Programmed death ligand-1 (PD-L1) expression in penile squamous cell carcinoma.

Abstract

393 Background: PD-1 protein is a co-inhibitory receptor expressed on B cells, T cell, and NK cells. Its ligand PD-L1 (B7-H1) leads to inhibition of T cell proliferation and cytokine production and is not expressed on normal tissues other than macrophages, but is expressed on various human carcinomas. Expression of PD-L1 in the HPV-associated disease penile carcinoma is unknown. Methods: Formalin-fixed paraffin-embedded tumor specimens were obtained from 19 patients. PD-L1 staining was done with an E1L3N rabbit monoclonal antibody with the summary of a positive score using H-score membrane staining, which considers both intensity and percentage of cells, with >5% score as a positive. HPV status was also evaluated using FISH or p16 immunohistochemical staining to evaluate for correlation with PD-L1. Results: 23 samples between primaries and lymph nodes were collected from the 19 patients with 5/23 samples (22%) positive for anti-PDL1 staining. 6 samples (26%) were positive for HPV by at least one method of testing with 2/6 (33%) HPV positive patients having positive PD-L1 membrane staining. In both of these samples, there was equivocal peritumoral inflammatory infiltration of PD-L1 cells. Conclusions: This analysis shows that PD-L1 is expressed in penile squamous cell carcinomas and may indicate a role for future anti-PD-L1/PD-1 drugs as therapeutic options. Further analyses of correlated clinical features, survival, and separate PD-L1 staining in peritumoral inflammatory cells are underway.