title: Metabolic bioactivation of oestradiol-17beta (E2beta) in mouse colon epithelial cells bearing ApcMin mutation.
abstract: Epidemiological studies have revealed a protective role of oestrogens against the promotion of colorectal cancer (CRC). Therefore, the oestrogen metabolism status of colonic cells is studied to explain it. Loss of function of adenomatous polyposis coli (Apc) gene product is an early and frequent event in human colorectal carcinogenesis. Normal (Apc(+/+)) and premalignant (Apc(multiple intestinal neoplasia (Min)/+)) mouse colonic epithelial cells were used to compare their respective metabolic capabilities towards oestradiol-17beta (E(2)beta), with or without an inducer of the CYP1 family, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In both cell types, the major metabolite was oestradiol-17beta-3-glucuronide. The formation of catechol (CE) metabolites by cytochromes P450 of the CYP1 family and their derivatives was shown. Among these metabolites, several O-methyl-ether derivatives were detected, as unconjugated metabolites in Apc(+/+) cells and as glucuroconjugates in Apc(Min/+) cells, after TCDD treatment. Apc(Min/+) cells are metabolically more competent than Apc(+/+) cells to produce different hydroxylated metabolites as well as glucuroconjugates. Quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR) experiments corroborate these results. Indeed, induction by TCDD has prevailing effects in gene expression of CYP1A1, CYP1A2 and CYP1B1 in Apc(Min/+) cells, compared with Apc(+/+) ones. Apc(Min/+) cells displayed higher rates of oestrogen metabolic biotransformation than Apc(+/+) ones, but exhibited two opposite tendencies. Apc(Min/+) cells were able to detoxify E(2)beta mainly by the formation of glucuronides and displayed at the same time a striking potential to bioactivate E(2)beta by producing only the electrophilic 2-CE derivatives, not the 4-CE ones, even though a significant CYP1B1 mRNA induction was noticed. These specific electrophilic metabolites may form DNA adducts but are not prone to generate new mutations. Interestingly, the ultimate 2-O-methyl-ether metabolite of E(2)beta may be an endogenous protective factor against CRC promotion given its recognised anti-angiogenic and pro-apoptotic properties.
authors.affiliation: UMR1089 - Laboratoire des Xénobiotiques, INRA/ENVT, 180, Chemin de Tournefeuille, BP 93173, F-31027 Toulouse cedex 3, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Bellocq
authors.forename: Jérôme
authors.initials: J
authors.lastname: Molina
authors.forename: Estelle
authors.initials: E
authors.lastname: Rathahao-Paris
authors.forename: Sylviane
authors.initials: S
authors.lastname: Taché
authors.forename: Fabrice
authors.initials: F
authors.lastname: Pierre
authors.forename: Alain
authors.initials: A
authors.lastname: Paris
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000502:physiology; D002396:Catechols / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003106:Colon / Q000166:cytology*; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000502:physiology; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000502:physiology; D065633:Cytochrome P-450 CYP1B1; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D013058:Mass Spectrometry; D051379:Mice; D009154:Mutation; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D002396:Catechols; D000072317:Polychlorinated Dibenzodioxins; D004958:Estradiol; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; C034221:catechol