CD274 and lung adenocarcinoma: As a histone methyltransferase, enhancer of zeste homolog 2 (EZH2) is responsible for mono-, di-, and tri-methylation of lysine residue 27 on histone H3 (H3K27) and showed a positive association with higher PD-L1 in lung adenocarcinomas, suggesting the regulation of immune checkpoints molecules through histone modification [64].