Green tea inhibits cycolooxygenase-2 in non-small cell lung cancer cells through the induction of Annexin-1

Elevated cyclooygenase-2 (COX-2) expression is frequently observed in human non-small cell lung cancer (NSCLC) and associated with poor prognosis, indicating critical involvement of the inflammatory pathway in lung carcinogenesis. Recently, we found that green tea extract (GTE) induced Annexin-1 (ANX1) in the lung adenocarcinoma A549 cells. ANX1 is a glucocorticoid-inducible 37kDa protein involved in a wide range biological function and is an important anti-inflammatory mediator. The present study further examines the interplay between the expressions and production of ANX1, COX-2, phospholipase A(2) (cPLA(2)) and prostaglandin E(2) (PGE(2)) following the treatment of NSCLC cell lines with GTE. We found that GTE induced ANX1 and inhibited COX-2 expression in lung cancer A549, H157 and H460 cell lines. Addition of pro-inflammatory cytokine IL-1β diminished GTE-induced ANX1. Silence of ANX1 in cells abrogates the inhibitory activity on COX-2, indicating that the anti-inflammatory activity of GTE is mediated at least partially by the up-regulation of ANX1. However, differential pattern of inhibitory effects of ANX1 on cPLA(2) expression was observed among various cell types, suggesting that the anti-inflammatory activity mediated by ANX1 is cell type specific. Our study may provide a new mechanism of GTE on the prevention of lung cancer and other diseases related to inflammation.