Programmed death‐1 ligands 1 and 2 expression in cutaneous squamous cell carcinoma and their relationship with tumour‐ infiltrating dendritic cells

Abstract

The programmed death‐1 (PD‐1) receptor ligands, PD‐L1 and PD‐L2, are co‐stimulatory molecules that contribute to the negative regulation of T lymphocyte activation. It is still unclear whether there is correlation between PD‐L1 or PD‐L2 and tumour‐infiltrating dendritic cells (TIDCs) in cutaneous squamous cell carcinoma (CSCC). The aim of this study was to analyse PD‐L1 and PD‐L2 expression and dendritic cells infiltration in tumour tissue of CSCC patients and investigate their clinical significance. Immunohistochemical analysis was used to evaluate the expression of PD‐L1, PD‐L2, CD1a and CD83 in 61 CSCC tissues. The immunofluoresence double‐labelling technique was performed to detect the co‐expression of PD‐L1 or PD‐L2 and CD1a or CD83 in tumour tissues. We found that 25 of 61 cases CSCC (40·98%) exhibited positivity for PD‐L1, whereas 37 of 61 cases CSCC (60·66%) exhibited positivity for PD‐L2. A higher percentage of CD1a‐positive cases were observed on both PD‐L1‐positive and PD‐L2‐positive specimens compared with that of CD83‐positive cases (92·29% versus 37·60%, 83·20% versus 33·16%). The expression of PD‐L1 and PD‐L2 on CD1a+ cells was significantly higher than that on CD83+ cells in tumour tissues of CSCC patients. Furthermore, the expression rate of PD‐L1 was associated with UICC stage, and the expression rate of PD‐L2 was associated with predominant differentiation and tumour size in CSCC. Our results indicated that higher expression of PD‐L1 and PD‐L2 on CD1a+ cells than that on CD83+ cells in CSCC tumour tissues may contribute to negative regulation in anti‐tumour immune responses.