Expression and prognostic significance of programmed death protein 1 and programmed death ligand-1, and cytotoxic T lymphocyte-associated molecule-4 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies and causes of death worldwide. In this study, we assessed the correlation between clinicopathologic factors with programmed cell death protein 1 (PD-1) and programmed cell death ligand-1 (PD-L1), and cytotoxic T lymphocyte-associated molecule-4 (CTLA-4) expressions. Furthermore, we analyzed the prognostic significance of these proteins in a subgroup of patients. We retrospectively evaluated the PD-1, PD-L1, and CTLA-4 expressions in 294 HCC tissue microarray samples using immunohistochemistry. PD-1 and PD-L1 expressions were significant related to high CD8+ tumor-infiltrating lymphocytes (TILs) (r = 0.664, p < 0.001 and r = 0.149, p = 0.012). Only high Edmondson-Steiner grade was statistically related to high PD-1 expression. High PD-L1 expression was demonstrated as an independent poor prognostic factor for disease-free survival in addition to previous known factors, size >5 cm and serum albumin ≤3.5 g/dL in high CD8+ TILs group. We have demonstrated that the combined high expression of PD-L1 and CD8+ TIL is an important prognostic factor related to the immune checkpoint pathway in HCC and furthermore, there is a possibility that it could be used as a predictor of therapeutic response. Also, this result would be helpful in evaluating the applicable group of PD-1/PD-L1 blocking agent for HCC patients.