p53 gene mutations occurring in spontaneous benign and malignant mammary tumors of the dog

Sixty-three cases of benign and malignant canine mammary tumors were analyz ed to define the alteration of exons 5-8 for the p53 tumor suppressor gene using polymerase chain reaction direct sequence analysis with paraffin-embe dded tissues. Four missense mutations were found in 38 benign mammary tumor s (11%), and five missense (one tumor had two missense mutations) and one n onsense mutations were found in 25 mammary carcinomas (20%). These data sug gest that the p53 gene alterations might be initiated at an early stage of canine mammary carcinogenesis and p53 mutations might be associated with ma lignancy. However, there was no evidence of any relationship between the p5 3 alterations and the histologic types of tumors or breeds of dogs.