Evaluation of immunohistochemical over expression of p53 protein and of mutations in exon 8 of Tp53 gene in canine mammary carcinomas and normal mammary glands

Teixeira M.J.D., Sobral A. P. V., Abreu-e-Lima M. C., Maia F. C. L., Christilis M., Souza D. M. B., Adriao M. & Wischral A. 2011. [Evaluation of immunohistochemical over expression of p53 protein and of mutations in exon 8 of Tp53 gene in canine mammary carcinomas and normal mammary glands.] Avaliacao da superexpressao da proteina p53 e das mutacoes no exon 8 do gene TP53 em carcinomas mamarios caninos e glandulas normais. Pesquisa Veterinaria Brasileira 31(6):521-523. Departamento de Medicina Veterinaria, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Recife, PE 52171-900, Brazil. E-mail: aurea@dmv.ufrpe.br This study was undertaken with the aim to evaluate the p53 expression, applying the immunohistochemical technique to malignant primary mammary neoplasms histopathologically diagnosed in female dogs, and to investigate exon 8 of the Tp53 suppressor gene for mutation types by means of PCR-RFLP pattern of bands. Nineteen healthy mammary glands were used as a control group (group 1). Samples from 18 cases diagnosed with malignant mammary tumors (group 2), and the contralateral mammary glands (group 3) were collected during the UFRPE Veterinary Hospital routine. The tumors were diagnosed by histopathology and subdivided into grades of malignity. The streptavidin-biotin peroxidase method was used to analyze the immunohistochemical expression of p53, evaluated according to the location and intensity of stain. Expression of p53 protein was not observed in the samples of group 1. On the contrary, it was observed in all malignant tumors; the protein p53 was localized either only in the nucleus or in the nucleus and in the cytoplasm, in samples of group 2. In group 3, expression of p53 protein was observed in the tumors (2 samples) and in normal mammary tissues (4 samples). For the molecular analyses, genomic DNA was extracted and submitted to PCR-RFLP with the following endonuclease enzymes: AluI, BsoBI, DdeI and SmaI. The band pattern showed polymorphism between groups, but not between histological variants of tumors. This polymorphism detected mutations in the fragment studied - exon 8 of Tp53 - which could account for changes in nucleotides, located in the restriction sites of the endonuclease enzymes. In conclusion, the immunoexpression of p53 had no relationship with histological subtype or malignity grade, but it can be related to the presence of mammary tumors in female dogs. The PCR-RFLP technique can be an important tool for the study of mammary carcinogenesis in bitches because the polymorphism obtained may allow early diagnosis in tissues of mammary glands.