Sensitization of lung cancer to EGFR tyrosine kinase inhibitors

描述（由申请人提供）： 选择性靶向表皮生长因子受体（EGFR）信号网络的肺癌治疗的主要限制是继发性耐药机制的出现。目前，40%的EGFR酪氨酸激酶抑制剂（TKI）获得性耐药病例在机制上无法解释。然而，对于携带继发性EGFR突变T790 M的非小细胞肺癌（NSCLC），仍然没有有效的治疗方法，T790 M占携带敏感EGFR突变的NSCLC中EGFR TKI获得性耐药的50%。最近的报告以及我们自己的初步研究结果表明，厄洛替尼，EGFR TKI，诱导细胞保护性自噬的NSCLC细胞不屈服于其抗肿瘤活性。因此，不依赖于对厄洛替尼耐药的分子机制，细胞保护性自噬被调用以克服由该TKI引起的细胞应激。具有不同厄洛替尼耐药机制的NSCLC细胞的这种共有适应反应可以作为目前没有任何其他有效疗法的肿瘤细胞的治疗靶点。此外，目前许多预防或延迟EGFR TKI获得性耐药的努力在一线环境中结合了第二种药物厄洛替尼。在本申请中，我们提出确定靶向新发现的自噬和细胞凋亡之间的交叉调节机制作为厄洛替尼治疗EGFR突变型NSCLC的额外组分的治疗效力。我们的初步研究确定了一个迄今未知的Atg 7和caspase-9之间的复合物，这是在细胞凋亡过程中下调，但在自噬过程中加强。我们的初步数据表明，根据细胞的情况下，每个复杂的组件交叉调节其他的活动：而Atg 7抑制caspase-9的凋亡活性，Latte增强Atg 7的自噬活性。在当前的应用中，我们建议利用我们的初步研究产生的分子见解来确定Atg 7/caspase-9复合物的靶向破坏的临床潜力。特别是，我们认为，该复合物的特定破坏将对厄洛替尼的NSCLC自噬反应产生负面影响，同时通过Atg 7去除胱天蛋白酶-9抑制来增强其凋亡反应。我们提出了3个具体的目标来检验我们的中心假设，即Atg 7/caspase-9复合物决定了EGFR突变型NSCLC对厄洛替尼的反应中自噬和凋亡之间的平衡。在具体目标1中，我们计划测试EGFR突变型NSCLC对厄洛替尼的反应中Atg 7和caspase-9之间的交叉调节。在具体目标2中，我们计划研究Atg 7/caspase-9复合物作为EGFR突变NSCLC细胞对厄洛替尼致敏的靶点的意义。在具体目标3中，我们计划将假设检验推进到动物模型。这些研究在初步发现和潜在的临床意义上都具有高度创新性。新发现的Atg 7/caspase-9复合物提供了一种令人兴奋的交叉调节机制，可用于增强厄洛替尼的自噬活性，并可能将其治疗益处扩展到没有其他有效疗法的疾病阶段。

DESCRIPTION (provided by applicant): The major limitation of lung cancer therapies that selectively target the Epidermal Growth Factor Receptor (EGFR) signaling network is the emergence of secondary drug resistance mechanisms. Currently, 40% of the cases of acquired resistance to EGFR Tyrosine Kinase Inhibitors (TKIs) are mechanistically unexplained. However, there are still no effective therapies for Non Small Cell Lung Cancer (NSCLC) harboring the secondary EGFR mutation, T790M, which accounts for 50% of acquired resistance to EGFR TKIs in NSCLC carrying sensitive EGFR mutations. Recent reports as well as our own preliminary findings suggest that erlotinib, an EGFR TKI, induces cytoprotective autophagy in NSCLC cells that do not succumb to its antitumor activity. Thus, independent of the molecular mechanism(s) of resistance to erlotinib, cytoprotective autophagy is invoked to overcome the cellular stress brought about by this TKI. Such a shared adaptation response of NSCLC cells with distinct erlotinib resistance mechanisms may serve as a therapeutic target for tumor cells that currently do not have any other effective therapy. Furthermore, many of the current efforts to prevent or delay the development of acquired resistance to EGFR TKIs incorporate a second agent with erlotinib in the first-line setting. In the current application, we propose to determine the therapeutic potentil of targeting a newly discovered mechanism of cross-regulation between autophagy and apoptosis as an additional component for the treatment of EGFR mutant NSCLC by erlotinib. Our preliminary studies identified a hitherto unknown complex between Atg7 and caspase-9, which is downregulated during apoptosis, but intensified during autophagy. Our preliminary data suggest that depending on the cellular context, each of the complex components cross-regulates the other's activity: while Atg7 represses the apoptotic activity of caspase-9, the latte enhances the autophagic activity of Atg7. In the current application, we propose to determine the clinical potential of a targeted disruption of the Atg7/caspase-9 complex, utilizing molecular insights produced by our preliminary studies. In particular, we suggest that a specific disruption of this complex will negatively impact the NSCLC autophagic response to erlotinib, while enhancing its apoptotic response via the removal of caspase-9 repression by Atg7. We propose 3 specific aims to test our central hypothesis that 'the Atg7/caspase-9 complex determines the balance between autophagy and apoptosis in the response of EGFR mutant NSCLC to erlotinib.' In Specific Aim 1, we plan to test the cross-regulation between Atg7 and caspase-9 in EGFR mutant NSCLC response to erlotinib. In Specific Aim 2, we plan to investigate the significance of the Atg7/caspase-9 complex as a target for sensitization of EGFR mutant NSCLC cells to erlotinib. In Specific Aim 3, we plan to advance the testing of the hypothesis to animal models. The proposed studies are highly innovative in both preliminary findings and potential clinical implications. The newly discovered Atg7/caspase-9 complex offers an exciting cross-regulation mechanism that may be utilized to enhance the apoptotic over the autophagic activity of erlotinib, and potentially extend its therapeutic benefit to a disease stage for which o other effective therapies are available.