EPAS1 and clear cell renal carcinoma: Accordingly, silencing of endothelial PAS domain protein 1 (EPAS1; best known as HIF2A) in clear cell renal cell carcinoma [75] or HIF1A in melanoma and prostate cells [76] reduced PD-L1 expression and restored cytotoxic T lymphocyte (CTL)-mediated tumor cell killing in vitro.