Abstract: Objective To investigate the effects of Rac1 on epithelial mesenchymal transition（EMT） induced by transforming growth factor β1（TGF-β1）,and on cell proliferation and apoptosis of L02 cells in vitro. Methods Rac1 plasmids with different activity including pExRed-NLS Flag（vector）,pExRed-NLS Flag Rac1（wild type）,pExRed-NLS Flag Rac1T17N（dominant negative mutant） and pExRed-NLS Flag Rac1G12V（constitutively active mutant） were transiently transfected into L02 cells,followed by stimulation of exogenous TGF-β1 at dose of 5ng/ml;Exogenous Flag-Rac1 fusion protein was determined by Western blot analysis;Immunofluorescence and Western blot were used to evaluate epithelial markers of Ck8 and mesenchymal markers of vimentin;Cell motility was assessed by transwell assay and wound healing assay;L02 cells were treated with different concentrations of Rac1 inhibitor （NSC23766）,and the influence of Rac1 on cell proliferation and apoptosis were detected by CCK-8 assay or Annexin V-FITC/PI double staining,respectively. Result All kinds of plasmids were successfully transiently transfected into L02 cells;Compared with the vector group and the wild type group,constitutively active mutant pExRed-NLS Flag Rac1G12V significantly increased the expression of vimentin,decreased the expression of CK8 and enhanced cell motility,whereas the effects of dominant negative mutant pExRed-NLS Flag Rac1T17N were just the opposite of above results（P<0.05）;Disruption of Rac1 activity with NSC23766 inhibited cell proliferation（P<0.05） without increasing cell apoptosis. Conclusions Rac1 promotes the EMT process and cell proliferation induced by TGF-β1 in L02 cells without affecting cell apoptosis in vitro.

Key words: L02 cells, Rac1, Epithelial-mesenchymal transition, Proliferation, Apoptosis