title: Xpa and Xpa/p53+/- knockout mice: overview of available data.
abstract: DNA repair deficient Xpa-/- and Xpa-/-/p53+/- knock-out mice in a C57BL/6 genetic background, referred to as respectively the XPA and XPA/p53 model, were investigated in the international collaborative research program coordinated by International Life Sciences Institute (ILSI)/Health and Environmental Science Institute. From the selected list of 21 ILSI compounds, 13 were tested in the XPA model, and 10 in the XPA/p53 model. With one exception, all studies had a duration of 9 months (39 weeks). The observed spontaneous tumor incidence for the XPA model after 9 months was comparable to that of wild-type mice (total 6%). For the XPA/p53 model, this was somewhat higher (9%/13% for males/females). The 3 positive control compounds used, B[a]P, p-cresidine, and 2-AAF, gave positive and consistent tumor responses in both the XPA and XPA/p53 model, but no or lower responses in wild-type mice. From the 13 ILSI compounds tested, the single genotoxic carcinogen (phenacetin) was negative in both the XPA and XPA/p53 model. Positive tumor responses were observed for 4 compounds, the immunosuppressant cyclosporin A, the hormone carcinogens DES and estradiol, and the peroxisome proliferator WY-14,643. Negative results were obtained with 5 other nongenotoxic rodent carcinogens, and 2 noncarcinogens tested. As expected, both DNA repair deficient models respond to genotoxic carcinogens. Combined with previous results, 6 out of 7 (86%) of the genotoxic human and/or rodent carcinogens tested are positive in the XPA model. The positive results obtained with the 4 mentioned nongenotoxic ILSI compounds may point to other carcinogenic mechanisms involved, or may raise some doubts about their true nongenotoxic nature. In general. the XPA/p53 model appears to be more sensitive to carcinogens than the XPA model.
authors.affiliation: RIVM, Laboratory of Health Effects Research, Bilthoven, The Netherlands. cf.van.kreyl@rivm.nl
authors.forename: C F
authors.initials: CF
authors.lastname: van Kreijl
authors.forename: P A
authors.initials: PA
authors.lastname: McAnulty
authors.forename: R B
authors.initials: RB
authors.lastname: Beems
authors.forename: A
authors.initials: A
authors.lastname: Vynckier
authors.forename: H
authors.initials: H
authors.lastname: van Steeg
authors.forename: R
authors.initials: R
authors.lastname: Fransson-Steen
authors.forename: C L
authors.initials: CL
authors.lastname: Alden
authors.forename: R
authors.initials: R
authors.lastname: Forster
authors.forename: J W
authors.initials: JW
authors.lastname: van der Laan
authors.forename: J
authors.initials: J
authors.lastname: Vandenberghe
mesh_terms: D000047:Academies and Institutes; D000826:Animal Testing Alternatives; D000818:Animals; D015197:Carcinogenicity Tests / Q000379:methods*; D002273:Carcinogens / Q000633:toxicity*; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D016158:Genes, p53; D007391:International Cooperation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009153:Mutagens / Q000633:toxicity*; D009374:Neoplasms, Experimental / Q000139:chemically induced* / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics*; D012958:Societies, Scientific; D051760:Xeroderma Pigmentosum Group A Protein
chemical_list: D002273:Carcinogens; D004268:DNA-Binding Proteins; D009153:Mutagens; D016601:RNA-Binding Proteins; D051760:Xeroderma Pigmentosum Group A Protein; C497315:Xpa protein, mouse