Ptch and Ptch-2. First, Northern blot analysis using a probe specific for Ptch-2 revealed high levels of patched-2 mRNA in the testis (FIG. 4). By this method, Ptch-2 expression was not detected in any other tissue analyzed including embryonic tissues (data not shown). This profile is very different from the one observed for Ptch which was not found in testis by Northern blot but in a large number of adult and embryonic tissues [Goodrich et al., Genes Dev. 10: 301-312 (1996)]. More detailed analysis of the expression pattern of Ptch and Ptch-2 was performed by in situ hybridization with particular attention to testis. As previously described (Motoyama et al., supra), low levels of Ptch-2 expression were detected in epithelial cells of the developing tooth and skin (data not shown). High levels of Ptch-2 are expressed inside the seminiferous tubule, on the primary and secondary spermatocytes (FIG. 6B,6E) while only low levels of Ptch can be detected on the Leydig cells located in the interstitium of the seminiferous tubules (FIG. 6A). The primary and secondary spermatocytes are in close contact with the supporting Sertoli cells, the source of Dhh in the testis [Bitgood et al., Curr. Biol. 6: 298-304 (1996)]. To determine which one of the 2 receptors is the most relevant mediator of Dhh activity in the testis, we have analyzed the expression profile of FuRK, a Fused Related Kinase that was shown to be a component of the Hh signaling pathway (Zhang et al., submitted; copending U.S.S.N. Ser. No. 09/031,563, filed 26 Feb. 1998). Consistent with the idea that Ptch-2 is the target of Dhh in the testis, we found that FuRK is expressed only in germ cells where it colocalizes with Ptch-2 (FIG. 4c,f). Dhh is required for proper differentiation of germ cells since male Dhh-deficient mice are sterile due to lack of mature sperm (Bitgood et al., supra). Our data suggest that Dhh acts directly on germ cells through Ptch-2 while the function of Ptch expressed at low levels on testosterone producing Leydig cells is unclear.
Discussion:
Loss of heterozygosity (LOH) for patched was reported to occur with high frequency in familial as well as sporadic basal cell carcinoma [Johnson et al., Science 272: 1668-71 (1996); Hahn et al., Cell 85: 841-51 (1996); Gailani et al., Nature Genetics 14: 78-81; Xie et al., Cancer Res. 57: 2369-72 (1997)], suggesting that it functions as a tumor suppressor. According to the receptor model described above, loss of patched function may result in aberrant signaling by Smo, leading to hyperproliferation of the skin basal cell layer. If, as suggested above, patched-2 mediates the function of Dhh, loss of Ptch-2 may lead to tumor formation in tissues where Smo activity is controlled by patched-2. The gene encoding patched-2 was mapped by fluorescence in situ hybridization and by PCR using a radiation hybrid panel to human chromosome 1p33-34 (data not shown). Interestingly, recent analysis of recurrent chromosomal abnormalities in testicular tumors, including seminomas, revealed a deletion of the region 1p32-36 [Summersgill et al., B. J. Cancer 77: 305-313 (1998)]. Loss of this region encompassing the patched-2 locus was consistent in 36% of the germ cell tumor cases. These data raise the possibility that, like patched in basal cell carcinoma and medulloblastoma, patched-2 may be a tumor suppressor in Dhh target cells such as spermatocytes, further implicating Hh signaling in cancer.
In summary, our data demonstrate that both patched and patched-2 are genuine Hh receptors and that they are both capable of forming a complex with Smo. Although binding data indicate that patched and patched-2 do not discriminate between the various Hh ligands through affinity differences, the distinct tissue distribution of these 2 receptors suggests that in vivo, patched may be the primary receptor for Shh whereas Ptch-2 will mediate mainly Dhh signaling. The function of patched expression in Leydig cells in the absence of some of the Hh signaling components remain to be explained. Similarly, it will be of interest to determine if patched-2 plays a role when expressed in Shh expressing cells present in the developing tooth and skin Motoyama et al., Nature Genet. 18: 104-106 (1998). Finally, the existence of patched-2 raises the question of whether additional patched receptors exist, in particular one that mediates the function of Ihh.
Material and Methods:
1. Isolation of Human Patched-2 cDNA Clones
An expressed sequence tag (EST) DNA database (LIFESEQ®, Incyte Pharmaceuticals, Palo Alto, Calif.) was searched for a human homologue of the Drosophila segment polarity gene patched-2. Two ESTs (Incyte #905531 and 1326258) (FIGS. 2A & 2B) (SEQ ID NOS:3 and 5, respectively) were identified as a potential candidates. In order to identify human cDNA libraries containing human patched-2 clones, human cDNA libraries in pRK5 were first screened by PCR using the following primers:












5′-905531(A):





5′-AGGCGGGGGATCACAGCA-3′
(SEQ ID NO: 19)



 




3′-905531(A):





5′-ATACCAAAGAGTTCCACT-3′
(SEQ ID NO: 20)






A fetal lung library was selected and enriched for patched-2 cDNA clones by extension of single stranded DNA from plasmid libraries grown in dut−/ung− host using the 3′-905531(A) primer in a reaction containing 10 μl of 10×PCR Buffer (Klentaq®), 1 μl dNTP (200 μM), 1 μl library DNA (200 ng), 0.5 μl primer, 86.5 μl H2O and 1 μl of Klentaq® (Clontech) added after a hot start. The reaction was denatured for 1 min. at 95° C., annealed for 1 min. at 60° C. then extended for 20 min. at 72° C. DNA was extracted with phenol/CHCl3, ethanol precipitated, then transformed by electroporation into DH10B (Gibco/BRL) host bacteria. Colonies from each transformation were replica plated on nylon membranes and screened with an overlapping oligo probe derived from the EST sequence (#905531) of the following sequence:









5′-Ptch2 probe:



5′-CTGCGGCGCTGCTTCCTGCTGGCCGTCTGCAT
(SEQ ID NO: 21)


CCTGCTGGTGTGC-3′



 


3′-Ptch2 probe:



5′-AGAGCACAGACGAGGAAAGTGCACACCAGCAG
(SEQ ID NO: 22)


GATGCAGACGGCC-3′







The oligo probe was labeled with [α-32P]-ATP and T4 polynucleotide kinase. Filters were hybridized overnight at 42° C. in 50% formamide, 5×SSC, 10×Denhardt's, 0.05M sodium phosphate (pH 6.5), 0.1% sodium pyrophosphate, 50 μg/ml of sonicated salmon sperm DNA. The filters were then rinsed in 2×SSC and washed in 0.1×SSC, 0.1% SDS then exposed to Kodak® X Ray films.

Using this procedure, a partial clone was isolated from the fetal brain library (clone 3A—FIG. 10) (SEQ ID NO:8). In order to isolate the missing 5′-sequence, a testis library (see northern blot analysis, infra) was screened. The primer set used to amplify a 204 by probe from clone 3A to probe the testis library was:













RACE 5:





5′-ACTCCTGACTTGTAGCAGATT-3′
(SEQ ID NO: 23)




and




 




RACE 6:





5′-AGGCTGCATACACCTCTCAGA-3′.
(SEQ ID NO: 24)






The amplified probe was purified by excision from an agarose gel and labeled with a random primer labeling kit (Boehringer Mannheim). Several clones were isolated, including one (clone 16.1—FIG. 11 (SEQ ID NO:9)) containing a potential initiation methionine. A full length cDNA encoding patched-2 was reconstructed by assembling several of these clones. The full length cDNA encoding human Ptch-2 (FIG. 1) (SEQ ID NO:1) has a 3612 nucleotide long open reading frame encoding a 1204 amino acid protein with a 144 kDa predicted molecular weight. Alignment with human Ptch reveals a 53% identity between the 2 molecules at the amino acid level (FIG. 3). All 12 transmembrane domains are conserved. The most significant difference is a shorter C-terminal intracellular domain in Ptch-2 compared to Ptch.

2. Northern blot analysis:

In order to determine the best tissue source for isolation of the complete full length Ptch-2 cDNA as well as to determine its expression profile, we probed human multiple tissue northern blots (Clontech) with a 752 by fragment amplified from the 3′ untranslated region of Ptch-2 using the following primers:












TM2: TM2





5-GCTTAGGCCCGAGGAGAT-3′
(SEQ ID NO: 25)



 




UTR2:





5′-AACTCACAACTTTCTCTCCA-3′.
(SEQ ID NO: 26)






The resulting fragment was gel purified and labeled by random priming. The blots were hybridized in ExpressHyb® hybridization solution (Clontech) in the presence of 1×106 cpm/ml 32P-labeled probe at 42° C. overnight. The blots were washed in 2×SSC at room temperature for 10 minutes and washed in 0.1×SSC/0.1% SDS at 42° C. for 30 minutes then exposed to x-ray film overnight. FIG. 4 shows that Ptch-2 message is expressed at high levels in only the testis.

3. Chromosomal Localization:

The primers TM2 (SEQ ID NO:25) and UTR2 (SEQ ID NO:26) described above were used to screen the Genome Systems (St. Louis, Mo.) BAC library. Two individual BAC clones were obtained from this library and chromosomal localization of both of the clones by FISH indicated that Ptch-2 maps to human chromosome 1p33-34 (FIG. 5). Loss of heterozyosity (LOH) for patched was reported to occur with high frequency in basal cell carcinoma. Loss of patched function is thought to lead to constitutive signaling by Smoothened (Smo), resulting in hyperproliferation of the basal layer of the dermis. A similar mechanism may lead to the formation of germ cell tumors. This model proposes that the first step in the progression of a germ cell tumor is an initial loss of DNA by a germ cell precursor, leading to a neoplastic germ cell which then forms a seminoma [De Jong et al., Cancer Genet. Cytogenet. 48: 143-167 (1990)]. From the invasive seminoma, all other forms of germ cell tumor types develop. Approximately 80% of all germ cell tumors correlate with an isochromosome 12p (i12p) and is found at a higher frequency in non-seminomas than seminomas [Rodriguez et al., Cancer Res. 52: 2285-2291 (1992)]. However, analysis of recurrent chromosomal abnormalities in testicular tumors including seminomas revealed a deletion of the region 1p32-36. Loss of this region was consistent in 36% of the germ cell tumor cases of in a recent study Summersgill et al., B. J. Cancer 57: 305-313 (1998)]. A similar deletion of chromosome 1p32-36 has been reported at a frequency of 28% in oligodendrogliomas Bello, et al., Int. J. Cancer 57: 172-175 (1994). While expression of patched-2 in the brain was not examined here in detail, patched-2 is thought to be the Dhh receptor (see below) and expression of Dhh by murine Schwann cells was previously reported [Bitgood et al, Develop. Biol. 172: 126-138 (1995)]. Since patched-2 localizes to chromosome 1p33-34 it is possible that patched-2 regulates Smo signaling in Dhh target cells and that loss of patched-2 function leads to abnormal Smo signaling in these cells and subsequent tumor formation.
4. In Situ Hybridization:
Mouse testis sections were cut at 16 μm, and processed for in situ hybridization by the method described in Phillips et al., Science 250: 290-294 (1990). 33P-UTP labeled RNA probes were generated as described in Melton et al., Nucleic Acids Res. 12: 7035-7052 (1984). Sense and antisense probes were synthesized from the 3′ non coding region of the mouse Ptch or Ptch-2 and from a mouse FuRK cDNA fragment corresponding to the region encoding amino acid 317-486 of the human sequence using T3 and T7, respectively.








Ptch:



503 (Anti-sense)



5′GGATTCTAATACGACTCACTATAGGGCCCAATG
(SEQ ID NO: 27)


GCCTAAACCGACTGC3′



 


503 (Sense)



5′CTATGAAATTAACCCTCACTAAAGGGACCCACG
(SEQ ID NO: 28)


GCCTCTCCTCACA3′



 


Ptch2:



504 (Anti-sense)



5′GGATTCTAATACGACTCACTATAGGGCCCCTAA
(SEQ ID NO: 12)


ACTCCGCTGCTCCAC3′



 


504 (Sense)



5′CTATGAAATTAACCCTCACTAAAGGGAGCTCCC
(SEQ ID NO: 11)


GTGAGTCCCTATGTG3′







FuRK sense and antisense were synthesized from a mouse fused DNA fragment using T3 and T7, respectively, corresponding to the region encoding amino acid residues 317-486 of the human sequence (Zhang et al., submitted, 1998; copending U.S. Ser. No. 09/031,563, filed 26 Feb. 1998).

FIG. 6 illustrates that, although both Ptch and Ptch-2 are expressed in testis, their expression pattern does not overlap. Ptch is expressed in the Leydig cells of the interstitium while Ptch-2 is expressed in the primary and secondary spermatocytes.
The expression of Ptch-2 specifically in the developing spermatogonia suggest that Ptch-2 is the immediate target of Dhh. Dhh is expressed by Sertoli cells and mice deficient in Dhh are sterile because of a defect in sperm production [Bitgood et al., Curr. Biol. 6: 298-304 (1996)]. Although this effect on germ cells was though to be indirect and mediated by Ptch present on Leydig cells, our data suggest that Dhh directly acts on germ cells through Ptch-2. This is further demonstrated by the localization of FuRK, an intracellular kinase homologous to Drosophila Fused and involved in transducing the Hedgehog (Hh) signal. As shown in FIG. 6, FuRK is colocalizes with Ptch-2 in germ cells and not with Ptch in Leydig cells, suggesting that Ptch-2 and not Ptch will be able to transduce the Dhh signal. These results suggest that Ptch-2 is a Dhh receptor.
Ptch-2 mRNA levels in Smo-M2 transgenic mice [A Smo mutation which results in autonomous phenotypes similar to BCC, Xie et al., Nature 391: 90-92 (1998)] can be increased upon abnormal activation of the Hh signaling pathway. As indicated in FIG. 9, patch-2 levers were high in tumor cells (although lower than Ptch levels). This suggests that antibodies directed toward Ptch-2 may be useful in the treatments of BCC.
5. Immunoprecipitation with Smo:
The binding of Ptch-2 to Smo was assessed by cotransfection using a transient transfection system of a myc-epitope tagged Smo and a FLAG-epitope tagged Ptch or Ptch2 expression construct in 293 cells using standard techniques (Gorman, C., DNA Cloning: A Practical Approach, Clover, D M ed., Vol. 11, pp. 143-190, IRL Press, Washington, D.C.). 36 hours after transfection, the cells were lysed in 1% NP-40 and immunoprecipitated overnight with the 9EI0 anti-myc antibody or with the M2 anti-FLAG antibody (IBI-Kodak) followed by protein A Sepharose, and then separated on a denatured 6% polyacrylamide gel. Proteins were detected by transfer to nitrocellulose and probing with antibodies to Flag or Myc epitopes, using the ECL detection system (Amersham). FIG. 7B indicates that both Ptch and Ptch-2 are expressed at the same level (IP Flag, Blot Flag) and that like Ptch, Ptch-2 forms a physical complex with Smo. These results suggest that like patched, patched-2 controls Hh signaling through its interaction with Smo.
6. Hh Binding:
To determine whether Ptch-2 is able to bind to the various hedgehog ligands, 293 cells were transfected with Ptch or Ptch-2 using standard procedures. Cells were incubated with 100 pM 125I-Shh (19 kD amino terminal fragment of murine Shh) in the presence or absence of excess unlabeled Shh or Dhh for 2 h at room temperature. After equilibrium was reached, the ligand bound cells were centrifuged through a continuous sucrose gradient to separate unincorporated and then counted in a scintillation counter. FIG. 7A shows that both Dhh and Shh bind to Ptch and Ptch-2. Varying concentrations of cold competitor indicate that the 2 ligands have similar affinity for Ptch and Ptch-2.
Example 2
Expression of Patched-2 in E. coli 
The DNA sequence encoding human patched-2 is initially amplified using selected PCR primers. The primers should contain restriction enzyme sites that correspond to the restriction enzyme sites on the selected expression vector. A variety of expression vectors may be employed. An example of a suitable vector is pBR322 (derived from E. coli; see Bolivar et al., Gene, 2:95 (1977)) which contains genes for ampicillin and tetracycline resistance. The vector is digested with restriction enzyme and dephosphorylated. The PCR amplified sequences are then ligated into the vector. The vector will preferably include sequences that encode for an antibiotic resistance gene, a trp promoter, a polyhis leader (including the first six STII codons, polyhis sequence, and enterokinase cleavage site), the vertebrate patched-2 coding region, lambda transcriptional terminator, and an argU gene.
The ligation mixture is then used to transform a selected E. coli strain using the methods described in Sambrook et al., supra. Transformants are identified by their ability to grow on LB plates and antibiotic resistant colonies are then selected. Plasmid DNA can be isolated and confirmed by restriction analysis and DNA sequencing.
Selected clones can be grown overnight in liquid culture medium such as LB broth supplemented with antibiotics. The overnight culture may subsequently be used to inoculate a larger scale culture. The cells are then grown to a desired optical density, during which the expression promoter is turned on.
After culturing the cells for several more hours, the cells can be harvested by centrifugation. The cell pellet obtained by the centrifugation can be solubilized using various agents known in the art, and the solubilized vertebrate patched-2 protein can then be purified using a metal chelating column under conditions that allow tight binding of the protein.
Example 3
Expression of Patched-2 in Mammalian Cells
The vector, pRK5 (see EP 307,247, published Mar. 15, 1989), is employed as the expression vector. Optionally, the vertebrate patched-2 DNA is ligated into pRK5 with selected restriction enzymes to allow insertion of the vertebrate patched-2 DNA using ligation methods such as described in Sambrook et al., supra. The resulting vector is called pRK5-patched-2.
In one embodiment, the selected host cells may be 293 cells. Human 293 cells (ATCC CCL 1573) are grown to confluence in tissue culture plates in medium such as DMEM supplemented with fetal calf serum and optionally, nutrient components and/or antibiotics. About 10 μg pRK5-patched-2 DNA is mixed with about 1 μg DNA encoding the VA RNA gene [Thimmappaya et al., Cell, 31:543 (1982)] and dissolved in 500 μl of 1 mM Tris-HCl, 0.1 mM EDTA, 0.227 M CaCl2. To this mixture is added, dropwise, 500 μl of 50 mM HEPES (pH 7.35), 280 mM NaCl, 1.5 mM NaPO4, and a precipitate is allowed to form for 10 minutes at 25° C. The precipitate is suspended and added to the 293 cells and allowed to settle for about four hours at 37° C. The culture medium is aspirated off and 2 ml of 20% glycerol in PBS is added for 30 seconds. The 293 cells are then washed with serum free medium, fresh medium is added and the cells are incubated for about 5 days.
Approximately 24 hours after the transfections, the culture medium is removed and replaced with culture medium (alone) or culture medium containing 200 μCi/ml 35S-cysteine and 200 μCi/ml 35S-methionine. After a 12 hour incubation, the conditioned medium is collected, concentrated on a spin filter, and loaded onto a 15% SDS gel. The processed gel may be dried and exposed to film for a selected period of time to reveal the presence of vertebrate patched-2 polypeptide. The cultures containing transfected cells may undergo further incubation (in serum free medium) and the medium is tested in selected bioassays.
In an alternative technique, vertebrate patched-2 may be introduced into 293 cells transiently using the dextran sulfate method described by Somparyrac et al., Proc. Natl. Acad. Sci., 12:7575 (1981). 293 cells are grown to maximal density in a spinner flask and 700 μg pRK5-patched-2 DNA is added. The cells are first concentrated from the spinner flask by centrifugation and washed with PBS. The DNA-dextran precipitate is incubated on the cell pellet for four hours. The cells are treated with 20% glycerol for 90 seconds, washed with tissue culture medium, and re-introduced into the spinner flask containing tissue culture medium, 5 μg/ml bovine insulin and 0.1 μg/ml bovine transferrin. After about four days, the conditioned media is centrifuged and filtered to remove cells and debris. The sample containing expressed vertebrate patched-2 can then be concentrated and purified by any selected method, such as dialysis and/or column chromatography.
In another embodiment, vertebrate patched-2 can be expressed in CHO cells. The pSVi-patched-2 can be transfected into CHO cells using known reagents such as CaPO4 or DEAE-dextran. As described above, the cell cultures can be incubated, and the medium replaced with culture medium (alone) or medium containing a radiolabel such as 35S-methionine. After determining the presence of vertebrate patched-2 polypeptide, the culture medium may be replaced with serum free medium. Preferably, the cultures are incubated for about 6 days, and then the conditioned medium is harvested. The medium containing the expressed vertebrate patched-2 can then be concentrated and purified by any selected method.
Epitope-tagged vertebrate patched-2 may also be expressed in host CHO cells. The vertebrate patched-2 may be subcloned out of the pRK5 vector. The subclone insert can undergo PCR to fuse in frame with a selected epitope tag such as a poly-his tag into an expression vector. The poly-his tagged vertebrate patched-2 insert can then be subcloned into a SV40 driven vector containing a selection marker such as DHFR for selection of stable clones. Finally, the CHO cells can be transfected (as described above) with the SV40 driven vector. Labeling may be performed, as described above, to verify expression. The culture medium containing the expressed poly-His tagged vertebrate patched-2 can then be concentrated and purified by any selected method, such as by Ni2+-chelate affinity chromatography.
Example 4
Expression of Vertebrate Patched-2 in Yeast
The following method describes recombinant expression of vertebrate patched-2 in yeast.
First, yeast expression vectors are constructed for intracellular production or secretion of vertebrate patched-2 from the ADH2/GAPDH promoter. DNA encoding vertebrate patched-2, a selected signal peptide and the promoter is inserted into suitable restriction enzyme sites in the selected plasmid to direct intracellular expression of vertebrate patched-2. For secretion, DNA encoding vertebrate patched-2 can be cloned into the selected plasmid, together with DNA encoding the ADH2/GAPDH promoter, the yeast alpha-factor secretory signal leader sequence, and linker sequences (if needed) for expression of vertebrate patched-2.
Yeast cells, such as yeast strain AB110, can then be transformed with the expression plasmids described above and cultured in selected fermentation media. The transformed yeast supernatants can be analyzed by precipitation with 10% trichloroacetic acid and separation by SDS-PAGE, followed by staining of the gels with Coomassie Blue stain.
Recombinant vertebrate patched-2 can subsequently be isolated and purified by removing the yeast cells from the fermentation medium by centrifugation and then concentrating the medium using selected cartridge filters. The concentrate containing vertebrate patched-2 may further be purified using selected column chromatography resins.
Example 5
Expression of Vertebrate Patched-2 in Baculovirus-Infected Insect Cells
The following method describes recombinant expression of vertebrate patched-2 in Baculovirus-infected insect cells.
The vertebrate patched-2 is patched-2 upstream of an epitope tag contained within a baculovirus expression vector. Such epitope tags include poly-his tags and immunoglobulin tags (like Fe regions of IgG). A variety of plasmids may be employed, including plasmids derived from commercially available plasmids such as pVL1393 (Novagen). Briefly, the vertebrate patched-2 or the desired portion of the vertebrate patched-2 (such as the sequence encoding the extracellular domain of a transmembrane protein) is amplified by PCR with primers complementary to the 5′ and 3′ regions. The 5′ primer may incorporate flanking (selected) restriction enzyme sites. The product is then digested with those selected restriction enzymes and subcloned into the expression vector.
Recombinant baculovirus is generated by co-transfecting the above plasmid and BaculoGoldTM virus DNA (Pharmingen) into Spodoptera frugiperda (“Sf9”) cells (ATCC CRL 1711) using lipofectin (commercially available from GIBCO-BRL). After 4-5 days of incubation at 28° C., the released viruses are harvested and used for further amplifications. Viral infection and protein expression is performed as described by O'Reilley et al., Baculovirus expression vectors: A laboratory Manual, Oxford: Oxford University Press (1994).
Expressed poly-his tagged vertebrate patched-2 can then be purified, for example, by Ni2+-chelate affinity chromatography as follows. Extracts are prepared from recombinant virus-infected Sf9 cells as described by Rupert et al., Nature, 362:175-179 (1993). Briefly, Sf9 cells are washed, resuspended in sonication buffer (25 mL Hepes, pH 7.9; 12.5 mM MgCl2; 0.1 mM EDTA; 10% Glycerol; 0.1% NP-40; 0.4 M KC1), and sonicated twice for 20 seconds on ice. The sonicates are cleared by centrifugation, and the supernatant is diluted 50-fold in loading buffer (50 mM phosphate, 300 mM NaCl, 10% Glycerol, pH 7.8) and filtered through a 0.45 μm filter. A Ni2+-NTA agarose column (commercially available from Qiagen) is prepared with a bed volume of 5 mL, washed with 25 mL of water and equilibrated with 25 mL of loading buffer. The filtered cell extract is loaded onto the column at 0.5 mL per minute. The column is washed to baseline A280 with loading buffer, at which point fraction collection is started. Next, the column is washed with a secondary wash buffer (50 mM phosphate; 300 mM NaCl, 10% Glycerol, pH 6.0), which elutes nonspecifically bound protein. After reaching A280 baseline again, the column is developed with a 0 to 500 mM Imidazole gradient in the secondary wash buffer. One mL fractions are collected and analyzed by SDS-PAGE and silver staining or western blot with Ni2+-NTA-conjugated to alkaline phosphatase (Qiagen). Fractions containing the eluted His10-tagged vertebrate patched-2 are pooled and dialyzed against loading buffer.
Alternatively, purification of the IgG tagged (or Fc tagged) vertebrate patched-2 can be performed using known chromatography techniques, including for instance, Protein A or protein G column chromatography.
Example 6
Preparation of Antibodies that Bind Vertebrate patched-2
This example illustrates preparation of monoclonal antibodies, which can specifically bind vertebrate patched-2.
Techniques for producing the monoclonal antibodies are known in the art and are described, for instance, in Goding, supra. Immunogens that may be employed include purified vertebrate patched-2, fusion proteins containing vertebrate patched-2, and cells expressing recombinant vertebrate patched-2 on the cell surface. Selection of the immunogen can be made by the skilled artisan without undue experimentation.
Mice, such as Balb/c, are immunized with the vertebrate patched-2 immunogen (E.g., extracellular portions or cells expressed Ptch-2) emulsified in complete Freund's adjuvant and injected subcutaneously or intraperitoneally in an amount from 1-100 micrograms. Alternatively, the immunogen is emulsified in MPL-TDM adjuvant (Ribi Immunochemical Research, Hamilton, Mont.) and injected into the animal's hind foot pads. The immunized mice are then boosted 10 to 12 days later with additional immunogen emulsified in the selected adjuvant. Thereafter, for several weeks, the mice may also be boosted with additional immunization injections. Serum samples may be periodically obtained from the mice by retro-orbital bleeding for testing in ELISA assays to detect vertebrate patched-2 antibodies.
After a suitable antibody titer has been detected, the animals “positive” for antibodies can be injected with a final intravenous injection of vertebrate patched-2. Three to four days later, the mice are sacrificed and the spleen cells are harvested. The spleen cells are then patched-2 (using 35% polyethylene glycol) to a selected murine myeloma cell line such as P3X63AgU.1, available from ATCC, No. CRL 1597. The fusions generate hybridoma cells which can then be plated in 96 well tissue culture plates containing HAT (hypoxanthine, aminopterin, and thymidine) medium to inhibit proliferation of non-patched-2 cells, myeloma hybrids, and spleen cell hybrids.
The hybridoma cells will be screened in an ELISA for reactivity against vertebrate patched-2. Determination of “positive” hybridoma cells secreting the desired monoclonal antibodies against vertebrate patched-2 is within the skill in the art.
The positive hybridoma cells can be injected intraperitoneally into syngeneic Balb/c mice to produce ascites containing the anti-vertebrate patched-2 monoclonal antibodies. Alternatively, the hybridoma cells can be grown in tissue culture flasks or roller bottles. Purification of the monoclonal antibodies produced in the ascites can be accomplished using ammonium sulfate precipitation, followed by gel exclusion chromatography. Alternatively, affinity chromatography based upon binding of antibody to protein A or protein G can be employed.
Example 7
Gli Luciferase Assay
The following assay may be used to measure the activation of the transcription factor GLI, the mammalian homologue of the Drosophila cubitus interruptus (Ci). It has been shown that GLI is a transcription factor activated upon SHh stimulation of cells.
Nine (9) copies of a GLI binding site present in the HNF3□ enhancer, (Sasaki et al., Development 124: 1313-1322 (1997)), are introduced in front of a thymidine kinase minimal promoter driving the luciferase reporter gene in the pGL3 plasmid (Promega). The sequence of the GLI binding sequence is: TCGACAAGCAGGGAACACCCAAGTAGAAGCTC (p9XGliLuc) (SEQ ID NO:31), while the negative control sequence is: TCGACAAGCAGGGAAGTGGGAAGTAGAAGCTC (p9XmGliLuc) (SEQ ID NO:32). These constructs are cotransfected with the full length Ptch-2 and Smo in C3H10T1/2 cells grown in F12, DMEM (50:50), 10% FCS heat inactivated. The day before transfection 1×105 cells per well was inoculated in 6 well plates, in 2 ml of media. The following day, 1 μg of each construct is cotransfected in duplicate with 0.025 mg ptkRenilla luciferase plasmid using lipofectamine (Gibco-BRL) in 100 μl OptiMem (with GlutaMAX) as per manufacturer's instructions for 3 hours at 37° C. Serum (20%, 1 ml) is then added to each well and the cells were incubated for 3 more hours at 37° C. Cells are then washed twice with PBS, then incubated for 48 hours at 37° C. in 2 ml of media. Each well is then washed with PBS, and the cells lysed in 0.5 ml Passive Lysis Buffer (Promega) for 15 min. at room temperature on a shaker. The lysate is transferred in eppendorf tubes on ice, spun in a refrigerated centrifuge for 30 seconds and the supernatant saved on ice. For each measure, 20 μl of cell lysate is added to 100 μl of LARII (luciferase assay reagent, Promega) in a polypropylene tube and the luciferase light activity measured. The reaction is stopped by the addition of Stop and Glow buffer (Promega), mixed by pipetting up and down 3 to 5 times and Renilla luciferase lights activity is measured on the luminometer.
Deposit of Material
The following materials have been deposited with the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md., USA (ATCC):















Designation:
ATCC Dep. No.
Deposit Date









pRK7.hptc2.Flag-1405
209778
Apr. 14, 1998










This deposit was made under the provisions of the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purpose of Patent Procedure and the Regulations thereunder (Budapest Treaty). This assures maintenance of a viable culture of the deposit for 30 years from the date of deposit. The deposit will be made available by ATCC under the terms of the Budapest Treaty, and subject to an agreement between Genentech, Inc. and ATCC, which assures permanent and unrestricted availability of the progeny of the culture of the deposit to the public upon issuance of the pertinent U.S. patent or upon laying open to the public of any U.S. or foreign patent application, whichever comes first, and assures availability of the progeny to one determined by the U.S. Commissioner of Patents and Trademarks to be entitled thereto according to 35 USC §122 and the Commissioner's rules pursuant thereto (including 37 CFR §1.14 with particular reference to 886 OG 638).
The assignee of the present application has agreed that if a culture of the materials on deposit should die or be lost or destroyed when cultivated under suitable conditions, the materials will be promptly replaced on notification with another of the same. Availability of the deposited material is not to be construed as a license to practice the invention in contravention of the rights granted under the authority of any government in accordance with its patent laws.
The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the invention. The present invention is not to be limited in scope by the construct deposited, since the deposited embodiment is intended as a single illustration of certain aspects of the invention and any constructs that are functionally equivalent are within the scope of this invention. The deposit of material herein does not constitute an admission that the written description herein contained is inadequate to enable the practice of any aspect of the invention, including the best mode thereof, nor is it to be construed as limiting the scope of the claims to the specific illustrations that it represents. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims.

## Claims

1. A method of screening for antagonists or agonists of patched-2 biological activity comprising:
(a) exposing target cells expressing a human patched-2 polypeptide having the amino acid sequence of SEQ ID NO:2 in culture to a candidate compound and Desert Hedgehog (Dhh) wherein said target cells are recombinant cells comprising a heterologous nucleic acid expressing said human patched-2 polypeptide; and
(i) analyzing the cells for binding of Dhh to patched-2; or
(ii) scoring phenotypic or functional changes in the treated cells; and

comparing the results to control cells which were not exposed to the candidate compound, wherein either:
(1) a decrease in binding of Dhh to patched-2 indicates that the candidate compound is an antagonist of patched-2 biological activity, and wherein an increase in binding of Dhh to patched-2 indicates that the candidate compound is an agonist of patched-2 biological activity; or
(2) wherein a phenotypic or functional change in the treated cells compared to control cells indicates that the candidate compound is an antagonist or agonist of patched-2 biological activity.

2. The method of claim 1 wherein said recombinant cells are eukaryotic cells.

3. The method of claim 2, wherein said eukaryotic cells are vertebrate cells.

4. The method of claim 3, wherein said vertebrate cells are mammalian cells.

5. The method of claim 2, wherein said eukaryotic cells are insect cells.

6. An in vitro method of screening for an antagonist or an agonist of patched-2 biological activity comprising:
(a) exposing a patched-2 ligand and a patched-2 polypeptide having the amino acid sequence of SEQ ID NO:2 and having patched-2 biological activity to a candidate compound; and
(b) analyzing the binding of the patched-2 ligand to the patched-2 polypeptide in the presence of the candidate compound; and comparing the results to a control reaction which was not exposed to the candidate compound, wherein a decrease in binding of the patched-2 ligand to the patched-2 polypeptide indicates that the candidate compound is an antagonist of patched-2 biological activity, and wherein an increase in binding of the patched-2 ligand to the patched-2 polypeptide indicates that the candidate compound is an agonist of patched-2 biological activity.

7. The method of claim 6 wherein said patched-2 polypeptide is an epitope-tagged patched-2.

8. The method of claim 7 wherein said epitope-tagged patched-2 comprises a polypeptide selected from the group consisting of poly-histidine, poly-histidine-glycine, flu hemagglutinin, c-myc, Herpes Simplex virus glycoprotein D, Flag-peptide, KT3 epitope peptide, α-tubulin epitope peptide, and T7 gene 10 protein.

9. The method of claim 6 wherein said patched-2 ligand is added after said candidate compound.

10. The method of claim 6 wherein said candidate compound is added after said patched-2 ligand.

11. The method of claim 6 wherein said candidate compound and said patched-2 ligand are added simultaneously.

12. An in vitro method of screening for an antagonist or an agonist of patched-2 biological activity comprising: (a) exposing a patched-2 ligand and a patched-2 immunoadhesin, to a candidate compound, wherein said patched-2 immunoadhesin comprises a polypeptide comprising the amino acid sequence of SEQ ID NO:2; and
(b) analyzing the binding of the patched-2 ligand to the patched-2 immunoadhesin in the presence of the candidate compound; and comparing the results to a control reaction which was not exposed to the candidate compound, wherein a decrease in binding of the patched-2 ligand to the patched-2 immunoadhesin indicates that the candidate compound is an antagonist of patched-2 biological activity, and wherein an increase in binding of the patched-2 ligand to the patched-2 immunoadhesin indicates that the candidate compound is an agonist of patched-2 biological activity.

13. The method of claim 12 wherein said immunoadhesin is attached to a solid phase.