Role of mLST8 in mTORC2-dependent lung cancer that are refractory to targeted therapies

项目总结/摘要 肺癌是美国癌症相关死亡的主要原因， 老兵目前对靶向治疗难治的肺癌亚型包括肿瘤 携带激活的K-Ras或耐药EGFR突变的肿瘤，以及基因突变的肿瘤。 变化是“未知的”。在“未知”类别中，Rictor（mTORC 2的独特组分） 扩增最近被确定为11-13%的非小细胞肺癌中的驱动遗传改变。 癌症（NSCLC）。对于耐药突变型EGFR肿瘤，靶向突变型EGFR或MAP K-Ras下游激酶途径通常导致诱导多个“旁路”受体酪氨酸 激酶（RTK）信号传导。由于mTOR是这些“旁路”下游的公共信令节点， 激酶，靶向mTOR代表了在多种耐药性环境中有希望的方法。 虽然mTORC 1的药理学抑制可能通过雷帕霉素和雷帕霉素类似物实现， mTORC 2特异性抑制剂尚未开发。选择性抑制mTORC 2， 不干扰mTORC 1依赖性负反馈回路和mTORC 1依赖性负反馈回路的优点 在突变Ras肿瘤中介导的巨胞饮抑制。然而，努力具体针对 迄今为止，mTORC 2在很大程度上是不成功的，因为对mTORC的结构知识有限。 复杂.基于新的Cryo-EM研究和mTOR-mLST 8的共晶结构，我们 发现虽然mLST 8是两种复合物的组分，但mLST 8的缺失选择性地抑制 mTORC 2，而不是mTORC 1。我们发现破坏mLST 8-mTOR结合的点突变 特异性地使mTORC 2不稳定，指出了抑制剂设计的可行策略。的总目标 这个建议是（1）获得mTORC 2对亚型的贡献的严格理解， 目前对靶向治疗难治的肺癌，以及（2）进一步研究靶向治疗是否有效。 mLST 8可用于选择性抑制mTORC 2。我们将在Rictor扩增中测试靶向mLST 8， 肿瘤（Aim 1）。我们还将剖析mTORC 1和mTORC 2在肿瘤中的相对贡献， EGFR酪氨酸激酶抑制剂的耐药性，并评估靶向治疗的潜力 mLST 8/mT 0 RC 2在预先存在的TKI耐药人肺癌中的作用（Aim 2）。 该项目的成功将对退伍军人群体产生重大的转化潜力。的 拟议的研究将提供目标验证的数据，并为筛选选择性药物铺平道路。 用于治疗携带Rictor扩增的肺癌亚型的mTORC 2抑制剂，或药物 耐药EGFR突变。在这项研究的同时，我们已经完成了一个计算机屏幕， 可以防止mTOR和mLST 8结合的药理学化合物，从而特异性地 抑制mTORC 2。虽然超出了本提案的范围，但未来的研究将包括测试 这些化合物用于mTORC 2特异性抑制，其可进一步转化用于治疗 非小细胞肺癌。

Project Summary/Abstract Lung cancer is the leading cause of cancer-related deaths in the US and disproportionally affects Veterans. Lung cancer subtypes that are currently refractory to targeted therapies include tumors carrying activated K-Ras or drug-resistant EGFR mutations, as well as tumors whose genetic alterations are “unknown”. Among the “unknown” category, Rictor (a unique component of mTORC2) amplification was recently identified as a driver genetic alteration in 11-13% of non-small cell lung cancer (NSCLC). In the case of drug-resistant mutant EGFR tumors, targeting mutant EGFR or MAP kinase pathway downstream of K-Ras often results in induction of multiple “bypass” receptor tyrosine kinase (RTK) signaling. As mTOR is a common signaling node downstream of these “bypass” kinases, targeting mTOR represents a promising approach in multiple settings of drug resistance. While pharmacological inhibition of mTORC1 is possible through rapamycin and the rapalogs, an mTORC2-specific inhibitor has yet to be developed. Selective inhibition of mTORC2 has the advantage of not perturbing the mTORC1-dependent negative feedback loops and mTORC1- mediated inhibition of macropinocytosis in mutant Ras tumors. However, effort to specifically target mTORC2 has been largely unsuccessful thus far because limited structural knowledge of the complex. Base on the new Cryo-EM studies and co-crystal structure of mTOR-mLST8, we discovered that while mLST8 is a component of both complexes, loss of mLST8 selectively inhibits mTORC2, but not mTORC1. We found that point mutations disrupting mLST8-mTOR binding specifically destabilize mTORC2, pointing to a viable strategy for inhibitor design. The overall goal of this proposal is (1) to gain a rigorous understanding of the contribution of mTORC2 to subtypes of lung cancer that are currently refractory to targeted therapies, and (2) to further investigate if targeting mLST8 can be used to selectively inhibit mTORC2. We will test targeting mLST8 in Rictor amplified tumor (Aim 1). We will also dissect the relative contribution of mTORC1 and mTORC2 in tumor resistance to EGFR tyrosine kinase inhibitors and assess therapeutic potential of targeting mLST8/mTORC2 in pre-existing TKI-resistant human lung cancer (Aim 2). Success of this project will have significant translational potential for the veteran populations. The proposed studies will provide data on target validation and pave the way for screening selective mTORC2 inhibitors for treatment of lung cancer subtypes that carry Rictor amplification, or drug- resistant EGFR mutations. In parallel to this study, we have completed an in silico screen of pharmacological compounds that may prevent binding of mTOR and mLST8, thereby specifically inhibiting mTORC2. Although out of the scope of this proposal, future studies will include testing of these compounds for mTORC2 specific inhibition that can be further translated for treatment of NSCLC.