Isoform-specific signaling as a determinant of RAS-driven oncogenesis

项目摘要/摘要：科尔图姆，罗伯特L. 我们的数据表明，RTK−SOS1/2−WT RAS信号是RAS突变癌症的关键治疗靶点。 我们的目标是区分抑制RTK−SO1/2−WT的RAS突变的癌症 RAS−效应信号应作为整体有效治疗策略的一部分。 直接抑制RAS作为一种单一疗法并不是长期有效的。RAS蛋白表现出不同的激活 RAF和PI3K通路：HRAS有效地激活PI3K，但对RAF的激活很弱，而KRAS有效 激活RAF，但激活PI3K效果不佳。由于这些差异，抑制突变的RAS不会有效 抑制RAF和PI3K通路。此外，与MEK抑制类似，突变的RAS抑制解除 负反馈控制导致RTK−WT RAS信号的快速过度激活。一个更全面的 了解突变体RAS和RTK−WT RAS信号之间的相互作用对发展至关重要 治疗RAS基因突变癌症的合理治疗方法。 我们发现，抑制RAS效应器被突变体RAS激活得很差，与抗药性协同并限制了抗药性 突变的HRAS和KRAS抑制剂。突变型HRAS抑制剂tipifarnib阻断PI3K信号并协同作用 对于MEK抑制剂，共价KRASG12C抑制剂阻断MEK信号并与PI3K抑制剂协同作用。我们 还发现RASGEF SOS1和SOS2具有促进突变的独特且重叠的功能 RAS驱动的转型。SOS1是突变体RAS激活的关键，抑制SOS1增加了 突变型RAS抑制剂的疗效。RTK−SOS2−PI3K信号保护细胞免受失巢诱导并介导突变体 KRAS驱动的转化依赖于PI3K突变状态。SOS2 KO与MEK抑制剂的协同作用 仅在PPIK3CA WT细胞中，而SRC抑制剂仅在PIK3CA突变的细胞中与MEK抑制剂协同作用 正如之前报道的那样。这些观察结果表明，抑制RTK−SO1/2−WT RAS−效应器信号转导将削弱对突变的RAS或 下游RAS效应器。我们将通过以下目标来检验这一假设： 这一建议阐明了SOS1/2−WT RAS信号驱动的分子机制 携带特定突变RAS亚型的癌症的转化。我们使用组合的方法进行研究 已定义的遗传模型系统和更多与癌症相关的系统，包括CRISPR修饰的人类癌症 细胞系、异种移植研究和使用GEMM模型的研究：确定WT RAS如何形成信号转导 与致癌RAS合作，促进致癌转化。描述SOS1在以下方面的角色 突变的RAS驱动的增殖和转化，包括独立的和与SOS2结合的。 建立SOS2和SRC作为结肠癌患者来源的有机化合物的治疗靶点 KRAS和PIK3CA突变状态。我们的发现将为根除癌症提供新的治疗方法 RAS基因突变的肿瘤亚群具有基因相关的精确度。

Project Summary/Abstract PI: Kortum, Robert L. Our data show that RTK−SOS1/2−WT RAS signaling is a critical therapeutic target in RAS-mutated cancers. Our objective is to differentiate between those RAS-mutated cancers in which inhibiting RTK−SOS1/2−WT RAS−effector signaling should be part of an overall effective therapeutic strategy. Direct RAS inhibition as a monotherapy is not effective long-term. RAS proteins show differential activation of RAF and PI3K pathways: HRAS potently activates PI3K but poorly activates RAF, whereas KRAS potently activates RAF but poorly activates PI3K. Because of these differences, inhibiting mutant RAS will not effectively inhibit both the RAF and PI3K pathways. Further, similar to MEK inhibition, mutant RAS inhibition relieves negative feedback controls leading to rapid hyperactivation of RTK−WT RAS signaling. A more comprehensive understanding of the interplay between mutant RAS and RTK−WT RAS signaling is essential to developing rational therapeutic approaches to treat RAS-mutated cancers. We found inhibition of RAS effectors activated poorly by mutant RAS synergizes with and limits resistance to mutant HRAS and KRAS inhibitors. The mutant HRAS inhibitor tipifarnib blocks PI3K signaling and synergizes with MEK inhibitors; covalent KRASG12C inhibitors block MEK signaling and synergize with PI3K inhibitors. We also found that the RASGEFs SOS1 and SOS2 have unique and overlapping functions that promote mutant RAS-driven transformation. SOS1 is critical for mutant RAS activation and SOS1 inhibition augments the efficacy of mutant RAS inhibitors. RTK−SOS2−PI3K signaling protects cells from anoikis and mediates mutant KRAS-driven transformation depending on the PI3K mutational status. SOS2 KO synergizes with MEK inhibitors only in PPIK3CA WT cells, whereas SRC inhibitors synergize with MEK inhibitors only in PIK3CA-mutated cells as was previously reported. These observations suggest the hypothesis that inhibiting RTK−SOS1/2−WT RAS−effector signaling will impair resistance to, and augment, current therapeutics targeting mutated RAS or downstream RAS effectors. We will test this hypothesis with the following Aims: This proposal elucidates the molecular mechanisms through which SOS1/2−WT RAS signaling drives transformation of cancers harboring specific mutant RAS isoforms. We perform studies using a combination of defined genetic model systems and more cancer-relevant systems including CRISPR-modified human cancer cell lines, xenograft studies, and studies using GEMM models to: Determine how WT RAS isoform signaling cooperates with oncogenic RAS to promote oncogenic transformation. Characterize the role of SOS1 in mutant RAS-driven proliferation and transformation, both independently and in combination with SOS2. Establish SOS2 and SRC as therapeutic targets in patient-derived colon cancer organoids based on KRAS and PIK3CA mutation status. Our findings will inform novel therapeutic approaches for eradicating subsets of RAS-mutated tumors with genotype-dependent precision.