[Nlrp6 overexpression inhibits lipid synthesis to suppress proliferation of hepatocellular carcinoma cells by regulating the AMPK-Srebp1c axis].

OBJECTIVE

To investigate the mechanism of Nlrp6 for regulating hepatocellular carcinoma (HCC) progression in light of lipid synthesis regulation.

METHODS

Nlrp6 expression level in HCC tissues of different pathological grades was investigated using RNA-seq data from The Cancer Genome Atlas (TCGA) database, and its correlation with the patients' survival was analyzed with Kaplan-Meier survival analysis. HepG2 cells with adenovirus-mediated Nlrp6 overexpression or knockdown were treated with palmitic acid (PA), and the changes in lipid deposition and cell proliferation were evaluated using Oil Red O staining, CCK-8 assay, EdU staining, and colony formation assay. RT-qPCR and Western blotting were used to detect the changes in expression of lipid synthesis-related genes and the proteins in the AMPK-Srebp1c axis. In a mouse model of hepatic steatosis established in liver-specific Nlrp6 knockout mice by high-fat diet feeding for 24 weeks, liver fibrosis was examined with histological staining, and the changes in expressions of HCC markers and the AMPK-Srebp1c signaling pathway were detected.

RESULTS

Nlrp6 expression was significantly reduced in HCC tissues with negative correlations with the pathological grades and the patients' survival ( < 0.0001). In HepG2 cells, Nlrp6 overexpression significantly inhibited lipid deposition and cell proliferation, whereas Nlrp6 knockdown produced the opposite effects. Nlrp6 overexpression strongly suppressed the expression of lipid synthesis-related genes, promoted AMPK phosphorylation, and inhibited Srebp1c expression. The mice with liver-specific Nlrp6 knockout and high-fat feeding showed increased hepatic steatosis, collagen deposition, and AFP expression with reduced AMPK phosphorylation and increased Srebp1c expression.

CONCLUSION

Nlrp6 overexpression inhibits lipid synthesis in HCC cells by regulating the AMPK-Srebp1c axis, which might be a key pathway for suppressing HCC cell proliferation.