title: The potential of acetaminophen as a prodrug in gene-directed enzyme prodrug therapy.
abstract: Acetaminophen is oxidized by human CYP1A2 to the cytotoxic metabolite N-acetylbenzoquinoneimine (NABQI). Incubation of cells transfected with human CYP1A2 (H1A2 MZ cells) with 4-20 mM acetaminophen for 6 hours at 37 degrees C caused extensive cytotoxicity (cell viability <10%). In contrast, nontransfected V79 MZ cells were unaffected (viability >95%). By mixing H1A2 MZ cells with V79 MZ cells in various proportions and incubating with 4 mM acetaminophen, it was shown that the NABQI released from H1A2 MZ cells also caused cytotoxicity of bystander cells. Thus, in a mixture containing 5% H1A2 MZ cells, exposure to 4 mM acetaminophen for 6 hours resulted in complete cell killing by 24 hours. A similar bystander effect was found by incubating the same proportion of CYP1A2-containing cells with ovarian tumor-derived SK-OV-3 cells or colon tumor-derived HCT116 cells. However, breast tumor-derived MDA-MB-361 cells displayed resistance to the cytotoxic effect of NABQI, and it was necessary to increase the proportion of H1A2 MZ cells to 50% to achieve complete cell killing. In conclusion, the use of acetaminophen as prodrug and CYP1A2 as an activating enzyme is a promising combination for gene-directed enzyme prodrug therapy.
authors.affiliation: Division of Medicine, Imperial College School of Medicine, London, United Kingdom.
authors.forename: N J
authors.initials: NJ
authors.lastname: Thatcher
authors.forename: R J
authors.initials: RJ
authors.lastname: Edwards
authors.forename: N R
authors.initials: NR
authors.lastname: Lemoine
authors.forename: J
authors.initials: J
authors.lastname: Doehmer
authors.forename: D S
authors.initials: DS
authors.lastname: Davies
mesh_terms: D000082:Acetaminophen / Q000627:therapeutic use / Q000633:toxicity*; D000818:Animals; D002384:Catalysis; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics* / Q000378:metabolism*; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D011355:Prodrugs / Q000627:therapeutic use / Q000633:toxicity*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D011355:Prodrugs; D000082:Acetaminophen; D019388:Cytochrome P-450 CYP1A2