Abstract: Liang Meiqi, Liang Guanzhao, Guo Jian, Duan Xinsuo, Lu Jie Department of Dermatology, Affiliated Hospital of Chengde Medical University, Chengde 067020, Hebei, China （Liang MQ, Liang GZ ［current affiliation: Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China］, Guo J, Duan XS, Lu J） Corresponding author: Lu Jie, Email: chengdejiel@163.com 【Abstract】 Objective To evaluate the effects of metformin on transforming growth factor?beta1 （TGF?β1）?induced epithelial?mesenchymal transition （EMT） in and invasion of the human melanoma cell line 1205Lu. Methods In vitro cultured 1205Lu cells were divided into 3 groups to be treated with serum?free culture medium （blank control group）, serum?free culture medium containing 5 ng/ml TGF?β1 （TGF?β1 group） and serum?free culture medium containing 5 ng/ml TGF?β1 and 1 mmol/L metformin （TGF?β1 + metformin group）, respectively. After 48?hour treatment, morphological changes of 1205Lu cells in the above groups were observed by using a microscope, and photos were taken at the same time. Transwell invasion assay was performed to estimate cellular invasive activity, Western blot analysis and real?time fluorescence?based quantitative RT?PCR were conducted to determine the mRNA and protein of N?cadherin and matrix metalloproteinase?9 （MMP?9）, respectively. Statistical analysis was carried out by one?way analysis of variance （ANOVA） and least significant difference （LSD） test. Results Compared with the blank control group, the stimulation of TGF?β1 could induce the epithelial?mesenchymal transition （EMT）?like morphological changes in 1205Lu cells, while TGF?β1 combined with metformin could reverse the EMT?like morpho?logical changes. The number of 1205Lu cells crossing the transwell Matrigel per high?power field （× 200） was significantly higher in the TGF?β1 group （412.2 ± 13.427） than in the blank control group （194.1 ± 8.295） and TGF?β1 + metformin group （175.3 ± 8.693）. Compared with the blank control group and TGF?β1 + metformin group, the TGF?β1 group also showed significantly increased mRNA and protein of N?cadherin （mRNA: 6.678 ± 0.043 vs. 1.000 ± 0.000, 1.035 ± 0.015; protein: 1.963 ± 0.016 vs. 0.603 ± 0.029, 0.207 ± 0.009） and MMP?9 （mRNA: 5.351 ± 0.604 vs. 1.000 ± 0.000, 0.930 ± 0.130; protein: 1.243 ± 0.027 vs. 0.575 ± 0.009, 0.629 ± 0.008）. Conclusion Metformin can obviously inhibit TGF?β1?induced EMT?like morphological changes in, the capacity to penetrate Matrigel?coated transwell chambers of and the mRNA and protein of N?cadherin and MMP?9 in 1205Lu cells.