Expression of Programmed Death-Ligand 1 in Cutaneous Squamous Cell Carcinoma Arising in Sun-Exposed and Nonsun-Exposed Skin

Background: A recent clinical trial has shown the efficacy of an anti-programmed death-1 (PD-1) antibody against advanced squamous cell carcinoma (SCC). The expression of PD-ligand 1 (PD-L1) in tumor cells correlates with a favorable response to anti-PD-1 therapy in various malignancies. In recent studies, it has been shown that SCC frequently expresses PD-L1. However, there has been no previous study focusing on the difference in PD-L1 expression between SCC in sun-exposed skin and that in nonsun-exposed areas. Aims: The purpose of this study was to investigate the relationship between sun-exposure status and PD-L1 expression in patients with SCC. Materials and Methods: We investigated 80 patients with SCC (40 patients with SCC in sun-exposed skin and 40 patients with SCC in nonsun-exposed skin) by immunohistochemical staining for PD-L1. Fisher's exact test was used for statistical analyses of the differences between the two groups. Results: Patients with SCC in sun-exposed skin showed a significantly higher expression level of PD-L1 in tumor cells than did patients with SCC in nonsun-exposed skin (P = 0.0133). Conclusions: We found that the expression level of PD-L1 in patients with SCC in sun-exposed skin was higher than in patients with SCC in nonsun-exposed skin. Practical data are needed for appropriate applications of new therapeutic options for SCC.