title: Cytochrome P450 CYP1B1 protein expression: a novel mechanism of anticancer drug resistance.
abstract: The overexpression of human cytochrome P450 CYP1B1 has been observed in a wide variety of malignant tumours, but the protein is undetectable in normal tissues. A number of cytochrome P450 enzymes are known to metabolise a variety of anticancer drugs, and the consequence of cytochrome P450 metabolism is usually detoxification of the drug, although bioactivation occurs in some cases. In this study, a Chinese hamster ovary cell line expressing human cytochrome P450 CYP1B1 was used to evaluate the cytotoxic profile of several anticancer drugs (docetaxel, paclitaxel, cyclophosphamide, doxorubicin, 5-fluorouracil, cisplatin, and carboplatin) commonly used clinically in the treatment of cancer. The MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) assay was used to determine the levels of cytotoxicity. The key finding of this study was that on exposure to docetaxel, a significant decrease in sensitivity towards the cytotoxic effects of docetaxel was observed in the cell line expressing CYP1B1 compared to the parental cell line (P = 0.03). Moreover, this difference in cytotoxicity was reversed by co-incubation of the cells with both docetaxel and the cytochrome P450 CYP1 inhibitor alpha-naphthoflavone. This study is the first to indicate that the presence of CYP1B1 in cells decreases their sensitivity to the cytotoxic effects of a specific anticancer drug.
authors.affiliation: Department of Pathology, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. m.mcfadyen@abdn.ac.uk
authors.forename: M C
authors.initials: MC
authors.lastname: McFadyen
authors.forename: H L
authors.initials: HL
authors.lastname: McLeod
authors.forename: F C
authors.initials: FC
authors.lastname: Jackson
authors.forename: W T
authors.initials: WT
authors.lastname: Melvin
authors.forename: J
authors.initials: J
authors.lastname: Doehmer
authors.forename: G I
authors.initials: GI
authors.lastname: Murray
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases; D016466:CHO Cells; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D006801:Humans; D017239:Paclitaxel / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D043823:Taxoids; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D043823:Taxoids; D000077143:Docetaxel; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1; D017239:Paclitaxel