Effect of transforming growth factor-β1 on the invasion and migration of human lung adenocarcinoma cells and epithelial mesenchymal transformation and autophagy

Objective To investigate the effect of transforming growth factor-β1 (TGF-β1) on the invasion and migration of lung adenocarcinoma cells and the epithelial-mesenchymal transition (EMT) and autophagy of epithelial cells. Methods Transwell assay was used to detect the effect of TGF-β1 on the migration and invasion of lung adenocarcinoma A549 and SK-LU-1 cells. The changes of autophagy in A549 cells induced by TGF-β1 were examined by immunofluorescence. The effect of TGF-β1 on the expression of EMT marker and autophagy regulatory genes in A549 cells was detected by Western blotting. Results The interference efficiency of sh-TGF-β1 was about 60% in A549 and SK-LU-1 cells, and the overexpression efficiency in GV358-TGF-β1 overexpression group was more than 4 times. The migration assay showed that in A549 cells, the migration was 1.02±0.06 in shNC group, and 5.14±0.43 in TGF-β1 overexpression group (t=16.440, P=0.004); In SK-LU-1 cells, the migration was 1.04±0.08 in shNC group, and 4.92±0.48 in TGF-β1 overexpression group (t=13.810, P=0.005). The invasion assay showed that in A549 cells, the invasion rate was 0.96±0.07 in the shNC group, and 4.28±0.51 in the TGF-β1 overexpression group (t=11.170, P=0.007); In SK-LU-1 cells, the invasion rate was 1.03±0.05 in the shNC group, and 4.11±0.36 in the TGF-β1 overexpression group (t=10.410, P=0.009). The results of immunofluorescence showed that as compared with the control group, the number of autophagic bodies punctured in TGF-β1 overexpression group was significantly increased (t=22.340, P=0.000), and the fluorescence intensity was significantly increased. The results of Western blotting revealed the expression of E-cadherin in TGF-β1 overexpression group was significantly decreased, and that of Vimentin, Twist and Snail significantly increased as compared with the control group. The autophagy-related protein Beclin1 and phosphorylated mammalian target of rapamycin (p-mTOR) were significantly upregulated. The results in the TGF-β1 interference group showed the opposite trend to the TGF-β1 over-expression group. Conclusion In lung adenocarcinoma cells, autophagy and EMT induced by TGF-β1 positive expression may be related to their ability to enhance invasion and migration of lung adenocarcinoma cells. Key words: Lung adenocarcinoma; Transforming growth factor-β1; Migration; Invasion; Epithelial-mesenchymal transition; Autophagy