(PQD1) Response and Resistance to Inhibitors of Ras Effectors in Blood Cancers

描述（由申请方提供）：RAS原癌基因在许多不同的恶性肿瘤中发生高频率突变。因此，开发用于逆转致癌Ras的生化后果的有效治疗策略是减少全球癌症负担的根本障碍。尽管致癌RAS等位基因编码在癌细胞中稳健表达的功能获得蛋白，但Ras/GT3激活蛋白（Ras/GAP）分子开关的内在特征对开发靶向抑制剂提出了困难（如果不是不可逾越的话）的挑战。致癌Ras/GAP开关的"不可治愈"的生化特性代表了癌症治疗中未解决的中心问题。活化的Ras参与激酶效应级联的复杂网络，其中Raf/MEK/ERK和磷酸肌醇-3-OH激酶（PI3K）、Akt、雷帕霉素的哺乳动物靶标（PI3K/Akt/mTOR）途径强烈涉及癌症的起始和维持。在这个项目中，我们将利用Nf1突变株和Kras/Nras "敲入"小鼠的可移植原发性骨髓和淋巴细胞白血病，这些小鼠准确地模拟人类癌症作为一个受控的进化系统和实验平台，用于询问对小分子抑制剂的反应。特别是，我们将约40例原发性白血病移植到小鼠队列中，并单独和联合使用MEK和PI3K抑制剂治疗这些受体。我们已经从这些临床前对照试验中分离出了多个独立的耐药白血病，并表明获得性耐药遵循不同的进化轨迹。这些数据非常精确地概括了用靶向抑制剂治疗的晚期人类癌症的初始反应和最终复发。这种通用方法具有额外的优点，即提供了一个易于处理的正向遗传系统，用于发现和验证从头和获得性抗性的机制。在这里，我们建议使用这些新的试剂来询问由致癌Ras信号传导驱动的癌症的体内克隆选择，以响应MEK和PI3K抑制剂的治疗以及响应和抗性机制。本PQ提案的具体目的是：（1）研究以Nf1失活或致癌Nras/Kras突变为特征的原发性AML中对MEK抑制剂获得性耐药性的演变;（2）阐明野生型和Kras突变小鼠T-ALL的克隆结构、演变和药物应答。我们的总体目标是：（1）揭示由MEK和/或PI3K抑制剂治疗施加的选择性压力如何导致体内Ras驱动的癌症的克隆进化的生物学原理;（2）发现赋予对靶向抗癌剂的抗性的特定基因和途径;并且，在本发明中，（三）使用这些数据来开发治疗范例，用于逆转致癌Ras的不良生化输出，人体临床试验

DESCRIPTION (provided by applicant): RAS proto-oncogenes are mutated at high frequency in many different malignancies. Thus, developing effective therapeutic strategies for reversing the biochemical consequences of oncogenic Ras is a fundamental obstacle to reducing the worldwide burden of cancer. Although oncogenic RAS alleles encode gain-of-function proteins that are robustly expressed in cancer cells, intrinsic characteristics of the Ras/GTPase activating protein (Ras/GAP) molecular switch pose difficult, if not insurmountable, challenges to developing targeted inhibitors. The "undruggable" biochemical properties of the oncogenic Ras/GAP switch represent a central unsolved problem in cancer therapeutics. Activated Ras engages a complex network of kinase effector cascades of which the Raf/MEK/ERK and phosphoinositide-3-OH kinase (PI3K), Akt, mammalian Target of Rapamycin (PI3K/Akt/mTOR) pathways are strongly implicated in cancer initiation and maintenance. In this project, we will exploit transplantable primary myeloid and lymphoid leukemias from strains of Nf1 mutant and Kras/Nras "knock in" mice that accurately model human cancers as a controlled evolutionary system and experimental platform for interrogating responses to small-molecule inhibitors. In particular, we have transplanted ~40 primary leukemias into cohorts of mice, and have treated these recipients with MEK and PI3K inhibitors alone and in combination. We have isolated multiple, independent drug resistant leukemias from these controlled preclinical trials, and have shown that acquired resistance follows distinct evolutionary trajectories. These data recapitulate, with remarkable fidelity, the initial response and ultimate relapse of advanced human cancers treated with targeted inhibitors. This general approach has the additional advantage of providing a tractable forward genetic system for discovering and validating mechanisms of de novo and acquired resistance. Here we propose to use these novel reagents to interrogate in vivo clonal selection of cancers driven by oncogenic Ras signaling in response to treatment with MEK and PI3K inhibitors as well as mechanisms of response and resistance. The specific aims of this PQ proposal are: (1) to investigate the evolution of acquired resistance to MEK inhibitors in primary AML characterized by Nf1 inactivation or by oncogenic Nras/Kras mutations; and (2) to elucidate the clonal architecture, evolution, and drug responses in T-ALLs from wild-type and Kras mutant mice. Our overall goals are: (1) to reveal biologic principles underlying how the selective pressure imposed by MEK and/or PI3K inhibitor treatment leads to clonal evolution of Ras-driven cancers in vivo; (2) to discover specific genes and pathways that confer resistance to targeted anti-cancer agents; and, (3) to use these data to develop therapeutic paradigms for reversing the adverse biochemical outputs of oncogenic Ras that can be translated through human clinical trials.