Molecular determinants in autophagic repression of intrinsic apoptosis

 描述(申请人提供)：我们已经确定了一种新的自噬和凋亡之间的交叉调节途径，它是由迄今未知的ATG7和caspase-9之间的复合体介导的。我们的发现表明，根据细胞环境，ATG7和caspase-9相互调节彼此的活性：虽然ATG7抑制caspase-9的凋亡活性，但后者增强形成膜性LC3-II所需的ATG7结合活性。目前的研究将集中在KRAS突变肺腺癌上，这代表了每年4万名新诊断的患者，对他们来说，没有有效的治疗方法。选择这种肿瘤模型进行这些研究是基于它对传统细胞毒疗法的耐受性，以及它对生存、增殖和治疗反应的自噬的依赖。突变的KRAS已被认为是“无法下药的”。然而，最近的研究报告了第二代热休克蛋白90抑制剂ganetespib在KRAS突变患者子集中的显著但短暂的单药活性。我们的初步结果表明，Ganetespib敏感的KRAS突变型非小细胞肺癌(NSCLC)细胞对Ganetespib的反应主要是生长停滞和凋亡，而Ganetespib耐药细胞的反应是细胞保护性自噬。我们建议研究新发现的ATG7和caspase-9之间的交叉调节通路，特别是ATG7/caspase-9复合体本身在Ganetespib耐药KRAS突变NSCLC细胞自噬反应中的治疗意义。我们还建议研究ATG7抑制caspase-9凋亡活性的分子决定因素。我们的研究旨在验证这样的假设，即ATG7/caspase-9复合体的破坏有助于减弱自噬小体形成过程中的早期事件，同时伴随着caspase-9凋亡活性的下调。如果我们的假设被证明是正确的，ATG7/caspase-9复合体的破坏与ganetespib结合可能导致一种针对KRAS突变NSCLC的新方法。

 DESCRIPTION (provided by applicant): We have identified a novel cross-regulation pathway between autophagy and apoptosis that is mediated by a hitherto unknown complex between Atg7 and caspase-9. Our findings suggest that depending on the cellular context, Atg7 and caspase-9 reciprocally regulate each other's activity: whereas Atg7 represses the apoptotic activity of caspase-9, the latter enhances the Atg7 conjugation activity required for formation of membranous LC3-II. The current studies will center on KRAS mutant lung adenocarcinoma, which represents 40,000 newly diagnosed patients per year, for whom no effective therapies exist. The selection of this tumor model for these studies is based on its refractoriness to conventional cytotoxic therapies and its dependence on autophagy for survival, proliferation, and response to therapy. Mutant KRAS has been considered "undruggable." Yet, recent studies reported significant, but transient, single-agent activity by ganetespib, a second generation heat-shock protein 90 inhibitor, in a subset of KRAS mutant patients. Our preliminary results suggest that ganetespib- sensitive KRAS mutant Non-Small Cell Lung Cancer (NSCLC) cells respond to ganetespib mainly with growth arrest and apoptosis, whereas ganetespib-resistant cells respond with cytoprotective autophagy. We propose to investigate the newly discovered cross-regulatory pathway between Atg7 and caspase-9, and in particular, the therapeutic significance of the Atg7/caspase-9 complex itself in the autophagic response of ganetespib- resistant KRAS mutant NSCLC cells. We also propose to investigate the molecular determinants of the Atg7 repression of caspase-9 apoptotic activity. Our studies are designed to test the hypothesis that disruption of the Atg7/caspase-9 complex serves to attenuate early events in the autophagosome formation process with concomitant de-repression of caspase-9 apoptotic activity. If our hypothesis is proven correct, disruption of Atg7/caspase-9 complex in combination with ganetespib may lead to a novel approach for targeting KRAS mutant NSCLC.