title: Formation of tamoxifen-DNA adducts in multiple organs of adult female cynomolgus monkeys dosed with tamoxifen for 30 days.
abstract: The use of the antiestrogen tamoxifen (TAM) is associated with an increase in endometrial cancer. TAM-induced endometrial carcinogenesis may proceed through a genotoxin-mediated pathway, although the detection of endometrial TAM-DNA adducts in exposed women is still controversial. In this study, a monkey model has been used to investigate the question of TAM-DNA adduct formation in primates. Two methods have been used to determine TAM-DNA adducts: a TAM-DNA chemiluminescence immunoassay (TAM-DNA CIA), using an antiserum that has specificity for (E)-alpha-(deoxyguanosin-N(2)-yl)-tamoxifen (dG-TAM) and (E)-alpha-(deoxyguanosin-N(2)-yl)-N-desmethyltamoxifen (dG-desmethyl-TAM) and electrospray ionization tandem mass spectrometry (ES-MS/MS) coupled with on-line sample preparation and high-performance liquid chromatography (HPLC). Mature (19 year old) cynomolgus monkeys were given either vehicle control (n = 1) or TAM (n = 3) twice daily for a total dose of 2 mg of TAM/kg body weight (bw)/day for 30 days by naso-gastric intubation. Tissues were harvested, and DNA was isolated from uterus, ovary, liver, brain cortex, and kidney. By TAM-DNA CIA, values for uterine TAM-DNA adducts in two monkeys were 0.9 and 1.7 adducts/10(8) nucleotides, whereas values for ovarian TAM-DNA adducts in the same animals were 0.4 and 0.5 adducts/10(8) nucleotides. Liver, brain cortex, and kidney DNA samples from the three exposed monkeys had TAM-DNA levels of 2.1-4.2 adducts/10(8) nucleotides, 0.4-5.0 adducts/10(8) nucleotides, and 0.7-2.1 adducts/10(8) nucleotides, respectively. By HPLC-ES-MS/MS, the levels of TAM-DNA adducts detected in all tissues were comparable with those observed by TAM-DNA CIA. Thus, values for uterine TAM-DNA adducts ranged from 0.5 to 1.4 adducts/10(8) nucleotides, whereas values for ovarian TAM-DNA adducts, measurable in two monkeys, were 0.2 and 0.3 adducts/10(8) nucleotides. Liver DNA contained the highest TAM-DNA adduct levels (7.0-11.1 adducts/10(8) nucleotides), whereas brain cortex DNA contained lower adduct levels (0.6-4.8 adducts/10(8) nucleotides) and the lowest levels were measured in the kidney (0.2-0.4 adducts/10(8) nucleotides). This study indicates that cynomolgus monkeys are capable of metabolizing TAM to genotoxic intermediates that form TAM-DNA adducts in multiple tissues.
authors.affiliation: Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-4255, USA.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Schild
authors.forename: Rao L
authors.initials: RL
authors.lastname: Divi
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Beland
authors.forename: Mona I
authors.initials: MI
authors.lastname: Churchwell
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Doerge
authors.forename: Gonçalo
authors.initials: G
authors.lastname: Gamboa da Costa
authors.forename: M Matilde
authors.initials: MM
authors.lastname: Marques
authors.forename: Miriam C
authors.initials: MC
authors.lastname: Poirier
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000378:metabolism* / Q000633:toxicity*; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000187:drug effects* / Q000378:metabolism*; D018736:DNA Adducts / Q000032:analysis / Q000096:biosynthesis*; D020847:Estrogen Receptor Modulators / Q000378:metabolism / Q000633:toxicity; D005260:Female; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008163:Luminescent Measurements; D008252:Macaca fascicularis; D010053:Ovary / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D013629:Tamoxifen / Q000378:metabolism* / Q000633:toxicity*; D014599:Uterus / Q000737:chemistry / Q000378:metabolism
chemical_list: D018931:Antineoplastic Agents, Hormonal; D018736:DNA Adducts; D020847:Estrogen Receptor Modulators; D013629:Tamoxifen; D004247:DNA