Modulation of cyclophosphamide activity by o6-alkylguanine-dna alkyltransferase

Henry S. Friedman, Anthony E. Pegg, Stewart P. Johnson, Natalia A. Loktionova, M. Eileen Dolan, Paul Modrich, Robert C. Moschel, Robert Struck, Thomas P. Brent, Susan Ludeman, Nancy Bullock, Cynthia Kilborn, Steve Keir, Qing Dong, Darell D. Bigner, O. Michael Colvin

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Purpose: The human medulloblastoma cell line D283 Med (4-HCR), a line resistant to 4-hydroperoxycyclophosphamide (4-HC), displays enhanced repair of DNA interstrand crosslinks induced by phosphoramide mustard. D283 Med (4- HCR) cells are cross-resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea, but partial sensitivity is restored after elevated levels of O6-alkylguanine- DNA alkyltransferase (AGT) are depleted by O6-benzylguanine (O6-BG). Studies were conducted to define the activity of 4-HC and 4- hydroperoxydidechlorocyclophosphamide against D283 Med (4HCR) after AGT is depleted by O6-BG. Methods: Limiting dilution and xenograft studies were conducted to define the activity of 4-HC and 4- hydroperoxydidechlorocyclophosphamide with or without O6-BG. Results: The activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4HCR) was increased after AGT depletion by O6-BG preincubation. Similar studies with Chinese hamster ovary cells, with or without stable transfection with a plasmid expressing the human AGT protein, revealed that the AGT- expressing cells were significantly less sensitive to 4-HC and 4- hydroperoxydidechlorocyclophosphamide. Reaction of DNA with 4-HC, phosphoramide mustard, or acrolein revealed that only 4-HC and acrolein caused a decrease in AGT levels. Conclusions: We propose that a small but potentially significant part of the cellular toxicity of cyclophosphamide in these cells is due to acrolein, and that this toxicity is abrogated by removal of the acrolein adduct from DNA by AGT.

Original languageEnglish (US)
Pages (from-to)80-85
Number of pages6
JournalCancer Chemotherapy and Pharmacology
Issue number1
StatePublished - 1999

All Science Journal Classification (ASJC) codes

  • Oncology
  • Toxicology
  • Pharmacology
  • Cancer Research
  • Pharmacology (medical)


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