EZH2经由miR-200b/Bmi1通路促进肝癌进展和化疗耐药的机制研究

We recently published a manuscrip in the Journal of hepatology in which we confirmed that EZH2 gene silencing can inhibit the progression and significantly increase the chemosensitivity of hepatocellular carcinoma, but the mechanism is not clear. According to the literature, we speculate that the effect was related to cancer stem cells. Our further studies showed that inactivation of putative tumor suppressor miR-200b can induce the formation of liver cancer stem cells through Bmi1 upregulation, and can promote the progression and chemoresistance of hepatocellular carcinoma. In addition, EZH2 can silence the expression of miR-200b. Therefore we hypothesized that EZH2 promotes tumor progression and chemoresistance of hepatocellular carcinoma through miR-200b/Bmi1 signaling pathway dependent liver cancer stem cells induction. In this project, firstly we propose to test whether EZH2 promotes tumor progression and chemoresistance of hepatocellular carcinoma through liver cancer stem cells induction. Next, gain/loss of function studies were performed to verify whether EZH2 induced liver cancer stem cells formation through miR-200b/Bmi1 signaling pathway. And lastly, the relationship between EZH2 expression, the rate of liver cancer stem cells, and tumor progression were detected. This project aims to elucidate the molecular mechanism responsible for the EZH2-medicated tumor progression and chemoresistance of hepatocellular carcinoma, and provide drug target for the precise treatment of hepatocellular carcinoma that target cancer stem cells.

我们近期在《Journal of hepatology》上发表文章证实：沉默EZH2基因可抑制肝癌进展并显著增加肝癌的化疗敏感性，然而机制未明，根据文献报道推测与癌干细胞有关。我们后继研究发现：起肿瘤抑制作用的miR-200b失活可靶向上调Bmi1基因诱生肝癌干细胞和促进肝癌进展、化疗耐药；而EZH2可沉默miR-200b的表达。据此我们假设：EZH2经由miR-200b激活Bmi1诱生肝癌干细胞促进肝癌进展和化疗耐药。本项目拟首先通过细胞分选及体内外实验探明EZH2是否经由诱生肝癌干细胞而促进肝癌进展和化疗耐药，其次通过基因沉默和过表达探明EZH2是否经由miR-200b/Bmi1通路而诱生肝癌干细胞，最后检测EZH2等相关基因在肝癌患者中的表达与肝癌干细胞比例、肿瘤进展等临床病理资料的相关性；以探明EZH2促进肝癌进展及诱导化疗耐药的分子机制，为针对癌干细胞的肝癌精准治疗提供药物靶点。

我们前期在《Journal of hepatology》上发表文章证实：沉默EZH2基因可抑制肝癌进展并显著增加肝癌的化疗敏感性，然而机制未明，根据文献报道推测与癌干细胞有关。我们后继研究发现：起肿瘤抑制作用的miR-200b失活可靶向上调Bmi1基因诱生肝癌干细胞和促进肝癌进展、化疗耐药；而EZH2可沉默miR-200b的表达。本项目是在上述研究基础上，进一步探索“EZH2能否经由miR-200b激活Bmi1诱生肝癌干细胞促进肝癌进展和化疗耐药”。我们首先证实EZH2基因拷贝数扩增导致肝癌组织高表达EZH2并与肝癌患者预后不良密切相关；然后证实EZH2基因的缺失导致肝癌细胞的增殖、迁移和成瘤能力受抑，而miR-200c基因敲除对沉默EZH2的肝癌细胞增殖、致瘤性和迁移能力具有修复作用；最后证实EZH2通过miR-200c的表观遗传抑制调节Bmi1依赖性肝癌的发生，且EZH2和Bmi1抑制剂联合治疗对肝癌细胞增殖具有抑制作用。此外我们还发现，EZH2促进肝癌进展和化疗耐药作用可能跟癌干细胞有关。上述结果表明，EZH2可经由miR-200家族激活Bmi1诱生肝癌干细胞促进肝癌进展和化疗耐药。上述成果利于我们更好的理解EZH2促进肝癌进展及诱导化疗耐药的分子机制，为针对癌干细胞的肝癌精准治疗提供药物靶点。