ErbB4通路激活介导非小细胞肺癌EGFR-TKIs获得性耐药的分子机制研究

In advanced NSCLC patients harboring EGFR mutations, the use of EGFR-TKIs as first-line treatment has provided an unusually large progression-free survival (PFS) benefit. Despite their ability to induce dramatic tumor responses with fewer side effects, the effectiveness of targeted therapies is currently limited because the majority of patients using these agents develop resistance over time, resulting in a relapse or worsening of the cancer. The key to unlocking the true potential of targeted therapies is unveiling molecular mechanisms behind drug resistance. The applicant found that the expression level of ErbB4 and PDGF were significantly higher in gefitinib-resistant NSCLC cells than that in parental sensitive cells. Further studies have shown that gefitinib effectively blocked ErbB4 and Akt phosphorylation in parental sensitive NSCLC cells, while it was less effective in gefitinib-resistant NSCLC cells. Moreover, PDGF treatment markedly diminished its capacity to inhibit phosphorylation of EGFR, ErbB4 and Akt. In this study, we address the hypothesis that ErbB4-PDGF interactions are associated with acquired resistance to EGFR-TKIs. Overall, the molecular mechanisms for the regulation of ErbB4- and PDGF-mediated EGFR-TKIs resistance in NSCLC will be examined, to determine its role in predicting the efficacy of targeted therapy as an effective biomarker.

EGFR酪氨酸激酶抑制剂 (TKIs) 作为EGFR突变阳性晚期非小细胞肺癌 (NSCLC) 患者的一线治疗方案，可有效延长患者的生存时间。然而，其无可避免的耐药现象成为进一步提高靶向药物疗效的瓶颈，目前其获得性耐药产生的机制仍未完全明确。申请人在研究中发现吉非替尼诱导耐药的NSCLC细胞中ErbB4和PDGF的表达水平显著增高，且吉非替尼对耐药细胞ErbB4和Akt磷酸化的抑制作用明显弱于敏感细胞。敏感细胞用PDGF诱导后，吉非替尼对其EGFR、ErbB4和Akt磷酸化的抑制作用均减弱。基于此我们推测ErbB4和PDGF交互作用，可能共同调控NSCLC细胞EGFR-TKIs获得性耐药的产生。本研究拟对ErbB4及PDGF过表达旁路活化EGFR下游信号通路，导致NSCLC细胞获得性耐药的调控机制进行探讨，并鉴定其能否成为有效预测靶向治疗疗效和指导选择NSCLC治疗方案的分子学标志。

原发和获得性耐药现象不可避免地发生使靶向治疗的应用产生了瓶颈，增加了临床治疗难度。由于EGFR-TKIs在改善晚期NSCLC患者生存期方面的突出作用，对EGFR-TKIs耐药机制的探索已成为国内外研究的热点。对其耐药机制的不断探索，可促进新的可以预测药物疗效并指导治疗方案的分子学标志物的发现和鉴定，从而使靶向药物的治疗效果进一步提高，并能更好地选择EGFR-TKIs的治疗对象。同时，通过对克服EGFR-TKIs 耐药发生的尝试，给耐药患者带来重获治疗的希望。. 我们研究中发现对EGFR-TKIs发生获得性耐药的NSCLC细胞中存在ErbB4/PI3K/Akt通路的异常活化。发现PDGF-AA诱导可直接激活Stat3，通过旁路激活途径促进NSCLC细胞获得性耐药的产生。这对于进一步提高靶向药物的治疗效果，更好地选择EGFR-TKI的治疗对象，同时为新一代TKIs的设计与研发提供新的靶点均具有重要的指导意义。阻滞肿瘤细胞中PDGFR的信号传导可能是有效克服EGFR-TKI耐药的途径之一，对于指导PDGF抑制剂联合其他TKI应用克服或延迟继发耐药具有重要意义。. 随着研究工作的开展，我们发现ErbB4调控NSCLC细胞获得性耐药的产生与MAPK12（p38γ）的功能密切相关。MAPK12可通过磷酸化底物蛋白PTPH1导致ErbB4去磷酸化，从而降低TKIs的靶向杀伤效应，导致NSCLC细胞获得性耐药的产生。此外，MAPK12可与c-Jun启动子区域结合，上调ErbB4的表达，引起NSCLC细胞耐药。而MAPK12抑制剂Pirfenidone是美国FDA批准临床用于治疗特发性肺纤维化的药物，若能明确MAPK12参与调控NSCLC细胞耐药性产生的作用，并体内外验证Pirfenidone单药或与其他药物联合用药治疗NSCLC的临床前药效，将有助于设计出更好、更能发挥互补和协同作用的联合疗法，有望改善NSCLC患者的临床治疗效果。