GPM6A在非酒精性脂肪性肝炎相关肝癌中的作用及机制探讨

非酒精性脂肪性肝病作为肝癌前病变已被人们所接受，但对非酒精性脂肪性肝炎（NASH）未出现肝硬化而直接进展为肝癌的分子机制不明。本课题组对肝癌与癌旁肝组织进行基因表达谱研究，发现肝癌组织中GPM6A表达比癌旁组织（伴脂肪性肝炎）明显降低，与癌基因c-myc、多能干性基因（KLF4、NANOG）及形态发生基因GLI-1的表达趋势相反。GPM6A为跨膜糖蛋白，仅有的研究显示该基因可能为B淋巴细胞性白血病的致癌基因。本立项旨在阐明GPM6A在NASH相关肝癌发生、进展及转移中的作用。本项目将在诱导GPM6A敲除小鼠形成NASH基础上继续诱导原发性肝细胞癌，并以野生型小鼠作对照，研究GPM6A在肝癌发生发展中的作用。同时利用低和高表达GPM6A的肝癌细胞株，研究其对肝癌细胞成瘤性、转移及耐药的影响，并进一步探讨该基因与c-myc、KLF-4、NANOG、GLI-1等的关系，明确该基因的信号调控机制。

It has been accepted that nonalcoholic fatty liver disease is a precancerous lesion; however, it is unclear how nonalcoholic steatohepatitis (NASH) leads to the development of hepatocellular carcinoma (HCC) prior to the occurrence of cirrhosis. We found that gene expression levels of transmembrane glycoprotein M6A (GPM6A) in HCC tissue was much lower than peri-cancerous liver tissue with NASH by RNA array, quantitative RT-PCR and immunohistochemistry. This pattern of GPM6A expression is in striking contrast to that of a oncogene (c-myc), pluripotent genes (KLF-4, Nanog) and a morphogen (GLI-1). GPM6A belongs to the proteolipid protein family, and growing evidence suggests that it is associated with neuronal differentiation, development, synaptic formation and stress response. A single study has shown that GPM6A could be an oncogenic gene for lymphoid leukemia. This study aims to investigate the role and molecular basis of GPM6A in the occurrence of HCC from NASH as a base liver disease, because the GPM6A gene was mapped to chromosome bands 4q33-->q34 adjacent to another type 2 diabetes-related gene, NEIL3, in 4q34-q35. We will further induce HCC occurrence in high-fat high Calorie (HFC) diet-fed GPM6A knock-out mice after development of NASH, and determine the role of GPM6A in normal liver, NASH and progression to HCC using wild-type mice as controls. We also will overexpress GPM6A and its mutants in human hepatoma cell lines that showed a low level of expression, and knock-down its expression in highly-expressed hepatoma cell lines in order to investigate the effects of GPM6A on tumorigenicity, proliferation, metastases and drug resistance. Moreover, we will dissect the molecular relationship of GPM6A with c-myc, Gli-1, Nanog, KLF4, etc. in order to determine its signaling network and modulating mechanisms in connection with the transformation of steatotic hepatocytes to malignancy. Significance: The completion of this study will enable to reveal, at least in part, the molecular basis of NASH progression to HCC.