Gluconeogenic enzyme PCK1 deficiency promotes CHK2 O-GlcNAcylation and hepatocellular carcinoma growth upon glucose deprivation
Although cancer cells often exist in environments with limited nutrients and oxygen, elevated hexosamine biosynthesis pathway (HBP) activity and protein O-GlcNAcylation, which acts as a nutrient sensor, contribute to the rapid growth of tumors and are emerging hallmarks of cancer. Inhibiting O-GlcNAcylation could be a promising anticancer strategy. The gluconeogenic enzyme phosphoenolpyruvate carboxykinase 1 (PCK1) is downregulated in hepatocellular carcinoma (HCC). However, the potential role of PCK1 in enhancing HBP activity and HCC carcinogenesis under glucose-limited conditions is not well understood. In this study, PCK1 knockout significantly increased global O-GlcNAcylation levels under low-glucose conditions. Mechanistically, metabolic reprogramming in PCK1-deficient hepatoma cells led to oxaloacetate accumulation and increased de novo uridine triphosphate synthesis, contributing to uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) biosynthesis. Additionally, the deletion of PCK1 resulted in the inactivation of the AMPK-GFAT1 axis, promoting UDP-GlcNAc synthesis and elevated O-GlcNAcylation. Notably, lower expression of PCK1 enhanced CHK2 threonine 378 O-GlcNAcylation, which reduced its stability and dimer formation, leading to increased CHK2-dependent Rb phosphorylation and HCC cell proliferation. Furthermore, AOA hemihydrochloride and 6-diazo-5-oxo-L-norleucine inhibited HBP-mediated O-GlcNAcylation and suppressed tumor progression in liver-specific Pck1-knockout mice. Our findings reveal a connection between PCK1 depletion and hyper-O-GlcNAcylation that contributes to HCC oncogenesis, suggesting that targeting O-GlcNAcylation could be a therapeutic strategy for HCC.