Akt activation by arachidonic acid metabolism occurs via oxidation and inactivation of PTEN tumor suppressor

Abstract

Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzymes are overexpressed during inflammation and multistage tumor progression in many neoplastic disorders including lung, breast and pancreatic cancers. Here we report that the tumor suppressor phosphatase and tensin homolog (PTEN) is oxidized and inactivated during arachidonic acid (AA) metabolism in pancreatic cancer cell lines expressing COX-2 or 5-LOX. Oxidation of PTEN decreases its phosphatase activity, favoring increased phosphatidylinositol 3,4,5-triphosphate production, activation of Akt and phosphorylation of downstream Akt targets including GSK-3beta and S6K. These effects are recapitulated with pancreatic phospholipase A(2), which hydrolyses the release of membrane-bound AA. Interference with PTEN's physiological antagonism of signals from growth factors, insulin and oncogenes may confer risk for hypertrophic or neoplastic diseases associated with chronic inflammation or unwarranted oxidative metabolism of essential fatty acids.