title: The effects of dexamethasone on C6 astrocytoma radiosensitivity.
abstract: Brain-tumor patients often undergo radiation therapy while receiving corticosteroids for the treatment of cerebral edema. Studies have demonstrated that dexamethasone is radioprotective in a number of cell lines. The C6 astrocytoma cell line is well established in vitro and is modulated by dexamethasone treatment. It has therefore been hypothesized that dexamethasone-treated C6 astrocytoma cells would be more resistant to radiation-induced damage. The present study was carried out to assess this hypothesis using both the in vitro C6 astrocytoma monolayer and three-dimensional multicellular spheroid models. Dexamethasone was inhibitory to the C6 astrocytoma cells in the monolayer preparation, increasing their doubling time by 13%. In the spheroid cultures, dexamethasone treatment decreased the number of cells per spheroid by 46%. Dexamethasone did not affect the plating efficiency of either the cells from the monolayer experiment or those dissociated from spheroids, however, suggesting that the inhibitory effect was not tumoricidal. At a clinical concentration (1.94 x 10(-5) M), dexamethasone did not significantly influence plating efficiency of irradiated C6 astrocytoma cells in monolayer or three-dimensional spheroid cultures.
authors.affiliation: Department of Clinical Neurological Sciences, Victoria Hospital, University of Western Ontario, London, Canada.
authors.forename: C D
authors.initials: CD
authors.lastname: Lordo
authors.forename: E C
authors.initials: EC
authors.lastname: Stroude
authors.forename: R F
authors.initials: RF
authors.lastname: Del Maestro
mesh_terms: D000818:Animals; D001254:Astrocytoma / Q000473:pathology*; D001932:Brain Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D003584:Cytological Techniques; D003907:Dexamethasone / Q000494:pharmacology*; D011837:Radiation-Protective Agents; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D011837:Radiation-Protective Agents; D003907:Dexamethasone