Molecular determinant of racial disparity in prostate cancer

描述（由申请人提供）：非裔美国人（AA）男性与其欧洲裔美国人（EA）男性之间前列腺癌（PCa）的发病率和临床结局存在显著差异。尽管有这样的认识，我们在理解与这种差异相关的分子原因方面还没有取得重大飞跃。这一建议是建立在我们强大的初步数据的原癌基因，Myb，这在很大程度上仍然是未开发的PCa。我们的新发现表明，1）与EA PCa相比，AA PCa中Myb表达显著升高，总体发生率更高，2）在AA患者的一些良性前列腺组织（BPH）中也检测到Myb的低强度表达，而在EA BPH中未检测到表达，3）AA PCa细胞系（MDaPCa-2b和RC-77/T）表现出高Myb表达和对细胞耗竭和多西他赛（DTX）毒性的显著抗性，4）AA PCa细胞还表现出高生长、迁移和侵袭潜力，5）Myb与AR相互作用，调节雄激素反应基因KLK 3/PSA的表达，提示它们在基因调控中的协同作用。基于这些有希望的发现，我们假设AA PCa细胞中Myb的相对更高的发病率和总体表达是其固有的更大的转移倾向和逃避治疗干预的基础。为了验证这一假设，我们提出了三个具体目标。在目的1中，我们将研究Myb在PCa侵袭性和治疗抵抗中的作用。使用酶标记的，Myb过表达或沉默，配对AA和EA PCa细胞系，我们将研究Myb与PCa生长和转移的功能相关性，以及它们对去势和多西他赛治疗的反应。在目标2中，我们将研究Myb-AR相互作用的功能后果，并确定其下游后果。我们将专门研究Myb是否在AR定位和转录激活中发挥作用。此外，我们将通过使用最先进的RNA-Seq和ChIP-Seq方法评估Myb对AR转录重编程的影响。我们将确定PCa细胞中Myb和AR的共同和独立靶点，并检查Myb是否改变AR靶基因特异性。在目标3中，我们将确定Myb在与PCa相关的种族差异中的临床相关性。我们将进行免疫组化（IHC）分析，以评估Myb和AR在前列腺癌、邻近BPH和AA和EA病例未累及的正常组织中的表达和定位（细胞质与细胞核）。然后，我们将研究它们与种族、肿瘤分级、转移发生率、PSA水平和患者生存率的相关性（单独和组合）。总之，这些研究将为Myb在PCa的攻击行为和治疗抗性中的作用提供实验、机制和临床证据，并支持Myb与观察到的种族差异的关联。从长远来看，由此产生的信息将有助于减少种族歧视， 通过建立Myb作为有效疾病管理的风险预测因子和/或治疗靶点的临床效用，评估PCa临床结局的差异。

DESCRIPTION (provided by applicant): Significant disparity in the incidence and clinical outcome of prostate cancer (PCa) exist between African- American (AA) men and their European American (EA) counterparts. Despite this recognition, we have not made a major leap in our understanding of the molecular causes associated with such disparity. This proposal is built upon our strong preliminary data on a proto-oncogene, Myb, which has remained largely unexplored in PCa. Our novel findings demonstrate that 1) Myb expression is significantly elevated in AA PCa with greater overall incidence as compared to EA PCa, 2) low intensity expression of Myb is also detected in some of the benign prostate tissues (BPH) from AA patients, while no expression is detected in EA BPH, 3) AA PCa cell lines (MDaPCa-2b and RC-77/T) exhibit high Myb expression and significant resistance to hormone-depletion and docetaxel (DTX) toxicity, 4) AA PCa cells also display high growth, migratory and invasive potential, which is associated with Myb overexpression, and 5) Myb interacts with AR and modulates the expression of androgen-responsive gene, KLK3/PSA, suggesting their cooperative role in gene regulation. Based on these promising findings, we hypothesize that relative greater incidence and overall expression of Myb in AA PCa cells underlies their inherently greater propensity to metastasize and evade therapeutic intervention. To test this hypothesis, we are proposing three specific aims. In aim 1, we will investigate the role of Myb in PCa aggressiveness and therapy-resistance. Using luciferase-tagged, Myb-overexpressing or -silenced, paired AA and EA PCa cell lines, we will examine the functional association of Myb with PCa growth and metastasis, and their response to castration- and docetaxel- therapies in an orthotopic mouse model. In Aim 2, we will examine the functional consequences of Myb-AR interaction and identify their downstream consequences. We will specifically examine whether Myb has a role in AR localization and transcriptional activation. Furthermore, we will assess the effect of Myb on transcriptional reprogramming of AR by using state of the art RNA-Seq and ChIP-Seq approaches. We will determine the shared and independent targets of Myb and AR in PCa cells and examine if Myb alters AR target gene specificity. In Aim 3, we will determine the clinical relevance of Myb in racial disparity associated with PCa. We will perform immunohistochemical (IHC) analysis to assess Myb and AR expression and localization (cytoplasmic vs. nuclear) in PCa, adjacent BPH, and uninvolved normal tissues from both AA and EA cases. We will then examine their correlation (alone and in combination) with race, tumor grade, metastasis incidence, PSA levels, and patient's survival. Together, these studies will provide experimental, mechanistic and clinical evidence for the role of Myb in aggressive behavior and therapeutic- resistance of PCa, and support the association of Myb with observed racial disparity. In the long-term, the resulting information will be useful in reducing the racial disparities in clinical outcomes of PCa by establishing the clinical utility of Myb as a risk predictor and/or therapeutic target for effective disease management.