Sensitization of lung cancer to EGFR tyrosine kinase inhibitors

描述(由申请人提供)： 选择性地针对表皮生长因子受体(EGFR)信号网络的肺癌治疗的主要限制是出现继发性耐药机制。目前，40%的获得性耐药病例对EGFR酪氨酸激酶抑制剂(TKI)的作用机制不明。然而，对于携带EGFR继发性突变T790M的非小细胞肺癌(NSCLC)，目前仍没有有效的治疗方法。在携带EGFR敏感突变的非小细胞肺癌中，T790M占50%的获得性EGFR TKI耐药。最近的报道和我们自己的初步研究结果表明，埃洛替尼是一种EGFR TKI，在不屈服于其抗肿瘤活性的NSCLC细胞中诱导细胞保护性自噬。因此，与厄洛替尼耐药的分子机制(S)无关，细胞保护性自噬被用来克服这种TKI带来的细胞压力。具有不同厄洛替尼耐药机制的NSCLC细胞的这种共同适应反应可能成为目前还没有任何其他有效治疗方法的肿瘤细胞的治疗靶点。此外，目前许多预防或延缓对EGFR TKI获得性耐药发展的努力都将第二种药物与厄洛替尼结合在一线设置中。在目前的应用中，我们建议确定以新发现的自噬和凋亡之间的交叉调节机制为靶点的治疗潜力，作为厄洛替尼治疗EGFR突变NSCLC的额外成分。我们的初步研究发现，ATG7和caspase-9之间存在一个迄今未知的复合体，它在细胞凋亡过程中表达下调，但在自噬过程中表达增强。我们的初步数据表明，根据细胞环境的不同，每个复杂的成分都会交叉调节另一个的活性：虽然ATG7抑制caspase-9的凋亡活性，但拿铁咖啡增强了ATG7的自噬活性。在目前的应用中，我们建议利用我们初步研究产生的分子洞察力来确定靶向破坏ATG7/caspase-9复合体的临床潜力。特别是，我们认为该复合体的特定破坏将对非小细胞肺癌对erlotinib的自噬反应产生负面影响，同时通过ATG7去除caspase-9抑制来增强其凋亡反应。我们提出了三个特定的目标来验证我们的中心假设，即ATG7/caspase-9复合体决定了EGFR突变体NSCLC对erlotinib的反应中自噬和凋亡之间的平衡。在特定的目标1中，我们计划测试ATG7和caspase-9在EGFR突变体NSCLC对erlotinib的反应中的交叉调节。在特定的目标2中，我们计划研究ATG7/caspase-9复合体作为EGFR突变的NSCLC细胞对厄洛替尼增敏的意义。在具体目标3中，我们计划将该假设的检验提前到动物模型。拟议的研究在初步发现和潜在的临床意义上都具有很高的创新性。新发现的ATG7/caspase-9复合体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，并有可能将其治疗优势扩展到其他有效治疗方法可用的疾病阶段。

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.