AIM: To investigate the expression of programmed death (PD)-1, PD ligand 1 (PD-L1) and PD-L2 in liver tissues in the context of chronic hepatitis and hepatocellular carcinoma (HCC).
METHODS: Liver biopsies and HCC specimens from patients were collected and histologically examined. The expression of PD-1, PD-L1, and PD-L2 in biopsy specimens of chronic hepatitis and HCC specimens was evaluated by immunohistochemical staining. The association between the expression level of PD-1, PD-L1, and PD-L2 and clinical and pathological variables was analyzed statistically.
RESULTS: Expression of PD-1 was found in liver-infiltrating lymphocytes. In contrast, PD-L1 and PD-L2 were expressed in non-parenchyma liver cells and tumor cells. The expression of PD-L1 was significantly correlated with hepatitis B virus infection (1.42 ± 1.165 vs 0.50 ± 0.756, P = 0.047) and with the stage of HCC (7.50 ± 2.121 vs 1.75 ± 1.500 vs 3.00 ± 0.001, P = 0.018). PD-1 and PD-Ls were significantly up-regulated in HCC specimens (1.40 ± 1.536 vs 5.71 ± 4.051, P = 0.000; 1.05 ± 1.099 vs 4.29 ± 3.885, P = 0.004; 1.80 ± 1.473 vs 3.81 ± 3.400, P = 0.020).
CONCLUSION: PD-L1 may contribute to negative regulation of the immune response in chronic hepatitis B. PD-1 and PD-Ls may play a role in immune evasion of tumors.