To investigate the effects of miR-21 in the trans-differentiation of fibroblasts into CAFs, we used a fibroblast-to-CAF conversion model, where human normal lung IMR-90 or MRC-5 fibroblasts were cultured in the presence of TGF-β1 or conditioned medium (CM) from the A549 lung adenocarcinoma cell line. This evidence concerns the gene TGFB1 and lung adenocarcinoma.