Both western blot (unpaired t test, P < 0.001) and flow cytometry (unpaired t test, P < 0.02) analyses demonstrated that treatment with celecoxib significantly down-regulated the total protein level and surface expression of PD-L1 in both A375 and SK-MEL-2 melanoma cells as compared to untreated cells (Fig. 6). This evidence concerns the gene CD274 and melanoma.