title: Human inter-individual variability in metabolism and genotoxic response to zidovudine.
abstract: A mainstay of the antiretroviral drugs used for therapy of HIV-1, zidovudine (AZT) is genotoxic and becomes incorporated into DNA. Here we explored host inter-individual variability in AZT-DNA incorporation, by AZT radioimmunoassay (RIA), using 19 different strains of normal human mammary epithelial cells (NHMECs) exposed for 24 h to 200 microM AZT. Twelve of the 19 NHMEC strains showed detectable AZT-DNA incorporation levels (16 to 259 molecules of AZT/10(6) nucleotides), while 7 NHMEC strains did not show detectable AZT-DNA incorporation. In order to explore the basis for this variability, we compared the 2 NHMEC strains that showed the highest levels of AZT-DNA incorporation (H1 and H2) with 2 strains showing no detectable AZT-DNA incorporation (L1 and L2). All 4 strains had similar (> or =80%) cell survival, low levels of accumulation of cells in S-phase, and no relevant differences in response to the direct-acting mutagen bleomycin (BLM). Finally, when levels of thymidine kinase 1 (TK1), the first enzyme in the pathway for incorporation of AZT into DNA, were determined by Western blot analysis in all 19 NHMEC strains at 24 h of AZT exposure, higher TK1 protein levels were found in the 12 strains showing AZT-DNA incorporation, compared to the 7 showing no incorporation (p=0.0005, Mann-Whitney test). Furthermore, strains L1 and L2, which did not show AZT-DNA incorporation at 24 h, did have measurable incorporation by 48 and 72 h. These data suggest that variability in AZT-DNA incorporation may be modulated by inter-individual differences in the rate of induction of TK1 in response to AZT exposure.
authors.affiliation: Carcinogen-DNA Interactions Section, Laboratory of Cancer Biology and Genetics, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20892-4255, USA. oliveroo@exchange.nih.gov
authors.forename: Ofelia A
authors.initials: OA
authors.lastname: Olivero
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Ming
authors.forename: Shreyasi
authors.initials: S
authors.lastname: Das
authors.forename: Irma L
authors.initials: IL
authors.lastname: Vazquez
authors.forename: Diana L
authors.initials: DL
authors.lastname: Richardson
authors.forename: Ainsley
authors.initials: A
authors.lastname: Weston
authors.forename: Miriam C
authors.initials: MC
authors.lastname: Poirier
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D007399:Interphase / Q000187:drug effects; D042361:Mammary Glands, Human / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects; D011863:Radioimmunoassay; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013937:Thymidine Kinase / Q000378:metabolism; D013997:Time Factors; D015215:Zidovudine / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D018894:Reverse Transcriptase Inhibitors; D001761:Bleomycin; D015215:Zidovudine; D004247:DNA; D013937:Thymidine Kinase; C092717:thymidine kinase 1