title: Tamoxifen-induced adduct formation and cell stress in human endometrial glands.
abstract: The beneficial effects of tamoxifen in the prevention and treatment of breast cancer are compromised by an increased risk of endometrial polyps, hyperplasia, and cancer. Tamoxifen is metabolized to an array of metabolites with estrogenic effects but also to reactive intermediates that may form protein and DNA adducts. The aim of this study was to investigate cellular [(3)H]tamoxifen adduct formation by light microscopic autoradiography and cell stress by immunohistochemical analysis of glucose-regulating protein 78 (GRP78), nuclear factor kappaB (NF-kappaB), and caspase 3 in human endometrial explants after short-term incubation with tamoxifen. The cellular expression of tamoxifen-metabolizing enzymes in human endometrial biopsy samples was also determined by immunohistochemistry. The results showed selective [(3)H]tamoxifen adduct formation in glandular and surface epithelia after incubation with a nontoxic concentration of [(3)H]tamoxifen (6 nM). There was also a selective expression of the endoplasmic reticulum stress chaperone GRP78 and activated caspase 3 at these sites after incubation with cytotoxic concentrations of tamoxifen (10-100 microM). The cell stress was preferentially observed in samples from women in the proliferative menstrual phase. No treatment-related expression of NF-kappaB was observed. Constitutive expression of the tamoxifen-metabolizing enzymes CYP1B1, CYP2A6, CYP2B6, CYP2C8/9/19, CYP2D6, and SULT2A1 in glandular and surface epithelia was shown, but there was a large interindividual variation. The colocalization of [(3)H]tamoxifen adducts, expression of GRP78, caspase 3, and tamoxifen-metabolizing enzymes in human glandular and surface epithelia suggest a local bioactivation of tamoxifen at these sites and that epithelial cells are early target sites for tamoxifen-induced cell stress.
authors.affiliation: Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden.
authors.forename: Helén
authors.initials: H
authors.lastname: Andersson
authors.forename: Malin
authors.initials: M
authors.lastname: Helmestam
authors.forename: Anna
authors.initials: A
authors.lastname: Zebrowska
authors.forename: Matts
authors.initials: M
authors.lastname: Olovsson
authors.forename: Eva
authors.initials: E
authors.lastname: Brittebo
mesh_terms: D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D001711:Biotransformation; D053148:Caspase 3 / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D065637:Cytochrome P-450 CYP2A6; D065702:Cytochrome P-450 CYP2B6; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004717:Endometrium / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D000091342:Endoplasmic Reticulum Chaperone BiP; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005498:Follicular Phase / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008183:Luteal Phase / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects*; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D015238:Sulfotransferases / Q000378:metabolism; D013629:Tamoxifen / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D016328:NF-kappa B; C400322:cytochrome P-450 CYP2C subfamily; D013629:Tamoxifen; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585710:CYP2A6 protein, human; C585599:CYP2B6 protein, human; D065633:Cytochrome P-450 CYP1B1; D065637:Cytochrome P-450 CYP2A6; D065702:Cytochrome P-450 CYP2B6; D019389:Cytochrome P-450 CYP2D6; D010089:Oxidoreductases, N-Demethylating; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D053148:Caspase 3