CD274 and cancer: Furthermore, dysregulated PD-L1/PD-1 interactions were demonstrated to contribute to several pathologies, for example, by maintaining T cell exhaustion in chronic viral infections and their participation in the onset of autoimmune diseases.19,20 Importantly, many tumors in vivo and cancer cell lines overexpress PD-L1, contributing to the strong inhibition of anti-cancer T cell responses in preclinical models and human neoplastic disease.21 Therefore, PD-L1 overexpression in tumors was generally found to be an indicator of progression and poor prognosis in cancer.