Galectin-3 as a Potential Therapeutic Target in Tumors Arising from Malignant Endothelia

Abstract

Angiosarcoma (ASA) in humans, hemangiosarcoma (HSA) in dogs are deadly neoplastic diseases characterized by an aggressive growth of malignant cells with endothelial phenotype, widespread metastasis, poor response to chemotherapy. Galectin-3 (Gal-3), a p-galactoside-binding lectin implicated in tumor progression, metastasis, endothelial cell biology, angiogenesis, regulation of apoptosis, neoplastic cell response to cytotoxic drugs, has not been studied before in tumors arising from malignant endothelia. Here, we tested the hypothesis that Gal-3 could be widely expressed in human ASA, canine HSA, could play an important role in malignant endothelial cell biology. Immunohistochemical analysis demonstrated that 100% of the human ASA (10 of 10), canine HSA (17 of 17) samples analyzed expressed Gal-3. Two carbohydrate-based Gal-3 inhibitors, modified citrus pectin (MCP), lactulosyl-l-leucine (LL), caused a dose-dependent reduction of SVR murine ASA cell clonogenic survival through the inhibition of Gal-3 antiapoptotic function. Furthermore, both MCP, LL sensitized SVR cells to the cytotoxic drug doxorubicin to a degree sufficient to reduce the in vitro IC50 of doxorubicin by 10.7-fold, 3.64old, respectively. These results highlight the important role of Gal-3 in the biology of ASA, identify Gal-3 as a potential therapeutic target in tumors arising from malignant endothelial cells.