Aspirin protects Caco-2 cells from apoptosis after serum deprivation through the activation of a phosphatidylinositol 3-kinase/AKT/p21Cip/WAF1 pathway

Our previous studies indicated that millimolar doses of aspirin induced growth arrest and resistance to anticancer drug treatment in Caco-2 cells. The present study was designed to better elucidate at the molecular level the effect of aspirin treatment on pathways that regulate cell death during serum withdrawal. Caco-2 cells were cultured under serum deprivation in the presence or absence of aspirin. Effects on cell cycle, phosphatidylinositol 3-kinase (PI3-kinase) and mitogen-activated protein ( MAP) kinase pathways were investigated. We found that aspirin, but not the selective cyclooxygenase-2 inhibitor N-[2(cyclohexyloxyl)- 4-nitrophenyl]-methane sulfonamide (NS-398); prevented apoptosis and G(2)/M transition after prolonged Caco-2 cells serum deprivation. Aspirin-dependent inhibition of apoptosis and G(2)/M transition was prevented by treatment with the PI3-kinase inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran4- one (LY294002), but not with the MAP kinase kinase inhibitor 2'-amino-3'-methoxyflavone (PD98059). The effects of aspirin were mediated at molecular levels, through activation of PI3-kinase/AKT pathway and increase in the p21(Cip/WAF1) level. The ability of aspirin to activate AKT protein was observed also in presence of etoposide cotreatment. Our data indicate a new intracellular target of aspirin with potential clinical impact for treatment schedules involving both anticancer agents and aspirin in malignancies.