C型凝集素样受体CLEC-2通过旁分泌信号途径调控胃癌干细胞niche以及化疗抵抗的功能机制研究

Gastric cancer is currently the world's third fatal malignant tumor, and tumor resistance to chemotherapy is the cause of recurrence in patients with gastric cancer and one of the main causes of poor prognosis. It is found that the metastasis and homing of cancer stem cells (CSC) are the essence of tumor metastasis. The changes in the components of cancer stem cell niche (CSC niche) play an important role in the process of CSC transfer and homing. Therefore, the treatment of CSC niche will provide a new strategy for the treatment of gastric cancer, especially in the field of chemotherapeutic drug resistance. CLEC-2 is a highly conserved C type lectin-like receptor, which was previously reported to be mainly expressed in platelets and mediated platelet activation. Our previous studies found that CLEC-2 was highly expressed in the normal gastric mucosa and downregulated in gastric cancer. The downregulation of CLEC-2 promoted the epithelial mesenchymal transition and metastasis of gastric cancer cells. In this project, we study the changes in the expression of CLEC-2 in gastric cancer cells in the regulation of CSC niche formation and chemotherapeutic resistance, and investigate the relationship of CLEC-2 expressional profiles in gastric cancer and CSC niche and chemotherapeutic resistance, and the function and molecular mechanism of CLEC-2 in regulating CSC niche through direct binding/ paracrine pathway. Under the basis, we yet study the role of CSC niche in CLEC-2 controlling gastric cancer chemotherapy resistance. Hence, this research may clarify that the new mechanism of gastric cancer cells in promoting chemotherapy resistance by shaping the CSC niche, and provide new clues for clinical treatment of gastric cancer.

胃癌是目前全球第三致死性的恶性肿瘤，而肿瘤化疗耐药是导致胃癌患者复发以及不良预后的主要原因。研究发现，肿瘤干细胞转移和归巢是肿瘤转移的本质。而肿瘤干细胞niche成分改变在CSC转移及归巢过程中发挥重要作用。因此，针对肿瘤干细胞niche的治疗将会给胃癌治疗，尤其是化疗耐药领域提供新策略。CLEC-2是一种高度保守的C型凝集素样受体，以往报道认为其主要表达在血小板并介导血小板活化。我们前期研究发现CLEC-2在正常胃粘膜高表达并在胃癌中下调，其表达下调促进胃癌上皮间质转化和转移。在本项目中，我们对CLEC-2在肿瘤干细胞niche形成和胃癌化疗耐药调控方面进行研究。我们拟探讨CLEC-2通过旁分泌途径影响肿瘤干细胞niche的功能和分子机制，并在此基础上研究肿瘤干细胞niche在CLEC-2调控胃癌化疗耐药中的作用，以期阐明胃癌细胞通过塑造肿瘤干细胞niche来促进胃癌化疗耐药的新机制。

由于肿瘤在发生发展过程中会出现大量的异常糖基化修饰，而这些糖基化携带蛋白质代谢去向信息，凝集素作为糖链结合蛋白，是糖链参与调控肿瘤生物学行为的重要工具，包括肿瘤发生、转移以及耐药。我们研究发现敲除C型凝集素CLEC-2的表达促进胃癌细胞的干性克隆形成，进一步利用转录组测序提示CLEC-2与视黄醇代谢通路相关，分子实验证明CLEC-2下调通过降低视黄酸合成的关键脱氢酶ALDH1A1的表达参与调控视黄醇代谢进而影响肿瘤细胞干性标志物的水平。此外，我们鉴定到天然活性产物岩藻聚糖Fucoidan通过与细胞表面CLEC-2结合，抑制肿瘤相关炎症反应以及恶性表型转化，揭示了凝集素糖配体在肿瘤发展过程中的抑制作用。此外，我们还发现C型凝集素LOX-1在消化道肿瘤组织中普遍上调，利用磷酸激酶芯片筛选到LOX-1通过MAPK信号途径影响肿瘤细胞自噬相关转录因子TFEB的核转位调控肿瘤细胞死亡，为肿瘤靶向治疗提供了新的理论依据和干预策略。