Dissecting and targeting a novel vulnerability in aggressive Rb1 and p53 doubly deficient prostate cancer

Rb 1和p53双重缺陷前列腺癌中新的脆弱性的剖析和靶向 前列腺癌是全球男性第二常见的癌症，也是第二大癌症病因 美国人的死亡Rb 1和p53是两种典型的肿瘤抑制因子。一个或两个等位基因缺失 任何一个基因都导致其功能的显著缺陷，这有助于肿瘤的发生和发展。 包括前列腺癌（PCa）在内的人类癌症的研究。Rb 1和P53缺乏症（RPD）常见于 PCa病例具有侵袭性，预后不良。RPD中癌症死亡率增加的机制- PCa还远未得到很好的理解，这阻碍了有效治疗方法的发展。我们的目标是 研究RPD PCa进展的潜在机制，并针对RPD的新漏洞- PCa细胞。我们已经发现GPCR-激酶3（GRK 3）在RPD-PCa中的表达显著高于在RPD-PCa中的表达。 非RPD-PCa。与此一致，GRK 3表达与Rb 1丢失或p53丢失基因特征相关。使用 我们已经获得了调节GRK 3的遗传和药理学工具，我们已经开始获得关键的 GRK 3和RPD在PCa中的作用机制。我们已经确定了一个关键的表观遗传调节因子， GRK 3作为其激酶底物激活。我们的初步数据显示GRK 3沉默优先消融 RPD-PCa细胞，并且其敲除抑制PCa进展并延长TRAMP小鼠的存活期，RPD-PCa细胞的基因敲除抑制PCa进展并延长TRAMP小鼠的存活期。 相关的基因工程小鼠（GEM）模型。基于这些结果，我们的总体假设是 GRK 3对RPD-PCa细胞的分子机制和适应性至关重要， 通过其底物的信号传导是RPD侵袭性机制的重要部分。以GRK 3为目标 为了深入研究其在RPD细胞中发挥作用的分子机制， 筛选并鉴定了两种有效阻断GRK 3活性的强效且一流的GRK 3抑制剂， 优先消融RPD-PCa细胞。我们还假设，用这些抑制剂阻断GRK 3， 阻止RPD肿瘤生长和转移。为了验证这些假设，我们提出了三个目标：1。 通过检查GRK 3在异种移植模型中沉默的影响，验证GRK 3在RPD-PCa中是一种新的脆弱性 及其在遗传定义的RPD GEM模型中的敲除; 2.确定GRK 3抑制剂对 RPD-PCa细胞的性质，以及对RPD-PCa细胞衍生的和患者衍生的肿瘤细胞中的癌症进展的影响。 异种移植模型; 3.剖析RPD中GRK 3介导的攻击性的分子机制。 这些工作的完成有望建立一个新的激酶-底物关系的基础RPD生物学 并将GRK 3定义为RPD-PCa的致命弱点。它还将验证将GRK 3作为新的方向， 开发有效的治疗致命前列腺癌的药物。我们的发现将对我们的理解产生影响， 靶向RPD常见的其他侵袭性癌症类型。

Dissecting and targeting a novel vulnerability in Rb1 and p53 doubly deficient prostate cancer Prostate cancer is the second most common cancer in men worldwide and the second leading cause of cancer death in American men. Rb1 and p53 are two prototypical tumor suppressors. Loss of one or both alleles of either gene leads to significant deficiency in its functions, which contributes to the oncogenesis and progression of human cancers, including prostate cancer (PCa). Concurrent Rb1 and P53 Deficiency (RPD) is common in PCa cases that are aggressive and have poor prognosis. The mechanisms of increased cancer mortality in RPD- PCa are far from well understood, which has hindered the development of effective treatments. Our goal is to investigate the mechanisms underlying RPD PCa progression and to target novel vulnerabilities of RPD- PCa cells. We have found that GPCR-kinase 3 (GRK3) is expressed significantly higher in RPD-PCa than in non-RPD-PCa. In line with this, GRK3 expression correlates with Rb1-loss or p53-loss gene signatures. Using the genetic and pharmacological tools that we have acquired to modulate GRK3, we have begun to gain critical insights into the mechanisms of GRK3 and RPD in PCa. We have identified a key epigenetic regulator that is activated by GRK3 as its kinase substrate. Our preliminary data show that GRK3 silencing preferentially ablates RPD-PCa cells, and that its knockout inhibits PCa progression and extend survival of the TRAMP mice, a RPD- related genetically engineered mouse (GEM) model. Our overarching hypothesis based on these results is that GRK3 is essential for the molecular mechanisms and the fitness of RPD-PCa cells, and that GRK3 signaling through its substrates is a vital part of the mechanisms of RPD aggressiveness. To target GRK3 and to dissect molecular mechanisms underlying its function in RPD cells, we have carried out compound library screens and identified two potent and first-in-class GRK3 inhibitors which effectively block GRK3 activity and preferentially ablate RPD-PCa cells. We also hypothesize that blocking GRK3 with these inhibitors will thwart RPD tumor growth and metastasis. To test these hypotheses, we propose to pursue three Aims: 1. validate GRK3 as a novel vulnerability in RPD-PCa by examining the effects of its silencing in xenograft models and its knockout in a genetically defined RPD GEM model; 2. determine the impact of GRK3 inhibitors on the properties of RPD-PCa cells, as well as on the cancer progression in RPD-PCa cell-derived and patient-derived xenograft models; 3. dissect the molecular mechanisms underlying GRK3-mediated aggressiveness in RPD. Completion of these works is expected to establish a novel kinase-substrate relationship underlying RPD biology and define GRK3 as an Achilles heel of RPD-PCa. It will also validate targeting GRK3 as a new direction for developing effective therapeutics for lethal PCa. Our findings will have an impact on our understandings and targeting of other aggressive cancer types where RPD is common.