Genetics and Molecular Mechanisms of Prostate Cancer

我们进行了转化研究，以了解控制前列腺癌发展和进展的遗传和分子机制，确定药物开发的新途径，并研究对治疗模式的耐药性机制。我们与前列腺癌预防试验（PCPT）研究人员有着长期的合作，以阐明可能有助于解释PCPT试验结果的分子和遗传机制。该项目的总体目标是：a）更好地了解重要雄激素调节基因多态性与CaP风险之间的关联;和B）评价这些多态性和血清激素浓度对使用非那匹德作为CaP化学预防剂的影响。我们最近确定，雌激素相关基因的SNV与前列腺癌风险之间的关联是复杂的，并且可能会受到循环激素水平和芬达治疗的影响。FDA最近批准了两种PARP抑制剂olaparib和rucaparib用于治疗生物标志物阳性转移性去势抵抗性前列腺癌（mCRPC）。PARP抑制的益处已在几种癌症中具有BRCA 1和BRCA 2突变的患者中得到充分表征。BRCA 1和BRCA 2在DNA损伤修复中起着关键作用，DNA损伤修复由几个不同的途径组成，参与者众多。DNA损伤修复途径中其他关键基因突变的患者也可能对PARP抑制剂治疗有反应，并且这些改变的鉴定可以显著增加可能从PARP抑制中获益的患者百分比。我们最近的遗传学研究（包括前列腺疾病研究中心在内的几个机构的合作）发现，生殖系BRCA 2突变频率的增加与种族多样性患者人群中的前列腺癌转移有关。BRCA 2的生殖系突变与前列腺癌的高风险有关，最近在mCRPC标本中报告了高频率的BRCA 1和BRCA 2（BRCA 1/2）基因改变。BRCA 2的突变在种族和民族群体中各不相同，包括非洲裔美国人（AA）和高加索裔美国人（CA）人群。对1240例PCa患者（包括30% AA患者）的存档血液DNA标本中的BRCA 1和BRCA 2基因进行测序（Ion AmpliSeq靶向测序），这些患者分为三个不同队列：局限性早期（T2）PCa（N = 935）;晚期PCa（50% T3-4）（N = 189）;和转移性PCa（N = 116）。分析BRCA 1/2中已知和新突变的序列。进行统计分析以确定突变与临床病理参数的关联。与器官局限性疾病患者（0.7%）相比，具有已知致病性注释的BRCA 2突变在晚期和转移性PCa男性患者（3.1%）中显著更普遍。与美国白人相比，AA患者携带未知意义的BRCA 1/2变异（VUS）的频率更高（分别为4.6%和1.6%）。值得注意的是，局部早期PCa患者的致病性BRCA 2突变增加了远处转移的风险。BRCA 1/2中意义未知的种系变异在AA患者中比CA PCa患者更常见;然而，致病性突变的患病率在种族间相似。携带BRCA 2致病性突变的患者更有可能进展为转移。我们也有兴趣了解雄激素转运的分子遗传学。有机阴离子转运体OATP 1B 3由SLCO 1B 3编码，参与类固醇激素的转运。我们已经表明，与正常或良性增生组织相比，前列腺癌过度表达OATP 1B 3，常见的SLCO 1B 3 GG/AA单倍型与CaP患者睾酮转运受损和生存率提高相关。我们发现，这种转运蛋白的多态性增加睾酮输入与接受ADT治疗的CaP患者雄激素非依赖性时间缩短相关。去势抵抗性前列腺癌（CRPC）的瘤内睾酮浓度高于性腺正常男性的类似肿瘤;简单扩散不能解释这一观察结果。我们最近进行了研究，以确定OATP 1B 3从头表达的雄激素摄取动力学、功能和临床相关性。我们发现，前列腺癌中OATP 1B 3的重新表达驱动了更大的雄激素摄取，这与之前的观察结果一致，即OATP 1B 3活性越高，雄激素剥夺治疗的耐药性越强，总生存期越短。正在进行研究以表征SLCO 1B 3转录的分子机制，包括在SLCO 1B 3启动子中不同调控元件处组装的转录因子复合物，以驱动前列腺癌中OATP 1B 3的组织特异性表达。了解OATP 1B 3表达的潜在调节机制和转运蛋白在前列腺癌进展中的作用将有助于其作为潜在治疗靶点的发展。为此，我们目前正在开发一种OATP 1B 3抑制剂筛选试验，该试验将被验证用于国家癌症研究所天然产物库化合物的高通量筛选。

We have conducted translational research to understand the genetic and molecular mechanism that govern prostate cancer development and progression, to identify novel pathways for drug development, and investigate mechanisms of resistance to treatment paradigms. We have a longstanding collaboration with the Prostate Cancer Prevention Trial (PCPT) investigators to elucidate the molecular and genetic mechanisms that may help explain the trial outcomes of the PCPT. The overall goals of this project are: a) to better understand associations between important androgen regulatory gene polymorphisms and CaP risk; and b) to evaluate the effects of these polymorphisms and serum hormone concentrations on the use of finasteride as a chemopreventive agent for CaP. We recently determined that associations between SNVs in estrogen-related genes and prostate cancer risk are complex and may be modified by circulating hormone levels and finasteride treatment. The FDA recently approved two PARP inhibitors, olaparib and rucaparib, for treatment of biomarker-positive metastatic castrate resistant prostate cancer (mCRPC). The benefits of PARP inhibition have been well characterized in patients that have BRCA1 and BRCA2 mutations in several forms of cancer. BRCA1 and BRCA2 occupy key roles in DNA damage repair, which is comprised of several different pathways with numerous participants. Patients with mutations in other key genes within the DNA damage repair pathway may also respond to treatment with PARP inhibitors, and identification of these alterations could significantly increase the percentage of patients that may benefit from PARP inhibition. Our most recent genetic study (in collaborative effort among several institutions including the Center for Prostate Disease Research) found that increased frequency of germline BRCA2 mutations associates with prostate cancer metastasis in a racially diverse patient population. Germline mutations in BRCA2 have been linked to a higher risk of prostate cancer, and high frequency of BRCA1 and BRCA2 (BRCA1/2) gene alterations was recently reported in mCRPC specimens. Mutations in BRCA2 vary in racial and ethnic groups including African-American (AA) and Caucasian-American (CA) populations. BRCA1 and BRCA2 genes were sequenced (Ion AmpliSeq targeted sequencing) in archived blood DNA specimens in 1240 PCa patients, including 30% AA patients, in three different cohorts: localized early stage (T2) PCa (N = 935); advanced PCa (50% T3-4) (N = 189); and metastatic PCa (N = 116). The sequences were analyzed for known and novel mutations in BRCA1/2. Statistical analyses were performed to determine associations of the mutations with clinico-pathological parameters. BRCA2 mutations with known pathogenic annotation were significantly more prevalent in men with advanced and metastatic PCa (3.1%) compared to patients with an organ-confined disease (0.7%). AA patients carried more frequently BRCA1/2 variants of unknown significance (VUS) when compared to Caucasian Americans (4.6 vs. 1.6%, respectively). Significantly, pathogenic BRCA2 mutations in men with localized early stage PCa increased the risk of distant metastasis. Germline variants of unknown significance in BRCA1/2 are more frequent in AA than CA PCa patients; however, the prevalence of pathogenic mutations were similar across the races. Patients carrying BRCA2 pathogenic mutations are more likely to progress to metastasis. We are also interested in understanding the molecular genetics of androgen transport. The organic anion transporter OATP1B3, encoded by SLCO1B3, is involved in the transport of steroid hormones. We have shown that prostate cancer overexpresses 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 CaP. We found that a polymorphism in this transporter increases testosterone import is associated with a shorter time to androgen independence in patients with CaP who are treated with ADT. Castration-resistant prostate cancer (CRPC) has greater intratumoral testosterone concentrations than similar tumors from eugonadal men; simple diffusion does not account for this observation. We recently conducted studies to ascertain the androgen uptake kinetics, functional, and clinical relevance of de novo expression of OATP1B3. We found that de novo OATP1B3 expression in prostate cancer drives greater androgen uptake and is consistent with previous observations that greater OATP1B3 activity results in the development of androgen deprivation therapy resistance and shorter overall survival. Studies are ongoing to characterize the molecular mechanisms of SLCO1B3 transcription including transcription factor complexes that assemble at distinct regulatory elements in the SLCO1B3 promoter for driving tissue-specific expression of OATP1B3 in prostate cancer. Understanding the underlying regulatory mechanisms of OATP1B3 expression and the transporter's role in prostate cancer progression will aid in its development as a potential therapeutic target. To this end, we are currently developing an OATP1B3 inhibitor screening assay that will be validated for use in a high-throughput screening of compounds from the National Cancer Institute's Natural Products Repository.