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

项目摘要/摘要 在美国，肺癌是与癌症相关的死亡的主要原因，而且对 退伍军人。目前靶向治疗无效的肺癌亚型包括肿瘤 携带激活的K-RAS或耐药的EGFR突变，以及其基因 变化是“未知的”。在“未知”类别中，Rictor(mTORC2的独特组成部分) 最近发现扩增是11%-13%的非小细胞肺癌的驱动基因改变 癌症(NSCLC)。对于耐药突变的EGFR肿瘤，靶向突变的EGFR或MAP K-RAS下游的激酶通路常导致多个“旁路”受体酪氨酸的诱导 激酶(RTK)信号转导。因为mTOR是这些“旁路”下游的公共信令节点 激酶，靶向mTOR代表了一种在多种耐药环境中很有前途的方法。 虽然通过雷帕霉素和雷帕罗格对mTORC1的药理抑制是可能的，但 MTORC2特异性抑制剂尚未开发出来。选择性抑制mTORC2具有 不扰动依赖于mTORC1的负反馈环路和mTORC1的优点 介导抑制突变型RAS肿瘤的巨噬细胞吞噬作用。然而，针对具体目标的努力 MTORC2到目前为止基本上没有成功，因为对mTORC2的结构了解有限 很复杂。基于最新的低温电子显微镜研究和mTOR-mLST8的共晶结构，我们 发现虽然mLST8是这两个复合体的一个成分，但mLST8的丢失选择性地抑制了 MTORC2，但不是mTORC1。我们发现点突变破坏了mLST8-mTOR结合 具体地说，破坏了mTORC2的稳定性，指出了一种可行的抑制剂设计策略。的总目标是 这项建议是：(1)严格了解mTORC2对亚型的贡献 目前靶向治疗无效的肺癌，以及(2)进一步调查是否有靶向治疗 MLST8可用于选择性抑制mTORC2。我们将在Rictor扩增中测试靶向mLST8 肿瘤(目标1)。我们还将剖析mTORC1和mTORC2在肿瘤中的相对贡献 EGFR酪氨酸激酶抑制剂的耐药性和靶向治疗潜力的评估 MLST8/mTORC2在先前存在的对TKI耐药的人肺癌中(目标2)。 该项目的成功将对退伍军人群体具有巨大的翻译潜力。这个 拟议的研究将提供目标验证的数据，并为选择性筛查铺平道路 MTORC2抑制剂用于治疗携带Rictor扩增的肺癌亚型，或药物- 耐药的EGFR突变。在这项研究的同时，我们已经完成了对 可阻止mTOR和mLST8结合的药理化合物，从而特异性地 抑制mTORC2。虽然不在这项提案的范围内，但未来的研究将包括测试 这些化合物对mTORC2的特异性抑制可进一步翻译用于治疗 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.