Gallotannin (GT) is a type of tannic acid derived from plant polyphenol, it is usually involved in plant defense mechanism. GT has been used in medical agents such as anti-cancer, anti-inflammatory, anti-virial, anti-vacterial and anti-parastic in a wide range of cells. We have investigated the effects of GT on apoptosis and inflammation in MDA-MB-231 human breast cancer cells. Treatment of GT induced apoptosis and reduced proliferation as detected by MTT assay, and increased the expression of active caspase-3 as determined by Western blot analysis. Also, treatment of GT increased the expression of cyclooxygenase-2 (COX-2) and the production of prostaglandin E₂ (PGE₂) in a dose- and time-dependent manner as determined by Western blot analysis and PGE₂ assay. We confirmed that GT dramatically caused phosphorylation of Akt and p38 kinase. Inhibition of PI3-kinase and p38 kinase with LY294002 and SB203580 prevented GT-induced apoptosis and COX-2 expression. Our results suggested that GT regulates apoptosis and COX-2 expression through PI3-kinase and p38 kinase pathway in MDA-MB-231 human breast cancer cells. (Cancer Prev Res 16, 200-209, 2011)

Keywords: Gallotannin (GT), Apoptosis, Cyclooxygenase-2 (COX-2), PI3-kinase, p38 kinase