CD274 and ovarian carcinoma: High PD-L1 expression in OC tissues has been associated with poor outcomes; however, in contrast to other solid cancers, such as non-small-cell lung cancer (NSCLC), where PD-L1 expression has been used as a clinical indicator to select patients for anti-PD-1/PD-L1 therapy, in ovarian cancer, surface PD-L1 expression is not a good biomarker, and PD-1/PD-L1 blockade therapy does not significantly prolong progression-free survival [130,131,132,133,134,135,136,137,138,139].