Legumain, a novel
asparaginyl endopeptidase, has been observed to be overexpressed in several types of human solid
tumors. Elevated levels of
legumain are found in human
cancers, and this
oncoprotein may facilitate
tumor invasion and
metastasis when overexpressed. These findings suggest that
legumain plays a malignant role in
cancer biology. However, currently, no publications have identified the role of
legumain in the development of canine
cancers. The present study first compared the expression patterns of
legumain in
paraffin-embedded canine
tumor tissues, with those of normal tissues, by immunohistochemistry. A total of 100 canine
tumor samples, including mast cell
tumors,
soft tissue sarcoma,
hemangiosarcoma,
lymphoma, mammary gland
carcinoma, hepatoid gland
tumor,
squamous cell carcinoma, trichoblastoma, and
melanoma were evaluated. Compared with the normal tissues, all
tumor samples displayed high intensities of
legumain expression. Mesenchymal-type
tumors displayed immunoreactivity for
legumain, with an average expression of 40.07% ± 1.70%, which was significantly lower than those of epithelial
tumors and other types of
tumors, which had median expressions of 49.12% ± 1.75% and 47.35% ± 2.71%, respectively (p < 0.05). These findings indicate that
legumain has a high potential to be a candidate for distinguishing
tumors from normal tissues. Although further studies on a larger number of cases are necessary to clarify the clinical application of
legumain, the overexpression patterns of
legumain in canine
tumor tissues are reported, for the first time, in this study.