TAZ调控AXL激活在肺癌EGFR-TKI非经典型获得性耐药中的作用及其机制研究

Activation of the AXL kinase is a new model in acquired drug resistance to EGFR-TKI besides the classical EGFR T790M and c-met gene amplification. It is largely unknown about how AXL was activated and the genetic change in the resistance process. Our Previous research found activation of Notch-1 played important role in the EMT and resistant feature of gefitinib-acquired resistant of lung cancer cells. Recently, we found TAZ and its target gene AXL was up-regulated in gefitinib resistant lung cancer cells. It was associated with Notch1 activation and the EMT feature. Over-expression TAZ or AXL caused resistance to gefitinib targeted therapy. In this project, we will further to explore the detail mechanism of AXL kinase activation by TAZ mediated transcription or through TAZ/Notch1 mediated EMT reprogramming in gefitinib acquired drug resistant cells. Then, we will study whether it will be prevented or overcome of gefitinib acquired drug resistance by combination gefitinib with AXL inhibitor or notch1 signal inhibitor. In the last part, we will certify whether the genetic mutation or protein level change of TAZ, Notch1 or AXL could be used as targets or biomarkers of non classical acquired drug resistance to EGFR-TKI.

AXL激活是EGFR-TKI耐药中除T790M突变、c-met扩增之外一种新的非经典型耐药模式，其激活机制、基因遗传水平改变仍不清楚。我们前期研究发现Notch1激活在吉非替尼体外获得性耐药细胞的EMT特征及耐药特性中起了重要作用；最近我们又发现TAZ及其靶基因AXL在吉非替尼耐药细胞中的表达明显上调，与Notch1的活性、EMT表型明显相关，过表达TAZ及AXL均可以诱导敏感细胞对吉非替尼产生耐药。本研究将进一步探讨TAZ通过直接转录机制或通过Notch1-EMT重编程间接机制调控AXL激活在吉非替尼耐药中的作用；再观察吉非替尼联合TAZ/AXL抑制或Notch1信号抑制在预防及逆转吉非替尼耐药中的作用；最后通过获得性耐药前后肿瘤组织标本，分析TAZ、Notch1、AXL基因或蛋白水平改变作为耐药标志物的可能性。本研究将为克服EGFR-TKI非经典型获得性耐药提供可能的靶点及鉴别标志物。

EGFR-TKI 耐药中除 T790M 突变、c-met 扩增之外有一种新的以无经典基因改变为特征，表现为上皮向间质转化为特征的非经典型耐药模式，其激活机制、耐药机理仍不清楚。我们前期研究发现 Notch1 激活在吉非替尼体外获得性耐药细胞的 EMT 特征及耐药特性中起了重要作用；我们发现 TAZ 及其靶基因 AXL 在吉非替尼耐药细胞中的表达明显上调，与 Notch1 的活性、EMT 表型明显相关，过表达 TAZ 及 AXL 均可以诱导敏感细胞对吉非替尼产生耐药。本课题针对EGFR-TKIs的耐药机制，影响EGFR-TKIs疗效的分子遗传机制，患者吸烟状态、EGFR不同突变亚型、获得性耐药机制、患者免疫微环境状态等各个方面进行了非常全面、系统的研究。我们的研究发现了EMT为特征的 EGFR-TKI 非经典耐药中 AXL 激活与TAZ活化达有关；联合EGFR-TKI和AXL的抑制剂可以克服和延缓耐药；未发现在EGFR-TKIs耐药后出现TAZ、AXL基因水平改变，EGFR-TKIs耐药后，Notch1 基因改变， AXL高表达，及EMT表型特征可以作为非经典型 （非T790M突变，非C-met扩增）EGFR-TKI 获得性耐药的标志物。除此之外，我们已在临床上开始了延缓EGFR-TKIs耐药, 克服、逆转EGFR-TKIs耐药的临床研究。本研究探索了影响EGFR-TKIs疗效的各种因素，为EGFR-TKIs的耐药后出现非T790M的非经典耐药类型探索了新的治疗手段。