IFNG and hepatocellular carcinoma: To investigate the clinical significance of NK cell activity in HCC recurrence, patients were classified into 2 groups according to the IFN-γ producing NK cell proportion as follows: group 1, patients with IFN-γ producing NK cell proportion ≥ 45%; and group 2, patients with IFN-γ producing NK cell proportion < 45% (Fig. 1B).