PRF1 and hepatocellular carcinoma: CD158a expression (HR = 2.47, P = 0.0398) (Fig. 5A), IFN-γ (HR = 2.73, P = 0.0419) (Fig. 5C), and perforin (HR = 3.00, P = 0.026) (Fig. 5D) were associated with the risk of HCC recurrence, but not NKG2D (HR = 2.32, P = 0.06) (Fig. 5B).