Background and Aims: We investigated the prognostic value of programmed death ligand 1 (PD-L1) expression, tumor-infiltrating CD8-positive T-cell status, and their combination in hepatocellular carcinoma (HCC). Their association with PD-L1 expression and vascular formation was further explored. Approach and Results: Using a database of 387 patients who underwent hepatic resection for HCC, immunohistochemical staining of PD-L1, CD8, and CD34 was performed. Additionally, we undertook an enzyme-linked immunosorbent assay for soluble PD-L1. Compared with patients with HCC and PD-L1–negative expression (n = 311), patients with HCC and PD-L1–positive expression (n = 76) showed significantly worse overall survival (OS; multivariate hazard ratio, 2.502; 95% confidence interval [CI], 1.716-3.649; P < 0.0001). The presence of tumor-infiltrating CD8-positive T cells was significantly correlated with longer OS (multivariate hazard ratio, 0.383; 95% CI, 0.274-0.537; P < 0.0001). Stratification based on PD-L1 expression in cancer cells and tumor-infiltrating CD8-positive T-cell status was also significantly associated with OS (log-rank, P < 0.0001). HCC with PD-L1–positive expression was significantly correlated with positivity for vessels that encapsulated tumor clusters. Serum PD-L1 levels were significantly higher in the group of patients who had PD-L1–positive expression than in the group of patients who had PD-L1–negative expression (P = 0.0158). Conclusions: PD-L1 expression in cancer cells was associated with a poor clinical outcome and vascular formation in patients with HCC. Additionally, the combination of PD-L1 expression with tumor-infiltrating CD8-positive T-cell status enabled further classification of patients based on their clinical outcome. Thus, PD-L1 expression in cancer cells and tumor-infiltrating CD8-positive T-cell status might serve as predictive tissue biomarkers.
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