Clinical and biological significance of PD-L1 expression within the tumor microenvironment of oral squamous cell carcinoma

Abstract

Background/Aim: Programmed death-ligand 1 (PD-L1) expression in tumor cells is regulated by a close interrelation between tumor and stromal cells within the tumor microenvironment. Our aim was to evaluate the clinical and biological significance of PD-L1 expression in oral squamous cell carcinoma (OSCC). Materials and Methods: PD-L1, cluster of differentiation (CD)4, CD8, and forkhead box P3 (FOXP3) expression in tumor tissues obtained from 77 patients with OSCC was evaluated by immunohistochemical staining, and then analyzed for associations with clinical and biological factors. Results: Among the clinicopathological factors tested, only vascular invasion showed a trend toward lower PD-L1 expression (p=0.05). Metabolic tumor volume (MTV), and total lesion glycolysis (TLG) significantly positively correlated with PD-L1 expression (MTV, p=0.04; TLG, p=0.03). In patients with OSCC with high PD-L1 expression, those whose tumors had abundant infiltrating CD4+ T-cells showed a longer progression-free survival than those with low CD4+ T-cell infiltration (p=0.0452). Conclusion: As regulation of PD-L1 expression is complex, its evaluation combined with other markers may be useful to determine clinical applications of PD-L1 expression.