Expression patterns of the erbB subfamily mRNA in canine benign and malignant mammary tumors

ErbB subfamily genes, known as proto-oncogenes, encode receptor tyrosine ki nases, and are expressed in relation to tumorigenesis of the mammary gland in humans. In this study, we examined the expression of erbB subfamily mRNA s in two canine normal mammary glands and 12 mammary tumor samples by rever se transcriptase-coupled polymerase chain reaction (RT-PCR). Each primer se t was designed from the nucleotide sequence of the region conserved in erbB subfamily cDNA among other species. No erbB subfamily mRNAs were expressed in the normal mammary gland. In contrast, all of the subfamily mRNAs were expressed in a benign mammary tumor, and more than one type of the subfamil y mRNA were observed in 11 malignant mammary tumors. The length of RT-PCR p roducts were 380 bp for erbB1, 500 bp for erbB2, 644 bp for erbB3, and 416 bp for erbB4. These sequences were highly homologous to the cDNA sequences of other species. Therefore, these results suggest that the expression of e rbB subfamily mRNAs in canine mammary tumors plays an important role in tum origenesis of the mammary gland.