ERRFI1 and hepatocellular carcinoma: These results were further confirmed by western blot analysis, which showed that only ERRFI1 protein levels increased in PLC8024, HepG2, and SMMC-7721 cells in response to tryptophan deficiency (Fig. 2D), suggesting that ERRFI1 expression upregulates in sensitive HCC cells in response to tryptophan deficiency.