Selectively Targeting Oncogenic NRAS in Cancer

 描述（由申请人提供）：RAS原癌基因在约30%的人类癌症中发生突变，但不存在用于逆转致癌Ras蛋白的生化输出的基于机制的治疗，这是合理药物发现的极其困难的靶点。我们的长期目标是实施机械策略，以选择性地抑制具有体细胞RAS突变的癌症的生长。在这个项目中，我们将研究Ras棕榈酰化/脱棕榈酰化循环，它调节N-Ras，H-Ras和K-Ras 4a亚型的亚细胞运输，作为选择性抑制致癌NRAS突变恶性肿瘤生长的治疗靶点。酰基蛋白硫酯酶1和2（APT 1和APT 2）催化N-Ras去棕榈酰化，并且我们发现设计用于抑制这些酶的“第一代”化学抑制剂（Palmostatin B和Palmostatin M）选择性地减少表达致癌N-RasG 12 D的原代造血祖细胞和白血病细胞的生长。然而，我们最近的研究也推断出这些化合物的其他生化靶点的存在，这些靶点对NRAS突变癌细胞的生长至关重要。该项目涉及跨学科合作，汇集了在合成化学（豪厄尔博士），酶学和化学生物学（Cravatt博士），血液癌症，Ras信号传导和临床前治疗（香农博士）方面具有广泛专业知识的研究人员。我们已经合作产生了广泛的初步数据和新试剂，我们将使用这些数据和试剂来实现以下目标：（1）鉴定palmostatin的其他生化靶标;（2）开发对palmostatin靶标具有改进的效力和选择性的新化学抑制剂;（3）使用这些抑制剂与遗传学方法相结合来识别调节癌细胞中N-Ras脱棕榈酰化的相关酶;和（4）利用人癌细胞系和新品系的小鼠来研究棕榈酰化/去棕榈酰化循环作为早期和晚期NRAS突变型癌症的治疗靶点。我们将通过两个高度综合的具体目标来解决这些问题。在目标1中，我们将确定palmostatin M的其他生化靶点，设计和表征新的化学抑制剂，并评估这些化合物在NRAS突变癌细胞中的疗效。在目标2中，我们将利用NrasG 12 D，C181 S“敲入”小鼠的新品系来询问棕榈酰化/去棕榈酰化循环是否是致癌Nras驱动的癌症在体内生长所需的。这些研究将严格评估棕榈酰化/脱棕榈酰化循环的重要性，并为具有致癌RAS突变的癌症的新治疗策略的开发提供信息。

 DESCRIPTION (provided by applicant): RAS proto-oncogenes are mutated in ~30% of human cancers, but no mechanism-based treatments exist for reversing the biochemical output of oncogenic Ras proteins, which are exceedingly difficult targets for rational drug discovery. Our long-term goal is to implement mechanistic strategies to selectively inhibit the growth of cancers with somatic RAS mutations. In this project, we will investigate the Ras palmitoylation/depalmitoylation cycle, which regulates the subcellular trafficking of the N-Ras, H-Ras, and K-Ras4a isoforms, as a therapeutic target for selectively inhibiting the growth of malignancies with oncogenic NRAS mutations. Acyl protein thioesterase 1 and 2 (APT1 and APT2) catalyze N-Ras depalmitoylation and we found that "first generation" chemical inhibitors designed to inhibit these enzymes (Palmostatin B and Palmostatin M) selectively reduced the growth of primary hematopoietic progenitors and leukemia cells expressing oncogenic N-RasG12D. However, our recent studies also infer the existence of additional biochemical targets of these compounds that are essential for the growth of NRAS mutant cancer cells. This project involves a cross-disciplinary collaboration that brings together investigators with extensive expertise in synthetic chemistry (Dr. Howell), enzymology and chemical biology (Dr. Cravatt), and hematologic cancer, Ras signaling, and preclinical therapeutics (Dr. Shannon). We have collaborated to generate extensive preliminary data and novel reagents, which we will use to pursue the goals of: (1) identifying additional biochemical targets of the palmostatins; (2) developing new chemical inhibitors with improved potency and selectivity for palmostatin targets; (3) using these inhibitors combined with genetic methods to discern the relevant enzyme(s) that regulate N-Ras depalmitoylation in cancer cells; and, (4) utilizing human cancer cell lines and a new strain of mice to interrogate the palmitoylation/depalmitoylation cycle as a therapeutic target in early stage and advanced NRAS-mutant cancers. We will address these questions through two highly integrated specific aims. In Aim 1, we will identify additional biochemical targets of palmostatin M, design and characterize new chemical inhibitors, and evaluate the efficacy of these compounds in cancer cells with NRAS mutations. In Aim 2, we will utilize a novel strain of NrasG12D,C181S "knock in" mice to ask if the palmitoylation/depalmitoylation cycle is required for the growth of oncogenic Nras-driven cancers in vivo. These studies will rigorously assess the importance of the palmitoylation/depalmitoylation cycle and inform the development of new therapeutic strategies for cancers with oncogenic RAS mutations.