| [ Summary ] |
Numerous studies indicate that green tea catechins can exert anticancer and chemopreventive effects on various organ sites, including the colorectum. (−)-Epigallocatechin-3-gallate(EGCG), the major biologically active component of green tea, inhibits cell growth and induces apoptosis in colorectal cancer cells by inhibiting the activation of certain types of receptor tyrosine kinases(RTKs), including the erb-B family(EGFR, HER2, and HER3), IGF-1R, and VEGFR2. EGCG also inhibits the activation of Ras/MAPK and PI3K/Akt signaling pathways, which are RTK-related cell signaling pathways, as well as the activation of AP-1 and NF-κB transcriptional factors. Green tea catechins effectively attenuate inflammation-related mouse colorectal carcinogenesis by inhibiting the expression of COX-2 and TNF-α in the colonic mucosa. EGCG also prevents the development of colonic premalignant lesions in an obesityrelated colorectal cancer model and this is associated with improvement of hyperinsulinemia and inhibition of the IGF/IGF-1R axis. The results of these in vivo studies are important because chronic inflammation and obesity are risk factors for colorectal cancer. In addition, a pilot study indicates that supplementation with green tea extract significantly prevents metachronous colorectal adenomas after polypectomy. These findings suggest that green tea catechins may be useful in the chemoprevention of colorectal cancer. |