转录因子PLAGL2负调控CYP27A1促进肝癌细胞增殖和迁移的机制研究

Chronic HBV infection is an important factor affecting the development of hepatocellular carcinoma，but the mechanism has not yet been clarified. In this study, we found that CYP27A1 and VDR were poorly expressed in the cancer nests and highly expressed in paracancer. The low expression of CYP27A1 was positively correlated with prognosis, CYP27A1 is involved in the regulation of VDR activation, the inhibition of CYP27A1 promoted the proliferation and migration of hepatocellular carcinoma cells, the transcription factor PLAGL2 was involved in the negative regulation of CYP27A1，HBx interacted with PLAGL2 directly, it is speculated that HBx protein negatively regulates CYP27A1 through PLAGL2. This project will focus on the following contents: (1) Systematic elucidation of the mechanism of low CYP27A1 expression inhibiting the proliferation and metastasis of hepatocellular carcinoma cells by VDR. (2) Exploring the molecular mechanism of transcription factor PLAGL2 negative regulation of CYP27A1. (3) Exploring the interaction structural domain between HBx and PLAGL2, elucidating the mechanism of HBx promoting the high expression of PLAGL2. Through this research to elucidate the new mechanism of HBx protein to promote the proliferation and migration of hepatocellular carcinoma cells by inhibiting VDR activation.

慢性HBV感染是肝癌发生发展的重要影响因素，但机制尚未阐明。本课题组前期分析临床病例及病理标本发现CYP27A1和VDR在癌巢中低表达，癌旁高表达，CYP27A1低表达与患者预后呈正相关，CYP27A1参与VDR活化的调控，抑制CYP27A1能够促进肝癌细胞的增殖和迁移，同时发现转录因子PLAGL2参与对CYP27A1的负调控，HBx蛋白与PLAGL2直接互作，推测HBx蛋白通过PLAGL2负调控CYP27A1。本项目主要研究内容：（1）系统阐明CYP27A1低表达抑制VDR活化促使肝癌细胞增殖和转移的机制；（2）探索转录因子PLAGL2负调控CYP27A1的分子机制；（3）探索HBx蛋白与PLAGL2互作的结构域，阐明HBx蛋白促进PLAGL2高表达的机制。通过上述研究阐明HBx蛋白通过抑制VDR活化促进肝癌细胞增殖和迁移的新机制，为开发新型肝癌治疗药物奠定理论基础和实验依据。

肝细胞癌(HCC)是世界范围内癌症相关死亡的第三大原因，是一个重大的公共卫生威胁。多形性腺瘤基因样蛋白2 (PLAGL2)已被证实在肿瘤发生过程中发挥重要的作用。但是其在HCC中的作用机制还不清楚。在本研究中，我们发现PLAGL2在HCC中表达显著高于邻近非肿瘤组织，与存活率呈负相关。我们进一步通过体外和体内试验证明PLAGL2能够促进肝癌细胞的增殖、迁移和侵袭。PLAGL2表达与表皮生长因子受体(EGFR)呈正相关，PLAGL2作为EGFR的转录调控因子通过活化EGFR-Akt信号通路来促进HCC增殖、迁移和侵袭。研究发现缺氧能够上调PLAGL2表达，PLAGL2通过EGFR来上调HIF1/2α，本研究证明了PLAGL2-EGFR-HIF-1/2α环路在促进HCC进展中的作用。同时还发现PLAGL2的表达抑制了HCC对EGFR抑制剂erlotinib的敏感性，敲低PLAGL2能显著上调erlotinib对HCC的敏感性。本研究证明了PLAGL2在促进HCC增殖，侵袭和对erlotinib敏感性调控的重要作用，证明PLAGL2可以作为HCC治疗的一个新型靶点。