Selectively Targeting Oncogenic NRAS in Cancer

 描述(申请人提供)：RAS原癌基因在约30%的人类癌症中发生突变，但没有基于机制的治疗方法来逆转致癌RAS蛋白的生化输出，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性策略，选择性地抑制带有体细胞RAS突变的癌症的生长。在这个项目中，我们将研究调节N-RAS、H-RAS和K-Ras4a亚型亚细胞转运的RAS棕榈化/去醛化循环，作为选择性抑制具有致癌NRAS突变的恶性肿瘤的治疗靶点。酰基蛋白硫酯酶1和2(APT1和APT2)催化N-Ras脱氨基转移，我们发现第一代抑制这些酶的化学抑制剂(Palmostatin B和Palmostatin M)选择性地抑制原代造血祖细胞和表达致癌基因N-RasG12D的白血病细胞的生长。然而，我们最近的研究也推断，这些化合物存在其他对NRAS突变癌细胞生长至关重要的生化靶点。该项目涉及跨学科合作，汇集了在合成化学(Howell博士)、酶学和化学生物学(Cravatt博士)、血液学癌症、RAS信号和临床前治疗(Shannon博士)等领域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颖的试剂，我们将利用这些数据和试剂实现以下目标：(1)确定Palmostatin的更多生化靶点；(2)开发针对Palmostatin靶点的具有更高效力和选择性的新型化学抑制剂；(3)将这些抑制剂与遗传学方法结合使用，以识别调节癌细胞N-RAS脱氨酸化的相关酶(S)；以及(4)利用人类癌细胞株和一种新的小鼠品系来研究Palmito化/脱醛核酸化循环，作为早期和晚期NRAS突变癌症的治疗靶点。我们将通过两个高度整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，并评估这些化合物对具有NRAS突变的癌细胞的疗效。在目标2中，我们将利用一种新的NrasG12D品系，C181S“敲入”小鼠来研究体内致癌NRAS驱动的癌症的生长是否需要棕榈酸化/去醛酸化循环。这些研究将严格评估棕榈酸化/去醛酸化循环的重要性，并为开发具有致癌RAS突变的癌症的新治疗策略提供信息。

 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.