The Experimental Study Of TGF-β1-Mediated Epithelial To Mesenchymal Transition And Invasion In Squamous Cell Carcinoma Of The Head And Neck

OBJECTIVE:More and more studies have suggested that epithelial to mesenchymal transition(EMT) play an important role in metastasis of epithelial-oriented tumors. Recent years, EMT has also been found in Squamous Cell Carcinoma of the Head and Neck(SCCHN), but the mechanism is not very clear. Transforming growth factor-β1 (TGF-β1) is an important inducer of EMT and tumor metastasis. We treated SCCHN cells with TGF-β1 to examine whether TGF-β1 could induce EMT in human SCCHN cell line, and attempt to find out the related mechanism.METHODS:Tu686 cells were treated with different concertration of TGF-β1 at different time points, and then, first, proliferation rates of Tu686 cells were compared by MTT method; second, cell morphology change was investigated under phase-contrast microscopy; third, E-cadherin, vimentin expression was evaluated by RT-PCR and western-blot analysis, Smad2, P-smad2 were also evaluated by western-blot analysis; fourth, Wound-healing assay and Transwell invasion assay were employed to determine the migration and invasion ability of the cells. siRNA was used to against Smad2, then E-cadherin expression was evaluated by western-blot anslysis and invasion ability of Tu686 cells was evaluated by Transwell invasion assay.RESULTS:First, the proliferation rates of Tu686 cells showed no significant deference after teated with TGF-β1. Second, following TGF-β1 treatment, phase-contrast microscopy revealed a loss of the adherent phenotype of Tu686 cells, decreased in cell-to-cell contact, and the induction of a fibroblast-like state. Third, Tu686 celles showed down-regulation of epithelial marker E-caherin and increased the expression of mesenchymal marker vimentin. And the alterations depended on the concentration of TGF-β1 and action time. The P-smad2 expression was elevated, though the expression of Smad2 had little change. Fourth, Migration and invasion ability of the Tu686 celles increased. Fifth, Smad2 RNAi abrogated the TGF-β1-induced suppression of E-cadherin expression and decreased the invasion ability of Tu686 cells.CONCLUSION:These results suggested that: first, TGF-β1 had little affection on the proliferation rates of Tu686 cells; second, TGF-β1 mediated morphological and molecular change of EMT, and increased migration and invasion ability of Tu686 cells in vitro; third, TGF-β1-mediated EMT and invasion in Tu686 cells were associated with the expression of P-smad2.