title: SR 4233 cytotoxicity and metabolism in DNA repair-competent and repair-deficient cell cultures.
abstract: In order to understand in more detail the mechanism underlying the preferential hypoxic cytotoxicity of the benzotriazine N-oxide SR 4233, we have compared the hypoxic cytotoxicity of this drug to the rates of hypoxic metabolism in both DNA double strand break repair-competent and repair-deficient cell cultures. Rodent SCCVII cells and repair deficient, radiation sensitive cells (rodent XR-1, V-3, and human AT5BI) were most sensitive to SR 4233 under hypoxia with a lethal dose needed to kill 50% of cells (LD50) of less than 5 microM. SR 4233 was less cytotoxic to human AG 1522 (LD50 = 18 microM), CHO 4364 (LD50 = 25 microM) and human HT 1080 cells (LD50 = 33 microM). The sensitivities to SR 4233 were found to be inversely proportional to the rates of SR 4233 metabolism in repair-competent cells (R2 = 0.9). However, XR-1 and V-3 cells were more sensitive to SR 4233 than predicted by the metabolism rate. Thus, the toxicity by SR 4233 towards hypoxic cells appears to result from two mechanisms; the rate of drug metabolism and the ability to repair DNA double strand breaks.
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, California 94305.
authors.forename: K A
authors.initials: KA
authors.lastname: Biedermann
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: R P
authors.initials: RP
authors.lastname: Graham
authors.forename: J M
authors.initials: JM
authors.lastname: Brown
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D015687:Cell Hypoxia; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair; D006801:Humans; D010084:Oxidation-Reduction; D051381:Rats; D000077704:Tirapazamine; D014227:Triazines / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D014227:Triazines; D000077704:Tirapazamine