DNMT1 and lung cancer: Moreover, it was reported that transforming growth factor β1 (TGFβ1) induces decreased expression of DNA methyltransferase 1 (DNMT1) and PD-L1 promoter demethylation, which subsequently results in PD-L1 overexpression in lung cancer cells undergoing epithelial-mesenchymal transition (EMT) (77).