Modulation of cyclophosphamide activity by O6-alkylguanine-DNA alkyltransferase.

Journal Article

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)- -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 (4-HCR) 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 (4-HCR) 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.

Full Text

Duke Authors

Cited Authors

  • Friedman, HS; Pegg, AE; Johnson, SP; Loktionova, NA; Dolan, ME; Modrich, P; Moschel, RC; Struck, R; Brent, TP; Ludeman, S; Bullock, N; Kilborn, C; Keir, S; Dong, Q; Bigner, DD; Colvin, OM

Published Date

  • 1999

Published In

Volume / Issue

  • 43 / 1

Start / End Page

  • 80 - 85

PubMed ID

  • 9923545

International Standard Serial Number (ISSN)

  • 0344-5704

Digital Object Identifier (DOI)

  • 10.1007/s002800050866

Language

  • eng

Conference Location

  • Germany