Identify SNPs and Polymorphisms Involved in the Development of Prostate Cancer

Project Details


The purpose of this project is to perform translational research to develop new agents, and/or therapeutic maneuvers, that appear to have antitumor activity in prostate cancer, and to develop molecular profiles of patients with prostate cancer to tailor an individualized treatment plan. To achieve this goal, we have become extensively involved in the efforts to understand the biology of prostate cancer. Currently, we are attempting to correlate biological variables associated with prostate cancer and response to therapy (e.g., important polymorphic markers, and microvessel counts). One early achievement by the Molecular Pharmacology Section was to report the first confirmation of the therapeutic efficacy of flutamide withdrawal, as well as the enhanced activity of simultaneous adrenal suppression. It has been hypothesized that the clinical improvement associated with flutamide is a result of the presence of a mutation within the ligand-binding domain of the androgen receptor. We remain interested in analyzing candidate genes at the genomic level for genetic variations that may predispose individuals to increased risk of prostate cancer. We have completed the analysis of genes involved in the natural production of endostatin (COL18A1, no statistical difference), a gene directly involved in the synthesis of testosterone from cholesterol (CYP17, the results suggest that the polymorphism is associated with overall survival in patients with androgen independent prostate cancer), a gene involved in the toxic metabolic breakdown of testosterone (CYP1B1, an association with decreased survival was observed), drug metabolism (CYP3A4 &5, the studied genetic variants are unlikely to have an important functional significance to phenotypic CYP3A activity in patients with cancer), and a gene involved in cellular transport and conjugation (UGT1A9, functional variants are rare in Caucasians and likely to be clinically insignificant in irinotecan regimens). The organic anion transporter OATP1B3, encoded by SLCO1B3, is involved in the transport of steroid hormones. However, its role in testosterone uptake and progression of prostate cancer is unknown. SLCO1B3 genotype was assessed in the NCI-60 panel of tumor cells by sequencing, while testosterone transport was analyzed in Cos-7 cells transfected with wild-type (WT), 334G and 699A SLCO1B3 variants. OATP1B3 expression in prostatic tissues was examined by fluorescence microscopy and the relationship between SLCO1B3 haplotypes and survival was examined in patients. Our recent study showed that prostate cancer over-expresses OATP1B3 compared to normal or benign hyperplastic tissue, and the common SLCO1B3 GG/AA haplotype is associated with impaired testosterone transport and improved survival in patients with prostate cancer. Furthermore, the analysis of other genes (SRD5A1&2, LOX, CYP19, ER) which have shown preliminary evidence that suggests that they may play important roles are ongoing and at various stages of completion. Other polymorphic containing genes of interest have been recently identified after screening the DNA from patients with prostate cancer against a gene chip designed to screen genes involved in metabolism and drug transport. These important genes will be added to the ongoing goal of a molecular fingerprint of prostate cancer. In association with our candidate gene analysis studies, we are also using physiological studies and observations to help elucidate the biology of prostate cancer. To investigate how thalidomide confers its survival benefit, we assessed its effect on circulating endothelial cells (CECs) and progenitors (CEPs) in a combination therapy of thalidomide and chemotherapy drugs in a human prostate cancer xenograft model. An increased level of apoptotic/dead CEC was observed shortly after the intravenous injection of docetaxel, and the addition of thalidomide further increased the apoptotic/dead CEC level, demonstrating that thalidomide enhances the cytotoxicity of docetaxel against tumor vascular endothelial cells. This study demonstrated that thalidomide increased the apoptotic/dead CECs and enhanced the cytotoxicity of docetaxel against tumor vascular endothelial cells, confirming its anti-angiogenic property in vivo in combinational anti-cancer treatments. In addition, we discovered a correlation between the increased apoptotic/dead CEC levels early into the treatment and anti-tumor efficacy later, suggesting apoptotic/dead CEC level could be used as a marker at an early stage to predict tumor response to anti-angiogenic therapies. In another recent study the significance of viable tumor in the prostate in patients with metastatic androgen independent prostate cancer (AIPC) was studied. Clinicopathological features, including follow-up, of 40 men with metastatic AIPC who underwent a biopsy of the prostate were evaluated. Prostate biopsies performed revealed viable tumor in 19 of 40 patients (48%). Of the 18 patients who had received radiation treatment, 9 (50%) had negative on-study biopsy. Previous history of radiation therapy was not associated with overall survival in patients with biopsy positive tumors (p=0.84). Also, there was no statistically significant association between positive or negative biopsy status and overall survival (OS) in these 40 patients (p=0.39), with similar median OS of 19.6 months for biopsy negative and 19.8 months for biopsy positive patients, respectively. These observations lead to the conclusion that performing prostate biopsies at the time of documented metastatic AIPC yielded tumor in about half of the cases. Prior history of radiation treatment was not associated with a negative prostate biopsy. A negative prostate biopsy does not appear to have an impact on prognosis. Some of the overall goals of this project are: (a) to better understand associations between important androgen regulatory gene polymorphisms and prostate cancer risk and (b) to evaluate the effects of these polymorphisms and serum hormone concentrations on the use of finasteride as a chemopreventive agent for prostate cancer. The recently completed Prostate Cancer Prevention Trial (PCPT) investigated the prevention of prostate cancer using the steroid 5 alpha-reductase inhibitor finasteride over a seven year treatment period. Through a longstanding collaboration we have access to tissue samples of the 18,800 men enrolled in this study. We are currently focusing on hormone-related factors that are associated with prostate cancer risk, which may help explain the findings of the PCPT (i.e., decreased overall occurrence of adenocarcinoma, but increased prevalence of high-grade disease in the finasteride treatment arm). We hypothesize that men with polymorphisms within genes that positively impact androgen levels will have a higher risk of developing prostate cancer and high grade disease than those with the wild-type alleles. In addition, long-term exposure to finasteride may select for somatic alterations and increase serum levels of testosterone and potentially harmful testosterone breakdown products. The evaluation of whether the polymorphic variations in the AR, SRD5A2 and HSD3B2 genes are associated with the risk of biopsy-detected prostate cancer in the PCPT are underway. We are identifying by laser-capture microdissection and direct nucleotide sequencing somatic alterations in the AR [summary truncated at 7800 characters]
StatusNot started


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