Truncated galectin-3 inhibits tumor growth and metastasis in orthotopic nude mouse model of human breast cancer.

PURPOSE The goal of this research was to evaluate a potential therapeutic agent for breast cancer based on galectin-3 that has been implicated in tumorigenicity and metastasis of breast cancer. The hypothesis was that therapy with NH(2)-terminally truncated form of galectin-3 (galectin-3C) will be efficacious for reduction in tumor growth and for inhibition of metastases. EXPERIMENTAL DESIGN Recombinant human galectin-3 was produced in Escherichia coli from which galectin-3C was derived by collagenase enzyme digestion. Toxicity, pharmacokinetic, and organ biodistribution studies were performed in nude mice. For efficacy studies, nude mice bearing orthotopically implanted tumors derived from breast cancer cell line MDA-MB-435 were treated with galectin-3C or a vehicle control i.m. twice daily for 90 days. RESULTS The maximum tolerated dose of galectin-3C in nude mice was determined to be >125 mg/kg without overt adverse effects. The elimination half-life when administered i.m. was found to be 3.0 h in the serum and 4.3 h in the cellular fraction of the blood. Organ biodistribution studies revealed that galectin-3C localized in the liver, kidneys, and spleen but not in the heart or lungs. We found that the mean tumor volumes and weights were statistically significantly less in mice treated with galectin-3C compared with control mice, and that fewer numbers of mice exhibited lymph node metastases in the treated group compared with the control group. CONCLUSIONS Galectin-3C is not overtly toxic, and is efficacious in reducing metastases and tumor volumes and weights in primary tumors in an orthotopic nude mouse model of human breast cancer.