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

项目摘要/摘要PI：Kortum，Robert L. 我们的数据表明，RTK− SOS 1/2−WT RAS信号是RAS突变癌症的关键治疗靶点。 我们的目标是区分那些RAS突变的癌症，其中抑制RTK− SOS 1/2−WT RAS效应信号应该是整体有效治疗策略的一部分。 直接RAS抑制作为单药治疗不是长期有效的。RAS蛋白表现出不同的激活作用， RAF和PI 3 K途径：HRAS有效激活PI 3 K，但激活RAF的能力较差，而KRAS有效激活PI 3 K， 激活RAF，但很难激活PI 3 K。由于这些差异，抑制突变型RAS将不能有效地 抑制RAF和PI 3 K通路。此外，与MEK抑制类似，突变型RAS抑制缓解了 负反馈控制导致RTK-WT RAS信号的快速超活化。更全面 理解突变型RAS和RTK-WT RAS信号之间的相互作用对于开发 治疗RAS突变癌症的合理治疗方法。 我们发现，抑制突变型RAS激活的RAS效应子，可协同并限制对 突变型HRAS和KRAS抑制剂。突变型HRAS抑制剂替吡法尼阻断PI 3 K信号传导并协同 与MEK抑制剂一起使用;共价KRASG 12 C抑制剂阻断MEK信号传导并与PI 3 K抑制剂协同作用。我们 我们还发现，RASGEFs SOS 1和SOS 2具有独特和重叠的功能，可以促进突变体的形成， RAS驱动的转型。SOS 1对突变型RAS激活至关重要，而SOS 1抑制可增强突变型RAS激活。 突变型RAS抑制剂的功效。RTK− SOS 2 − PI 3 K信号通路保护细胞免于失巢凋亡并介导突变 KRAS驱动的转化取决于PI 3 K突变状态。SOS 2 KO与MEK抑制剂协同作用 仅在PPIK 3CA WT细胞中，而SRC抑制剂仅在PIK 3CA突变的细胞中与MEK抑制剂协同作用 如先前所报道的。这些观察结果表明，抑制RTK− SOS 1/2−WT RAS效应信号传导将削弱对当前靶向突变RAS或RAS受体的疗法的抵抗力，并增强这种抵抗力。 下游RAS效应物。我们将以下列目标检验这一假设： 该提案阐明了SOS 1/2−WT RAS信号转导驱动 具有特定突变RAS同种型的癌症的转化。我们使用以下组合进行研究： 定义的遗传模型系统和更多的癌症相关系统，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，以确定WT RAS亚型信号传导 协同致癌RAS促进致癌转化。描述SOS 1在 突变RAS驱动的增殖和转化，无论是独立的还是与SOS 2组合。 基于以下研究确定SOS 2和SRC作为患者来源的结肠癌类器官的治疗靶点： KRAS和PIK 3CA突变状态。我们的发现将为根除癌症的新治疗方法提供信息。 具有基因型依赖性精确度的RAS突变肿瘤子集。

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.