Identification of resistance mechanisms to direct KRAS inhibition in pancreatic cancer

项目摘要/摘要 胰腺癌是美国癌症死亡的第三大原因，对有效治疗的需求是 太可怕了。KRAS在~95%的胰腺导管腺癌(PDAC)中突变激活，PDAC是主要的胰腺癌 癌症亚型。细胞培养和小鼠模型分析为突变的KRAS的作用提供了强有力的验证 在PDAC的维护方面，NCI已将KRAS靶向疗法的开发确定为四种 该领域的主要优先事项。Sotorasib最近被FDA批准为第一个用于治疗 KRASG12C-突变肺癌。然而，索托拉西布和所有其他临床候选药物在PDAC中的临床应用 有两个主要原因。首先，sotorasib针对的是KRASG12C，这是一种突变，代表着不到2%的 PDAC中的KRAS突变。针对其他KRAS突变的KRAS抑制剂目前处于临床前阶段 发展。其次，最初对KRASG12C抑制剂有反应的患者很快都会复发。早期的研究表明 开始确定驱动抗性的遗传事件，并在 病人。然而，在大约一半的复发患者中，还没有明确的机制。完整的描述 将需要这些机制中的一个来开发有效的组合，以延长患者对 KRAS-靶向治疗。该建议建立在理解KRAS驱动程序的新兴概念基础上 机制，不同的突变对KRAS功能造成不同的后果。因此，有 突变特异性驱动功能，可用于开发突变选择性联合疗法。 这些研究集中在PDAC-KRASG12R中两个较少研究的非典型KRAS突变，这是出人意料的 和KRASQ61H，这是出人意料的罕见。拟议的研究将利用直接的药理学 PDAC中KRASG12R和KRASQ61H的抑制剂。全系统无偏遗传功能丧失CRISPR/CAS9 致癌信号通路文库将用于确定对KRAS的治疗耐药机制 抑制力。初步数据有力地表明了已知和新的抗性机制。最后，因为 KRASG12R和KRASQ61H突变的胰腺癌表现出明显的功能差异，这些研究将 可能识别对KRAS抑制的共同和不同的抗性机制，这将导致不同的 KRAS抑制剂联合应用的方法。该方案还描述了KrasG12R和KrasQ61H的开发 同基因原位胰腺癌小鼠模型。这些新模型将被用来定义突变- 特定的癌症功能，并能够评估肿瘤微环境对 单独和联合抑制KRAS的后果。这项提议的首要目标是进一步 阐明两个非典型KRAS突变是如何推动PDAC生长的，并为鉴定 可以提高突变特异性抗KRAS策略在PDAC中的临床疗效。

Project Summary/Abstract Pancreatic cancer is the 3rd leading cause of cancer death in the USA and the need for effective therapies is dire. KRAS is mutationally activated in ~95% of pancreatic ductal adenocarcinoma (PDAC), the major pancreatic cancer subtype. Cell culture and mouse model analyses provide strong validation for the role of mutant KRAS in the maintenance of PDAC, and the NCI has identified development of KRAS-targeted therapies as one of four major priorities for the field. Sotorasib was recently FDA-approved as the first direct KRAS inhibitor for use in KRASG12C-mutant lung cancer. However, the clinical utility of sotorasib and all other clinical candidates in PDAC is limited for two main reasons. First, sotorasib targets KRASG12C, a mutation that represents less than 2% of KRAS mutations in PDAC. KRAS inhibitors that target other KRAS mutations are currently under preclinical development. Second, patients initially responsive to KRASG12C inhibitors all soon relapse. Early studies have begun to identify genetic events that drive resistance, with expected components of RAS signaling identified in patients. However, no clear mechanisms have been identified in about half of relapsed patients. A full delineation of these mechanisms will be needed to develop effective combinations that can prolong patient response to KRAS-targeted therapies. This proposal builds on the emerging concept in understanding KRAS driver mechanisms, that different mutations cause distinct consequences on KRAS function. Consequently, there are mutation-specific driver functions that can be exploited to develop mutation-selective combination therapies. These studies focus on two lesser-studied, atypical KRAS mutations in PDAC – KRASG12R, which is unexpectedly enriched, and KRASQ61H, which is unexpectedly rare. The proposed studies will utilize direct pharmacologic inhibitors of KRASG12R and KRASQ61H in PDAC. System-wide unbiased genetic loss-of-function CRISPR/Cas9 oncogenic signaling pathway libraries will be used to identify therapeutic resistance mechanisms to KRAS inhibition. Preliminary data strongly implicate both known and novel resistance mechanisms. Finally, because KRASG12R and KRASQ61H-mutant pancreatic cancers exhibit distinct functional differences, these studies will likely identify both common and distinct resistance mechanisms to KRAS inhibition, which will lead to distinct KRAS inhibitor combination approaches. This proposal also describes the development of KrasG12R and KrasQ61H syngeneic, orthotopic pancreatic cancer mouse models. These new models will be used to define mutation- specific cancer functions, and to enable assessment of the influence of the tumor microenvironment on the consequences of KRAS inhibition alone and in combination. The overarching goals of this proposal are to further elucidate how two atypical KRAS mutations drive PDAC growth and to inform identification of combinations that can increase the clinical effectiveness of mutation-specific anti-KRAS strategies in PDAC.