GSE193213
SIRT5 loss promotes hepatocarcinogenesis via bile acid-induced immunosuppressive microenvironment
Hepatocellular carcinoma (HCC) is a prototypical inflammation-associated cancer and the tumor microenvironment (TME) plays a pivotal role in HCC pathogenesis and response to therapy. The liver is a metabolically active organ, but how liver metabolism impacts TME during HCC development and response to immunotherapy are poorly understood. Here, we show that the metabolic regulator SIRT5 is downregulated in human primary HCC samples, and that Sirt5 deficiency in mice synergizes with oncogenes to increase bile acid (BA) production, which is due to hypersuccinylation and increased BA biosynthesis in the peroxisome. BA acts as a cell-signaling mediator to stimulate its nuclear receptor and promotes M2-like macrophage polarization, thereby creating an immunosuppressive microenvironment favorable for HCC initiating cells. Furthermore, high serum taurocholic acid, a major primary BA, correlates with low SIRT5 expression and increased M2-like tumor-associated macrophages (TAMs) in liver tissue samples from HCC patients. Importantly, administration of cholestyramine, a BA sequestrant and FDA-approved medication for hyperlipemia, reverses the effect of Sirt5 deficiency on promoting M2-like polarized TAMs and liver tumor growth. Our study thus uncovers a novel function of SIRT5 in orchestrating BA metabolism to prevent tumor immune evasion and suppress HCC. These results also suggest a potential strategy using clinically proven bile acid sequestrants for the treatment of HCC patients, especially those with decreased SIRT5 and abnormally high BAs. Overall design: RNA-seq of 3 Sirt5+/+ and 3 Sirt5-/- livers at 20 days after YAP5SA hydrodynamic injection.