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. 2000 Jan 18;82(3):651–656. doi: 10.1054/bjoc.1999.0977

NADPH:cytochrome c (P450) reductase activates tirapazamine (SR4233) to restore hypoxic and oxic cytotoxicity in an aerobic resistant derivative of the A549 lung cancer cell line

M P Saunders 1, A V Patterson 1, E C Chinje 1, A L Harris 2, I J Stratford 1
PMCID: PMC2363339  PMID: 10682679

Abstract

Tirapazamine (TPZ, SR4233, WIN 59075) is a bioreductive drug that is activated in regions of low oxygen tension to a cytotoxic radical intermediate. This labile metabolite shows high selective toxicity towards hypoxic cells, such as those found in solid tumours. Under aerobic conditions, redox cycling occurs with subsequent generation of superoxide radicals, which are also cytotoxic. NADPH:cytochrome c (P450) reductase (P450R) is a one-electron reducing enzyme that efficiently activates TPZ. Recently a derivative of the A549 non-small cell lung cancer cell line (A549c50) was generated that showed substantially reduced P450R activity compared to its parental line (Elwell et al (1997) Biochem Pharmacol54: 249–257). Here, it is demonstrated that the A549c50 cells are markedly more resistant to TPZ under both aerobic and hypoxic conditions. In addition, these cells have a dramatically impaired ability to metabolize TPZ to its two-electron reduction product, SR4317, under hypoxic conditions when compared to wild-type cells. P450R activity in the A549c50 cells was reintroduced to similar levels as that seen in the parental A549 cells by transfection of the full-length cDNA for human P450R. These P450R over-expressing cells exhibit restored sensitivity to TPZ under both aerobic and hypoxic conditions, comparable to that found in the original parental A549 cells. Further, the ability of the transfected cells to metabolize TPZ to SR4317 under hypoxic conditions is also shown to be restored. This provides further evidence that P450R can play an important role in the activation, metabolism and toxicity of this lead bioreductive drug. © 2000 Cancer Research Campaign

Keywords: tirapazamine, cytochrome P450 reductase, bioreductive drugs, hypoxia

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Selected References

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  1. Adams G. E., Stratford I. J. Bioreductive drugs for cancer therapy: the search for tumor specificity. Int J Radiat Oncol Biol Phys. 1994 May 15;29(2):231–238. doi: 10.1016/0360-3016(94)90267-4. [DOI] [PubMed] [Google Scholar]
  2. Brown J. M., Lemmon M. J. 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] [Google Scholar]
  3. Brown J. M. SR 4233 (tirapazamine): a new anticancer drug exploiting hypoxia in solid tumours. Br J Cancer. 1993 Jun;67(6):1163–1170. doi: 10.1038/bjc.1993.220. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chaplin D. J., Olive P. L., Durand R. E. Intermittent blood flow in a murine tumor: radiobiological effects. Cancer Res. 1987 Jan 15;47(2):597–601. [PubMed] [Google Scholar]
  5. Dorie M. J., Brown J. M. Tumor-specific, schedule-dependent interaction between tirapazamine (SR 4233) and cisplatin. Cancer Res. 1993 Oct 1;53(19):4633–4636. [PubMed] [Google Scholar]
  6. Elwell J. H., Siim B. G., Evans J. W., Brown J. M. Adaptation of human tumor cells to tirapazamine under aerobic conditions: implications of increased antioxidant enzyme activity to mechanism of aerobic cytotoxicity. Biochem Pharmacol. 1997 Jul 15;54(2):249–257. doi: 10.1016/s0006-2952(97)00171-8. [DOI] [PubMed] [Google Scholar]
  7. Evans J. W., Yudoh K., Delahoussaye Y. M., Brown J. M. Tirapazamine is metabolized to its DNA-damaging radical by intranuclear enzymes. Cancer Res. 1998 May 15;58(10):2098–2101. [PubMed] [Google Scholar]
  8. Forkert P. G., Lord J. A., Parkinson A. Alterations in expression of CYP1A1 and NADPH-cytochrome P450 reductase during lung tumor development in SWR/J mice. Carcinogenesis. 1996 Jan;17(1):127–132. doi: 10.1093/carcin/17.1.127. [DOI] [PubMed] [Google Scholar]
  9. Forrester L. M., Hayes J. D., Millis R., Barnes D., Harris A. L., Schlager J. J., Powis G., Wolf C. R. Expression of glutathione S-transferases and cytochrome P450 in normal and tumor breast tissue. Carcinogenesis. 1990 Dec;11(12):2163–2170. doi: 10.1093/carcin/11.12.2163. [DOI] [PubMed] [Google Scholar]
  10. Jain R. K. Determinants of tumor blood flow: a review. Cancer Res. 1988 May 15;48(10):2641–2658. [PubMed] [Google Scholar]
  11. Laderoute K., Wardman P., Rauth A. M. 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. doi: 10.1016/0006-2952(88)90010-x. [DOI] [PubMed] [Google Scholar]
  12. Lloyd R. V., Duling D. R., Rumyantseva G. V., Mason R. P., Bridson P. K. 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] [Google Scholar]
  13. Patterson A. V., Barham H. M., Chinje E. C., Adams G. E., Harris A. L., Stratford I. J. Importance of P450 reductase activity in determining sensitivity of breast tumour cells to the bioreductive drug, tirapazamine (SR 4233). Br J Cancer. 1995 Nov;72(5):1144–1150. doi: 10.1038/bjc.1995.478. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Patterson A. V., Robertson N., Houlbrook S., Stephens M. A., Adams G. E., Harris A. L., Stratford I. J., Carmichael J. The role of DT-diaphorase in determining the sensitivity of human tumor cells to tirapazamine (SR 4233). Int J Radiat Oncol Biol Phys. 1994 May 15;29(2):369–372. doi: 10.1016/0360-3016(94)90291-7. [DOI] [PubMed] [Google Scholar]
  15. Patterson A. V., Saunders M. P., Chinje E. C., Patterson L. H., Stratford I. J. Enzymology of tirapazamine metabolism: a review. Anticancer Drug Des. 1998 Sep;13(6):541–573. [PubMed] [Google Scholar]
  16. Patterson A. V., Saunders M. P., Chinje E. C., Talbot D. C., Harris A. L., Strafford I. J. Overexpression of human NADPH:cytochrome c (P450) reductase confers enhanced sensitivity to both tirapazamine (SR 4233) and RSU 1069. Br J Cancer. 1997;76(10):1338–1347. doi: 10.1038/bjc.1997.558. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Plumb J. A., Workman P. Unusually marked hypoxic sensitization to indoloquinone EO9 and mitomycin C in a human colon-tumour cell line that lacks DT-diaphorase activity. Int J Cancer. 1994 Jan 2;56(1):134–139. doi: 10.1002/ijc.2910560124. [DOI] [PubMed] [Google Scholar]
  18. Riley R. J., Hemingway S. A., Graham M. A., Workman P. Initial characterization of the major mouse cytochrome P450 enzymes involved in the reductive metabolism of the hypoxic cytotoxin 3-amino-1,2,4-benzotriazine-1,4-di-N-oxide (tirapazamine, SR 4233, WIN 59075). Biochem Pharmacol. 1993 Mar 9;45(5):1065–1077. doi: 10.1016/0006-2952(93)90251-q. [DOI] [PubMed] [Google Scholar]
  19. Robertson N., Haigh A., Adams G. E., Stratford I. J. Factors affecting sensitivity to EO9 in rodent and human tumour cells in vitro: DT-diaphorase activity and hypoxia. Eur J Cancer. 1994;30A(7):1013–1019. doi: 10.1016/0959-8049(94)90134-1. [DOI] [PubMed] [Google Scholar]
  20. Workman P., Stratford I. J. The experimental development of bioreductive drugs and their role in cancer therapy. Cancer Metastasis Rev. 1993 Jun;12(2):73–82. doi: 10.1007/BF00689802. [DOI] [PubMed] [Google Scholar]

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