Slit, a secreted protein, functions as a chemorepellent factor in axon guidance and neuronal migration and as an inhibitor in leukocyte chemotaxis. In humans,
slit2 protein attracts endothelial cells and promotes tube formation in the tumor angiogenic mechanism. In this study, we cloned a part of the canine
slit subfamily and examined the expression of
slit subfamily mRNAs in 3 normal canine mammary glands and 11 mammary tumor samples by RT-PCR. The cloned part of the
slit gene sequences showed high similarity to those of the human, mouse, and rat. The mRNAs were expressed at low levels in the normal mammary gland. The expression levels of
slit1 mRNA were low in both the normal and tumor tissues. In contrast, the expression of
slit2 mRNA increased in most of the malignant mammary tumors, and an increase in
slit3 mRNA expression was observed in 2 of the malignant mixed tumors. These results suggest that the expression of
slit2 plays an important role in tumor angiogenesis in canine mammary gland tumors and that
slit2 can be a putative marker for malignancy diagnosis of these tumors.
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