MED12缺失或突变在EGFR-TKIs耐药中作用及其机制

The tyrosine kinase inhibitors (TKIs) of epidermal growth factor receptor (EGFR) have been demonstrated to play a significant role in the successful treatment for the patients with non-small cell lung cancer (NSCLC). But the resistance limited the efficacy of TKI. Impotantly, the mechanisms of intrinsic or acquired resistance to anti-EGFR therapy are unknown, although many molecular events have been implicated. Our group and Huang (cell 2012) found the loss of MED12 conferred to the resistance of TKIs. Here we will examine the expression level and mutation of MED12 by immnohistochemical and gene sequencing methods, respecitvely, and investigate the clinical significance of MED12 expression level, such as resistance of TKIs, time-to progression (TTP) and overall survival time (OS) and so on. And the MED12-mediated epithelial-mesenchymal transition (EMT and TKI resistance will be confirmed in characterized cell model. We are going to find the key signal molecules regulated by MED12 and explore the mechanisms inveloved in inducing EMT and TKI resistance. These results will reveal the status of MED12 expression and mutation in NSCLC and its action in EGFR-TkI resistance, understand the mechamisms of MED12 expression regulation and inducing TKI resistance, and suggest the strategies of personal chemotherapy of TKIs and reversal of TKI resistance.

EGFR酪氨酸激酶抑制剂（TKIs）是治疗非小细胞性肺癌患者的主要药物，但易产生抗药性，制约着其疗效，其耐药机制仍未阐明。我们和Huang (Cell 2012)的研究均表明MED12缺失与TKIs耐药有关。本研究拟以免疫组化及基因测序等技术，对肺癌标本MED12表达水平及基因突变分别进行检测，分析MED12缺失或突变与EGFR-TKIs 治疗效果的关系及其临床意义；同时，以分子生物学方法体外验证MED12缺失或突变诱生上皮间质转化（EMT）、介导TKIs耐药作用及其MED12表达调控机制。发现MED12缺失所致的差异表达的信号分子，研究其在诱生EMT、介导耐药作用及其信号通路，为揭示MED12在肺癌中的表达、突变及调控规律，阐明MED12功能状态与EGFR-TKIs耐药的关系及其机理，为肿瘤病人EGFR-TKIs个体化治疗提供依据，为克服EGFR-TKIs的耐药性提供新策略。

本研究深入探讨了MED12在非小细胞肺癌和卵巢癌中表达、突变及调控机制。在非小细胞肺癌中发现敲除MED12后细胞胞质分裂失败，细胞衰老并失去再生长能力，显著抑制细胞的体内外增殖能力。机制研究发现MED12通过LIMK2/Cofilin信号通路维持非小细胞肺癌细胞中F-actin聚合与解聚间的动态平衡调控细胞的胞质分裂，从而影响细胞增殖和病人预后。在上皮性卵巢癌中发现MED12能够结合到EGFR启动子的-22bp至-773bp区间并激活EGFR的转录，通过调节EGFR的转录活性调控上皮性卵巢癌细胞的休眠、G0/G1期阻滞与化疗耐药。上述研究成果为MED12作为治疗靶点，开发新的抗肿瘤药物及克服化疗耐药奠定了坚实的理论基础，具有重大的科学意义。