(-)-Epigallocatechin-3-gallate inhibits VEGF expression induced by IL-6 via Stat3 in gastric cancer

Figure 4 (-)-Epigallocatechin-3-gallate inhibits signal transducer and activator of transcription 3 nuclear translocation and DNA binding activity in human gastric cancer cells. Signal transducer and activator of transcription 3 (Stat3) nuclear translocation was determined by Western blotting with extraction of nuclear proteins. A: After treated with 50 μmol (-)-epigallocatechin-3-gallate (EGCG) and interleukin-6 (IL-6) (50 ng/mL) for 1 h, phospho-Stat3 in the nucleus was visualized with an anti-p-Stat3 antibody; B: IL-6 apparently increased phospho-Stat3 expression in the nucleus, but EGCG treatment markedly decreased this effect. Stat3-DNA binding activity was determined by chromatin immunoprecipitation (ChIP) assay. Immunoprecipitation was conducted with Stat3 antibody followed by polymerase chain reaction (PCR) using oligonucleotide primers that yielded a 235 bp band spanning Stat3 binding site in vascular endothelial growth factor promoter. IL-6 apparently increased Stat3-DNA binding activity. When treated with EGCG, Stat3-DNA binding activity was also markedly decreased.