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生和进展的遗传和分子机制，确定药物开发的新途径，并研究对治疗范式的耐药机制。我们与前列腺癌预防试验（PCPT）的研究人员长期合作，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风险之间的关系；b)评估这些多态性和血清激素浓度对使用非那雄胺作为CaP化学预防药物的影响。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，可能会被循环激素水平和非那雄胺治疗所改变。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的转移性去势抵抗性前列腺癌（mCRPC）。PARP抑制的益处已经在几种形式的癌症中具有BRCA1和BRCA2突变的患者中得到了很好的表征。BRCA1和BRCA2在DNA损伤修复中起着关键作用，DNA损伤修复由几种不同的途径组成，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，识别这些改变可以显著增加可能受益于PARP抑制的患者的百分比。我们最近的基因研究（在包括前列腺疾病研究中心在内的几个机构的合作努力下）发现，在不同种族的患者群体中，种系BRCA2突变的频率增加与前列腺癌转移有关。BRCA2的种系突变与前列腺癌的高风险有关，最近在mCRPC标本中报道了BRCA1和BRCA2 （BRCA1/2）基因改变的高频率。BRCA2突变在种族和民族群体中有所不同，包括非裔美国人（AA）和高加索美国人（CA）。对1240例PCa患者（包括30% AA患者）存档的血液DNA标本进行BRCA1和BRCA2基因测序（Ion AmpliSeq靶向测序）：局部早期（T2） PCa (N = 935)；晚期PCa (50% T3-4) (N = 189)；转移性前列腺癌（N = 116）。分析了BRCA1/2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系。具有已知致病注释的BRCA2突变在晚期和转移性前列腺癌患者中（3.1%）比器官局限性疾病患者（0.7%）更为普遍。与高加索美国人相比，AA患者携带未知意义BRCA1/2变异（VUS）的频率更高（分别为4.6%和1.6%）。值得注意的是，在局限性早期前列腺癌患者中，致病性BRCA2突变增加了远处转移的风险。BRCA1/2中意义未知的种系变异在AA患者中比CA患者更常见；然而，致病突变的患病率在不同种族之间是相似的。携带BRCA2致病突变的患者更有可能进展为转移。我们对了解雄激素运输的分子遗传学也很感兴趣。由SLCO1B3编码的有机阴离子转运体OATP1B3参与类固醇激素的转运。我们已经证明，与正常或良性增生组织相比，前列腺癌过度表达OATP1B3，常见的SLCO1B3 GG/AA单倍型与CaP患者睾酮转运受损和生存率提高有关。我们发现，这种转运体的多态性增加了睾酮进口，与接受ADT治疗的CaP患者较短的雄激素独立时间相关。去势抵抗性前列腺癌（CRPC）的瘤内睾酮浓度高于来自性腺正常男性的类似肿瘤；简单的扩散不能解释这一观察结果。我们最近进行了研究，以确定ooatp1b3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，在前列腺癌中，新的OATP1B3表达会导致更大的雄激素摄取，这与之前的观察结果一致，即更高的OATP1B3活性会导致雄激素剥夺治疗耐药性的发展和更短的总生存期。目前正在研究SLCO1B3转录的分子机制，包括转录因子复合物在SLCO1B3启动子中聚集在不同的调控元件上，以驱动OATP1B3在前列腺癌中的组织特异性表达。了解OATP1B3表达的潜在调控机制以及该转运体在前列腺癌进展中的作用，将有助于其成为潜在的治疗靶点。为此，我们目前正在开发OATP1B3抑制剂筛选试验，该试验将用于美国国家癌症研究所天然产物库中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.