Ligand activation of peroxisome proliferator-activated receptor-β/δ suppresses liver tumorigenesis in hepatitis B transgenic mice

Peroxisome proliferator-activated receptor-beta/delta (PPAR beta/delta) inhibits steatosis and inflammation, known risk factors for liver cancer. In this study, the effect of ligand activation of PPAR beta/delta in modulating liver tumorigenesis in transgenic hepatitis B virus (HBV) mice was examined. Activation of PPAR beta/delta in HBV mice reduced steatosis, the average number of liver foci, and tumor multiplicity. Reduced expression of hepatic CYCLIN D1 and c-MYC, tumor necrosis factor alpha (Tnfa) mRNA, serum levels of alanine aminotransaminase, and an increase in apoptotic signaling was also observed following ligand activation of PPAR beta/delta in HBV mice compared to controls. Inhibition of Tnfa mRNA expression was not observed in wild-type hepatocytes. Ligand activation of PPAR beta/delta inhibited lipopolysaccharide (LPS)-induced mRNA expression of Tnfa in wild-type, but not in Ppar beta/delta-null Kupffer cells. Interestingly, LPS-induced expression of Tnfa mRNA was also inhibited in Kupffer cells from a transgenic mouse line that expressed a DNA binding mutant form of PPAR beta/delta compared to controls. Combined, these results suggest that ligand activation of PPAR beta/delta attenuates hepatic tumorigenesis in HBV transgenic mice by inhibiting steatosis and cell proliferation, enhancing hepatocyte apoptosis, and modulating anti-inflammatory activity in Kupffer cells. (C) 2016 Elsevier Ireland Ltd. All rights reserved.