title: PGE2 inhibits apoptosis in human adenocarcinoma Caco-2 cell line through Ras-PI3K association and cAMP-dependent kinase A activation.
abstract: PGE2 plays a critical role in colorectal carcinogenesis. We have previously shown that COX-2 expression and PGE2 synthesis are mediated by IGF-II/IGF-I receptor signaling in the Caco-2 cell line and that the pathway of phosphatidylinositol 3-kinase (PI3K)/Akt protects the cell from apoptosis. In the present study, we demonstrate that PGE2 has the ability to increase Ras and PI3K association and decrease the level of apoptosis in the same experimental system. The effect of PGE2 on PI3K/Ras association is dependent on the activation of EP4 receptor, the increase of cAMP levels, and the activation of PKA. In fact, treatment of cells with the PKA inhibitor H89 decreases the association of Ras and PI3K and Ras-associated PI3K activity. PKA inhibitor H89 is able to decrease threonine phosphorylation of Akt and to increase serine phosphorylation of Akt by p38 MAPK and counteracts the cytoprotective effect induced by PGE2. In addition, PGE2 is able to activate p38 MAPK and the inhibition of p38 MAPK, with SB203580 specific inhibitor or with dominant negative MKK6 kinase, is able to revert the apoptotic effect of H89 and serine phosphorylation of Akt. The effect of PGE2 on Caco-2 cell survival through PKA activation is mediated and regulated by the balance of threonine/serine phosphorylation of Akt by p38 kinase and PI3K. In conclusion, our data elucidate a novel mechanism for regulation of colon cancer cell survival and provide evidences for new combinatory treatments of colon cancer.
authors.affiliation: Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano, Università degli Studi di Napoli Federico II, Via Pansini, 5, 80131, Napoli, Italy.
authors.forename: Vincenza
authors.initials: V
authors.lastname: Leone
authors.forename: Antonella
authors.initials: A
authors.lastname: di Palma
authors.forename: Paolo
authors.initials: P
authors.lastname: Ricchi
authors.forename: Fabio
authors.initials: F
authors.lastname: Acquaviva
authors.forename: Maria
authors.initials: M
authors.lastname: Giannouli
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Di Prisco
authors.forename: Francesca
authors.initials: F
authors.lastname: Iuliano
authors.forename: Angela M
authors.initials: AM
authors.lastname: Acquaviva
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D018938:Caco-2 Cells; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D015232:Dinoprostone / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D018631:ras Proteins / Q000502:physiology*
chemical_list: D007093:Imidazoles; D007546:Isoquinolines; D011725:Pyridines; D013449:Sulfonamides; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D018631:ras Proteins; D015232:Dinoprostone; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093642:SB 203580