ULBP3 and hepatocellular carcinoma: Then, the correlation coefficients of the above three NKG2D ligands were determined and the risk score of each HCC patient was calculated according to the following formula: Risk score = 0.29795 × (MICA) ‐ 0.79165 × (ULBP3) + 1.28571 × (ULBP5).