CD274 and lung adenocarcinoma: To examine the possible post-transcriptional regulation of PD-L1 under an MAPK signal, miR-200a, miR-200b, and miR-200c, which were previously described as being responsible for the post-transcriptional suppression of PD-L1 in human lung cancers [12], were quantified in the three KRAS-mutant lung adenocarcinoma cell lines after DMSO or U0126 treatment (S2 Fig).