SMAD3 and lung adenocarcinoma: In this study, we further investigated the roles of miRNAs in lung adenocarcinoma through TGF-β1/Smad pathway, and found that miR-206 and miR-140, as signal factors in TGF-β1/Smad pathway, could inhibit lung adenocarcinoma cell proliferation and metastasis by downregulating p-Smad3/Smad3 and that this may be related to p-Smad3's promotion of cell growth or invasion41 in TGF-β1 pathway.