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

Abstract

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 (P < 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.