The mechanism of green tea against breast cancer

Nowadays, there is two opposite insight into the anticancer therapy in medical community: absolute necessity of using isolated or synthesized chemical compounds and treatment based on natural sources, including extracts from plants. In this regard, natural products of plants are available sources with both curative and protective role for different cancers, particularly breast cancer. Breast cancer is the most common cancer among women and despite advances in its treatment, its mortality is still high. In recent years, many studies indicate that green tea inhibits proliferation of breast cancer cells and block carcinogenesis. This abstract attempt to highlight the green tea bioactive components and their mechanisms of action in prevention and treatment of breast cancer. Green tea contains polyphenols, which include flavanols, flavandiols, flavonoids, and phenolic acids. Most of the green tea polyphenols are flavonols commonly known as catechins. Four kinds of catechins mainly find in green tea: epicatechin (EC), epigallocatechin (EGC), epicatechin-3-gallate (ECG), and epigallocatechin-3-gallate (EGCG). EGCG is the most abundant flavonoid in green tea. Experimental studies collectively show that green tea components lead to wide range of responses in breast cancer cells which are as following: Anti-angiogenesis effect that inhibits new blood vessel growth required for tumor growth and metastasis. Also green tea catechins interact with target proteins including phosphoinositide 3 kinase(PI3K), Ras-GTPase activating protein (GAP), Bcl-xL and Bcl-2, insulin like growth factor 1 receptor (IGF-1R) and so on which are important for apoptosis induction and growth inhibition of cancer cells. Additionally, inhibition of cell signaling pathways such as Her-2/neu and Wnt signaling and inhibition of enzyme activities such as cyclin-dependent kinase (CDK) 2 and CDK4 that leads to cell cycle arrest are among other anti cancer mechanism of catechins. Green tea components also affect on epigenetic alterations such as microRNAs, DNA methylation and histone acethylation that are mainly responsible in breast carcinogenesis. Therefore, green tea catechins have been shown to inhibit proliferation of breast cancer cells and to block carcinogenesis through different molecular mechanisms which finally lead to inhibit growth and /or promote apoptosis. So applying this priceless plant could have been much more noticed as a new drug for breast cancer prevention and treatment.