The role of PD-L1 in the radiation response and clinical outcome for bladder cancer

Identification of potential factors that can stratify a tumor's response to specific therapies will aid in the selection of cancer therapy. The aim was to highlight the role of programmed cell death 1 ligand 1 (PD-L1) in bladder cancer. In this study, 92 of muscle-invasive bladder cancers and 28 of non-muscle invasive bladder cancers were selected for immunohistochemical staining analysis. Furthermore, human and murine bladder cancer cell lines were used to examine the correlation between PD-L1 and radiation response. Our data revealed that PD-L1 was overexpressed in the bladder tumor specimens compared with adjacent non-malignant specimens. Furthermore, the staining of PD-L1 was significantly linked to higher clinical stage, lower complete response rates and reduced diseasefree survival rates. By in vitro and in vivo experiments, irradiation up-regulated the expression of PD-L1 in tumor cells, and its increase correlated with the irradiation dose. In immunocompetent mouse models, blocking PD-L1 induced a longer tumour growth delay following irradiation. The inhibition of T cell functions including proliferation and cytotoxicity against tumor cells was responsible to the effects of PD-L1 on radiation response. In conclusion, PD-L1 could be a significant clinical predictor for clinical stage and treatment response of bladder cancer.