Frequent expression of the c-kit proto-oncogene in canine malignant mammary tumor

The mammary tumor is one of the popular neoplastic diseases in female dogs. In the present study, the expression of canine c-kit proto-oncogene in mam mary tumor specimens was investigated to evaluate its potential usefulness as a tumor marker. By comparing the homology among the nucleotide sequences reported for human, mouse, rat and feline c-kit c-DNA, a pair of primers w as synthesized for the reverse transcriptase-polymerase chain reaction (RT- PCR) method, The RT-PCR product of canine spleen total RNA was shown to hav e 756 bp in size and to be highly homologous to the corresponding sequences reported for the mammalian species. The expression of c-kit transcript was detected in 11 mammary tumors of different histopathology including adenoc arcinomas, benign and malignant mixed tumors. The level of the transcriptio n in adenocarcinomas was significantly higher than those in malignant mixed tumors. Fifteen canine tumor specimens originated from various tissues wer e also tested for their c-kit transcript. In all of the mastocytoma samples examined, high expression of the mRNA was detected. Of other 12 tumors, on ly low level of RT-PCR products were detected in 5 samples, whereas no appa rent amplification was observed in 7 tumors. These results indicate that th e high expression of c-kit transcript is helpful for the diagnosis of canin e mammary tumors.