Diethylstilbestrol (DES): carcinogenic potential in Xpa-/-, Xpa-/- / p53+/-, and wild-type mice during 9 months' dietary exposure.

DES carcinogenicity has been investigated in 2 mouse knockout models, the Xpa homozygous knockout, and the combined Xpa homozygous and p53 heterozygous knockout. Wild-type (WT) mice were also included. Xpa mice received diets containing DES at concentrations of 0, 100, 300, and 1500 ppb for 39 weeks; Xpa/p53 and WT mice received diets containing 0 or 1500 ppb. There were 15 of each sex per group. Both Xpa and WT mice had a similar incidence of tumors at the high dosage of 1500 ppb, including pituitary adenomas in 4 WT mice and 7 Xpa mice, and single incidences of osteosarcoma (Xpa), T-cell lymphoma (WT and Xpa), and testicular interstitial cell adenoma (WT and Xpa). The incidence of tumors was higher in the Xpa/p53 mice at 1500 ppb, mainly attributable to 5 osteosarcomas in males and 2 in females, but also 4 pituitary adenomas, testicular interstitial cell adenomas in 4 males, and single incidences of cerebral glioma, phaeochromocytoma, and cervical fibrosarcoma. The incidence of osteosarcomas was related to the severity of fibro-osseous lesions in the bone marrow. It was concluded that for carcinogenicity screening, Xpa mice were no more sensitive than wild-type mice for compounds like DES, but the Xpa/p53 model showed an increased sensitivity.