Functional Genetic variants as modifiers of prostate cancer progression in Native Americans

前列腺癌(PCA)的发病率和死亡率在美国不同种族之间差异很大。在所有男性中，前列腺癌是最常见的癌症诊断形式，但美洲原住民男性在确诊后患前列腺癌的死亡率几乎是白人的两倍。这种差异的程度并没有反映在其他常见的癌症类型上，这表明美洲原住民男性与前列腺癌相关的死亡率是一种独特的负担。在纳瓦霍人中，前列腺癌更多的是在癌症扩散到前列腺癌边缘之外的阶段被诊断出来的(在纳瓦霍人中，17.9%的前列腺癌诊断病例，在新墨西哥州的非西班牙裔白人中为3.3%)。这些数据强调了了解所有男性，特别是美洲原住民临床侵袭性前列腺癌背后的分子机制的必要性。在所有种族中，前列腺癌具有高度的异质性，可以是不需要积极治疗的潜伏性局部性疾病，也可以是与高死亡风险相关的侵袭性疾病。我们的目标是更好地了解侵袭性前列腺癌的遗传和分子相关性。我们的实验方法将使我们能够表征对美洲原住民群体特别重要的遗传风险因素。 以前的研究已经确定了许多体细胞和生殖系遗传变异会增加侵袭性前列腺癌的风险。尤其重要的是影响肿瘤抑制基因PTEN剂量的突变。PTEN等位基因缺失发生在20-40%的局限性前列腺癌和~60%的转移癌中。最近的证据还表明，在没有缺失突变的情况下，45%的原发肿瘤会发生PTEN蛋白丢失，这表明PTEN沉默受到其他机制的影响。我们的研究将集中在microRNA介导的(MiRNA)对PTEN的调控作用，这是该抑癌基因的关键调控机制。具体地说，我们将鉴定和分析PTEN及其表达的假基因PTENP1的miRNA反应元件的变体。这两个基因通过竞争miRNAs参与调节串扰，因此PTENP1的等位基因变异可以间接影响PTEN的表达。这项研究扩展了我们的试点项目的发现，该项目发现PTEN受到miRNA相互作用网络中的等位基因变异的影响，并在PTEN的miRNA反应元件中发现了美洲原住民特有的特定遗传变异。我们提出了一个一般模型，在这个模型中，PTEN/PTENP1 3‘非编码区miRNA反应元件中的胚系遗传变异扰乱了竞争的内源RNA网络，并作为PCa侵略性特征的修饰物。为了验证这一假设，并确定在美洲原住民中具有潜在影响的变异，我们提出了以下具体目标： 具体目的1.鉴定针对PTEN和PTENPI miRNA反应元件中功能性单核苷酸多态性的miRNA，并测定miRNA在前列腺癌中的表达。我们推测，影响PTEN/PTENP1基因/假基因对miRNA靶向的变异等位基因与前列腺癌复发有关。 具体目的2.探讨靶向miRNAs的候选等位基因突变体在前列腺癌进展相关信号通路中的作用。我们假设PTENP1中存在多态，这将改变miRNA：mRNA相互作用的PTEN网络。因此，关键通路中候选miRNAs的改变将与侵袭性PCa背后的肿瘤分化机制相关。 具体目的3.发现影响抑癌基因功能的美洲原住民特有的单核苷酸多态，并检测这些SNPs与前列腺癌的相关性。我们假设，在美国原住民和美国原住民-混血人群(即拉美裔)中存在着与其他世界人口不同的丰富的基因变异，并且这种变异可能与前列腺癌风险有关。我们在这里研究可能影响基因/假基因配对之间的调节串扰并在癌症易感性和进展中发挥作用的3‘非编码区变异。

Prostate cancer (PCA) incidence and mortality rates vary widely among races in the United States. Among all men, PCA is the most commonly diagnosed form of cancer, but Native American men suffer a nearly two-fold higher rate of PCA mortality than whites following diagnosis. The extent of this disparity is not mirrored by other common cancer types, suggesting a unique burden of PCA-associated mortality in Native American men. Among the Navajo, PCA is more often diagnosed at a stage when the cancer has extended beyond the margins of the prostate (17.9% of PCA diagnoses among the Navajo, 3.3% among non-Hispanic Whites in New Mexico).These data underscore the need to understand the molecular mechanisms underlying clinically aggressive prostate cancer in all men, and Native Americans in particular. Among all races, PCA is highly heterogeneous and can vary from latent localized disease that does not require active treatment to aggressive disease associated with a high risk of mortality. Our goal is to better understand the genetic and molecular correlates of aggressive PCA. Our experimental approach will allow us to characterize genetic risk factors of particular importance to Native American populations. Previous studies have identified numerous somatic and germline genetic variants that increase risk for aggressive PCA. Of particular importance are mutations that affect the dosage of the tumor suppressor gene PTEN. Deletion of one PTEN allele occurs in 20-40% of localized PCA cancers and ~60% of metastases. Recent evidence also shows that PTEN protein loss occurs in 45% of primary tumors in the absence of deletion mutations, suggesting alternative mechanisms by which PTEN silencing is affected. Our proposed study will focus on the role of microRNA-mediated (miRNA) regulation of PTEN, which is a critical regulatory mechanism for this tumor suppressor gene. Specifically, we will identify and analyze variants in miRNA response elements of PTEN and its expressed pseudogene, PTENP1. These two genes engage in regulatory crosstalk mediated by competition for miRNAs, such that allelic variations in PTENP1 can affect indirectly the expression of PTEN. This research extends the findings of our Pilot Project which found PTEN to be affected by allelic variation in miRNA interaction networks, and identified specific genetic variants in the miRNA response elements of PTEN that are unique to Native Americans. We propose a general model whereby germline genetic variants in the miRNA response elements of PTEN/PTENP1 3'UTR perturb competing endogenous RNA networks and function as modifiers of aggressive features of PCA. To test this hypothesis, and to identify variants with potential for effects in Native Americans, we propose the following specific aims: Specific Aim 1. To identify miRNAs that target functional single nucleotide polymorphisms in PTEN and PTENPI miRNA response elements and determine miRNA expression in prostate cancer. We hypothesize that a variant alleles affecting miRNA-targeting of the PTEN/PTENP1 gene/pseudogene pair will be associated with recurrent prostate cancer Specific Aim 2.To evaluate the function of candidate allelic variant targeting miRNAs in relevant signaling pathways in prostate cancer progression. We hypothesize that there are polymorphisms in PTENP1 that will alter the PTEN network of miRNA: mRNA Interactions. Thus, alteration of candidate miRNAs in key pathways will be correlated with mechanisms of carcinoma differentiation that underlie aggressive PCA. Specific Aim 3.To discover uniquely Native American single nucleotide polymorphisms affecting tumor suppressor gene function and to test for an association of these SNPs with prostate cancer. We hypothesize that there Is abundant genetic variation in Native American and Native American-admixed populations (i.e. Hispanics) that is not shared with other world populations, and that variation may be associated with prostate cancer risk. We examine here 3'UTR variants that may affect regulatory crosstalk between gene/pseudogene pairings and play a role in cancer susceptibility and progression.