NDRG2 inhibits tumorigenesis of hepatocellular carcinoma by regulating metabolism of phospholipids and triglyceride: a metabonomic analysis

Abstract

To explore the role of the tumor suppressor gene NDRG2 in regulating lipid metabolism in hepatoma cells. We analyzed the differential expression of NDRG2 gene between hepatocellular carcinoma tissues (n=809) and normal liver tissues (n=379) based on data from TNMplot database, and investigated the correlation between NDRG2 mRNA expression and the overall survival of the patients with hepatocellular carcinoma using THPA database, which was also used for analysis of NDRG2 expression levels in tumor cell lines for screening hepatoma cell lines. Human hepatoma cell line HepG2 was infected with a lentivirus containing NDRG2 cDNA, and the expression level of NDRG2 in the infected cells was detected using qPCR and Western blotting. Lipid metabolomics analysis was performed to analyze the regulatory effect of NDRG2 overexpression on lipid metabolism in HepG2 cells, and ELISA and Oil Red O staining were used to examine the changes in contents of phospholipids and triglyceride in NDRG2-overexpressing HepG2 cells. Analysis of the TNMplot database showed that NDRG2 expression level was significantly lower in hepatocellular carcinoma tissues than in normal liver tissues (P < 0.001). Analysis of THPA database showed that the patients with high NDRG2 mRNA levels had a longer survival time than those with low NDRG2 mRNA levels, and NDRG2 expression level was the highest in HepG2 cell line among the tumor cell lines. Metabolomics analysis showed that in HepG2 cells, NDRG2 overexpression led to changes in the contents of phospholipids, and among them lecithin PC, phosphatidyl glycerol PG, phosphatidyl ethanolamine PE, sphinophosphatidyl serine SM, and ceramide Cer exhibited significant changes. The results of ELISA and Oil Red O staining demonstrated that NDRG2 overexpression obviously reduced the contents of multiple phospholipids and significantly lowered the contents of triglyceride in HepG2 cells. NDRG2 regulates tumorigenesis of hepatocellular carcinoma by modulating the metabolism of phospholipids and triglyceride.