To determine whether PD1 and PD-L1 are epigenetically regulated, 11 out of 13 lung cancer cell lines were treated with a DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine (5-Aza), and a histone deacetylase inhibitor, Trichostatin A (TSA), respectively. The gene discussed is PDCD1; the disease is lung cancer.