Effect of epigallocatechin-3-gallate on epitheliai-mesenchymal transition in melanoma via the trans-forming growth factor-151/signal transducer and activators of transcription 3 pathway

Objective To investigate the effects of epigallocatechin-3-gallate （EGCG） on epithe- lial-mesenchymal transition （EMT） through transforming growth factor （TGF）-l/signal transducer and activators of transcription 3 （ STAT3 ） signal pathway in malignant melanoma. Methods The cell morphol- ogy, migration and invasion ability of TGFq31-stimulated B16 cells were studied under a phase-contrast mi- croscope 24 h after co-incubation with different concentrations （5, 25, and 50 rag/L） of EGCG. The mi- gration ability of the cells was detected by Scrape-wound migration assay, and the invasion ability was stud- ied by Transwell. Western blotting was employed to study the expression of p-stat3 and E-cadherin. The animal model of B16 tumour was established, and E-cadhein mRNA expression was detected by using re- verse transcription-polymerase chain reaction （RT-PCR）. Results （ 1 ） TGF-I （ 5 pg/L）-stimulated B16 cells were long-spindle shaped with loose cell-cell connection. Twenty-four h later after co-incubation with different concentrations of EGCG, B16 cells became more connected, with the degree of change pro- portional to EGCG concentrations. There were increased distance in Scrape-wound migration assay, and Tr- answell number was 97. 00 ＋9. 97, 60. 30 ±4. 00 and 38.75 ±7. 18 respectively. The invasion ability was negatively correlated to the EGCG concentration （ r = - 0. 92, P 〈 0. 05 ） ; （ 2 ） The effects of reduced p- STAT3 expression and increased E-cadherin expression under the effects of different concentrations of EGCG were concentration-dependent. The expression levels of p-STATS and E-Cadherin were also nega- tively correlated （ r = - 0. 805, P 〈 0. 05 ） ; （ 3 ） The obviously increased level of E-cadhein mRNA inEGCG intervened tumour tissue had statistically significant difference （ P 〈 O. O1 ）. Conclusion EGCG in- hibits EMT of B16 cells clearly through the TGF-[31/STAT 3 signal pathway. Key words: Epigallocatechin-3-gallate ;  Epithelial-mesenehymal transition ;  Transforminggrowth factor-131 ;  Melanoma