Histological analysis of mice ectopically expressing FGF19 revealed that glutamine synthetase-positive HCC tumours developed exclusively in Stat3f/f mice, but were not observed in Stat3ΔHep mice (Fig. 1d,g, and Supplementary Fig. 1b), suggesting that Stat3 deficiency in hepatocytes prevents HCC initiation and progression in response to FGF19. This evidence concerns the gene STAT3 and hepatocellular carcinoma.