Evaluation of the epithelial cell markers, E-cad and CK8, and the mesenchymal cell markers, α-SMA and vimentin, expression in A549 cells. Western blot analysis was used to examine the levels of E-cad, CK8, α-SMA and vimentin in the cells. Densitometric analysis of protein expression with β-actin as the control. The results demonstrated that treatment with BMSCs-CM or SIS3 significantly increased the expression of E-cad and CK8, and decreased α-SMA and vimentin protein expression following exposure to TGF-β1 (*P<0.05 vs. control group; #P<0.05 vs. TGF-β1 group). The bars are labeled as follows: A, control group; B, TGF-β1 group; C, SIS3 group; and D, BMSCs-CM group. The cell groups were as follows: control, cells cultured in serum-free DMEM; TGF-β1, cells cultured in serum-free DMEM and exposed to 5 ng/ml TGF-β1; SIS3, cells were treated with 3 μM SIS3 (specific inhibitor of Smad3) which was added 4 h prior to 5 ng/ml TGF-β1 exposure; BMSCs-CM, BMSCs-CM was added prior to 5 ng/ml TGF-β1 exposure. BMSCs, bone marrow-derived mesenchymal stem cells; CM, conditioned medium; TGF-β1, transforming growth factor-β1; E-cad, E-calcium mucins; α-SMA, α-smooth muscle actin.