Caracterização do padrão de expressão e metilação do gene P21CDKN1A/CIP1 em tumores mamários caninos

Abstract

The most of canine mammary tumors are malignant and associated with the animal death. One of the factors involved in this pathogenesis is the change in the expression level of the gene P21, which in turn encodes a protein that can inhibit tumor initiation and tumor progression. The methylation profile of gene can affect the cellular level of p21 and lead gene silencing or overexpression. Whereas the functional importance of the P21 gene, this study aimed to evalu-ate the methylation profile and expression in mammary tumors of dogs, in order to identify molecular markers of early diagnosis, survival and prognosis. Therefore, 83 tumor and non-tumor tissue samples were collected from dogs, undergoing surgery at the Veterinary Hospital "Mário Dias Teixeira”, in Belém -Pará. the DNA and RNA from each sample were submitted to extraction using a commercial kit. For the methylation analyzes, the obtained DNA was sub-mitted to the modification process, with a subsequent technique of Bisulfite Sequencing PCR, using region-specific primers and subsequent visualization in 2% agarose gel. The sequencing results were analyzed in BiQ Analyzer software in order to evaluate the methylation pattern. For gene expression analysis, the target gene mRNA was quantified using the real-time PCR technique using the GAPDH and HPRT1 genes as constitutive controls. Statistical data was performed using the Fisher Exact, Odds Ratio and Mann-Whitney tests in the GraphPad Prism program, considering the significant results when p ≤0.05, with a 95% confidence inter-val. In order to evaluate the methylation profile, the CpG islands of the P21 gene were characterized. The island 1 is located in an intron with 34 CGs, while an island 2 was identified in the exon, with 22 CGs. Both amplified generating a fragment of ~ 300bp. At island 1 no methylation was detected, whereas island 2 was methylated, but the island methylation profile was not different between the tumor, non-tumor and control samples. With these results was impossible compare the methylation values with clinical and expression data, suggesting that these regions are not altered. The expression levels of the tumor samples were low when compared to the non-tumor samples and control, with p (0.0001), show that the role of p21 in these tumors may be altered but not statistically significant when correlated with clinical histopathological data of patients. However, a reduced expression in the survival of animals> 1 year of age was observed, and a high expression in animals with survival <1 year of age, suggesting the influence of p21 as a marker of prognosis. More detailed studies of the P21 gene are still needed to see if these changes could be used as molecular markers, and thus aid on the prognosis and detection of cancer in the species.