Molecular control of tumor-initiating cells in Ras-driven cancers

项目摘要 肿瘤起始细胞（TIC）是肿瘤细胞的亚群，由它们自我更新和增殖的能力定义。 使异质性肿瘤再生。TIC改变了代谢和药物外排特性，使其能够 在治疗过程中作为耐药细胞的避难所群体持续存在。因此，TIC介导肿瘤复发 和转移，这是死亡率的关键因素。然而，到目前为止，还没有针对 实体瘤中的TIC人群。我的数据表明，在RAS驱动的TIC的形成和维持， 结肠直肠和肺肿瘤细胞系严重依赖于分子支架激酶抑制剂， Ras 1（KSR 1）。KSR1通过致癌Ras下游的Raf-MEK-ERK级联来协调信号传导。 KSR1对于Ras驱动的肿瘤形成是必需的，但对于正常细胞生长是必需的。此外，ksr1-/- 小鼠的表型正常但对癌症形成具有抗性。这些特点凸显了 KSR1作为潜在的治疗靶点。我们的数据进一步表明，KSR1 KO可以阻止MEK抑制剂 曲美替尼介导的TIC人群扩增，并恢复NSCLC和NSCLC患者对曲美替尼的敏感性。 耐药性目前限制了该药物的临床应用的CRC。使用KSR 1的进一步表征 在下游效应物结合区具有确定突变的转基因已经确定了KSR1与 ERK和AMPK均涉及TIC群体的维持、体外克隆形成，以及 曲美替尼耐药这些数据表明KSR1依赖的ERK和AMPK激活 在Ras驱动的癌症中，在肿瘤起始细胞的形成和药物抗性中起选择性作用。 由这个亚群传播。我将通过以下方式检验这一假设：1）定义近端KSR 1依赖性 控制TIC和曲美替尼耐药性的信号通路;和2）评估靶向KSR1的能力， 在临床前肿瘤类器官模型中，肿瘤细胞降解以损害肿瘤起始能力。实现这些目标 将扩大对Ras驱动的TIC形成和维持的机械理解，并可能揭示一种新的 治疗TIC介导的抗性、复发和转移的治疗方法。

Project Summary Tumor Initiating Cells (TICs) are a subpopulation of tumor cells defined by their ability to self-renew and regenerate the heterogeneous tumor. TICs have altered metabolic and drug efflux properties, allowing them to persist as a sanctuary population of resistant cells during treatment. As such, TICs mediate tumor recurrence and metastasis, which are key contributors to mortality. To date, however, there are no therapies targeting the TIC population in solid tumors. My data show that the formation and maintenance of TICs in Ras-driven colorectal and lung tumor cell lines are critically dependent on the molecular scaffold Kinase Suppressor of Ras 1 (KSR1). KSR1 coordinates signaling through the Raf-MEK-ERK cascade downstream of oncogenic Ras. KSR1 is necessary for Ras-driven tumor formation, but dispensable for normal cell growth. Moreover, ksr1-/- mice are phenotypically normal but resistant to cancer formation. These characteristics highlight the value of KSR1 as a potential therapeutic target. Our data further show that KSR1 KO can prevent MEK inhibitor trametinib-mediated expansion of the TIC population and restore sensitivity to trametinib in both NSCLC and in CRC where resistance currently limits clinical utility of this drug. Further characterization using KSR1 transgenes with defined mutations in downstream effector-binding regions has identified KSR1 interaction with both ERK and AMPK to be implicated in maintenance of the TIC population, in vitro clonogenicity, and resistance to trametinib. These data suggest the hypothesis that KSR1-dependent ERK and AMPK activation in Ras-driven cancers plays a selective role in the formation of tumor-initiating cells and the drug resistance conveyed by this subpopulation. I will test this hypothesis by 1) defining the proximal KSR1-dependent signaling pathways that control TICs and trametinib resistance; and 2) assessing the ability of targeted KSR1 degradation to impair tumor-initiating capacity in a preclinical tumor organoid model. Completion of these aims will expand mechanistic understanding of Ras-driven TIC formation and maintenance and may reveal a novel therapeutic approach to treat TIC-mediated resistance, recurrence, and metastasis.