Compounds and related methods for mutant p53 reactivation

Ketoamine compounds and related methods for reactivation of tumor suppressor protein p53.

BACKGROUND OF THE INVENTION

The protein p53 is an important tumor suppressor. Under normal conditions, cells do not contain high levels of this protein. If a healthy cell is damaged, p53 is expressed and its cellular level increases, followed by inhibition of cell growth or programmed cell death (apoptosis). In order to induce apoptosis, p53 must bind to a specific DNA sequence. Numerous studies have demonstrated that p53 plays a very important role in directing a cell to stop growing or to undergo apoptosis. Therefore, p53 has been recognized as one of the most important guardians in the body to prevent damaged cells from developing into tumors. In approximately 50% of human tumors, a mutated form of p53 (mutant p53) is present that is unable to bind target DNA sequences, allowing an unregulated growth and division of such tumor cells. Indeed, mutation of p53 is considered the most frequent genetic alteration occurring in human cancer. Further, tumors associated with mutant p53 are often more resistant to chemotherapy than tumors with wild-type p53.

However, once a mutant p53 protein regains the ability to bind DNA, the tumor suppressor activity is restored and apoptosis is induced, consequently killing the cancer cell. The potential for small organic molecules to reactivate mutant forms of this protein has created a revolutionary new strategy for attacking cancer. In tumor cells, mutant forms of p53 are commonly present at elevated levels compared to wild-type p53 in healthy cells. This imbalance offers the possibility of selectively killing cancer cells over healthy cells via reactivation of mutant p53, which could lead to medications without the devastating side effects often associated with conventional chemotherapy. In addition to potential clinical applications, the ability to reactivate mutant p53 has also generated a fundamentally new approach in biomedical research: the possibility of designing organic molecules to re-establish the normal functions of a mutated protein.

Random screenings of combinatorial libraries have identified a handful of small organic molecules that affect the activity of p53 (FIG. 1). One of these molecules (PFTA) inhibits the DNA binding activity of wild-type p53, while others (e.g., CP-31398, CP-257042, PRIMA-1) restore or reactivate the DNA-binding activity of mutant p53 proteins. Although each of these molecules is structurally very different, there are common features among them that indicate the types of molecules to target p53. For example, each of these molecules has one or more amine functional groups that convey a net cationic charge under aqueous or physiological conditions. Most of these compounds also have aromatic groups, suggesting that aromatic-aromatic interactions promote binding to p53. In compounds CP-31398 and CP-257042, aromatic portions of these molecules are similar to known compounds that intercalate between the bases of DNA (such as ethidium bromide and acridine). It has been suggested that these molecules restore DNA-binding activity to p53 by binding simultaneously to both DNA and p53. However, while intercalation of aromatic groups into DNA is a favorable process, aromatic intercalators can also have mutagenic properties and thus are not suitable motifs for further development.

Among the compounds inFIG. 1, PRIMA-1 is an interesting target: it lacks an aromatic group (and therefore should not intercalate into DNA), yet it still restores DNA-binding activity to mutant p53. Although detailed knowledge about the interactions of PRIMA-1 with p53 are not known, it most likely involves a positioning of cationic charge and hydrogen bonding groups into proper orientations for p53 protein binding. This binding event may somehow induce a conformational change in mutant p53 such that DNA binding is restored. Alternatively, PRIMA-1 could also interact with a different protein target that then affects p53. However, the chemistry en route to PRIMA-1 precludes most structural analogs. The synthesis of PRIMA-1 does not readily allow introduction of chemical modifications, limiting access to analogs that target different mutant forms of p53 or derivatives that probe the mechanism of action.

P53 reactivation has been an on-going concern in the art. As outlined above, new approaches in organic chemistry are needed to synthesize new molecules that interact with p53. By examining the activity of such novel compounds, structure-activity relationships can be determined that will provide crucial information for development of new medications and understanding the mechanism(s) of action. These results can provide important insights into p53 reactivation and possibly new cancer chemotherapies.

SUMMARY OF THE INVENTION

In light of the foregoing, it is an object of the present invention to provide a wide range of readily-synthesized compositions and/or methods for their use in the inhibition of tumor cell growth, reactivation of the tumor suppressor function of mutant p53 and/or examination of the related DNA binding mechanism of reactivated p53, thereby addressing various concerns of the prior art, including those outlined above. It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more other aspects can meet certain other objectives. Each objective may not apply equally, in all its respects, to every aspect of this invention. As such, the following objects can be viewed in the alternative with respect to any one aspect of this invention.

It is an object of the present invention to provide one or more compounds or compositions capable of restoring wild-type DNA p53 binding capabilities to mutant p53 protein, in particular and without limitation, compounds having the general structural scaffold of either compound 4 or compound 7.

It can be another object of the present invention to provide a structural scaffold for p53 reactivating compounds in which multiple moieties or functional groups can be readily substituted in order to examine structure-activity relationships between each such moiety or functional group and the DNA binding mechanism of p53.

It can also be an object of the present invention to identify structural or functional moieties of new p53 reactivating compounds or compositions, as recited above, to selectively target specific types of cancer cells over non-cancerous cells.

It can be a related object to provide one or more compositions with a degree of conformational control, as described herein, that interact with mutant p53, having a functional group structure so as to achieve or induce selective p53 binding, thereby inhibiting the growth of cancerous tumors.

It can be another object of the present invention to provide a method of using compounds and/or compositions, of the type consistent with the preceding objectives, to reactivate p53 binding capabilities in order to inhibit or prevent the growth of cancer cells.

It can be a related object of the present invention to provide a method for characterizing the structure-activity relationship of compounds comprising a structural scaffold, as described herein, in order to design anticancer therapies that selectively target and treat a specific type of cancer.

Other objects, features, benefits and advantages of the present invention will be apparent from this summary and its descriptions of various preferred embodiments, and will be readily apparent to those skilled in the art having knowledge of mutant p53 and p53 reactivation. Such objects, features, benefits and advantages will be apparent from the above as taken in conjunction with the accompanying examples, data, figures and all reasonable inferences to be drawn therefrom.

Accordingly, the present invention relates to a new class of compounds readily synthesized via conventional methods and believed to function via reactivation of mutant p53 protein. The core organic structure of the newly developed compounds allows for facile introduction of different functional groups so that structure-activity relationships for reactivation of mutant p53 can be readily prepared and rapidly explored. Furthermore, the approach is quite versatile, allowing creation of compounds to target different forms of mutant p53 or access to compounds specifically designed to probe the mechanism of p53 reactivation.

In part, the present invention can comprise one or more compounds of a formula

and salts thereof. In such compounds, R1is H; R2is selected from phenyl and substituted phenyl moieties; X is selected from H, hydroxymethyl and acetoxymethyl; and Y is acetoxymethyl. In certain embodiments thereof, R2is phenyl. In certain other embodiments, such a phenyl moiety can be halo-substituted. Without limitation, as illustrated below, a fluoro-substituted phenyl moiety can be incorporated into one or more of such compounds. Likewise, the compounds of this invention can incorporate various other halo-substituent(s), as would be understood by those skilled in the art made aware of this invention. Regardless, where X is H, such a compound can be selected from the (R)-enantiomer, the (S)-enantiomer and a racemic mixture thereof. Salts of such compounds can include those as would be understood by those skilled in the art made aware of this invention. Without limitation, in particular, ammonium salts can comprise the conjugate base of a protic acid.

In various other embodiments, this invention can comprise one or more compounds of a formula

and salts thereof, wherein R1and R3can be independently selected from H, alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, aromatic, substituted aromatic, acyl and substituted acyl moieties; R2can be selected from alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, alkoxy, substituted alkoxy, aromatic, substituted aromatic, heterocyclic, substituted heterocyclic, acyl and substituted acyl moieties; R4can be selected from H, alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, acyl and substituted acyl moieties; and R5can be selected from H, alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, alkoxy and substituted alkoxy and CH2OR4. In certain embodiments thereof, R2can be phenyl or substituted phenyl, such substitutions including but limited to one or more alkyl, substituted alkyl and/or halogen moieties. Without limitation, one or more embodiments can comprise a fluoro-substituted phenyl moiety. Likewise, other such R2moieties can comprise one or more of the aforementioned substituents. In certain other embodiments, without regard to substitution, R2can comprise an acyl moiety, such moieties including but not limited to acetyl, propanecarbonyl and benzenecarbonyl moieties. Likewise, without regard to identity of R2, R4can comprise an acyl moiety. Independently, in addition to those embodiments mentioned above, R5can likewise comprise such an acyl moiety.

Without restriction to the preceding compounds, the present invention can also comprise a method of using a ketoamine structural component to examine a structural activity relationship. Such a method comprises (1) providing a compound of a formula

and salts thereof, wherein R1and R3can be independently selected from H, alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, aromatic, substituted aromatic, acyl and substituted acyl moieties; R2can be selected from alkyl and substituted alkyl, including cyclic alkyl and substituted cyclic alkyl, alkoxy, substituted alkoxy, aromatic, substituted aromatic, heterocyclic, substituted heterocyclic, acyl and substituted acyl moieties; X and Y can be independently selected from H, alkyl, substituted alkyl, acyl and substituted acyl moieties; (2) contacting such a compound with cells expressing a mutant p53 protein; and (3) determining activity of such a compound against such cells. Moieties R1-R3, X and Y include those discussed above. Chosen or selective change of at least one such moiety can be made to determine affect of such a change on the activity of such a compound.

In further embodiments, the present invention can comprise a method of inhibiting growth of cells expressing a mutant p53 protein. Such a method comprises (1) providing cells expressing a mutant p53 protein; and contacting said cells with a compound of a formula

and salts thereof, wherein moieties R1-R5include those discussed above in conjunction with such a compound. In alternate embodiments, the present invention can comprise a method of using a phenylketone compound to selectively inhibit growth of cells expressing a mutant p53 protein. Such a method comprises (1) providing a phenylketone compound of a formula

and salts thereof, wherein moieties R1, R2, X and Y include those discussed above; and (2) contacting such a compound with cells expressing a mutant p53 protein.

For purposes of illustration, compounds of the present invention can include but are not necessarily limited to those available from a scaffold affording a spatial arrangement functionally comparable to but without the structural and chemical impediments of PRIMA-1. A schematic structural evolution is illustrated inFIG. 2. Such a scaffold is not limited by the bicyclic core of PRIMA-1 and thus, provides more flexibility in compound design and synthesis.

FIG. 2illustrates an approach to the development of certain compositional aspects of this invention, from PRIMA-1.FIG. 3shows, by way of compound 4, the design flexibility available with this invention as compared to the prior art (e.g., PRIMA-1). Several such compounds, as illustrated inFIGS. 4-5, can be prepared from 2-aminoacetophenone, with Boc protection, followed by side chain introduction using one or two equivalents of formaldehyde in the presence of base. Boc removal optionally with acetylation, gives desired amines and/or the corresponding acid salts. It will be readily appreciated by those skilled in the art that starting materials, other than 2-aminoacetophenone, including other ketones or substituted ketones providing a comparable chemical structure, scaffold and/or spatial orientation can be used.

Likewise, compounds within the bis and mono-sidechain series were prepared with varying functionality at the amino, hydroxyl, and carbonyl positions. Initially, compounds were prepared starting from 2-aminoacetophenone hydrochloride, and all molecules with one sidechain were racemic (Table 1, 1-7, 10-12).

Cellular growth studies were performed on Saos-2 cells, derived from a human osteosarcoma cancer cell line, according to the method described in Example 44. The cells had either no p53 (null) or mutant (mt) p53 at residues 175 and/or 281 (R175H and R281G, respectively). Selective arrest of mutant cells indicates good anticancer activity.

Compound 7 was particularly effective at selectively killing cells expressing R175H and R281G p53 mutants at lower concentrations than PRIMA-1 (racemic 7,FIG. 6B). Compound 4 also showed selectivity for R281G mutants (FIG. 6A). It should be noted that PRIMA-1 is also toxic to p53-null cells at slightly higher concentrations (75 μM), an observation applicable to the design of derivatives more potent and less toxic for therapeutic applications.

These findings are notable, in that the complex PRIMA-1 scaffold can be simplified to the structures of compounds 4 and 7 with the overall activity retained; and that compounds with acetate groups show activity while PRIMA-1 functions without acetate substitution. The present invention is not limited to any particular mechanism of action, and an understanding of any such mechanism is not necessary to practice this invention. However, it is contemplated that these results indicate that compounds 4 and 7 could have an alternative mechanism of action than PRIMA-1, implying that there might be several pathways for reactivating mutant p53, pathways which can be taken using the compounds of this invention.

The positive results obtained with racemic 7 underlined the need to produce both enantiomers of 7 (8 and 9). Therefore, an asymmetric synthesis was developed to produce enantiomerically pure material.

Starting from serine (commercially available as either enantiomer), a synthesis of both enantiomers of 7 was developed (Scheme 1). The first step toward (S)-7 (i.e. molecule 8) converted N-Boc-D-serine to Weinreb amide 21. Hydroxyl group protection afforded 22, which was followed by reaction with phenylmagnesium bromide to give 23. Removal of the silyl protecting group using acetic acid was essential for producing 24 without racemization at the α-stereocenter. Finally, acetylation and tert-butyl carbamate deprotection afforded 8 as a single enantiomer. Interestingly, (S)-7 showed improved activity over (±)-7, indicating that chirality plays a role in the observed activity; however, (R)-7 had comparable activity to (±)-7 (Table 1, entries 7-9).

The syntheses developed can be readily modified to afford numerous other analogs of 7. (See, e.g.,FIG. 7.) With regard to Scheme 1, and further illustrated inFIG. 7, synthetic intermediate 22 is an entry point to a large number of analogs that possess different functional groups attached to the carbonyl, oxygen, or nitrogen centers. Using such synthetic routes, compounds 11 to 17 were prepared (in racemic form) to gain some insight into SAR for this series of molecules (Table 1). With reference to non-limitingFIG. 7, each of R1-R4can be independently varied, as described above, by choice of reagent and reaction condition.

While molecules 11 to 17 were not selective in arrest of growth of cells expressing mutant p53 under the conditions employed, the results of these studies can suggest, in certain embodiments the use of a carbonyl as a feature for targeting cells with mutant p53. If the phenyl ketone of 7 is changed to a methyl ester (14), morpholine amide (15), or even an ethyl ketone (16), the desired activity is lost. Therefore, it is shown that ketone structure and electronics can be employed for selective targeting of cells with mutant p53. Furthermore, attaching a methyl group to the nitrogen of 7 (molecule 16) or a methyl group to the α-carbon of 7 (molecule 17) eliminates the desired activity.

Upon identification of those compounds, developing new compounds and/or compositions that reactivate mutant p53 in cellular studies and details of this mechanism in vitro (outside the cell) can be examined. For instance, a determination of whether the new molecules directly refold p53 using conformation specific antibodies can be made. Similar studies with PRIMA-1 have demonstrated that this molecule does indeed refold mutant p53 into a native conformation. However, due to the synthetic limitations of PRIMA-1, it is not possible to probe many properties of this interesting binding interaction. In contrast, with the present invention, a wide variety of different functional groups and substituents are introduced in order to determine the nature of the interactions between p53 and the new compounds. By analyzing a series of different compounds for their ability to refold p53, the most appropriate size, shape, and accessible functional groups of the ideal target molecule can be determined. Such studies will reveal important information about the three-dimensional size and shape of the binding site that leads to refolding of p53. Furthermore, the synthetic strategy of the present invention allows incorporation of photoaffinity labels (such as azide) into these molecules so that specific sites of interaction between these new molecules and p53 can be determined.

Clearly, the reactivation of mutant p53 holds great potential for development of novel anticancer therapies that selectively target tumors, a potential which can be realized through use of compounds and/or methods of this invention. As shown above, several compounds have been identified by selectively arrest growth of cells expressing mutant p53 protein. This initial SAR data should prove useful for elucidation of a mechanism of p53 reactivation by small organic molecules. Importantly, these compounds permit rapid exploration of many different analogs of the newly synthesized molecules and incorporates functional group optimization and selectivity of the molecules of the present invention to identify the optimal target structures for mutated p53. Compared to the prior art, synthetic routes associated with the present class of compounds allow facile variation of molecular components and ready accumulation of corresponding SAR data. Such results will enhance the understanding of mutant p53 reactivation, validate mutant p53 as a therapeutic target, contribute to the general understanding of how organic molecules restore normal protein function, and ultimately may impact new development of therapies for a range of cancer disease states.

EXAMPLES OF THE INVENTION

The following non-limiting examples and data illustrate various aspects and features relating to the compositions and/or related methods of the present invention, including synthesis of compounds 1-6 and/or any of the compounds described above, as are available through the synthetic methodologies described herein. In comparison with the prior art, the present compositions and related methods provide results and data which are surprising, unexpected, and contrary to the prior art. While the utility of this invention is illustrated through the use of several compositions and methods which can be used therewith, it will be understood by those skilled in the art that comparable results are obtainable with various other compositions and/or their methods of use, as are commensurate with the scope of this invention. (Several compounds and/or intermediates are schematically identified with reference to a serine core structure (H2NCH2(O)C), whether or not prepared from serine.)

General Methods. All reactions were performed in oven dry glassware under a positive pressure of nitrogen unless otherwise noted. Tetrahydrofuran (THF) was distilled from sodium and benzophenone prior to use. Methylene chloride (CH2Cl2) was distilled from calcium hydride prior to use. Dimethylformamide (DMF) was purified by passage through a bed of activated alumina.1Melting points (mp) were obtained on a Thomas Hoover Capillary Melting Point Apparatus and are uncorrected. Optical rotations ([α]D) were measured on a Perkin-Elmer 241 Polarimeter using sodium light (D line, 589.3 nm) and are reported in degrees; concentrations (c) are reported in g/100 mL. Infrared spectra (IR) were obtained on a Bio-Rad FTS-40 FTIR spectrophotometer. Infrared spectra for liquid products were obtained as a thin film on a KBr disk, and spectra for solid products were collected by preparing a KBr pellet containing the title compound. Proton nuclear magnetic resonances (1H NMR) were recorded in deuterated solvents on a Mercury 400 (400 MHz) or a Varian Inova 500 (500 MHz) spectrometers. Chemical shifts are reported in parts per million (ppm, δ) relative to tetramethylsilane (δ0.00). If tetramethylsilane was not present in the deuterated solvent, the residual protio solvent is referenced (CDCl3, δ 7.27; D2O, δ 4.80; DMSO-d6, δ 2.50).1H NMR splitting patterns are designated as singlet (s), doublet (d), triplet (t), quartet (q), or septet (sep). Splitting patterns that could not be interpreted or easily visualized are designated as multiplet (m) or broad (br). Coupling constants are reported in Hertz (Hz). Proton-decoupled (13C-NMR) spectra were recorded on a Mercury 400 (100 MHz) or a Varian Inova 500 (125 MHz) spectrometer and are reported in ppm using the solvent as an internal standard (CDCl3, δ 77.23; DMSO, δ 39.52). Electrospray mass spectra (ESI-MS) were obtained using a Micromass Quattro II Triple Quadrupole HPLC/MS/MS Mass Spectrometer. Elemental Analysis data were collected by Atlantic Microlab, Inc. High performance liquid chromatography (HPLC) chiral analysis was conducted on a Varian Workstation using a (S,S) WHELK-O Column eluting with a solvent system of 9:1 Hexanes:IPA at 1.5 mL/min. Boc-N-methyl-L-serine was purchased from Chem-Impex International, Inc. All amino acid starting materials, Boc2O, and EDC were purchased from Advanced ChemTech and used without further purification. Unless otherwise noted, all other commercially available reagents and solvents were purchased from Aldrich and used without further purification.

Generally, transformation from serine (D- or L-) to numerous compounds of this invention can proceed by reaction with a Grignard (or alkylithium) reagent (see, Scheme 1, above andFIG. 7). Because compound 22 contains a Weinreb amide, this reaction allows control over the R2position in the final compound. (See, e.g., example 46b and comparative use of several phenyl-substituted derivatives.) Deprotection of the t-butyldimethylsilyl (TBS)-protected alcohol using tetrabutylammonium fluoride (TBAF) will afford a primary hydroxyl group that can be acylated or alkylated, providing control of the group at R4. Finally, deprotection of the t-butoxycarbonyl (Boc)-protected nitrogen with trifluoroacetic acid (TFA) will give a free amine that can be alkylated or acylated to control the groups at R1and R3. Since there are large numbers of Grignard, alkylithium, alkylating, and acylating reagents available, there are an enormous number of different structures that are represented by the final compound represented inFIG. 7. In comparison to the synthesis of PRIMA-1, a synthetic route of the type described herein allows examination of the effects of many different functional groups in the greatest number of positions—a strategy to yield classes of molecules that can be optimized for activity with different versions of mutant p53 that come from different cancer cells.

Compound 7 is resynthesized via the route outlined inFIG. 7to determine whether one enantiomer of compound 7 is more active than the other. As shown, the primary amine in compound 7 is converted to a series of secondary and tertiary amines, through choice of alkylation or acylation reagent, that bear more resemblance to the nitrogen in PRIMA-1. Once useful groups for positions R1and R3are determined, the groups at positions R2and R4can be varied.

Side chain modification is possible, as would be understood by those skilled in the art—without undue experimentation—as provided herein or using straight forward modifications of known techniques. For instance, starting from D- or L-homoserine, diaminopropionic acid, or diaminobutyric acid (FIG. 8) and using the synthetic procedures outlined inFIG. 7and provided elsewhere herein, the effects of lengthening the sidechain, and replacing the sidechain oxygen with a nitrogen can be examined. With analysis of appropriate R group substitution, different aspects of combinatorial chemistry are applied to expand the diversity of the target molecules and, thus, speed up the rate at which analogs of these molecules can be synthesized to generate libraries of compounds that can be screened against different forms of mutant p53.

Cellular growth studies were performed on Saos2 cells. Human osteosarcoma Saos2 cells are devoid of endogenous p53 due to biallelic deletion of the p53 gene. Previously, a series of Saos2 cell lines were engineered to express several human p53 mutants that are commonly found in human cancers. The derivative Saos2 cell lines used in the present study included the following: 1) Saos2-CMV, which is the vector-only control cell line that is negative for p53 protein. 2) Saos2-175, which expresses the human mutant p53-R175H protein. The 175H substitution disrupts the structure of the protein resulting in the loss of DNA binding and tumor suppressor function. This mutation is found in ˜6% of all cancers of diverse tumor types. 3) Saos2-273, which expressed the human mutant p53-R273H protein. The 273H substitution eliminates a DNA contact point resulting in the loss of DNA binding and tumor suppressor function. This mutation represents the second most common hot spot mutation and is found in nearly 8% of all cancers. 4) Saos2-281, which expresses the human mutant p53-D281G protein. This mutation disrupts a stabilizing salt bridge resulting in the loss of DNA binding and tumor suppressor function.

The cells were grown at 37° C. in Dulbecco's modified Eagle's medium (Cambrex, East Rutherford, N.J.) supplemented with 10% fetal bovine serum (Hyclone, Logan, Utah) under 5% CO2. The cells were plated at 1×106per 10 cm tissue culture plates and treated with escalating doses of the indicated compounds (Table 1) for varying lengths of time. Routine concentrations of the synthesized compounds ranged from 1-75 μM. After 72-96 hours, the cells were refed with fresh medium containing the appropriate concentration of the compound. In addition, parallel cultures were prepared and maintained under identical conditions without drug treatment as negative controls. The cells were microscopically analyzed during the course of treatment and the overall effectiveness of the drug treatment on cell growth and survival was assessed on day 7 by staining the cells with Giemsa Stain GS500 (SIGMA, St. Louis, Mo.). Prima-1 was included in all experiments for comparison purposes. As shown in the figure below, compound 7 efficiently and selectively inhibited the growth of the Saos2 cell lines expressing mutant p53, either by inducing cell death and/or cell cycle arrest, while having no effect on the CMV-only cells which lack p53 protein. The few Saos2 mutant p53 cells remaining after treatment with compound 7 were quite large and flat, reminiscent of a differentiated cell.

Cellular growth studies were also performed through treatment with several phenyl-substituted derivatives of compound 8. Using protocols described above, cells were treated with the p-fluorophenyl-, p-methoxyphenyl- and p-methylphenyl-derivatives of the (S)-enantiomer. Such compounds and other derivatives can be prepared from the corresponding Grignard (or alkylithium) reagent in reaction with a Weinreb amide. (See, e.g., intermediate 22 and subsequent reaction thereof, in Scheme 1.) As above, such compounds selectively inhibited growth of cell lines expressing mutant p53.

p53 DNA Binding Assays: Active compound 4 and derivative compounds thereof in the restoration of DNA binding function to mutant p53. To assess this property, p53 is prepared as RIPA lysates from Saos-1 and (10)3 cells and analyzed by Electromobility Shift Assays (EMSA) as previously described (Gu et al., 1996). Specifically, synthetic double-strand oligonucleotides useful in this study are known in the art and include: p53CON, p53RE, and p53MRE. The probes are radiolabeled with [g-32P]ATP and T4 polynucleotide kinase. As a positive control, the probes are incubated with 100 ng of baculovirus-expressed human p53 protein (>95% pure) alone or together with 2 mg of PAb421 (Oncogene Research Products, Cambridge, Mass.) in binding buffer containing 20 mM HEPES (pH 7.9), 25 mM KCl, 0.1 mM EDTA, 2 mM MgCl2, 0.5 mM dithiothreitol, 0.25% Nonidet P-40, 2 mM spermidine, 10% glycerol, 0.1 ng bovine and 0.04 mg poly[dG-dC] at 22° C. for 15 min. Lysates containing no p53 or mutant p53 from vehicle-only or compound 2 treated cells are analyzed by EMSA in parallel. The protein-DNA complexes are resolved in a native 4% polyacrylamide gel and analyzed by autoradiography.

The effect of compound 4 derivatives are also addressed in vitro by adding the compounds to baculovirus purified mutant p53 proteins. Mutant p53 is unable to bind DNA in a sequence specific manner and therefore is unable to shift the probe unless compound 4 and derivative compounds are competent for restoring wild-type p53 biochemical properties.

(a) Promoter-reporter studies Promoter-reporter studies rely on the wild-type p53-responsive promoter-luciferase reporter construct (50-2 Luc), which has been described previously (Zambetti et al., 1993). The wild-type p53-responsive reporter contains the luciferase gene under the transcriptional control of the adenovirus major late TATA box and terminal deoxynucleotidyl-transferase initiator element. Upstream of this minimal promoter are two copies of the p53 response element from the murine muscle creatine kinase gene, both of which are arranged in the forward orientation. The (10)1 cells are transiently transfected with 250 ng of the 50-2 Luc reporter construct by the calcium phosphate method. Cells are then treated with compound 4 or its derivatives and after varying time intervals are harvested, protein extracts prepared and quantified, and equal amounts of protein used in a standard luciferase assay (Promega Corp, Madison, Wis.). Prima-1 reactivates wild-type p53 function in cells expressing mutant p53, which results in an increase in CAT expression from 50-2 Luc reporter, but not the parental vector lacking the p53 consensus sites. By contrast, no increase in CAT expression is observed in Prima-1-treated cells lacking mutant p53. Active compound 4 and its derivative compounds are believed to restore wild-type p53 function and lead to a selective increase in CAT expression only in cells expressing mutant p53.

(b) Endogenous target gene expression studies compound 4 and derivative compounds that reactivate mutant p53 should result in an increase in expression of endogenous genes that are normally regulated by wild-type p53, such as p21Cip1, Puma and Mdm2. To assess the effectiveness of compound 4 and derivative compounds, the Saos-2 and (10)3 cells described above are treated with drug for varying time intervals, washed and harvested. Total RNA is prepared using the RNeasy Mini Kit as recommended by the manufacturer (Qiagen, Valencia, Calif.). The RNA samples (10 ug) are denatured in 1 M glyoxal-10 mM NaH2PO4 [pH 7.0] for one hour at 50° C. and resolved through a 1.2% agarose gel. The RNA samples are transferred to a Zeta-Probe Blotting Membrane (Bio-Rad) in transfer buffer containing 10 mM NaCl. The membrane is blocked in hybridization solution (1 mM EDTA, 0.25 M Na2HPO4 [pH 7.2] and 7% SDS) for 5 min and hybridized with [32P]-radiolabeled DNA probes for 16 hours in fresh hybridization solution at 65° C. The membrane is washed twice at 65° C. for 30 min per wash in buffer I (1 mM EDTA, 40 mM Na2HPO4 [pH 7.2] and 5% SDS) followed by two washes in buffer II (1 mM EDTA, 40 mM Na2HPO4 [pH 7.2] and 1% SDS). Target gene expression is quantitated by Phosphorimager analysis using Imagequant Software. Zambetti G, Bargonetti J, Walker K, Prives C, Levine A. Wild-type p53 mediates positive regulation of gene expression through a specific DNA sequence element. Genes Dev 6:1143-1152, 1992. Gu Z, Flemington C, Jenkins N A, Copeland N G, Chittenden T, Zambetti, G P. EI24: A p53 response gene involved in growth suppression and apoptosis. Mol Cell Biol 18:3735-3743, 2000.