RET Regulation and Targeting in Neuroendocrine Prostate Cancer

项目摘要/摘要 前列腺癌(PCA)是美国男性癌症相关死亡的第二大原因。通常， 前列腺癌的治疗包括阻断雄激素合成或雄激素受体(AR)信号传递，称为 雄激素剥夺疗法(ADT)。尽管最初的应答率是有希望的，但所有男性最终都会进步 抗去势前列腺癌(CRPC)伴发转移负担。 转移性CRPC是无法治愈的，越来越多的男性患上了一种高度致命的CRPC变种 被称为侵袭性变异前列腺癌(AVPC)。AR信令在AVPC中丢失，导致现有 激素靶向治疗无效。大约三分之一的AVPC肿瘤也表达神经内分泌(NE)。 基因，被归类为神经内分泌前列腺癌(NEPC)，这是我们研究的重点。非常 目前存在的治疗方法很少，而且在这种情况下只提供最低限度的生存益处。因此，功能评估 需要其他蛋白质药物靶点才能有效治疗NEPC。我们之前已经证明了激酶信号转导 通路可能是治疗慢性前列腺癌的有前景的替代方案。我们研究的目标是了解 调节增加的激酶基因表达，导致激酶途径激活的机制，以及如何 有效地靶向NEPC中的这些激酶。我们的假设是，RET mRNA和蛋白质的上调是由 通过ASCL1，一种主要的神经转录调节因子，RET激酶介导的活性作为一种 NEPC的治疗脆弱性。众所周知，RET基因突变是人类免疫缺陷的关键驱动因素和治疗靶点。 其他具有NE特征的癌症，如乳头状甲状腺癌和小细胞肺癌。重要的是， RET激酶信号在NEPC活性中的作用尚未完全阐明。我们的初步数据显示 RET激酶通过激活神经元分化转录因子ASCL1而过表达 在小鼠模型和有机体中被酶激活的NEPC，在人类细胞系中，在临床NEPC中 肿瘤。我们的工作还表明，抑制RET激酶在体内和体外都能减少异种移植瘤的生长 NEPC的小鼠器官模型。这个项目的目标是：1)确认ASCL1是一个直接转录的 RET调节器，2)定义RET活动特征并评估该特征与治疗的关联 临床样本中的耐药性和NEPC，以及3)优化与新型RET抑制剂的联合靶向策略 NEPC模型系统。这些目标共同设计来研究RET激酶作为一种 NEPC的关键治疗靶点，它是PCA的一个不可治愈的变种。而激酶抑制剂被批准用于治疗 在几种上皮性癌症中，用于治疗前列腺癌的激酶抑制剂的临床试验一直令人失望。我们的数据 表明这很可能是由于缺乏适当的患者分层，在错误的临床环境下实施， 以及不恰当的联合治疗。因此，拟议工作的结果将为 选择治疗NEPC的联合疗法，使用可能实施的重新调整用途的激酶抑制剂 迅速在临床试验中对这一亚型致命性前列腺癌患者进行试验。

PROJECT SUMMARY/ABSTRACT Prostate cancer (PCa) is the second leading cause of cancer related death in American men. Typically, treatment for PCa involves blocking androgen synthesis or androgen receptor (AR) signaling known as androgen deprivation therapy (ADT). Although initial response rates are promising, all men eventually progress on ADT and develop castration resistant prostate cancer (CRPC) concomitant with metastatic burden. Metastatic CRPC is incurable and an increasing number of men are developing a highly lethal variant of CRPC known as aggressive variant prostate cancer (AVPC). AR signaling is lost in AVPC rendering the existing hormone targeting treatments ineffective. About a third of AVPC tumors also express neuroendocrine (NE) genes and are classified as neuroendocrine prostate cancer (NEPC), which is the focus of our studies. Very few therapies exist and only offer minimal survival benefits in this setting. Hence, functional assessment of other protein drug targets is needed to effectively treat NEPC. We have previously shown that kinase signaling pathways may be promising therapeutic alternatives in CRPC. The goal of our research is to understand the mechanisms regulating increased kinase gene expression, leading to kinase pathway activation, and how to effectively target these kinases in NEPC. Our hypothesis is that RET mRNA and protein up-regulation is driven by ASCL1, a master neural transcriptional regulator, and that RET kinase-mediated activity serves as a therapeutic vulnerability in NEPC. It is known that RET mutations are key drivers and therapeutic targets in other cancers with NE features such as papillary thyroid carcinoma and small cell lung cancer. Importantly, the contribution of RET kinase signaling in NEPC viability is not entirely elucidated. Our preliminary data shows that RET kinase is overexpressed via activation of a neuronal differentiation transcription factor, ASCL1, and enzymatically activated in mouse models and organoids of NEPC, in human cell lines, and clinical NEPC tumors. Our work also shows that RET kinase inhibition reduces in vivo xenograft tumor growth and in in vitro mouse organoid models of NEPC. The goals of this project are to: 1) confirm ASCL1 as a direct transcriptional regulator of RET, 2) define a RET activity signature and assess the association of this signature to treatment resistance and NEPC in clinical samples, and 3) optimize co-targeting strategies with novel RET inhibitors in NEPC model systems. These goals are collectively designed to investigate the mechanism of RET kinase as a key therapeutic target in NEPC, an incurable variant of PCa. While kinase inhibitors are approved for treatment of several epithelial cancers, clinical trials of kinase inhibitors in PCa have been disappointing. Our data indicate this is likely due to lack of appropriate patient stratification, administered in the wrong clinical context, and improper combination therapies. Hence, the outcomes of the proposed work will provide new insights into select combination therapies for treating NEPC, using re-purposed kinase inhibitors that may be implemented quickly in clinical trials of patients with this subset of lethal PCa.