2-2-bis(hydroxymethyl)-1-azabicyclo(2-2-2-)octan-3-one and Breast-Neoplasms

Breast cancer progression depends upon the elaboration of a vasculature sufficient for the nourishment of the developing tumor. Breast tumor cells frequently contain a mutant form of p53 (mtp53), a protein which promotes their survival. The aim of this study was to determine whether combination therapy targeting mtp53 and anionic phospholipids (AP) on tumor blood vessels might be an effective therapeutic strategy for suppressing advanced breast cancer. We examined the therapeutic effects, singly, or in combination, of p53 reactivation and induction of massive apoptosis (PRIMA-1), which reactivates mtp53 and induces tumor cell apoptosis, and 2aG4, a monoclonal antibody that disrupts tumor vasculature by targeting AP on the surface of tumor endothelial cells and causes antibody-dependent destruction of tumor blood vessels, leading to ischemia and tumor cell death. Xenografts from two tumor cell lines containing mtp53, BT-474 and HCC-1428, were grown in nude mice to provide models of advanced breast tumors. After treatment with PRIMA-1 and/or 2aG4, regressing tumors were analyzed for vascular endothelial growth factor (VEGF) expression, blood vessel loss, and apoptotic markers. Individual drug treatment led to partial suppression of breast cancer progression. In contrast, combined treatment with PRIMA-1 and 2aG4 was extremely effective in suppressing tumor growth in both models and completely eradicated approximately 30% of tumors in the BT-474 model. Importantly, no toxic effects were observed in any treatment group. Mechanistic studies determined that PRIMA-1 reactivated mtp53 and also exposed AP on the surface of tumor cells as determined by enhanced 2aG4 binding. Combination treatment led to significant induction of tumor cell apoptosis, loss of VEGF expression, as well as destruction of tumor blood vessels. Furthermore, combination treatment severely disrupted tumor blood vessel perfusion in both tumor models. The observed in vitro PRIMA-1-induced exposure of tumor epithelial cell AP might provide a target for 2aG4 and contribute to the increased effectiveness of such combination therapy in vivo. We conclude that the combined targeting of mtp53 and the tumor vasculature is a novel effective strategy for combating advanced breast tumors.

Topics: Animals; Antibodies, Monoclonal; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cell Proliferation; Female; Fluorescent Antibody Technique; Genes, p53; Humans; Mammary Neoplasms, Experimental; Mice; Mice, Nude; Mutant Proteins; Neovascularization, Pathologic; Phospholipids; Protein Conformation; Tumor Suppressor Protein p53; Vascular Endothelial Growth Factor A; Xenograft Model Antitumor Assays

Inverse docking is a relatively new technique that has been used to identify potential receptor targets of small molecules. Our docking software package MDock is well suited for such an application as it is both computationally efficient, yet simultaneously shows adequate results in binding affinity predictions and enrichment tests. As a validation study, we present the first stage results of an inverse-docking study which seeks to identify potential direct targets of PRIMA-1. PRIMA-1 is well known for its ability to restore mutant p53's tumor suppressor function, leading to apoptosis in several types of cancer cells. For this reason, we believe that potential direct targets of PRIMA-1 identified in silico should be experimentally screened for their ability to inhibit cancer cell growth. The highest-ranked human protein of our PRIMA-1 docking results is oxidosqualene cyclase (OSC), which is part of the cholesterol synthetic pathway. The results of two followup experiments which treat OSC as a possible anti-cancer target are promising. We show that both PRIMA-1 and Ro 48-8071, a known potent OSC inhibitor, significantly reduce the viability of BT-474 and T47-D breast cancer cells relative to normal mammary cells. In addition, like PRIMA-1, we find that Ro 48-8071 results in increased binding of p53 to DNA in BT-474 cells (which express mutant p53). For the first time, Ro 48-8071 is shown as a potent agent in killing human breast cancer cells. The potential of OSC as a new target for developing anticancer therapies is worth further investigation.

Topics: Antineoplastic Agents; Aza Compounds; Benzophenones; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cell Survival; Computational Biology; DNA; Drug Discovery; Enzyme Inhibitors; Female; Humans; Intramolecular Transferases; Models, Molecular; Protein Binding; Protein Interaction Domains and Motifs; Tumor Suppressor Protein p53

PRIMA-1 has been identified as a compound that restores the transactivation function to mutant p53 and induces apoptosis in cells expressing mutant p53. Studies on subcellular distribution of the mutant p53 protein upon treatment with PRIMA-1Met, a methylated form of PRIMA-1, have suggested that redistribution of mutant p53 to nucleoli may play a role in PRIMA-1 induced apoptosis. Here, we specifically investigated the influence of PRIMA-1 on cellular localization of mutated p53-R280K endogenously expressed in tumour cells. By using immunofluorescence staining, we found a strong nucleolar redistribution of mutant p53 following PRIMA-1 treatment. This subcellular localization was associated to p53 degradation via ubiquitylation. When cells were treated with adriamycin, neither nucleolar redistribution nor mutant p53 down modulation and degradation were observed. Interestingly, cells where p53-R280K was silenced were more sensitive to PRIMA-1 than the parental ones. These results indicate that in some cellular context, the cell sensitivity to PRIMA-1 could depend on the abolition of a gain-of-function activity of the mutated p53, through a protein degradation pathway specifically induced by this compound.

Topics: Antineoplastic Agents; Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Cell Nucleus; Drug Resistance, Neoplasm; Female; Humans; Mutation; Tumor Suppressor Protein p53

Specific changes in gene expression during cancer initiation should enable discovery of biomarkers for risk assessment, early detection and targets for chemoprevention. It has been previously demonstrated that altered mRNA and proteome signatures of morphologically normal cells bearing a single inherited "hit" in a tumor suppressor gene parallel many changes observed in the corresponding sporadic cancer. Here, we report on the global gene expression profile of morphologically normal, cultured primary breast epithelial and stromal cells from Li-Fraumeni syndrome (LFS) TP53 mutation carriers. Our analyses identified multiple changes in gene expression in both morphologically normal breast epithelial and stromal cells associated with TP53 haploinsufficiency, as well as interlocking pathways. Notably, a dysregulated p53 signaling pathway was readily detectable. Pharmacological intervention with the p53 rescue compounds CP-31398 and PRIMA-1 provided further evidence in support of the central role of p53 in affecting these changes in LFS cells and treatment for this cancer. Because loss of signaling mediated by TP53 is associated with the development and survival of many human tumors, identification of gene expression profiles in morphologically normal cells that carry "one-hit" p53 mutations may reveal novel biomarkers, enabling the discovery of potential targets for chemoprevention of sporadic tumors as well.

Topics: Adolescent; Adult; Aza Compounds; Biomarkers, Tumor; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Carcinoma, Ductal, Breast; Cells, Cultured; Epithelial Cells; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Genetic Predisposition to Disease; Germ-Line Mutation; Haploinsufficiency; Humans; Li-Fraumeni Syndrome; Neoplasm Proteins; Oligonucleotide Array Sequence Analysis; Pyrimidines; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stromal Cells; Tumor Suppressor Protein p53

Mutation of the p53 tumor suppressor gene is a common event in many types of tumors, including breast cancers. Mutant p53 (mtp53) protein is thought to promote tumor cell survival and resistance to chemotherapeutic drugs. Therefore, restoring p53 function by converting existing mtp53 to the wild-type p53 (wtp53) conformation is being pursued as one strategy to promote apoptosis of tumor cells. PRIMA-1 (p53 re-activation and induction of massive apoptosis) is a non-toxic small molecule that converts mtp53 to the active conformation and induces apoptosis in tumor cells. Here we examined whether PRIMA-1 activates mtp53 and induces cell death in vitro and in vivo in estrogen-responsive breast cancer cell lines that express mtp53 (BT-474, HCC-1428, and T47-D). Fluorescent staining with conformation-specific p53 antibodies demonstrated that PRIMA-1 converted mtp53 into the wtp53 conformation. In vitro treatment of tumor cells with PRIMA-1 (0-50 microM) led to a dose-dependent loss of cell viability and induced cell death markers. In contrast, PRIMA-1 had no effect on the viability of MCF-7 cells, normal breast cells, and endothelial cells, all of which express wtp53 protein. PRIMA-1 treatment of mice inhibited the growth of tumors from xenografts of BT-474, HCC-1428, and T47-D cells but did not influence xenografts obtained from MCF-7 cells. Mechanistic studies showed that PRIMA-1 induced the mitochondrial-dependent apoptotic pathway in mtp53-expressing breast cancer cells. Our findings suggest that PRIMA-1 renews the susceptibility of mtp53-expressing breast tumors to apoptosis and should be investigated for use in breast cancer therapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Aza Compounds; Blotting, Western; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Female; Fluorescent Antibody Technique; Humans; Mice; Mice, Nude; Mutation; Tumor Suppressor Protein p53

Mutations in wild-type p53 (wtp53) protein lead to loss of its tumor suppressor function in breast cancer cells, facilitating uncontrolled tumor growth. Consequently, procedures to repair defective p53 functions in tumor cells are being actively pursued. We sought to determine whether expression of wtp53 protein, or conversion of endogenous mutant p53 (mtp53) into a functional p53 protein with small molecule PRIMA-1, can override the tumor-promoting effects of naturally occurring mtp53 protein in hormone-responsive T47-D human breast cancer cells. We show that transfection of wtp53 gene into T47-D cells suppresses their proliferation in regular media, and inhibits estrogen-dependent cell proliferation in media containing dextran-coated charcoal treated serum. Growth inhibition was not due to the absence of estrogen receptor-alpha or estrogen receptor-beta though receptor levels for estrogen receptor-alpha were drastically reduced in wtp53 expressing cells. Focused microarray analysis of wtp53 expressing cells revealed suppression of PCNA cell-cycle regulatory mRNA and protein. Wild-type p53 transfected T47-D cells also failed to grow in vivo in estrogen supplemented nude mice. Furthermore, xenografts obtained with parental T47-D cells expressing mtp53 grew poorly in nude mice treated with PRIMA-1. PRIMA-1 treated tumors exhibited a low proliferation index, even though mice were estrogen-supplemented. PRIMA-1 treatment of tumor cells suppressed VEGF and induced expression of estrogen receptor-beta though expression of estrogen receptor-alpha and progesterone receptors was unaffected. These data indicate that alteration of the p53 signal transduction pathway by re-expression of wtp53 protein in T47-D cells, or treatment of parental cells with PRIMA-1, can prevent in vivo and in vitro proliferation of T47-D breast cancer cells.

Topics: Animals; Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Nucleus; Cell Proliferation; Female; Humans; Immunoblotting; In Vitro Techniques; Mice; Mice, Nude; Mutation; Neoplasms, Hormone-Dependent; Receptors, Estrogen; Receptors, Progesterone; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Xenograft Model Antitumor Assays

Recent clinical trials indicate that synthetic progestins may stimulate progression of breast cancer in postmenopausal women, a result that is consistent with studies in chemically-induced breast cancer models in rodents. However, progestin-dependent progression of breast cancer tumor xenografts has not been shown. This study shows that xenografts obtained from BT-474 and T47-D human breast cancer cells without Matrigel in estrogen-supplemented nude mice begin to regress within days after tumor cell inoculation. However, their growth is resumed if animals are supplemented with progesterone. The antiprogestin RU-486 blocks progestin stimulation of growth, indicating involvement of progesterone receptors. Exposure of xenografts to medroxyprogesterone acetate, a synthetic progestin used in postmenopausal hormone replacement therapy and oral contraception, also stimulates growth of regressing xenograft tumors. Tumor progression is dependent on expression of vascular endothelial growth factor (VEGF); growth of progestin-dependent tumors is blocked by inhibiting synthesis of VEGF or VEGF activity using a monoclonal anti-VEGF antibody (2C3) or by treatment with PRIMA-1, a small-molecule compound that reactivates mutant p53 into a functional protein and blocks VEGF production. These results suggest a possible model system for screening potential therapeutic agents for their ability to prevent or inhibit progestin-dependent human breast tumors. Such a model could potentially be used to screen for safer antiprogestins, antiangiogenic agents, or for compounds that reactivate mutant p53 and prevent progestin-dependent progression of breast disease.

Topics: Angiogenesis Inhibitors; Animals; Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Growth Processes; Disease Progression; Female; Humans; Medroxyprogesterone Acetate; Mice; Mifepristone; Neoplasms, Hormone-Dependent; Neovascularization, Pathologic; Progesterone; Progesterone Congeners; Progestins; Receptors, Estrogen; Receptors, Progesterone; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2; Xenograft Model Antitumor Assays

PRIMA-1 has emerged as a small molecule that restores the wild type function to mutant p53. To identify molecular targets that are involved in PRIMA-1-induced apoptosis, we used a proteomics approach with two-dimensional gel electrophoresis coupled with liquid chromatography-tandem mass spectrometry for protein identification. By comparing the proteome of the PRIMA-1-treated MDA-231 breast carcinoma cells with that of MCF-7 cells, we have identified seven proteins that upregulated only in MDA-231 cells as a result of PRIMA-1-induced apoptosis. The identified proteins are involved in anaerobic glycolysis and in mitochondrial intrinsic apoptosis. Treatment of MDA-231 cells with PRIMA-1 resulted in the release of mitochondrial cytochrome c as well as the activation of caspase-3, which are essential for the execution of apoptosis. We present evidence to suggest that PRIMA-1-induced apoptosis in breast cancer cells with mutated p53 function involved the expression of proteins required for the activation of mitochondrial intrinsic pathway that is glycolysis-relevant.

Topics: Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Caspase 3; Caspases; Cell Line, Tumor; Electrophoresis, Gel, Two-Dimensional; Enzyme Activation; Gene Expression Regulation, Neoplastic; Humans; Mass Spectrometry; Microscopy, Electron, Transmission; Proteomics; Tumor Suppressor Protein p53

A loss of p53 function resulting from mutation is prevalent in human cancers. Thus, restoration of p53 function to mutant p53 using small compounds has been extensively studied for cancer therapy. We previously reported that PRIMA-1 (for 'p53 reactivation and induction of massive apoptosis') restored the transcriptional activity of p53 target genes in breast cancer cells with a p53 mutation. By using functional proteomics approach, we sought to identify molecular targets that are involved in the restoration of normal function to mutant p53.. PRIMA-1 treated cell lysates were subjected to immunoprecipitation with DO-1 primary antibody against p53 protein, and proteins bound to p53 were separated on a denaturing gel. Bands expressed differentially between control and PRIMA-1-treated cells were then identified by matrix-assisted laser desorption ionization-time-of-flight spectrometry. Protein expression in whole cell lysates and nuclear extracts were confirmed by Western blotting. The effect of combined treatment of PRIMA-1 and adriamycin in breast cancer cells was determined with a cytotoxicity assay in vitro.. PRIMA-1 treated cells distinctly expressed a protein band of 90 kDa that was identified as heat shock protein 90 (Hsp90) by the analysis of the 90 kDa band tryptic digest. Immunoblotting with isoform-specific antibodies against Hsp90 identified this band as the alpha isoform of Hsp90 (Hsp90alpha). Co-immunoprecipitation with anti-Hsp90alpha antibody followed by immunoblotting with DO-1 confirmed that p53 and Hsp90alpha were interacting proteins. PRIMA-1 treatment also resulted in the translocation of Hsp90alpha to the nucleus by 8 hours. Treatment of cells with PRIMA-1 alone or in combination with adriamycin, a DNA-targeted agent, resulted in increased sensitivity of tumor cells.. The studies demonstrate that PRIMA-1 restores the p53-Hsp90alpha interaction, enhances the translocation of the p53-Hsp90alpha complex and reactivates p53 transcriptional activity. Our preliminary evidence also suggests that PRIMA-1 could be considered in combination therapy with DNA-targeted agents for the treatment of breast cancer, especially for tumors with aberrant p53 function.

Topics: Amino Acid Substitution; Aza Compounds; Breast Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Doxorubicin; Female; HSP90 Heat-Shock Proteins; Humans; Immunohistochemistry; Mutagenesis, Site-Directed; Mutation; Proteome; Tumor Suppressor Protein p53