LKB1调控MEK/ERK信号通路介导非小细胞肺癌第三代EGFR-TKI 耐药的机制研究

Development of acquired resistance to small cancer therapeutic molecules has become a major obstacle in the clinic for a long-term efficacy. We recently reported that modulation of MEK/ERK-dependent Bim and Mcl-1 degradation critically mediates resistance of EGFR-mutant NSCLC cells to AZD9291.And we found that the expression of LKB1 is decreased and p-ERK is increased in AZD9291 resistant NSCLC cells compared to parental sensitive cells. A previous study demonstrated that the nonreceptor tyrosine kinases Src and FAK are activated by LKB1 Loss. PXN is phosphorylated by FAK and Src and in turn binds to other downstream proteins including ERK. Another study showed that Paxillin (PXN)-mediated ERK activation is responsible for 1st generation TKIs resistance. We thus hypothesized that MEK/ERK hyperactivation in a LKB1/ FAK/Src/ PXN dependent pathway may result in resistance to AZD9291. Based on the above ideas, this project tends to use cell culture in vitro and xenograft in nude mice to explore molecular mechanism of resistance to third generation EGFR-TKI in EGFR-mutant lung cancers confered by LKB1 via activating MEK/ERK pathway. The accomplishment of this project will help to deepen the understanding the mechanism of resistance to target therapy in order to develop effective strategies to delay or overcome resistance.

获得性耐药是NSCLC靶向治疗的最大障碍。我们前期研究发现MEK/ERK旁路激活导致NSCLC对第三代EGFR-TKI耐药，并且与敏感细胞相比，耐药细胞LKB1表达下调，p-ERK表达上调。研究显示，LKB1缺失可激活FAK/Src。FAK/Src/PXN信号级联反应可磷酸化激活ERK。另有研究显示，Paxillin (PXN)介导的ERK激活导致了NSCLC对第一代EGFR-TKIs耐药。因此，我们推测，LKB1可能通过FAK/Src/PXN信号级联反应调控ERK磷酸化水平，介导NSCLC第三代EGFR-TKI AZD9291耐药。基于上述设想，本项目拟通过细胞水平和动物模型两个方面研究，系统探讨LKB1与FAK/Src/PXN、MEK/ERK信号通路的调控关系及其在第三代EGFR-TKI耐药中的作用，为探索和发现新的耐药机制，以制定有效的治疗策略提供重要理论依据。

特异性针对 EGFR 激活突变的酪氨酸激酶抑制剂（EGFR-TKIs）可显著延长具有 EGFR 敏感突变的非小细胞肺癌（NSCLC）患者的无进展生存期（PFS），开启了 NSCLC 临床治疗的新时代。然而，获得性耐药不可避免地发生，导致药物临床效用丧失，疾病最终进展，成为 NSCLC 靶向治疗所面临的最棘手的问题。如何才能延缓或逆转耐药一直都是基础医学和临床医学关注的热点。因此，探索和发现新的耐药机制具有重要的科学意义。. LKB1 与 EGFR 均是 NSCLC 中常见的基因突变形式，分别作为与肿瘤的发生发展关系密切的抑癌基因通路（LKB1）与促癌基因通路（EGFR），两者之间是否存在相互作用及作用机制值得我们深入探讨。本研究发现，抑制EGFR信号通路，可通过ERK/P90RSK信号轴激活LKB1/AMPK信号通路，并伴随凋亡现象的发生。并且，奥西替尼对LKB1/AMPK信号通路的激活作用表现为浓度依赖性及时间依赖性效应。与奥西替尼敏感细胞相比，耐药细胞中 LKB1 表达下调， FAK/Src/PXN/ERK 信号通路（p-FAK、p-Src、p-PXN、p-ERK）激活。下调 LKB1表达，可削弱奥西替尼对EGFR突变敏感细胞的生长抑制效应，同时Src/FAK/PXN/ERK 信号轴（p-Src/Src、p-FAK/FAK、p-PXN/PXN、p-ERK/ERK）被激活。过表达 LKB1 能够恢复耐药细胞对奥西替尼敏感性，同时能够阻断耐药细胞 MEK/ERK 信号通路（p-Src/Src、p-FAK/FAK、p-PXN/PXN、p-ERK/ERK）激活。