c-KIT mutation analysis and its relationship with degree of aggression in MCTs (Mast Cell Tumors) in two dog breeds.

Mast cell tumors (MCTs) are one of the most frequent malignant cutaneous neoplasms in dogs therapeutic management is based to histological grade (Patnaik scale) and clinical stage. Some breeds showed a higher incidence of MCTs development than others, suggesting a possible genetic influence on both susceptibility to tumors and tumor aggressiveness. In this order, mutations in c-KIT, a gene that encodes Kit, a transmembrane tyrosine kinase receptor binding the ligand stem cell factor, have been identified and associated with the development of MCTs in both dogs and humans. The aim of this study was to identify mutations in the juxtamembrane region of c-KIT and to evaluate their association with grade of tumor and breed. Tissues samples from 2 dog (Whippet and Jack Russell Terrier) were used to extract DNA for PCR amplification and sequencing with the ABI PRISM® 3500 (Applied Biosystems) after cytological examination. The diagnosis was consistent with a II grade MCTs (according to Patnaik’s histological grading). 2 healthy dogs (Boxer) were used to as control. The DNA sequences were aligned using MEGA7. Our analysis revealed that both tumors contained mutations: a duplication of 45 bp was detected in Whippet (in exon 11 but no change to the protein is made) while a deletion of 30 bp (encompasses intron 10 and part of the 5′ end of exon 11) was identified in Jack Russel Terrier. Our results confirm the relationship between the histological degree of the tumor and the presence of mutations in c-kit.