P53 ACCUMULATION IN N-METHYL-N-NITROSOUREA-INDUCED RAT MAMMARY-TUMORS

P53 aberrant protein expression and mutation is a component of many hu man tumors but less information is available regarding involvement in relevant animal models. We have examined invasive mammary epithelial n eoplasms for p53 aberrant protein expression from Sprague-Dawley rats induced by two intrajugular injections of N-methyl-N-nitrosourea (NMU, 50 mg/kg), 7 days apart, beginning at 44-49 days of age. Positive nuc lear staining was observed in 8/10 mammary tumor frozen sections using PAb 421, a mouse monoclonal antibody, compared to a mixed mouse IgG n egative control antibody. Paraffin sections from two additional sets o f similarly induced rat mammary tumors also showed positive nuclear st aining (22/37 tumors) with CM-5, a rabbit polyclonal antibody. Our res ults indicate that elevated cellular content of p53 is a common event in invasive palpable mammary tumors induced by NMU in this dual-inject ion model system.