Association between Polymorphic Variants of RAF1 Gene with Occurrence of Mammary Tumor and Aging in Canines

The induction of carcinogenesis as well as cancer growth and development are often associated with an altered expression of genes encoding protooncogenes and proteins responsible for regulation of cell division cycle. Although the role of RAF1 protein in development of apoptosis resistance mechanisms is well known in many types of human cancer, the association between changes in the structure of RAF1 gene and induction of canine carcinogenesis and/or aging remains still poorly recognized. Therefore, the goal of this study was focused on new mutations in the RAF1 gene as well as on association between frequency of RAF1 gene polymorphisms and the occurrence of mammary tumor in groups of domestic bitches of various ages. In this study, blood samples were obtained from 22 female dogs diagnosed with mammary tumors. Moreover, blood samples were also collected from geriatric (>5 to 10 years old; n=15), mature adult (>2 to 5 years old; n=10) and young (from 1 to 2 years old; n=11) dogs. Thirty six bitches examined for other reasons served as controls. After Sanger sequencing analysis, 13 single nucleotide variations were identified, of which two were localized in coding regions (exons 3 and 9) and the rest 11 - in introns (introns 3, 4, 5, 7, 8, 10 and 16). We observed differences in prevalence of heterozygotes and alternative alleles between study groups in 4 polymorphisms, two of which could indicate the putative protective variants (c.T237C, c.A918C) and the other two could indicate the putative risk variants (g.A4805C, g.A6902C) with reference to the cancer occurrence in dogs. In conclusion, we demonstrated that RAF1 polymorphisms may serve as a protective and/or risk factor for the occurrence of mammary tumor in domestic bitches, manifesting a type- and localization of mutation-dependent manner. Although the frequency of occurrence of these polymorphisms was often not statistically significant, haplotype blocks revealed strong linkage between investigated polymorphisms.