RET Regulation and Targeting in Neuroendocrine Prostate Cancer

项目总结/摘要 前列腺癌（PCa）是美国男性癌症相关死亡的第二大原因。典型地， 前列腺癌的治疗包括阻断雄激素合成或雄激素受体（AR）信号传导， 雄激素剥夺疗法（ADT）。虽然最初的反应率是有希望的，所有的人最终进展 接受ADT治疗并发生去势抵抗性前列腺癌（CRPC）伴转移性负荷。 转移性CRPC是不可治愈的，越来越多的男性正在发展CRPC的高致命性变体 称为侵袭性变异前列腺癌（AVPC）。AR信令在AVPC中丢失， 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） 前列腺癌属于神经内分泌性前列腺癌（NEPC），是我们研究的重点。非常 在这种情况下，存在很少的治疗方法并且仅提供最小的生存益处。因此，功能评估 需要其他蛋白质药物靶点来有效治疗NEPC。我们之前已经证明，激酶信号 可能是CRPC中有前途的治疗替代方案。我们研究的目的是了解 调节激酶基因表达增加的机制，导致激酶途径活化，以及如何 有效靶向NEPC中的这些激酶。我们的假设是RET mRNA和蛋白的上调是由 ASCL 1是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突变是免疫缺陷综合征的关键驱动因素和治疗靶点。 其他具有NE特征的癌症，如甲状腺乳头状癌和小细胞肺癌。重要的是 RET激酶信号在NEPC活力中的作用还没有完全阐明。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ASCL 1而过表达， 在NEPC的小鼠模型和类器官、人细胞系和临床NEPC中酶促活化 肿瘤的我们的工作还表明，RET激酶抑制减少体内异种移植肿瘤生长和体外 NEPC的小鼠类器官模型。本项目的目标是：1）确认ASCL 1作为直接转录因子， RET的调节因子，2）定义RET活性特征并评估该特征与治疗的关联 临床样品中的耐药性和NEPC，以及3）优化与新型RET抑制剂的共靶向策略， NEPC模型系统。这些目标被共同设计来研究RET激酶作为一种 NEPC（PCa的一种不可治愈变体）中的关键治疗靶点。虽然激酶抑制剂被批准用于治疗 在几种上皮癌中，激酶抑制剂在PCa中的临床试验令人失望。我们的数据 表明这可能是由于缺乏适当的患者分层，在错误的临床背景下给药， 和不适当的联合治疗。因此，拟议工作的成果将为以下方面提供新的见解： 选择联合疗法治疗NEPC，使用可实施的再用途激酶抑制剂 在临床试验中迅速地应用于患有这种致命性前列腺癌的患者。

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.