title: Tumor radiosensitization by antiinflammatory drugs: evidence for a new mechanism involving the oxygen effect.
abstract: We hypothesized that nonsteroidal antiinflammatory drugs (NSAIDs) might enhance tumor radiosensitivity by increasing tumor oxygenation (pO2), via either a decrease in the recruitment of macrophages or from inhibition of mitochondrial respiration. The effect of four NSAIDs (diclofenac, indomethacin, piroxicam, and NS-398) on pO2 was studied in murine TLT liver tumors and FSaII fibrosarcomas. At the time of maximum pO2 (t(max), 30 minutes after administration), perfusion, oxygen consumption, and radiation sensitivity were studied. Local pO2 measurements were done using electron paramagnetic resonance. Tumor perfusion and permeability measurements were assessed by dynamic contrast-enhanced magnetic resonance imaging. The oxygen consumption rate of tumor cells after in vivo NSAID administration was measured using high-frequency electron paramagnetic resonance. Tumor-infiltrating macrophage localization was done with immunohistochemistry using CD11b antibody. All the NSAIDs tested caused a rapid increase in pO2. At t(max), tumor perfusion decreased, indicating that the increase in pO2 was not caused by an increase in oxygen supply. Also at t(max), global oxygen consumption decreased but the amount of tumor-infiltrating macrophages remained unchanged. Our study strongly indicates that the oxygen effect caused by NSAIDs is primarily mediated by an effect on mitochondrial respiration. When irradiation (18 Gy) was applied at t(max), the tumor radiosensitivity was enhanced (regrowth delay increased by a factor of 1.7). These results show the potential utility of an acute administration of NSAIDs for radiosensitizing tumors, and shed new light on the mechanisms of NSAID radiosensitization. These results also provide a new rationale for the treatment schedule when combining NSAIDs and radiotherapy.
authors.affiliation: Laboratory of Medicinal Chemistry and Radiopharmacy, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Crokart
authors.forename: Kim
authors.initials: K
authors.lastname: Radermacher
authors.forename: Bénédicte F
authors.initials: BF
authors.lastname: Jordan
authors.forename: Christine
authors.initials: C
authors.lastname: Baudelet
authors.forename: Gregory O
authors.initials: GO
authors.lastname: Cron
authors.forename: Vincent
authors.initials: V
authors.lastname: Grégoire
authors.forename: Nelson
authors.initials: N
authors.lastname: Beghein
authors.forename: Caroline
authors.initials: C
authors.lastname: Bouzin
authors.forename: Olivier
authors.initials: O
authors.lastname: Feron
authors.forename: Bernard
authors.initials: B
authors.lastname: Gallez
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D003131:Combined Modality Therapy; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism / Q000532:radiotherapy; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism / Q000532:radiotherapy*; D009578:Nitrobenzenes / Q000494:pharmacology; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D011836:Radiation Tolerance / Q000187:drug effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D009578:Nitrobenzenes; D011838:Radiation-Sensitizing Agents; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D010100:Oxygen