Tea polyphenol EGC suppresses colorectal cancer cell proliferation both in vitro and in vivo via downregulation of STAT3

Epigallocatechin (EGC) is one of the main bioactive polyphenols in green tea. This study aims to determine the anti-tumor effect of EGC against colorectal cancer. Our results revealed that treatment of EGC led to significant suppression of cell proliferation and apoptosis in three colorectal cancer cells. Western blot confirmed that EGC activated Caspase-3 and PARP, down-regulated the phosphorylation of STAT3 and decreased Bcl-2 expression. Luciferase-reporter-activity assay further determined that EGC suppressed the promoter activity of STAT3 and downregulated the transcription of STAT3. Besides, in vivo study proved that EGC (100 mg/kg) resulted in significant suppression of tumor volume and tumor weight (decreased by 63.7 %) in mice bearing SW620 tumors. Tumor organoid assays demonstrated the inhibitory efficacy of EGC in colorectal organoids. In conclusion, our study present evidence that EGC inhibited colon cancer cell proliferation both in vitro and in vivo by downregulation phosphorylated STAT3 and activated downstreams.