Differential expression of galectin-1 and galectin-3 in canine non-malignant and malignant mammary tissues and in progression to metastases in mammary tumors

Background: Galectin-1 and galectin-3 are carbohydrate-binding proteins that have been implicated in the pathobiology of several types of cancer. The aim of the present study was to investigate the expression pattern of both these galectins in canine non-neoplastic mammary tissues and mammary tumors (CMT). Materials and Methods: Protein and mRNA expression of galectin-1 and-3 were assessed in 12 benign and 41 malignant CMT. Results: Galectin-1 was overexpressed in the majority of malignant CMT cases in tumor cells and stroma. Its expression in malignant tumor cells was associated with smaller-sized tumours. Distant metastases presented a strong intensity of galectin-1 and reduced galectin-3 expression, while the opposite was observed in circulating tumor cells. Interestingly intravascular tumor cells presented galectin-3 up-regulation at the mRNA level. Double-labelling further made it clear that galectin-3 and galectin-1 expression did not overlap in normal-Adjacent mammary and CMT cells. Conclusion: Taken together, our data suggest that malignant CMT cell sub-populations have alternating expression of galectin-1 or-3. This might confer survival advantage to tumour cells in different phases of tumour progression.