Galectins in the Blood Circulation: Potential Therapeutic Targets of Cancer Metastasis

Elevated concentrations of several galectin members (e.g. galectin-2, -3, -4 and -8) occur in the bloodstream of patients with many types of cancers including colorectal, breast, bladder, head and neck, lung, pancreatic and melanoma. Patients with metastatic disease are also seen to have even higher levels of circulating galectins than those with only localized tumours. Recent investigations have demonstrated that the increased circulation of these galectins actively promotes tumour cell haematogenous dissemination in metastasis. Targeting the actions of circulating galectins in the bloodstream of cancer patients therefore represents a very promising therapeutic strategy for preventing metastasis. Such a strategy may include natural or synthetic inhibitors to target the galectin molecule directly or indirectly by targeting the galectin binding ligands in the circulation. More effective inhibitors are also likely to be those that can simultaneously target the actions of multiple galectin members.