title: Bioreductive GDEPT using cytochrome P450 3A4 in combination with AQ4N.
abstract: The bioreductive drug, AQ4N, is metabolized under hypoxic conditions and has been shown to enhance the antitumor effects of radiation and chemotherapy drugs. We have investigated the role of cytochrome P450 3A4 (CYP3A4) in increasing the metabolism of AQ4N using a gene-directed enzyme prodrug therapy (GDEPT) strategy. RIF-1 murine tumor cells were transfected with a mammalian expression vector containing CYP3A4 cDNA. In vitro AQ4N metabolism, DNA damage, and clonogenic cell kill were assessed following exposure of transfected and parental control cells to AQ4N. The presence of exogenous CYP3A4 increased the metabolism of AQ4N and significantly enhanced the ability of the drug to cause DNA strand breaks and clonogenic cell death. Cotransfection of CYP reductase with CYP3A4 showed a small enhancement of the effect in the DNA damage assay only. A single injection of CYP3A4 into established RIF-1 murine tumors increased the metabolism of AQ4N, and when used in combination with radiation, three of nine tumors were locally controlled for >60 days. This is the first demonstration that CYPs alone can be used in a GDEPT strategy for bioreduction of the cytotoxic prodrug, AQ4N. AQ4N is the only CYP-activated bioreductive agent in clinical trials. Combination with a GDEPT strategy may offer a further opportunity for targeting radiation-resistant and chemo-resistant hypoxic tumor cells.
authors.affiliation: Radiation Science Research Group, School of Biomedical Sciences, University of Ulster at Jordanstown, Newtownabbey, County Antrim, UK.
authors.forename: Helen O
authors.initials: HO
authors.lastname: McCarthy
authors.forename: Anita
authors.initials: A
authors.lastname: Yakkundi
authors.forename: Verna
authors.initials: V
authors.lastname: McErlane
authors.forename: Ciara M
authors.initials: CM
authors.lastname: Hughes
authors.forename: Gillian
authors.initials: G
authors.lastname: Keilty
authors.forename: Margaret
authors.initials: M
authors.lastname: Murray
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Patterson
authors.forename: David G
authors.initials: DG
authors.lastname: Hirst
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: McKeown
authors.forename: Tracy
authors.initials: T
authors.lastname: Robson
mesh_terms: D000818:Animals; D000880:Anthraquinones / Q000378:metabolism* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D001711:Biotransformation; D015153:Blotting, Western; D015687:Cell Hypoxia; D003131:Combined Modality Therapy; D020552:Comet Assay; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004273:DNA, Neoplasm / Q000187:drug effects; D005354:Fibrosarcoma / Q000201:enzymology / Q000628:therapy*; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics; D011355:Prodrugs / Q000378:metabolism* / Q000494:pharmacology; D011829:Radiation Dosage; D014162:Transfection; D014410:Tumor Stem Cell Assay
chemical_list: D000880:Anthraquinones; D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D011355:Prodrugs; C094428:AQ4N; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D009251:NADPH-Ferrihemoprotein Reductase