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Br J Cancer. 1993 February; 67(2): 321–325.
PMCID: PMC1968170

Metabolism of the bioreductive cytotoxin SR 4233 by tumour cells: enzymatic studies.


SR 4233 (3-amino-1,2,4-benzotriazine 1,4-dioxide) is an anti-tumour agent that has a highly selective toxicity to hypoxic cells. In this study we delineate the role of several different bioreductive enzymes in the metabolism of SR 4233 by two tumour cell lines HT 1080 (human fibrosarcoma) and SCCVII (mouse carcinoma). Enzyme kinetics demonstrates similar KM of HT 1080 and SCCVII cell sonicates and differing Vmax. Among all cofactors tested, NADPH was the most important one in reducing SR 4233 by both tumour cell sonicates. NADH was the second most important cofactor while hypoxanthine and N-methylnicotinamide were less involved in the reduction of SR 4233. Carbon monoxide inhibited the reduction by about 60% suggesting that cytochrome P-450 may play a major role in the reduction of SR 4233 under hypoxia in both SCCVII and HT 1080 cells. DT diaphorase is also involved, particularly in HT 1080 cells, in this drug reduction. The level of functional cytochrome P-450, cytochrome P-450 reductase activity and DT diaphorase activity in both cell lines were assayed. These enzyme levels were all higher in SCCVII cells than in HT 1080 cells. This result correlated the higher Vmax of SR 4233 reduction in SCCVII cells than in HT 1080 cells.

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Selected References

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  • Bachur NR, Gordon SL, Gee MV. A general mechanism for microsomal activation of quinone anticancer agents to free radicals. Cancer Res. 1978 Jun;38(6):1745–1750. [PubMed]
  • Baker MA, Zeman EM, Hirst VK, Brown JM. Metabolism of SR 4233 by Chinese hamster ovary cells: basis of selective hypoxic cytotoxicity. Cancer Res. 1988 Nov 1;48(21):5947–5952. [PubMed]
  • Biedermann KA, Wang J, Graham RP, Brown JM. SR 4233 cytotoxicity and metabolism in DNA repair-competent and repair-deficient cell cultures. Br J Cancer. 1991 Mar;63(3):358–362. [PMC free article] [PubMed]
  • Brown JM, Lemmon MJ. Potentiation by the hypoxic cytotoxin SR 4233 of cell killing produced by fractionated irradiation of mouse tumors. Cancer Res. 1990 Dec 15;50(24):7745–7749. [PubMed]
  • Cahill A, White IN. Reductive metabolism of 3-amino-1,2,4-benzotriazine-1,4-dioxide (SR 4233) and the induction of unscheduled DNA synthesis in rat and human derived cell lines. Carcinogenesis. 1990 Aug;11(8):1407–1411. [PubMed]
  • Costa AK, Baker MA, Brown JM, Trudell JR. In vitro hepatotoxicity of SR 4233 (3-amino-1,2,4-benzotriazine-1,4-dioxide), a hypoxic cytotoxin and potential antitumor agent. Cancer Res. 1989 Feb 15;49(4):925–929. [PubMed]
  • De Graeve J, Kremers P, Frankinet C, Gielen J. A new highly sensitive assay for ethoxycoumarin deethylase in cultured hepatocytes. Anal Biochem. 1980 May 15;104(2):419–424. [PubMed]
  • Hirst DG, Brown JM, Hazlehurst JL. Enhancement of CCNU cytotoxicity by misonidazole: possible therapeutic gain. Br J Cancer. 1982 Jul;46(1):109–116. [PMC free article] [PubMed]
  • Laderoute K, Wardman P, Rauth AM. Molecular mechanisms for the hypoxia-dependent activation of 3-amino-1,2,4-benzotriazine-1,4-dioxide (SR 4233). Biochem Pharmacol. 1988 Apr 15;37(8):1487–1495. [PubMed]
  • Lloyd RV, Duling DR, Rumyantseva GV, Mason RP, Bridson PK. Microsomal reduction of 3-amino-1,2,4-benzotriazine 1,4-dioxide to a free radical. Mol Pharmacol. 1991 Sep;40(3):440–445. [PubMed]
  • Mason RP, Chignell CF. Free radicals in pharmacology and toxicology--selected topics. Pharmacol Rev. 1981 Dec;33(4):189–211. [PubMed]
  • Mc Lane KE, Fisher J, Ramakrishnan K. Reductive drug metabolism. Drug Metab Rev. 1983;14(4):741–799. [PubMed]
  • Omura T, Takesue S. A new method for simultaneous purification of cytochrome b5 and NADPH-cytochrome c reductase from rat liver microsomes. J Biochem. 1970 Feb;67(2):249–257. [PubMed]
  • Redinbaugh MG, Turley RB. Adaptation of the bicinchoninic acid protein assay for use with microtiter plates and sucrose gradient fractions. Anal Biochem. 1986 Mar;153(2):267–271. [PubMed]
  • Riley RJ, Workman P. DT-diaphorase and cancer chemotherapy. Biochem Pharmacol. 1992 Apr 15;43(8):1657–1669. [PubMed]
  • Rosenberg DW, Roque H, Kappas A. A fluorometric method for measuring ethoxycoumarin O-deethylase activity by reversed-phase high performance liquid chromatography. Anal Biochem. 1990 Dec;191(2):354–358. [PubMed]
  • Sun JR, Brown JM. Enhancement of the antitumor effect of flavone acetic acid by the bioreductive cytotoxic drug SR 4233 in a murine carcinoma. Cancer Res. 1989 Oct 15;49(20):5664–5670. [PubMed]
  • Walton MI, Wolf CR, Workman P. Molecular enzymology of the reductive bioactivation of hypoxic cell cytotoxins. Int J Radiat Oncol Biol Phys. 1989 Apr;16(4):983–986. [PubMed]
  • Walton MI, Workman P. Enzymology of the reductive bioactivation of SR 4233. A novel benzotriazine di-N-oxide hypoxic cell cytotoxin. Biochem Pharmacol. 1990 Jun 1;39(11):1735–1742. [PubMed]
  • Wang J, Biedermann KA, Brown JM. Repair of DNA and chromosome breaks in cells exposed to SR 4233 under hypoxia or to ionizing radiation. Cancer Res. 1992 Aug 15;52(16):4473–4477. [PubMed]
  • Wolf CR, Oesch F. Isolation of a high spin form of cytochrome P-450 induced in rat liver by 3-methylcholanthrene. Biochem Biophys Res Commun. 1983 Mar 16;111(2):504–511. [PubMed]
  • Wolpert MK, Althaus JR, Johns DG. Nitroreductase activity of mammalian liver aldehyde oxidase. J Pharmacol Exp Ther. 1973 May;185(2):202–213. [PubMed]
  • Zeman EM, Brown JM, Lemmon MJ, Hirst VK, Lee WW. SR-4233: a new bioreductive agent with high selective toxicity for hypoxic mammalian cells. Int J Radiat Oncol Biol Phys. 1986 Jul;12(7):1239–1242. [PubMed]
  • Zeman EM, Hirst VK, Lemmon MJ, Brown JM. Enhancement of radiation-induced tumor cell killing by the hypoxic cell toxin SR 4233. Radiother Oncol. 1988 Jul;12(3):209–218. [PubMed]

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