1: Clin Cancer Res. 2007 Jan 15;13(2 Pt 1):630-5. Glucocorticoids modulate tumor radiation response through a decrease in tumor oxygen consumption. Crokart N, Jordan BF, Baudelet C, Cron GO, Hotton J, Radermacher K, Gregoire V, Beghein N, Martinive P, Bouzin C, Feron O, Gallez B. Laboratories of Medicinal Chemistry and Radiopharmacy, Universite Catholique de Louvain, B-1200 Brussels, Belgium. PURPOSE: We hypothesized that glucocorticoids may enhance tumor radiosensitivity by increasing tumor oxygenation (pO(2)) through inhibition of mitochondrial respiration. EXPERIMENTAL DESIGN: The effect of three glucocorticoids (hydrocortisone, dexamethasone, and prednisolone) on pO(2) was studied in murine TLT liver tumors and FSaII fibrosarcomas. At the time of maximum pO(2) (t(max), 30 min after administration), perfusion, oxygen consumption, and radiation sensitivity were studied. Local pO(2) measurements were done using electron paramagnetic resonance. The oxygen consumption rate of tumor cells after in vivo glucocorticoid administration was measured using high-frequency electron paramagnetic resonance. Tumor perfusion and permeability measurements were assessed by dynamic contrast-enhanced magnetic resonance imaging. RESULTS: All glucocorticoids tested caused a rapid increase in pO(2). At t(max), tumor perfusion decreased, indicating that the increase in pO(2) was not caused by an increase in oxygen supply. Also at t(max), global oxygen consumption decreased. When irradiation (25 Gy) was applied at t(max), the tumor radiosensitivity was enhanced (regrowth delay increased by a factor of 1.7). CONCLUSION: These results show the potential usefulness of the administration of glucocorticoids before irradiation. PMID: 17255286 [PubMed - in process] Related Links Tumor radiosensitization by antiinflammatory drugs: evidence for a new mechanism involving the oxygen effect. [Cancer Res. 2005] PMID:16140962 Insulin increases the sensitivity of tumors to irradiation: involvement of an increase in tumor oxygenation mediated by a nitric oxide-dependent decrease of the tumor cells oxygen consumption. [Cancer Res. 2002] PMID:12068004 Effect of RSR13, an allosteric hemoglobin modifier, on oxygenation in murine tumors: an in vivo electron paramagnetic resonance oximetry and bold MRI study. [Int J Radiat Oncol Biol Phys. 2004] PMID:15183487 Nitric oxide-mediated increase in tumor blood flow and oxygenation of tumors implanted in muscles stimulated by electric pulses. [Int J Radiat Oncol Biol Phys. 2003] PMID:12605986 Potentiation of radiation-induced regrowth delay by isosorbide dinitrate in FSaII murine tumors. [Int J Cancer. 2003] PMID:12455068