# Patent

## Title
Protease sensitivity expression system

## Abstract

The present invention uses co-expression of protease inhibitors and protease sensitive therapeutic agents that results in their localized production within the target tissue and inactivation outside of the target tissue, thereby increasing therapeutic activity and reducing the systemic toxicity. Inactivation is also accomplished by engineering protease degradation sites within the therapeutic construct for proteases, preferably those that are under-expressed within the target tissue yet present in non-target tissues within the body, resulting in therapeutic activity within the target tissue and inactivation outside of the target tissue. Novel chimeric proteins secreted by bacteria are also described. The chimeric proteins include chimeric toxins targeted to neoplastic cells and cells of the immune system. Novel combination therapies of these protease inhibitor:chimeric toxin-expressing bacteria together with small-molecule and biologic agents are also described. Non-conjugative bacteria capable of delivering phage/phagemids expression cassettes for DNA and RNA-based therapeutics are also described.

## Background
1. BACKGROUND OF THE INVENTION
1.1. Field of the Invention
This invention is generally in the field of therapeutic delivery systems, systems and methods for providing co-expression of protease inhibitors with genetically engineered protease sensitive therapeutic constructs, and chimeric proteins.
1.2. Relevant Art
Citation or identification of any reference herein, or any section of this application shall not be construed as an admission that such reference is available as prior art to the present application.
Tumor-targeted bacteria offer tremendous potential advantages for the treatment of solid tumors, including the targeting from a distant inoculation site and the ability to express therapeutic agents directly within the tumor. However, the primary shortcoming of tumor-targeted bacteria investigated in the human clinical trials (Salmonella strain VNP20009 and its derivative TAPET-CD) is that no significant antitumor activity was observed, even in patients where the bacteria was documented to target the tumor. One method of increasing the ability of the bacteria to kill tumor cells is to engineer the bacteria to express conventional bacterial toxins, but this approach poses risks of systemic toxicity. See, e.g., U.S. Pat. Nos. 7,452,531, 7,354,592, 6,962,696, 6,923,972, 6,863,894, 6,685,935, 6,475,482, 6,447,784, 6,190,657, 6,080,849 and US Pub. 2003/0059400, each of which is expressly incorporated herein by reference. These patents disclose, inter alia, pharmaceutical formulations and methods of administration to humans and animals, useful in conjunction with the present technique.
Use of protein toxins for treatment of various disorders including inflammation, autoimmunity, neurological disorders and cancer has long-suffered from off-target toxicity. Some toxins have a natural degree of specificity for their target, such as botulinum toxin which is specific for neurons. Toxin specificity has been achieved by attachment of a specific antibodies or peptide ligands (e.g., Pseudomonas endotoxin A (PE-ToxA) antibody conjugate, known as an immunotoxin). Based upon the binding specificity of the attached antibody moiety for a specific target, enhanced specificity of the target is achieved. Other toxins have been engineered to achieve specificity based upon their sight of activation. For example, aerolysin requires proteolytic activation to become cytotoxic. Substitution of the natural protease cleavage site for a tumor-specific protease cleavage site (e.g., that of the PSA protease or urokinase) results in a toxin selectively activated within tumors. However, in both these types of engineered toxins, off-target toxicity can occur. In the case of the Pseudomonas immunotoxin, several dose-limiting toxicities have been identified. Vascular leakage syndrome (VLS) is associated with hypoalbuminemia, edema, weight gain, hypotension and occasional dyspnea, which is suggested to occur by immunotoxin-mediated endothelial cell injury (Baluna et al., 2000, Exp. Cell Res. 258: 417-424), resulting in a dose-limiting toxicity. Renal injury has occurred in some patients treated with immunotoxins, which may be due to micro-aggregates of the immunotoxin (Frankel et al., 2001, Blood 98: 722a). Liver damage from immunotoxins is a frequent occurrence that is believed to be multifactorial (Frankel, 2002, Clinical Cancer Research 8: 942-944). To date, antibodies with proteinaceous toxins have limited success clinically. One explanation for the off target toxicity is that although a specific agent is targeted to the tumor and/or specifically activated there, the agent is also toxic if it diffuses out of the tumor, which is likely to occur due to the high osmotic pressure that occurs within tumors (Jain, R. K., 1994, Barriers to drug delivery in solid tumors, Scientific American 271 (11): 58-65). Once activated inside the tumor and diffused back outside, toxins such as aerolysin remain active and are able to contribute to non-target toxicity.
Another method of increasing the therapeutic activity of tumor-targeted bacteria is to use F′ Salmonella for the purpose of liberating filamentous phage within the tumor that are capable of delivering genetic material to tumor cells (See, WO/2001/014579, expressly incorporated herein by reference). However, the presence of the F′ factor in those studies is known to enhance the genetic exchange of the Salmonella with other bacteria such as E. coli, and therefore poses risks of releasing genes into the environment that could enhance the pathogenic potential of other bacteria. Moreover, no antitumor activity was demonstrated.
2. SUMMARY OF THE INVENTION
A Protease Inhibitor: Protease Sensitivity Expression System Improving the Therapeutic Specificity
The present invention consists of the co-expression by the expression system, or a combination of expression systems, of a protease inhibitor together with a protease sensitive therapeutic agent. Within the local high-concentration of the targeted tissue or cells such as a tumor environment, the protease inhibitor prevents the degradation of the agent, which is therapeutically active against the target tissue such as a tumor. Upon egress from the confined space of the targeted tissue such as the tumor, the inhibitor falls below the inhibitory concentration, and the therapeutic agent is freely degraded, resulting in cell or tissue-specific activity and non-target cell or tissue inactivity (Table I). A schematic diagram illustrating the effect of co-expression is shown in FIG. 1.







TABLE 1







Relative effect of toxin forms with and without


protease sensitivity and protease inhibitor.










Tumor
Systemic


Composition
Efficacy
Toxicity





Protease activated and/or insensitive toxin
+++
++


Protease sensitive toxin
+
−


Protease sensitive toxin + protease inhibitor
+++++
−









The therapeutic agent can be a peptide or protein, toxin, chimeric toxin, cytokine, antibody, biospecific antibody including single chain antibodies, chemokine, prodrug converting enzyme or phage/phagemid. In a preferred embodiment the therapeutic agent is a toxin, or modified toxin. In another preferred embodiment, the therapeutic agent is a phage or phagemid capable of delivering DNA or RNA.
Toxins useful in conjunction with the present invention that can be modified uniquely to suit the delivery by a bacterium and may be further engineered to have tumor-selective targeting include, azurin, carboxyesterase Est55 (a prodrug converting enzyme from Geobacillus that activates CPT-11 to SN-38), Bacillus sp. cytolysins, cytolethal distending toxin (cldt), typhoid toxin (pltAB), cldt:plt hybrids, cytotoxic nectrotic factor (cnf), dermonecrotic factor (dnf), shiga toxin and shiga-like toxins, colicins including colicin E492, colE3, colE7 and col-Ia, membrane lytic peptides from Staphalococcus (listed below), bacterial collegenases (e.g., that from Salmonella strain DT104, see WO/2005/018332, the entirety of which is expressly incorporated herein by reference), repeat in toxin (RTX) family members (together with the necessary acylation and secretion genes) including Actinobacillus leucotoxin, a leuckotoxin:E. coli HlyA hybrid, E. coli HlyA hemolysin, and Bordetella adenylate cyclase toxin, heat stable enterotoxins from E. coli and Vibrio sp., autotransporter toxins including picU espC, and sat, chlostridium enterotoxin, aerolysin, subtilase, saporin, ricin, pertussus toxin, and porB.
The toxin may be further modified by addition of one or more protease cleavage sites that enhance its degradation outside of the tumor. Preferred protease cleavage sites are those for proteases that are under-expressed within the tumor compared to normal tissues (rather than over-expressed within the tumor as utilized for aerolysin activation). However, the expression levels of many proteases are elevated within tumors. Proteases for which inhibitory peptides may be expressed include furin, tissue plasminogen activator, activated protein C, factor Xa, granzymes (A, B & M), cathepsins (A, B, C, D, E, F, G, H, K, L, S, W & X), thrombin, plasmin, urokinase, matrix metaloproteaes, prostate specific antigen (PSA) and kallikrein 2.
Furin recognizes a number of specific cleavage sites, including RXRAKR↓SEQ ID NO:57. In accordance with the present invention, the presence of this cleavage site, whether naturally occurring or introduced through genetic modification, may be compensated for within the target tissue by co-expression of a furin inhibitor, stabilizing its activity unless it escapes the target tissue such as a tumor. Use of protease inhibitors alone or in combination by bacterial delivery vectors has not previously been suggested. Indeed, Wang et al. 2008 suggested furin inhibitors could be used as antibiotics to suppress bacterial infection which would thereby interfere with delivery by a bacterial vector. Therefore, it has not been considered desirable to use a furin inhibitor or other protease inhibitors to have a positive effect on the bacteria and/or the therapeutics they release.
The peptide inhibitors are engineered to be secreted from the bacteria secretion signals known to those skilled in the arts, including ompA, OmpF, M13 pIII, cldt N-terminal signal sequences or hlyA C-terminal signal sequence (requires addition of hlyBD and TolC). The inhibitors can be further modified to have the protease cleavage signal of the protease that they inhibit or for a different protease. Multiple protease inhibitor sequences may alternate between protease cleavage sequences or recognition sites.
Chimeric toxins may be further modified by the addition of known cell penetrating (ferry) peptide which further improves their entry into target cells. Cell penetrating peptides include those derived from the HIV TAT protein, the antennapedia homeodomain (penetraxin), Kaposi fibroblast growth factor OCT) membrane-translocating sequence (MTS), herpes simplex virus VP22, hexahistidine, hexylysine, or hexaarginine.
The present invention also provides in accordance with some embodiments, unique chimeric modifications of the above listed toxins that contain specific combinations of components resulting in secretion by and gram-negative bacteria (e.g., Salmonella, Shigella, E. coli) and selective anti-tumor activity. The invention also provides protease sensitivity (deactivation) which may include the addition of protease cleavage sites and may be co-expressed with a protease inhibitor. The chimeric proteins may have one or more additional features or protein domains known to those skilled in the arts which are designed to 1) be active or catalytic domains that result in the death of the cell or make them susceptible to other known anticancer agents, 2) allow or facilitate them being secreted or released by autolytic peptides such as colicin release peptides, 3) membrane protein transduction (ferry) peptides, 4) autotransporter domains, 5) have targeting peptides that direct them to the target cells, and 6) protease cleavage sites for activation (e.g., release from parent peptide). However, the specific organization and combination of these domains is unique and specific to the invention.
Bombisin and gastrin are amidated peptides. Amidation of these peptides would not be expected to occur in bacteria. A unique composition in accordance with one embodiment of the present invention is the co-expression of the C-terminal amidating enzyme, which results in amidating these peptides in order for them to confer their targeting specificity.
Small lytic peptides (less than 50 amino acids) are used to construct chimeric proteins for more than one purpose. The chimeric proteins containing lytic peptides may be directly cytotoxic for the cancer cells, and/or other cells of the tumor including the tumor matrix cells and immune cells which may diminish the effects of the bacteria by eliminating them. Furthermore, the lytic peptides are useful in chimeric proteins for affecting release from the endosome. Small lytic peptides have been used in the experimental treatment of cancer. However, it is evident that most, if not all, of the commonly used antitumor small lytic peptides have strong antibacterial activity, and thus are not compatible with delivery by a bacterium (see Table 1 of Leschner and Hansel, 2004 Current Pharmaceutical Design 10: 2299-2310, the entirety of which is expressly incorporated herein by reference). Small lytic peptides useful in the invention are those derived from Staphylococcus aureus, S. epidermidis and related species, including the phenol-soluble modulin (PSM) peptides and delta-lysin (Wang et al., 2007 Nature Medicine 13: 1510-1514, expressly incorporated herein by reference). The selection of the lytic peptide depends upon the primary purpose of the construct, which may be used in combination with other constructs providing other anticancer features. Construct designed to be directly cytotoxic to cells employ the more cytoxic peptides, particularly PSM-α-3. Constructs which are designed to use the lytic peptide to affect escape from the endosome se the peptides with the lower level of cytotoxicity, such as PSM-alpha-1, PSM-alpha-2 or delta-lysin.
2.2 Non-Conjugative, Bacteria Capable of Delivering DNA and RNA Interference (RNAi) Mediated by Small Interfering RNAs (siRNA) and/or MicroRNAs (MiRNA).
The present invention provides, according to some embodiments, a composition that would minimize the effect of bacteria released into the environment by eliminating the ability of the bacteria to exchange genetic information with related bacteria, as well as provide a delivery enhancing bacteria resulting in a greater therapeutic effect. Conjugative transfer is a major genetic exchange mechanism that may occur between Salmonella and the normal commensal gut bacterium E. coli, requiring the presence of an F′ factor. The present invention provides gram-negative bacteria including E. coli, Vibrio, Shigella and Salmonella that are genetically modified in one or more ways to eliminate conjugative transfer of DNA with closely related species including E. coli. One of the modifications works on both male (F′+) and female (F′−) bacteria. These modifications facilitate the safety of a bacteria carrying phage capable of delivering DNA or small interfering RNA (siRNA) or microRNA (miRNA) molecules that mediate RNA interference (RNAi), as well as for bacteria expressing chimeric toxins. The phage/phagemids may be further modified to express membrane lytic peptides enhancing their release from the endosome. See, e.g., U.S. Pat. No. 7,390,646, US 2008/0311081, 2009/0123426, WO 2008/091375, WO 1999/010485, WO 1999/010014, WO 2009/086116, each of which is expressly incorporated herein by reference it its entirety
MicroRNAs (miRNA) are single-stranded RNA molecules of, for example, about 21-23 nucleotides in length, which regulate gene expression. miRNAs are encoded by genes from whose DNA they are transcribed but miRNAs are not translated into protein (non-coding RNA; instead each primary transcript (a pri-miRNA) is processed into a short stem-loop structure called a pre-miRNA and finally into a functional miRNA. Mature miRNA molecules are partially complementary to one or more messenger RNA (mRNA) molecules, and their main function is to down-regulate gene expression.
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of 19-25 nucleotide-long double-stranded RNA molecules with 3′′ overhangs. Asymmetric interfering RNAs have 3′′ and 5′′ antisense overhangs and may be only 15 base pairs in length (Sun et al. 2008 Nature Biotechnology 26: 1379-1382, incorporated in its entirety herein). Interfering RNAs play a variety of roles in biology. Most notably, siRNA is involved in the RNA interference (RNAi) pathway, where it interferes with the expression of a specific gene. In addition to their role in the RNAi pathway, siRNAs also act in RNAi-related pathways, e.g., as an antiviral mechanism or in shaping the chromatin structure of a genome.
The bacterial strains according to various aspects of the invention useful for delivery of phage/phagemids especially include any of those expressing protease inhibitors, and/or chimeric toxins. The bacteria may also be modified variously in order to accommodate the production of the phage such that they are stably maintained and released from the bacteria. These modifications may include: introduction of an F′ pilus factor which allows the filamentous phage to infect the bacteria, a “helper phage” which provides phage genes and functions in trans necessary to package a phagemid, a phagemid containing a modified phage coat protein (e.g., pIII, pVIII) into which a targeting ligand is inserted, and phagemid effector genes, which may include eukaryotic promoters for tumor cell expression of anticancer genes, or genes that are transcribed into short hairpin RNAs that function as interfering RNA molecules (RNAi). More than one gene and/or siRNA and/or miRNA may be expressed from a single phagemid and may employ ribosomal reentry signals (RESs). A preferred bacterial phagemid with eukaryotic expression components (including an SV40 origin of replication, HSV-TK polyadenylation signal, a CVM IE promoter and an SV40 polyadenylation signal) is pEGFP-N1. The siRNA and/or miRNA molecules may utilize the T7 promoter. Constructs using the T7 promoter may contain one or more copies of the T7 polymerase under control of a eukaryotic promoter, which, when transcribed and translated, is capable of expressing the siRNA and/or miRNA constructs under control of the T7 promoter.
The phagmid-expressed genes may serve multiple purposes. The phagemid genes may serve to suppress certain immune responses within the tumor, including T-cells, macrophages and neutrophils that may limit the ability of the bacteria to effectively reach all the tumor cells within a tumor. The phagmid genes may also serve to directly inhibit tumor cells, either through the expression of anti-tumor genes (e.g., tumor suppressor genes such as p53) or by generating siRNA and/or miRNA or other RNAi molecules, which suppress the presence of mRNA transcripts, suppressing the neoplastic genes such as KRAS.
The F′ pilus factors are provided by the F′ plasmid, and are needed for phage to be able to infect a bacterial cell. The F′ factor provides other functions which may be undesirable in conjunction with aspects of the present invention, including mating stabilization and DNA transfer. The present invention therefore provides, according to one aspect, a composition lacking these features by their genetic disruption on the F′ factor or by the cloning of the pilus factor genes into the tumor-targeted bacterium in the absence of the other factors, and hence, resulting in a strain which is non-conjugative and significantly less likely to transfer DNA to other bacteria. The invention may also incorporate entry exclusion into the bacteria and the fertility inhibition complex (finO and finP), and thus, even in tumor-targeted bacterial strains in which the pilus factors are not incorporated (i.e., F−), the bacterial strain will remain resistant to mating with F′ bacteria.
3. OBJECTS OF THE INVENTION
The present invention provides, according to one embodiment, improved live attenuated therapeutic bacterial strains that express one or more therapeutic molecules together with one or more protease inhibitor polypeptides that inhibit local proteases that could deactivate the therapeutic molecules. In particular, one aspect of the invention relates to live attenuated tumor-targeted bacterial strains that may include Salmonella vectoring chimeric anti-tumor toxins to an individual to elicit a therapeutic response against cancer. Another aspect of the invention relates to live attenuated tumor-targeted bacterial strains that may include Salmonella vectoring filamentous phage that encode anti-tumor DNA and RNA molecules to an individual to elicit a therapeutic response against cancer including cancer stem cells. The filamentous phage may also be targeted to tumor matrix cells, and immune cells.
Whereas the prior strains of Salmonella studied in human clinical trails used either no heterologous antitumor protein (i.e., VNP20009) or an antitumor protein located within the cytoplasm of the bacterium (i.e., cytosine deaminase expressed by TAPET-CD), the invention provides, according to some embodiments, methods and compositions comprising bacterial vectors that secrete protease inhibitors that protect coexpressed protease sensitive antitumor molecules that are also secreted into the tumor for the treatment of cancer.
The bacteria according to a preferred embodiment of the present invention have little or no ability to undergo bacterial conjugation, limiting incoming and outgoing exchange of genetic material, whereas the prior art fails to limit exchange of genetic material. In addition, certain of the therapeutic molecules have co-transmission requirements that are distal to the therapeutic molecule location further limiting known forms of genetic exchange.
Aspects of the present invention also provide novel chimeric bacterial toxins particularly suited for expression by gram-negative bacteria. The toxins may have added targeting ligands that render them selectively cytotoxic for tumor cells, tumor stem cells and/or matrix and tumor-infiltrating immune cells. The invention also provides means to determine optimal toxin combinations which are preferably additive or more preferably synergistic. The invention also provides means to determine the optimal combination of protein toxin with conventional cancer chemotherapeutics or biologics. Accordingly, administration to an individual, of a live Salmonella bacterial vector, in accordance with an aspect of the present invention, that is genetically engineered to express one or more protease inhibitors as described herein co-expressed with one or more cytotoxic proteins has the ability to establish a population in the tumor, kill tumor cells, tumor stem cells as well as tumor matrix and immune infiltrating cells, resulting in a therapeutic benefit.
A preferred composition will contain, for example, a sufficient amount of live bacteria expressing the protease inhibitors and cytotoxin(s) to produce a therapeutic response in the patient. Accordingly, the attenuated Salmonella strains described herein are both safe and useful as live bacterial vectors that can be orally administered to an individual to provide therapeutic benefit for the treatment of cancer.
Although not wishing to be bound by any particular mechanism, an effective antitumor response in humans by administration of genetically engineered, attenuated strains of Salmonella strains as described herein may be due to the ability of such mutant strains to persist in the tumor and to supply their own nutrient needs by killing tumor cells and further expanding the zone of the tumor that they occupy. Bacterial strains useful in accordance with a preferred aspect of the invention may carry the ability to produce a therapeutic molecule (or releases an agent such as a phagemid that carries the ability to generate therapeutic molecules) expressing plasmid or chromosomally integrated cassette that encodes and directs expression of one or more therapeutic molecules together with one or more protease inhibitors, as described herein. The protease inhibitors serve to prevent the destruction of the therapeutic molecule while within the tumor. If the cytotoxin and protease inhibitor diffuse outside of the tumor, they fall below the protease inhibitory concentration, and the cytotoxins are inactivated. Thus the protease inhibitor system both increases activity and provides tumor specificity.
The serovars of S. enterica that may be used as the attenuated bacterium of the live compositions described in accordance with various embodiments herein include, without limitation, Salmonella enterica serovar Typhimurium (“S. typhimurium”), Salmonella montevideo, Salmonella enterica serovar Typhi (“S. typhi”), Salmonella enterica serovar Paratyphi B (“S. paratyphi 13”), Salmonella enterica serovar Paratyphi C (“S. paratyphi C”), Salmonella enterica serovar Hadar (“S. hadar”), Salmonella enterica serovar Enteriditis (“S. enteriditis”), Salmonella enterica serovar Kentucky (“S. kentucky”), Salmonella enterica serovar Infantis (“S. infantis”), Salmonella enterica serovar Pullorum (“S. pullorum”), Salmonella enterica serovar Gallinarum (“S. gallinarum”), Salmonella enterica serovar Muenchen (“S. muenchen”), Salmonella enterica serovar Anaturn (“S. anatum”), Salmonella enterica serovar Dublin (“S. dublin”), Salmonella enterica serovar Derby (“S. derby”), Salmonella enterica serovar Choleraesuis var. kunzendorf (“S. cholerae kunzendorf”), and Salmonella enterica serovar minnesota (S. minnesota). A preferred serotype for the treatment of bone marrow related diseases is S. dublin. 
By way of example, live bacteria in accordance with aspects of the invention include known strains of S. enterica serovar Typhimurium (S. typhimurium) and S. enterica serovar Typhi (S. typhi) which are further modified as provided by various embodiments of the invention. Such Strains include Ty21a, CMV906, CMV908, CMV906-htr, CMV908-htr, Ty800, aroA-/serC-, holavax, M01ZH09, VNP20009. See also, U.S. Pat. No. 6,548,287, and EP 0,973,911, each of which expressly incorporated herein by reference. These strains contain defined mutations within specific serotypes of bacteria. The invention also includes the use of these same mutational combinations contained within alternate serotypes or strains in order to avoid immune reactions which may occur in subsequent administrations. In a preferred embodiment, S. Typhimurium, S. montevideo, and S. typhi which have non-overlapping O-antigen presentation (e.g., S. typhimurium is 0-1, 4, 5, 12 and S. typhi is Vi, S. montevideo is 0-6, 7) may be used. Thus, for example, S. typhimurium is a suitable serotype for a first injection and another serotype such as S. typhi or S. montevideo are used for a second injection and third injections Likewise, the flagellar antigens are also selected for non-overlapping antigenicity between different injections. The flagellar antigen may be H1 or H2 or no flagellar antigen, which, when combined with the three different O-antigen serotypes, provides three completely different antigentic profiles. Methods for deriving heterologous O-antigens have been described by Favre et al., WO/1997/014782, and Roland WO/2000/004919, each of which is expressly incorporated herein by reference.
Novel strains are also encompassed that are, for example, attenuated in virulence by mutations in a variety of metabolic and structural genes. The invention therefore may provide a live composition for treating cancer comprising a live attenuated bacterium that is a serovar of Salmonella enterica comprising an attenuating mutation in a genetic locus of the chromosome of said bacterium that attenuates virulence of said bacterium and wherein said attenuating mutation is the Suwwan deletion (Murray et al., Journal of Bacteriology, 2004) or combinations with other known attenuating mutations. Other attenuating mutation useful in the Salmonella bacterial strains described herein may be in a genetic locus selected from the group consisting of phoP, phoQ, edt, cya, crp, poxA, rpoS, htrA, nuoG, pmi, pabA, pts, damA, pur, purA, purB, purl, purF, zwf, aroA, aroB, aroC, aroD, serC, gua, cadA, rfc, rjb, rfa, ompR, msbB and combinations thereof.
The invention also encompasses gram-positive bacteria. Preferred bacteria of the invention are group B Streptococcus including S. agalaciae, and Listeria species including L. monocytogenes. It is known to those skilled in the arts that minor variations in molecular biology techniques such as use of gram-positive origins of replication, gram-positive signal sequences gram-positive promoters and filamentous phage (e.g., phage B5; Chopin et al., 2002 J. Bacteriol. 184: 2030-2033) are required and substituted as needed.
The invention also provides, according to one embodiment, a process for preparing genetically stable therapeutic bacterial strains comprising genetically engineering the therapeutic genes of interest into a bacterially codon optimized expression sequence within a bacterial plasmid expression vector or chromosomal localization expression vector for any of the deleted genes or IS200 genes within the strain and further containing engineered restriction endonuclease sites such that the bacterially codon optimized expression gene contains subcomponents which are easily and rapidly exchangeable, and the bacterial strains so produced. Administration of the strain to the patient is therapeutic for the treatment of cancer.
The present invention provides, for example, and without limitation, live bacterial compositions that are genetically engineered to express one or more protease inhibitors combined with antitumor effector molecules or phagemids capable of delivering DNA and RNA therapeutics for the treatment of cancer.
4. DEFINITIONS
In order that the invention may be more fully understood, the following terms are defined.
As used herein, “attenuated”, “attenuation”, and similar terms refer to elimination or reduction of the natural virulence of a bacterium in a particular host organism, such as a mammal.
“Virulence” is the degree or ability of a pathogenic microorganism to produce disease in a host organism. A bacterium may be virulent for one species of host organism (e.g., a mouse) and not virulent for another species of host organism (e.g., a human). Hence, broadly, an “attenuated” bacterium or strain of bacteria is attenuated in virulence toward at least one species of host organism that is susceptible to infection and disease by a virulent form of the bacterium or strain of the bacterium.
As used herein, the term “genetic locus” is a broad term and comprises any designated site in the genome (the total genetic content of an organism) or in a particular nucleotide sequence of a chromosome or replicating nucleic acid molecule (e.g., a plasmid), including but not limited to a gene, nucleotide coding sequence (for a protein or RNA), operon, regulon, promoter, inducible promoters (including tetracycline, arabinose, (EP1,655,370 A1, expressly incorporated in its entirety herein), salicylic acid, hypoxic, tumor cell specific inducible promoters) regulatory site (including transcriptional terminator sites, ribosome binding sites, transcriptional inhibitor binding sites, transcriptional activator binding sites), origin of replication, intercistronic region, and portions therein. It is understood that all protein expression constructs require a stop signal. A genetic locus may be identified and characterized by any of a variety of in vivo and/or in vitro methods available in the art, including but not limited to, conjugation studies, crossover frequencies, transformation analysis, transfection analysis, restriction enzyme mapping protocols, nucleic acid hybridization analyses, polymerase chain reaction (PCR) protocols, nuclease protection assays, and direct nucleic acid sequence analysis
The terms “oral”, “enteral”, “enterally”, “orally”, “non-parenteral”, “non- parenterally”, and the like, refer to administration of a compound or composition to an individual by a route or mode along the alimentary canal. Examples of “oral” routes of administration of a vaccine composition include, without limitation, swallowing liquid or solid forms of a vaccine composition from the mouth, administration of a vaccine composition through a nasojejunal or gastrostomy tube, intraduodenal administration of a vaccine composition, and rectal administration, e.g., using suppositories that release a live bacterial vaccine strain described herein to the lower intestinal tract of the alimentary canal.
The term “recombinant” is used to describe non-naturally altered or manipulated nucleic acids, cells transformed, electroporated, or transfected with exogenous nucleic acids, and polypeptides expressed non-naturally, e.g., through manipulation of isolated nucleic acids and transformation of cells. The term “recombinant” specifically encompasses nucleic acid molecules that have been constructed, at least in part, in vitro using genetic engineering techniques, and use of the term “recombinant” as an adjective to describe a molecule, construct, vector, cell, polypeptide, or polynucleotide specifically excludes naturally existing forms of such molecules, constructs, vectors, cells, polypeptides, or polynucleotides.
Cassette, or expression cassette is used to describe a nucleic acid sequence comprising (i) a nucleotide sequence encoding a promoter, (ii) a first unique restriction enzyme cleavage site located 5′ of the nucleotide sequence encoding the promoter, and (iii) a second unique restriction enzyme cleavage site located 3′ of the nucleotide sequence encoding the promoter. The cassette may also contain a multiple cloning site (MCS) and transcriptional terminator within the 5′ and 3′ restriction endonuclease cleavage sites. The cassette may also contain cloned genes of interest.
As used herein, the term “salmonella” (plural, “salmonellae”) and “Salmonella” refers to a bacterium that is a serovar of Salmonella enterica. A number of serovars of S. enterica are known. Particularly preferred salmonella bacteria useful in the invention are attenuated strains of Salmonella enterica serovar Typhimurium (“S. typhimurium”) and serovar Typhi (“S. typhi”) as described herein.
As used herein, the terms “strain” and “isolate” are synonymous and refer to a particular isolated bacterium and its genetically identical progeny. Actual examples of particular strains of bacteria developed or isolated by human effort are indicated herein by specific letter and numerical designations (e.g. strains Ty21a, CMV906, CMV908, CMV906-htr, CMV908-htr, Ty800, holavax, M01ZH09, VNP20009).
The definitions of other terms used herein are those understood and used by persons skilled in the art and/or will be evident to persons skilled in the art from usage in the text.



5. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a comparison of tumor-protease activated toxin with tumor protease inhibitor and protease sensitive toxin expression system.
FIG. 2 shows secreted protease inhibitors.
FIG. 3 shows chimeric colicins.
FIG. 4 shows lytic peptide chimeras.
FIG. 5 shows protease activated lytic peptide chimera prodrugs.
FIG. 6 shows cytolethal distending toxin subunit B (cldtB) chimeras.
FIG. 7 shows repeat in toxin (RTX) family members and hybrid operons.
FIG. 8 shows a non-conjugative bacterium with and without the F′ factor.
FIG. 9 shows segregation of required colicin toxin and immunity factors.
FIG. 10 shows a non-conjugative bacterium capable of releasing phage/phagemids carrying expression constructs for DNA and RNA therapeutics.



6. DETAILED DESCRIPTION OF THE INVENTION
The present invention provides, according to various embodiments, improved live attenuated therapeutic bacterial strains that express one or more therapeutic molecules together with one or more protease inhibitor polypeptides that inhibit local proteases that could deactivate the therapeutic molecules. In particular, one aspect of the invention relates to live attenuated tumor-targeted bacterial strains that may include Salmonella vectoring novel chimeric anti-tumor toxins to an individual to elicit a therapeutic response against cancer. The types of cancer may generally include solid tumors, leukemia, lymphoma and multiple myeloma. In addition, certain of the therapeutic molecules have co-transmission requirements that are genetically unlinked to the therapeutic molecule(s), limiting certain forms of genetic exchange. Another aspect of the invention relates to live attenuated tumor-targeted bacterial strains that may include Salmonella vectoring filamentous phage that encode anti-tumor DNA and RNA molecules to an individual to elicit a therapeutic response against cancer including cancer stem cells. The filamentous phage may also be targeted to tumor matrix cells, and immune cells. Another aspect of the invention relates to reducing or eliminating the bacteria's ability to undergo conjugation, further limiting incoming and outgoing exchange of genetic material.
For reasons of clarity, the detailed description is divided into the following subsections: protease sensitivity; protease inhibitors; targeting ligands; chimeric bacterial toxins; co-expression of protease inhibitors with bacterial toxins, segregation of required colicin cofactors; limiting bacterial conjugation; phage/phagemid producing gram negative bacteria encoding therapeutic DNA and RNA molecules.
6.1. Protease Sensitivity.
The therapeutic proteins of the invention are sensitive to proteases (in contrast pro-aerolysin or urokinase chimeric toxins that are activated by proteases). Protease digestion sites may be added to the therapeutic agent to enhance protease sensitivity. Preferred proteases for conferring greater sensitivity are those that are under-expressed in tumors and over-expressed in normal tissues. Other proteases for which sensitivity sights may be added include tissue plasminogen activator, activated protein C, factor Xa, granzyme (A, B, M), cathepsins, thrombin, plasmin, urokinase, matrix metaloproteaes, prostate specific antigen (PSA) and kallikrein 2.
6.2.1 Protease Inhibitors
Protease inhibitors of the invention are preferably based on known polypeptide inhibitors. The inhibitors include both synthetic peptides and naturally occurring, endogenous peptides.
To result in the desired activity, the peptides should be secreted outside of the bacteria. Accordingly, the peptides are modified by fusing them to secretion signals. The secretion signals may be either N-terminal (derived from ompA, ompF, M13 pIII, cldt) or C-terminal (last 60 amino acids of the E. coli HlyA hemolysin, together with the required HlyBD supplied in trans and endogenous tolC) as shown in FIG. 2. The N-terminal signal sequences are well known and characterized by the presence of a protease cleavage site for an endogenous bacterial protease. Thus, N-terminal signal sequences provide free protease inhibitors, free from the signal sequence. The C-terminal signal sequence may be further engineered to have a protease cleavage site in between the protease inhibitory peptide and the signal sequence. The cleaveage site may be for the same protease that the peptide inactivates. Thus, the protease activates its own inhibitor. The protease cleavage site may also be for a protease other than for the protease inhibitor, thus deactivating another protease. Proteases upregulated within tumors for which protease cleavage sites may be engineered include: tissue plasminogen activator, activated protein C, factor Xa, granzyme (A, B, M), cathepsin, thrombin, plasmin, urokinase, matrix metaloproteaes, prostate specific antigen (PSA) and kallikrein 2.
Suitable protease inhibitors, include, but are not limited to, those listed below.
Furin Inhibitors:
PAAATVTKKVAKSPKKAKAAKPKKAAKSAAKAVKPK SEQ ID NO:1
TKKVAKRPRAKRAA SEQ ID NO:2
TKKVAKRPRAKRDL SEQ ID NO:3
GKRPRAKRA SEQ ID NO:4
CKRPRAKRDL SEQ ID NO:5
CVAKRPRAKRDL SEQ ID NO:6
CKKVAKRPRAKRDL SEQ ID NO:7
RRRRRR L6R (hexa-L-arginine) SEQ ID NO:8
Inhibitors of kallikrein 2:
SRFKVWWAAG SEQ ID NO:9
AARRPFPAPS SEQ ID NO:10
PARRPFPVTA SEQ ID NO:11
Tissue Protease Inhibitor
DSLGREAKCYNELNGCTKIYDPVCGTDGNTYPNECVLCFENRKRQTSILIQKSGPC (serine protease inhibitor, Kazal type 1, mature) SEQ ID NO:12
Other suitable protease inhibitors are described in Rawlings et al., 2010, MEROPS: The Peptidase Database, Nucleic Acids Res. 2010 (Database issue):D227-33, the entirety of which ius expressly incorporated herein by reference. Suitable protease inhibitors also encompass functional fragments, respective homologs, and respective analogs, of the sequences described in Rawlings et al., and also other known peptide protease inhibitors including those described in Brinkmann et al, 1991 Eur J. Biochem 202: 95-99; Dunn et al., 1983 Biochem J 209: 355-362; Feng et al., (WO 2004/076484) PEPTIDE INHIBITORS OF THROMBIN AS POTENT ANTICOAGULANTS); and Markowska et al., 2008, Effect of tripeptides on the amindolytic activities of urokinase, thrombin, plasmin and trypsin. Int. J. Peptide Research and Therapeutics 14: 215-218, each of which is expressly incorporated herein by reference.
Targeting Ligands
Targeting ligands are used to both confer specificity to chimeric proteins or phages, but also to direct internalization. The ligands of various aspects of the present invention are peptides that can be expressed as fusions with other bacterially-expressed proteins. The peptides may be further modified, as for gastrin and bombisin, in being amidated by a peptidylglycine-alpha-amidating monoxygenase or C-terminal amidating enzyme, which is co-expressed in the bacteria that use these peptides using standard molecular genetic techniques.







TABLE 2







Examples of targeting peptides









Peptide sequence or ligand name
Receptor or Target
Reference





TGF-alpha
EGFR



SYAVALSCQCALCRR

Rivero-Muller et al.,


CG-beta

Moleclar and Cellular


SEQ ID NO:13

Endocrinology 2007: 17-




25




Morbeck et al., 1993


AVALSCQCALCRR

Jia et al., Journal of


CG-beta (ala truncation)

Pharmacy and


SEQ ID NO:14

Pharmacology 2008; 60:




1441-1448


Leuteinizing hormone-releasing
LHRH receptor



hormone (LHRH)




pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-




Arg-Pro-Gly CONH2




SEQ ID NO:15




IL2
IL2R
Frankel et al. 2000,




Clinical Cancer Research




6: 326-334.


Tf
TfR
Frankel et al. 2000,




Clinical Cancer Research




6: 326-334.


IL4
IL4R
Frankel et al. 2000,




Clinical Cancer Research




6: 326-334.


GM-CSF
GM-CSFR
Frankel et al. 2000,




Clinical Cancer Research




6: 326-334.



CD-19



Bombesin
Gastrin releasing
Dyba et al., 2004 Crrent



peptide receptor
Pharmacetical Design 10:




2311-2334


Gastrin releasing peptide
Gastrin releasing




peptide receptor



somatostatin octapeptide RC-121




(D-Phe-Cys-Tyr-D-Trp-Lys-Val-




Cys-Thr-NH2




SEQ ID NO:16




somatostatin




Vasoactive intestinal peptide (VIP




Neurtensin)




Parathyroid hormone-related
Parathyroid hormone



protein PTHrP N-terminal 36
receptor G-protein



resides also has nuclear targeting
coupled receptor



KLAKLAKKLALKLA
Proapoptotic peptide



SEQ ID NO:17





Endoglin (CD105)




KCNK9




Mesothelin




EGFR




Mcin



Heat stable enterotoxin (ST)
Guanylyl cyclase C



NSSNYCCELCCNPACTGCY




SEQ ID NO:18




Mature peptide




1 VLSFSPFAQD AKPVESSKEK
Heat stable enterotoxin



ITLESKKCNI AKKSNKSDPE
unprocessed



SMNSSNYCCE LCCNPACTGC




61Y




SEQ ID NO:19




CM-CSF
AML




Alfa(V)Beta(3) integrin




STEAP-1 (six




transmembrane antigen




of the prostate)



CDCRGDCFC
RGD 4C: active
Line et al. 46 (9): 1552.


SEQ ID NO:20
peptide targeting the
(2005) Journal of Nuclear



vβ3 integrin)
Medicine


LGPQGPPHLVADPSKKQGP
bind to the gastrin receptor, also



WLEEEEEAYGWMDF
known in the art as the 



SEQ ID NO:59
cholecystokinin B (CCKB) receptor



(gastrin-34) or big gastrin




MGWMDF




SEQ ID NO:21




N-terminal truncation of gastrin




VPLPAGGGTVLTKM
Gastrin releasing



YPRGNHWAVGHLM
peptide



SEQ ID NO:22




CAYHLRRC
AML
Nishimra et al., 2008. J


SEQ ID NO:23

Biol Chem 283: 11752-




11762


CAY (cys-ala-tyr)
Lymph node homing
Nishimra et al., 2008. J


SEQ ID NO:24

Biol Chem 283: 11752-




11762


RLRR (arg-le-arg-arg)
Cell penetrating
Nishimra et al., 2008. J


SEQ ID NO:25

Biol Chem 283: 11752-




11762


VRPMPLQ
Colonic dysplasia
Hsi u ng et al, Natre


SEQ ID NO:26

Medicin 14: 454-458


HVGGSSV
2622 Radiation-Induced
International Journal of


SEQ ID NO:27
Expression of Tax-
Radiation



Interacting Protein 1
OncologyBiologyPhysics,



(TIP-1) in Tumor
Volume 66, Issue 3, Pages



Vasculature
S555-S556



Binds irradiated tumors
H. Wang, A. Fu, Z. Han,



ie, ones responding to
D. Hallahan



therapy



CGFECVRQCPERC
Lung vasculature—
Mori 2004 Current


SEQ ID NO:28
MOSE
Pharmaceutical Design



Binds membrane
10: 2335-2343



dipeptidase (MDP)



SMSIARL
MURINE PROSTATE
Mori 2004 Current


SEQ ID NO:29
VASCULATURE
Pharmacetical Design 10:




2335-2343


VSFLEYR
MURINE PROSTATE
Mori 2004 Current


SEQ ID NO:30
VASCULATURE
Pharmaceutical Design




10: 2335-2343


Fragment 3 of the high mobility




group (HMG)N2




CKDEPQRRSARLSAKPAPP




KPEPKPKKAPAKK




SEQ ID NO:31




H-VEPNCDIHVMW
VEGF BINDING
(WO/2006/116545)


EWECFERL-NH2
PEPTIDE
SPATIAL CONTROL OF


SEQ ID NO:32

SIGNAL




TRANSDUCTION


RLLDTNRPLLPY
L-PEPTIDE
Let al., 2004. Cancer


SEQ ID NO:33
Nasopharyngeal
Research 64: 8002-8008.



Phage derived—causes




internalization




of phage



RGDLATL truncated
Alfa(v) beta (6) integrin
Shunzi et al. (Kathyll C


RGDLATLRQLAQEDGVVGVR

Brown


SEQ ID NO:34









6.3 Small Lytic Peptides
Small lytic peptides (less than 50 amino acids) are used to construct chimeric proteins for more than one purpose. The chimeric proteins containing lytic peptides may be directly cytotoxic for the cancer cells, and/or other cells of the tumor including the tumor matrix cells and immune cells which may diminish the effects of the bacteria by eliminating them. In order to be cytotoxic they must be secreted (FIGS. 4 and 5) and may be provided with cell specificity by the addition of a targeting ligand. Furthermore, the lytic peptides are useful in chimeric proteins for affecting release from the endosome. Small lytic peptides have been used in the experimental treatment of cancer. However, it is evident that most, if not all, of the commonly used antitumor small lytic peptides have strong antibacterial activity, and thus are not compatible with delivery by a bacterium (see Table 1 of Leschner and Hansel, 2004 Current Pharmaceutical Design 10: 2299-2310, expressly incorporated herein by reference). Small lytic peptides useful in the invention are those derived from Staphylococcus aureus, S. epidermidis and related species, including the phenol-soluble modulin (PSM) peptides and delta-lysin (Wang et al., 2007 Nature Medicin 13: 1510-1514, expressly incorporated herein by reference). The selection of the lytic peptide depends upon the primary purpose of the construct, which may be used in combination with other constructs providing other anticancer features. That is, the therapies provided in accordance with aspects of the present invention need not be provided in isolation, and the bacteria may be engineered to provide additional therapies or advantrageous attributes. Constructs designed to be directly cytotoxic to cells employ the more cytoxic peptides, particularly PSM-alpha-3. Constructs which are designed to use the lytic peptide to affect escape from the endosome use the peptides with the lower level of cytotoxicity, such as PSM-alpha-1, PSM-alpha-2 or delta-lysin.







TABLE 3







Membrane lytic peptides useful in the invention








Peptide and



source
Peptide Sequence





Processed
MAQDIISTISDLVKWIIDTVNKFTKK


<< short >> 
SEQ ID NO:35


active



delta lysin



S aureus



Delta lysin
MMAADIISTI GDLVKWIIDTVNKFKK


processed
SEQ ID NO:36


S epidermitidis



Delta lysin 
MAQDIISTISDLVKWIIDTVNKFTKK


from
SEQ ID NO:37


CA-MRSA



PSM-alpha-1
MGIIAGIIKVIKSLIEQFTGK



SEQ ID NO:38


PSM-alpha-2
MGIIAGIIKFIKGLIEKFTGK



SEQ ID NO:39


PSM-alpha-3
MEFVAKLFKFFKDLLGKFLGNN



SEQ ID NO:40


PSM-alpha-4
MAIVGTIIKIIKAIIDIFAK



SEQ ID NO:41


PSM-beta-1
MEGLFNAIKDTVTAAINNDGAKLGTSIVS IVENGVG



LLGKLFGF



SEQ ID NO:42


PSM-beta-2
MTGLAEAIANTVQAAQQHDSVKLGTSIVDIVANGV



GLLGKLFGF



SEQ ID NO:43









6.4 Chimeric Bacterial Toxins
Chimeric toxins are used to adapt secreted bacterial proteins to provide therapeutic molecules that are effective in treating tumor cells, tumor stem cells as well as immune infiltrating cells. Targeting to a particular cell type uses the appropriate ligand from the Table 2 above or from other known sources.
6.4.1 Chimeric colicins. Colicins lack tumor cell targeting. In the present invention, the colicin targeting and translocation domains are replaced with an M13 pIII-derived signal sequence and truncated membrane anchor together with a targeting ligand. A lytic peptide may also be added. Examples of the unique organization for chimeric colE3, colE7 and col-Ia are shown in FIG. 3.
6.4.2 Chimeric cytolethal distending toxin. Cytolethal distending toxin (cldt) is a three component toxin of E. coli, Citrobacter, Helicobacter and other genera. Cldt is an endonuclease toxin and has a nuclear localization signal on the B subunit. Chimeric toxins are provided that utilize fusion to apoptin, a canary virus protein that has a tumor-specific nuclear localization signal, a normal cell nuclear export signal (FIG. 6). The cytolethal distending toxin B and chimeric cltdB may be expressed as a polycistronic construct consisting of cldtABC. The cytolethal distending toxin B and chimeric cltdB may be expressed as a polycistronic construct consisting containing the typhoid pertussis-like toxin (plt) AB genes.
6.4.3 RTX toxins and hybrid operons. E. coli HlyA(s) operon hlyCABD (+TolC), Actinobacillus actinomycetemcomitans leukotoxin ltxCABD, and a hybrid CABD operon are shown in FIG. 7. The ltxA may be generated as a chimera wherein it contains the C-terminal 60 amino acids of the E. coli HlyA. The ltx genes and chimeras may be expressed together with prtF and/or cyaE.
6.4.4 Saporin and ricin chimeras. Saporin and ricin can be replaced for the active portion of the colicin chimeras (FIG. 3). It can also be generated as a targeting peptide, saporin, HlyA C-terminus.
6.4.5 Cytotoxic necrotic factor (cnf) and Bordetella dermonecrotic factor (dnf) chimeras. Cnf and dnf can be expressed as chimeras, where the N-terminal binding domain (amino acids 53 to 190 of cnf) is replaced with a tumor cell binding ligand, such as TGF-alpha.
6.4.6 Shiga toxin (ST) and shiga-like toxin (SLT) chimeras. ST and SLT chimeras are generated wherein the GB3-binding domain is replaced with a tumor cell binding ligand, such as TGF-alpha.
6.4.7 Subtilase toxin chimeras. Subtilase chimeras are generated by replacing the binding domain with a tumor cell binding ligand, such as TGF-alpha.
6.5 Limiting Bacterial Conjugation.
The fertility inhibition complex (finO and finP), are cloned onto the chromosome using standard genetic techniques such that strains either with or without the pilus resistant to mating with F′ bacteria (FIG. 8). Other known inhibitory factors may also be used.
The F′ pilus factors in a Salmonella strain needed for phage to be able to infect the cell are provided by the F′ plasmid using standard mating techniques from an F′ E. coli. The F′ factor provides other functions such as traD and the mating stabilization which are deleted using standard techniques.
6.6 Co-Expression of Protease Inhibitors with Bacterial Toxins and Determination of Synergy
Each of the bacterial toxins listed herein may be improved in its therapeutic activity by co-expression with a protease inhibitor. Inhibitors are expressed as secreted proteins as described above. The effect of the protease inhibitor on in vitro cytotoxicity is determined using standard cell culture techniques and cytotoxicity assays such as MTT known to those skilled in the arts. The contribution of the protein cytotoxin and protease inhibitors is determined individually and in combination. Synergy may determined using the median effect analysis (Chou and Talaly 1981 Eur. J. Biochem. 115: 207-216) or other standard methods. The assay may be further modified to include addition of a specific protease. The assay may also be used to determine synergy, additivity or antagonism of two or more bacterial cytotoxins. The assay may also be used to determine synergy, additivity or antagonism a bacterial cytotoxin together with a conventional small molecule cytotoxin (e.g., Cisplatin, doxorubicin, irinotecan, Paclitaxel or vincristine), targeted therapeutic (e.g., imatinib, irissa, cetuximab), proteosome inhibitor (bortezomib), mTOR inhibitor. In vivo studies may also be performed with antiangiogenic inhibitors such as Avastin, combretastatin, or thalidomide. In vivo studies with reticuloendothelial system (RES) blocker such as chlodronate which have the potential to improve the circulation time of the bacteria, vascular permeability inducing agents such as bradykinin, hyperthermia or carbogen which have the potential to improve the permeability of the tumor enhancing entry of the bacteria, or aldose reductase inhibitors.
6.7 Segregation of Required Colicin Toxin Cofactors.
The chimeric colicin toxins have active colicin components that require their respective immunity proteins, which are usually genetically linked. By unlinking the two genes and separating them on the chromosome, a single fragment or phage transduction is highly unlikely to contain both elements. Without both elements, the toxin portion cannot be carried and will kill most bacteria. Any additional genes such as other chimeric therapeutic molecules genetically linked to the colicin will also be inhibited from being transferred to other bacteria (FIG. 9)
6.8 Phage/Phagemid Producing Gram-Negative Bacteria Encoding Therapeutic DNA and RNA Molecules (FIG. 10).
The F′ pilus containing bacterium (FIG. 8) with deletions relating to conjugation and is expressing a protease inhibitor (PI) that is secreted into the medium are first infected with a helper phage, such as M13K07 which is able to use the pilus for entry. The helper phage may be further modified to lack an antibiotic resistance maker such as the kanamycin marker. Next, a phagemid (hybrid plasmid:phage which has the F′ origin such as one derived from pEFGP-N1) containing a pIII fusion with a targeting peptide, and optionally, a lytic peptide fusion to pVIII, and one or more therapeutic genes which could be a DNA encoding a functional p53 protein, or a gene encoding small interfering RNA molecules (siRNA) or microRNA (miRNA) molecules or other RNA interfering (RNAi) molecules or constructs that mediate RNA interference for an oncogene such as KRAS is transfected into the bacterial cell. The phagemid may also encode the T7 polymerase, and the effector gene such as one encoding the siRNA and/or miRNA and/or RNAi construct may be driven by the T7 promoter. The phage may also contain self-complementary sequences that induce the formation of double-stranded filamentous phage. Pieto and Sanchez 2007 Biochmica et Biophysica Acta 1770:1081-1084 regarding self-complementary sequences that induce the formation of double-stranded filamentous phage), expressly herein incorporated by reference. Now, the phagemid, in the presence of the helper phage, is replicated as single stranded DNA and packaged into a filamentous phagemid that is secreted outside of the bacterium. Because the phagmid contains pIII fusions with a targeting ligand, such as TGF-alpha, the phage are able to bind to the target cell, enter, release their DNA which then is transcribed into the respective therapeutic molecules and results in an antitumor effect. When administered to a patient with a tumor for which the appropriate receptor has been selected, the bacterium carrying the phagemids results in a therapeutic effect. The effect may be further enhanced by co-administration of camptothecin as described by Burg et al. See, Burg et al., “Enhanced Phagemid Particle Gene Transfer in Camptothecin-treated Carcinoma Cells”, Cancer Research 62: 977-981 (2002), expressly incorporated herein by reference.
7. FIGURE LEGENDS
FIG. 1. Comparison of tumor-protease activated toxin with tumor protease inhibitor and protease sensitive toxin expression. A) Intravenously injected tumor protease activated toxin remains active if it diffuses out of the tumor. B) Intratumoral bacteria co-expressing a protease inhibitor and a protease sensitive toxin achieve high intratumoral activity and degredation following diffusion out of the tumor. The co-expression system results in high intratumoral activity, achieving a therapeutic benefit with low toxicity.
FIG. 2. Secreted protease inhibitors. A) An N-terminal signal sequence from a cytolethal distending toxin gene followed by a protease inhibitor (PI). B) A PI followed by the hlyA C-terminal signal sequence. C) A PI followed by the hlyA C-terminal signal sequence with a protease cleavage site (downward arrow).
FIG. 3. Chimeric colicins. A) An M13 pIII signal sequence with amino acids 1 to 18 followed by a targeting peptide (TGF-alpha), a membrane anchor truncated M13 pIII amino acids 19 to 372 and the C-terminus of ColE3 (ribonuclease). The colicin is secreted, the signal sequence cleaved and the targeting peptide targets the EGFR-expressing cancer cell. B) A lytic peptide is added between the signal sequence and the targeting peptide. Following cleavage of the signal sequence, the targeting peptide localizes to the EFGF-expressing cancer cell and the lytic peptide assists in its release from the endosome. C) A ColE7 (DNAase) chimera. D) A ColE7 chimera with a lytic peptide. E) A Col-Ia (membrane channel forming peptide) chimera. F) A Col-Ia chimera with a lytic peptide.
FIG. 4. Lytic peptide chimeras. A) A lytic peptide followed by the hlyA signal sequence. B) A lytic peptide, targeting peptide (TGF-alpha), hlyA signal peptide chimera. C) The M13 pIII signal sequence followed by a lytic peptide, the membrane anchor truncated M13 pIII amino acids 19 to 372 and a targeting peptide (TGF-alpha). D) The M13 pIII signal sequence followed by a lytic peptide and a targeting peptide (TGF-alpha).
FIG. 5. Protease activated lytic peptide chimera prodrugs. A) A blocking peptide followed by a tumor protease cleavage site, a lytic peptide followed by the hlyA signal sequence. The bracket underneath shows the active portion of the chimera following proteolytic cleavage. B) A blocking peptide followed by a tumor protease cleavage site, a lytic peptide, targeting peptide (TGF-alpha) followed by a second tumor protease cleavage site and the hlyA signal peptide. C) The M13 pIII signal sequence followed by a blocking peptide with a tumor protease cleavage site, a lytic peptide, the membrane anchor truncated M13 pIII amino acids 19 to 372 and a targeting peptide (TGF-alpha). D) The M13 pIII signal sequence followed by a blocking peptide with a tumor protease cleavage site, a lytic peptide, a targeting peptide (TGF-alpha) with a tumor protease cleavage site and the membrane anchor truncated M13 pIII amino acids 19 to 372.
FIG. 6. Cytolethal distending toxin subunit B (cldtB) chimeras. It is understood that full functionality requires cltdA and cltdC. A) CldtB followed by apoptin 1 to 121. B) CldtB followed by apoptin 33 to 121. C) CldtB followed by apoptin 33-46. D) CldtB followed by apoptin 81-121.
FIG. 7. Repeat in toxin (RTX) family members and hybrid operons. A) HlyCABD from E. coli. B) LtxCABD from Actinobacillus. C) A hybrid CABD of E. coli (HlyBD) and Actinobacillus (HlyCA). D) A hybid ltxCA with E. coli BD where the ltxA contains the C-terminal 60 amino acids of HlyA.
FIG. 8. A non-conjugative bacterium with and without the F′ factor. The bacterial chromosome contains a secreted protease inhibitor construct (PI) that results in a secreted protease inhibitor. The chromosome also contains the FinO and FinP genes in order to inhibit conjugation. When present, the F′ factor containing the pilus genes with deletions relating to conjugation in traD and the mating stabilization (MS) results in a pilus expressed by the bacterium.
FIG. 9. Segregation of colicin toxin and required immunity factor(s). The bacterial chromosome has a colicin immunity protein integrated into a neutral sight (e.g., attenuating mutation or IS200 element). The colicin, or colicin hybrid is not linked to the immunity protein, but is distal to it. Other therapeutic molecules may be in the same proximity, such as in a polycistronic organization. Based on this organization, a random DNA fragment, or a portion of the genome packaged by a transducing phage, could not contain the immunity protein. If such a fragment were transferred to another bacterium, expression of the colicin without the immunity protein would kill the bacterium.
FIG. 10. A.) A1. The bacterial chromosome contains a secreted protease inhibitor construct (PI) that results in a secreted protease inhibitor. A2. The F′ factor containing the pilus genes with deletions relating to conjugation in traD and the mating stabilization results in a pilus expressed by the bacterium. The FinO and FinP genes are inserted onto the F′ in order to further inhibit conjugation. A3. A helper phage such as M13K07 provides phage functions for replication and packaging. A4. A phagemid (hybrid plasmid:phage which has the F′ origin) containing a pIII fusion with a targeting peptide, and optionally, a lytic peptide fusion to pVIII, and one or more therapeutic genes which could be a DNA encoding a functional p53 protein, or a gene encoding small interfering RNA or microRNA molecules (siRNA or miRNA) that mediate RNA interference for an oncogene such as KRAS has been transfected into the bacterial cell. B. Now, the phagemid, in the presence of the helper phage, is replicated as single stranded DNA and packaged into a filamentous phagemid that is secreted outside of the bacterium. Because the phagmid contains pIII fusions with a targeting ligand, such as TGF-alpha, the phage are able to bind to the target cell (C), enter, release their DNA which then is transcribed into the respective therapeutic molecules and results in an antitumor effect. When administered to a patient with a tumor for which the appropriate receptor has been selected, the bacterium carrying the phagemids results in a therapeutic effect.
8. EXAMPLES
In order to more fully illustrate the invention, the following examples are provided.
8.1. Example 1
Secreted Protease Inhibitors
Secreted protease inhibitors are generated using standard molecular genetic techniques and expressed in bacteria using methods known to those skilled in the arts, operably linking a promoter, ribosomal binding site and initiating methionine if not provided by the first portion of the construct. The construct may either be a plasmid or a chromosomal integration vector, for which many different integration sites exist, including but not limited to any of the attenuation mutations or any of the IS200 elements. The constructs may also be polycistronic, having multiple genes and/or gene products separated by ribosomal binding sites. The different forms of the protease inhibitor constructs are shown in FIG. 2. The constructs used have three basic forms: 1) An N-terminal signal sequence, such as that from M13pIII MKKLLFAIPLVVPFYSHS SEQ ID NO:44, followed by a protease inhibitor such as the furin inhibitor GKRPRAKRA; 2) a protease inhibitor such as the furin inhibitor GKRPRAKRA SEQ ID NO:45 followed by the C-terminal signal sequence of hlyA STYGS QDYLNPLINEISKIISAAGNLDVKEERSAASLLQLSGNASDFS YGRNSITLTASA SEQ ID NO:46, or 3) a protease inhibitor such as the furin inhibitor GKRPRAKRA SEQ ID NO:47, followed by a furin cleavage signal RXRAKR↓DL SEQ ID NO:47 NO:57 followed by the C-terminal signal sequence of hlyA STYGSQDYLNPLINEISKIISAAGNLDVKEERSAASLLQLSGNASDFSYGRNSITLTASA SEQ ID NO:48
8.2 Example 2
A Targeted Colicin E3 (Cole3) Chimera
First, the colicin colE3 immunity protein is synthesized as an expression cassette and cloned into a chromosomal localization vector for an integration site distal to the that of the chimeric effector gene vector described below, e.g., an IS200 deletion vector at location. The amino acid sequence of the immunity protein is given as:
MGLKLDLTWFDKSTEDFKGEEYSKDFGDDGSVMESLGVPFKDNVNNGCFDVIAEWVP LLQPYFNHQIDISDNEYFVSFDYRDGDW SEQ ID NO:49
The sequence is reverse translated using codons optimal for Salmonella. The entire chimeric effector protein and expression cassette components are synthesized using standard DNA synthesis techniques at a contract DNA synthesis facility and integrated into the chromosome (Donnenberg and Kaper, 1991, Low et al., 2003, each of which is expressly incorporated herein by reference). The recipient stain can be any tumor-targeted gram-negative bacterium.
This example follows the chimeric pattern shown in FIG. 3A. This chimera is targeted to cancer cells over-expressing EGFR via a TGF-alpha ligand. The chimera consists of the M13 filimenous phage pIII protein 18 amino acid signal sequence, followed by the natural alanine and a 3 glycine spacer. The spacer is followed by the mature 50 amino acid peptide for TGF-alpha, the remaining pIII protein truncated after amino acid 372 of pIII, followed by the enzymatically active (ribonuclease) C-terminus of colicin E3, followed by a stop signal. The complete amino acid sequence is:
MKKLLFAIPLVVPFYSHSAGGGVVSHFNDCPDSHTQFCFHGTCRFLVQEDKPACVCHSG YVGARCEHADLLAAETVESCLAKSHTENSFTNVWKDDKTLDRYANYEGCLWNATGVV VCTGDETQCYGTWVPIGLAIPENEGGGSEGGGSEGGGSEGGGTKPPEYGDTPIPGYTYIN PLDGTYPPGTEQNPANPNPSLEESQPLNTFMFQNNRFRNRQGALTVYTGTVTQGTDPVK TYYQYTPVSSKAMYDAYWNGKFRDCAFHSGFNEDLFVCEYQGQSSDLPQPPVNAGGG SGGGSGGGSEGGGSEGGGSEGGGSEGGGSGGGSGSGDFDYEKMANANKGAMTENADE NALQSDAKGKLDSVATDYGAAIDGFIGDVSGLANGNGATGDFAGSNSQMAQVGDGDN SPLMNNFRQYLPSLPQSVECRFAHDPMAGGHRMWQMAGLKAQRAQTDVNNKQAAFD AAAKEKSDADAALSSAMESRKKKEDKKRSAENNLNDEKNKPRKGFKDYGHDYHPAPK TENIKGLGDLKPGIPKTPKQNGGGKRKRWTGDKGRKIYEWDSQHGELEGYRASDGQHL GSFDPKTGNQLKGPDPKRNIKKYL* SEQ ID NO:50
The entire chimeric effector protein and expression cassette components are synthesized using standard DNA synthesis techniques, for example, at a contract DNA synthesis facility, and cloned into a chromosomal localization vector, e.g., an IS200 deletion vector, and integrated into the chromosome (Donnenberg and Kaper, 1991, Low et al., 2003, each of which is expressly incorporated herein by reference).
8.3 Example 3
A Targeted Colicin Chimera Containing a Lytic Peptide Resulting in Endosomal Release and/or Increased Anti-Cancer Cell Cytotoxicity
The lytic peptide PSM-alpha-3 is inserted between the pIII signal sequence and the TGF-alpha (FIG. 3B). The complete sequence of the construct is as follows:
MKKLLFAIPLVVPFYSHSAMEFVAKLFKFFKDLLGKFLGNN VVSHFNDCPDSHTQFCFHGTCRFLVQEDKPACVCHSGYVGARCEHADLLAAETVESCL AKSHTENSFTNVWKDDKTLDRYANYEGCLWNATGVVVCTGDETQCYGTWVPIGLAIP ENEGGGSEGGGSEGGGS EGGGTKPPEYGDTPIPGYTYINPLDGTYPPGTEQNPANPNPSL EESQPLNTFMFQNNRFRNRQGALTVYTGTVTQGTDPVKTYYQYTPVSSKAMYDAYWN GKFRDCAFHSGFNEDLFVCEYQGQSSDLPQPPVNAGGGSGGGSGGGSEGGGSEGGGSE GGGSEGGGSGGGSGSGDFDYEKMANANKGAMTENADENALQSDAKGKLDSVATDYG AAIDGFIGDVSGLANGNGATGDFAGSNSQMAQVGDGDNSPLMNNFRQYLPSLPQSVEC RFAHDPMAGGHRMWQMAGLKAQRAQTDVNNKQAAFDAAAKEKSDADAALSSAMES RKKKEDKKRSAENNLNDEKNKPRKGFKDYGHDYHPAPKTENIKGLGDLKPGIPKTPKQ NGGGKRKRWTGDKGRKIYEWDS QHGELEGYRASDGQHLGSFDPKTGNQLKGPDPKRN IKKYL SEQ ID NO:51
8.4 Example 4
A Chimeric Colicin E7
As for the other colicin E3 constructs, the colicin colE7 immunity protein is synthesized as an expression cassette and cloned into a chromosomal localization vector for an integration site distal to the that of the chimeric effector gene vector described below, e.g., an IS200 deletion vector at location.
The genetic construct of the first colicin E7 chimera follows the same pattern as shown in FIG. 3A, except that the ColE3 C-terminus is replaced with the colE7 (a DNAase) C-terminus comprising amino acids 444 to 576 (FIG. 3 C).
The genetic construct of the second colicin E7 chimera follows the same pattern as shown in FIG. 3C, except that the lysis peptide is inserted between the M13 pIII signal sequence and the targeting peptide (TGF-alpha) (FIG. 3D).
8.5 Example 5
A Chimeric Colicin Ia
As for the other colicin E3 constructs, the colicin Ia immunity protein is synthesized as an expression cassette and cloned into a chromosomal localization vector for an integration site distal to the that of the chimeric effector gene vector described below, e.g., an IS200 deletion vector at location.
The genetic construct of the first colicin Ia chimera follows the same pattern as shown in FIG. 3A, except that the ColE3 C-terminus is replaced with the Ia (pore forming) C-terminus comprising amino acids 450 to 626 (FIG. 3 E).
The genetic construct of the second colicin Ia chimera follows the same pattern as shown in FIG. 3B, except that the lysis peptide is inserted between the M13 pIII signal sequence and the targeting peptide (TGF-alpha) (FIG. 3F).
8.6 Example 6
Expression of a C-Terminal Amidating Enzyme Required to Post-Translationally Modify Gastrin and Bombisin Targeting Peptides
A C-terminal amidating enzyme composition known form serum or plasma which comprises a C-terminal amidating enzyme capable of amidating a C-terminal glycine which amidates the carboxy terminus of the C-terminal glycine of a peptide terminating in Gly-Gly.
The enzyme participating in such amidation is called peptidylglycine-α-amidating monoxygenase (C-terminal amidating enzyme) (EC.1.14.17.3) (Bradbury et al, Nature, 298, 686, 1982: Glembotski et al, J. Biol, Chem., 259, 6385, 1984, expressly incorporated herein by reference), is considered to catalyze the following reaction:
—CHCONHCH2 COOH−CHCONH2+glyoxylic acid
is produced by the recombinant.
8.7 Example 7
Expression of Antitumor Lytic Peptides
Examples of antitumor lytic peptides are shown in FIG. 4. It is understood that those peptides utilizing the hlyA signal sequence requires hlyBD in trans together with a functional tolC. The lytic peptide constructs consist of A) lytic peptide joined to the HlyA signal sequence, B) lytic peptide, targeting peptide, signals sequence, C) M13 pIII signal sequence, lytic peptide, M13 pIII amino acids 19 to 372, targeting peptide, D) M13 signal sequence, lytic peptide, targeting peptide, M13 pIII amino acids 19 to 372.
8.8 Example 8
Expression of Antitumor Lytic Peptide Prodrugs
Examples of antitumor lytic peptide prodrugs are shown in FIG. 5. It is understood that those peptides utilizing the hlyA signal sequence requires hlyBD in trans together with a functional tolC. The lytic peptide prodrug constructs consist of A) a neutral (e.g., beta sheet) blocking peptide of 50 amino acids, a protease cleavage site shown by downward arrow (for a protease not being blocked by a protease inhibitor), a lytic peptide, and the hlyA signal sequence, which may contain the same protease cleavage site shown by a downward arrow, B) a neutral (e.g., beta sheet) blocking peptide of 50 amino acids, a lytic peptide, a targeting peptide (e.g., TGF-alpha), a protease cleavage site shown by downward arrow (for a protease not being blocked by a protease inhibitor), and the hlyA signal sequence, which may contain the same protease cleavage site shown by a downward arrow, C) the M13 pIII signal sequence, a blocking peptide, a protease cleavage sequence, a lytic peptide, M13 pIII amino acids 19 to 372, and a targeting peptide (e.g., TGF-α), and D) the M13 pIII signal sequence, a blocking peptide, a protease cleavage sequence, a lytic peptide, a targeting peptide (e.g., TGF-alpha), and M13 pIII amino acids 19 to 372.
8.9 Example 9
Cytolethal Distending Toxin cltdB Fusion with Apoptin (FIG. 6)
A cytolethal distending toxin subunit B with tumor-specific nuclear localization and normal cell nuclear export is generated by a fusion with apoptin containing a five glycine linker in between (FIG. 6A). The complete sequence of the construct is as follows:
MKKYIISLIVFLSFYAQADLTDFRVATWNLQGASATTESKWNINVRQLIS GENAVDILAVQEAGSPPSTAVDTGTLIPSPGIPVRELIWNLSTNSRPQQV YIYFSAVDALGGRVNLALVSNRRADEVFVLSPVRQGGRPLLGIRIGNDAF FTAHAIAMRNNDAPALVEEVYNFFRDSRDPVHQALNWMILGDFNREPADL EMNLTVPVRRASEIISPAAATQTSQRTLDYAVAGNS VAFRPSPLQAGIVY GARRTQISSDHFPVGVSRRGGGGGMNALQEDTPPGPSTVFRPPTSSRPLETPHCREIRIGI AGITITLSLCGCANARAPTLRSATADNSESTGFKNVPDLRTDQPKPPSKKRSCDPSEYRV SELKESLITTTPSRPRTAKRRIRL SEQ ID NO:52
8.10 Example 10
Cytolethal Distending Toxin cltdB Fusion with a Truncated Apoptin
A cytolethal distending toxin subunit B with tumor-specific nuclear localization and normal cell nuclear export is generated by a fusion with a truncated apoptin amino acids 33 to 121 containing a five glycine linker in between (FIG. 6B). The complete sequence of the construct is as follows:
MKKYIISLIVFLSFYAQADLTDFRVATWNLQGASATTESKWNINVRQLIS GENAVDILAVQEAGSPPSTAVDTGTLIPSPGIPVRELIWNLSTNSRPQQV YIYFSAVDALGGRVNLALVSNRRADEVFVLSPVRQGGRPLLGIRIGNDAF FTAHAIAMRNNDAPALVEEVYNFFRDSRDPVHQALNWMILGDFNREPADL EMNLTVPVRRASEIISPAAATQTSQRTLDYAVAGNS VAFRPSPLQAGIVY GARRTQISSDHFPVGVSRRGGGGGITPHCREI RIGIAGITITLSLCGCANARAPTLRSATADNSESTGFKNVPDLRTDQPKPPSKKRSCDPSE YRVSELKESLITTTPSRPRTAKRRIRL SEQ ID NO:53
8.11 Example 11
Cytolethal Distending Toxin cltdB Fusion with a Truncated Apoptin
A cytolethal distending toxin subunit B with tumor-specific nuclear retention signal is generated by a fusion with a truncated apoptin amino acids 33 to 46 containing a five glycine linker in between (FIG. 6C). The complete sequence of the construct is as follows:
MKKYIISLIVFLSFYAQADLTDFRVATWNLQGASATTESKWNINVRQLIS GENAVDILAVQEAGSPPSTAVDTGTLIPSPGIPVRELIWNLSTNSRPQQV YIYFSAVDALGGRVNLALVSNRRADEVFVLSPVRQGGRPLLGIRIGNDAF FTAHAIAMRNNDAPALVEEVYNFFRDSRDPVHQALNWMILGDFNREPADL EMNLTVPVRRASEIISPAAATQTSQRTLDYAVAGNSVAFRPSPLQAGIVY GARRTQISSDHFPVGVSRRGGGGGIRIGIAGITITLSL SEQ ID NO:54
8.12 Example 12
Cytolethal Distending Toxin cltdB Fusion with a Truncated Apoptin
A cytolethal distending toxin subunit B with a normal cell nuclear export signal is generated by a fusion with a truncated apoptin amino acids 81 to 121 containing a five glycine linker in between (FIG. 6D). The complete sequence of the construct is as follows:
MKKYIISLIVFLSFYAQADLTDFRVATWNLQGASATTESKWNINVRQLIS GENAVDILAVQEAGSPPSTAVDTGTLIPSPGIPVRELIWNLSTNSRPQQV YIYFSAVDALGGRVNLALVSNRRADEVFVLSPVRQGGRPLLGIRIGNDAF FTAHAIAMRNNDAPALVEEVYNFFRDSRDPVHQALNWMILGDFNREPADL EMNLTVPVRRASEIISPAAATQTS QRTLDYAVAGNSVAFRPSPLQAGIVY GARRTQISSDHFPVGVSRRGGGGGTDQPKPPSKKRSCDPSEYRVSELKESLITTTPSRPRT AKRRIRL SEQ ID NO: 55
8.13 Example 13
Exchange of the Variable Loop in cldtB to Enhance Activity
The amino acid sequence FRDSRDPVHQAL SEQ ID NO:56 which is associated with dimerization and inactivation can be exchanged for the loop NSSSSPPERRVY SEQ ID NO:56 from Haemophilus which is associated with stabile retention of cytotoxicity.
8.14 Example 14
Expression of Repeat in Toxin (RTX) Family Members
RTX family members, including E. coli hemolysin operon hlyCABD and Actinobacillus actinomycetemcomitans leucotoxin ltxCABD are expressed in coordination with protease inhibitors as shown in FIG. 7. E. coli hemolysin operon hlyCABD is expressed as a non-chimera (FIG. 7A). Actinobacillus actinomycetemcomitans leucotoxin ltxCABD operon is expressed as either a non-hybrid (FIG. 7B) or as a hybrid (FIG. 7C). It is understood that a functional tolC gene is required in the gram-negative bacterial strain for functional expression of each of these operons.
It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

## Claims

1. An isolated genetically engineered bacterium adapted for administration to a human, wherein the genetically engineered bacterium co-expresses at least one protease sensitive therapeutic molecule and at least one protease inhibitor in sufficient quantity to increase a therapeutic effect of the at least one protease sensitive therapeutic molecule at a target tissue of the human that contains a protease effective for degrading the at least one protease sensitive therapeutic molecule and which is inhibited by the at least one protease inhibitor.

2. A bacterium according to claim 1, wherein the target tissue is a solid tumor.

3. A bacterium according to claim 1, wherein the target tissue comprises multiple myeloma.

4. A bacterium according to claim 1, wherein the target tissue is enriched in inflammatory immune cells.

5. A bacterium according to claim 1, wherein the bacterium is genetically engineered to express the therapeutic molecule, selected from the group consisting of a peptide or protein, toxin, chimeric toxin, cytokine, antibody, bispecific antibody including single chain antibodies, chemokine, and a prodrug converting enzyme.

6. A bacterium according to claim 5, wherein the therapeutic molecule comprises a toxin selected from the group consisting of one or more of: cytolethal distending toxin (cldt), cytotoxic nectrotic factor (cnf), dermonecrotic factor (dmf), shiga toxin and shiga-like toxin, colicin colE3, colicin colE7, colicin col-Ia, membrane lytic peptides from Staphalococcus, leucotoxin, leuckotoxin:HlyA hybrid, heat stable enterotoxin, autotransporter toxins picU, autotransporter toxins espC, autotransporter toxins sat, chlostridium enterotoxin, aerolysin, typhoid toxin, subtilase, Bordetella adenylate cyclase toxin, pertussus toxin, and porB.

7. A bacterium according to claim 1, wherein the therapeutic molecule comprises cldt which is fused to a peptide containing the nuclear localization signal from apoptin.

8. A bacterium according to claim 1, wherein the therapeutic molecule comprises typhoid toxin fused to a nuclear localization signal from apoptin.

9. A bacterium according to claim 1, wherein the therapeutic molecule comprises a colicin col-Ia.

10. A bacterium according to claim 1, wherein the therapeutic molecule comprises a colicin, in which targeting and translocation sequences are replaced with an M13 pIII signal sequence fused to a targeting peptide, followed by a membrane anchor-truncated M13 pIII and fused to the C-terminal catalytic portion of the colicin.

11. A bacterium according to claim 10, wherein the targeting peptide is the mature form of TGF-alpha.

12. A bacterium according to claim 10, wherein a Staphalococcus lytic peptide is inserted between the M13 signal sequence and the targeting peptide.

13. A bacterium according to claim 1 where the protease inhibitor that is targeted is furin.

14. A bacterium according to claim 1, wherein the bacterium is genetically engineered to be conjugation deficient.

15. A bacterium according to claim 14, wherein the therapeutic molecule comprises a phage or phagemid.

16. A bacterium according to claim 15, wherein the phage or phagemid encodes a therapeutic DNA molecule which encodes the p53 suppressor gene.

17. A bacterium according to claim 15, wherein the phage or phagemid delivers a therapeutic RNA molecule comprising at least one of small interfering RNA (siRNA) mediating RNA interference (RNAi).

18. A pharmaceutically acceptable formulation suitable for administration to a mammal, comprising a live isolated genetically engineered bacterium that is configured to co-express: (a) at least one protease sensitive therapeutic molecule, and (b) at least one protease inhibitor within a target tissue wherein the isolated live genetically engineered bacterium is adapted to grow within the target tissue of the human to produce in situ the at least one protease sensitive therapeutic molecule and the at least one protease inhibitor, the target tissue containing a protease effective for degrading the at least one protease sensitive therapeutic molecule and which is inhibited by the at least one protease inhibitor.

19. An isolated genetically engineered live bacterium configured for pharmaceutically acceptable administration to a human, which is adapted to selectively replicate within a selected tissue type within the human, and concurrently produce within the selected tissue type at least one protease-sensitive cytotoxic molecule which is degradable by proteases within the selected tissue type, and at least one protease inhibitor to inhibit the proteases within the selected tissue type from degrading the protease sensitive cytotoxic molecule, and wherein the isolated genetically engineered live bacterium is further configured to expose a tissue adjacent the selected tissue type to a sufficiently low concentration of the at least one protease inhibitor to permit degradation by a protease within the tissue adjacent to the selected tissue type of a portion of the protease sensitive cytotoxic molecule produced by the genetically engineered live bacteria in the selected tissue type which is present in the adjacent tissue.

20. The isolated genetically engineered live bacterium according to claim 19, wherein the isolated genetically engineered live bacterium is adapted to selectively target and replicate in the selected tissue type which underexpresses a protease which is active to degrade the protease sensitive cytotoxic molecule and is inhibited by the protease inhibitor, with respect to the adjacent tissue.