ATR-Chk1通路调控西妥昔单抗敏感性的机制研究

The resistance mechanism to cetuximab and reversing strategy are important to be resolved in colon cancer therapy. Besides RAS gene mutations, there are other factors that limit the clinical application of cetuximab. ATR-Chk1 pathway plays an important role in regulating DNA damage repair and progression of cell cycle. Recent studies reported Chk1 phosphorylated the tumor suppressor Mig-6 to regulate the activation of EGF signalling, and Mig-6 was also a negative regulator of MET pathway that promoting cetuximab resistance, suggesting that ATR-Chk1 pathway may be involved in regulating the sensitivity of cetuximab. Our preliminary data confirmed that Chk1 activation acted as a novel resistance mechanism to cetuximab in colon cancer cells, and ATR inhibition could obviously enhance sensitivity to cetuximab. In addition, we found a mutual regulation between ATR-Chk1 and MET pathway, therefore ATR inhibition exerted antitumor effects through inhibiting MET activation to further enhance the sensitivity of cetuximab, and Akt might be the critical regulator between ATR-Chk1 and MET. This study will investigate the molecular mechanisms of ATR-Chk1 pathway in regulating cetuximab sensitivity in colon cancer cells, providing the novel issue for understanding the mechanism of cetuximab resistance and new strategy to overcome drug resistance, and screening new targets for targeted therapy of colon cancer.

西妥昔单抗的耐药机制及逆转策略是结肠癌治疗中亟待解决和深入研究的问题，RAS基因突变以外的耐药机制限制了西妥昔单抗的临床应用。最新的研究报道，调节DNA损伤修复和细胞周期的重要通路ATR-Chk1通路可调控抑癌基因Mig-6活化EGFR通路，而Mig-6也是调节与西妥昔单抗耐药相关的MET通路的因子，间接提示ATR-Chk1通路可能参与调节西妥昔单抗的敏感性。我们的数据证实，Chk1磷酸化是西妥昔单抗耐药的新机制，抑制ATR可逆转结肠癌细胞对西妥昔单抗耐药，并且抑制ATR可通过抑制MET活化进一步增强西妥昔单抗的敏感性，而Akt可能是ATR-Chk1和MET两条通路交汇点的重要调节分子。本研究将进一步明确西妥昔单抗耐药的作用机制，为逆转西妥昔单抗耐药提供新的策略，并为筛选结肠癌靶向治疗的新靶点提供科学依据。

本研究首次探索了调控DNA损伤和细胞周期的ATR-Chk1通路在结直肠细胞对抗EGFR单抗西妥昔单抗敏感性中的作用。1.明确了ATR-Chk1通路活化及Chk1磷酸化降低了消化道肿瘤的靶向治疗和化学治疗药物敏感性的具体机制，包括结肠癌细胞对抗EGFR单抗西妥昔单抗耐药、胃癌细胞对抗HER2抑制剂拉帕替尼、胰腺癌细胞对化疗药吉西他滨和奥沙利铂等。抑制Chk1磷酸化可通过抑制S期阻滞、增强凋亡、抑制AKT/ERK活化和增强DNA损伤等机制增强靶向药物敏感性，为临床提高部分靶向药物及化疗药物的敏感性及逆转耐药提供了新的思路。2.发现了调控Chk1磷酸化新的机制。HGF-MET通路可通过中间因子AKT调控Chk1磷酸化，而AKT可通过调控TopBP1和RAD51表达直接调控Chk1磷酸化，为进一步探讨结肠癌的关键预后因子及治疗敏感性提供了依据。3.发现了影响ATR抑制剂VE-821敏感性的新机制，上皮向间质转化过程（EMT）中的转录因子ZEB1可参与调控VE-821的敏感性。抑制ZEB1通过逆转EMT及增强DNA损伤增强VE-821的敏感性；并首次证明了ZEB1负调控Chk1磷酸化，为提高ATR抑制剂在临床上的应用潜能提供了理论依据。4.证明了ATR-Chk1通路与MET通路之间有相互调节作用，抑制ATR可通过调控miRNA抑制MET蛋白表达，进一步抑制p-MET活性。本课题已发表课题相关SCI共6篇，其中第一作者SCI论文4篇，IF为9.29。本研究为深入探讨ATR-Chk1通路的抗肿瘤机制及与其他抗肿瘤药物联合的最佳方案、发现西妥昔单抗新的耐药机制提供了理论依据，也为ATR抑制剂在临床上的推广应用提供了基础证据。