To determine whether the negative regulation of YY1 expression by miR-125a-3p observed in HEK293T cells also occurred in lung epithelial cells, we used, as a cell model, the A549 human lung adenocarcinoma cell line to test endogenous YY1 expression in response to a miR-125a-3p mimic. This evidence concerns the gene YY1 and lung adenocarcinoma.