CD274 and neoplasm: Indeed, this adaptive immunosuppression mediated by IFNγ-induced PD-L1 expression is an important obstacle to efficient immune cell mediated tumor killing as it can inhibit cytotoxic CD8+ T and NK cells (136–139), although PD-L1 expression in tumors is considered a predictive biomarker for the effectiveness of immune checkpoint inhibitor therapy (140, 141).