title: Synergy between celecoxib and radiotherapy results from inhibition of cyclooxygenase-2-derived prostaglandin E2, a survival factor for tumor and associated vasculature.
abstract: Previous work has demonstrated that selective cyclooxygenase-2 (COX-2) inhibitors can act synergistically with radiotherapy to improve tumor debulking and control in preclinical models. The underlying mechanism of this remarkable activity has not yet been determined. Here, we report that radiation can elevate intratumoral levels of COX-2 protein and its products, particularly prostaglandin E(2) (PGE(2)). Furthermore, inhibition of COX-2 activity or neutralization of PGE(2) activity enhances radiotherapy even in tumors where COX-2 expression is restricted to the tumor neovasculature. Direct assessment of vascular function by direct contrast enhancement-magnetic resonance imaging showed that the combination of radiation and celecoxib lead to enhanced vascular permeability. These observations suggest that an important mechanism of celecoxib-induced radiosensitization involves inhibition of COX-2-derived PGE(2), thus removing a survival factor for the tumor and its vasculature.
authors.affiliation: Oncology Discovery Research, Pfizer Corporation, St. Louis, Missouri 63017, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Davis
authors.forename: Janet M
authors.initials: JM
authors.lastname: O'Neal
authors.forename: Mark D
authors.initials: MD
authors.lastname: Pagel
authors.forename: Ben S
authors.initials: BS
authors.lastname: Zweifel
authors.forename: Pramod P
authors.initials: PP
authors.lastname: Mehta
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Heuvelman
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Masferrer
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002277:Carcinoma / Q000188:drug therapy* / Q000532:radiotherapy*; D000068579:Celecoxib; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000627:therapeutic use*; D015232:Dinoprostone / Q000037:antagonists & inhibitors*; D004195:Disease Models, Animal; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011720:Pyrazoles; D013449:Sulfonamides / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D011720:Pyrazoles; D013449:Sulfonamides; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D000068579:Celecoxib; D015232:Dinoprostone