Development and Optimization of AlphaScreen Assay for Discovery of Galectin-1/-3 Inhibitors

Galectin-1 is a beta-galactoside-binding protein implicated in regulating apoptosis, cell proliferation and cell differentiation. The objective of our research was to develop and optimize an assay format for the discovery of new inhibitors of galectin-1 using AlphaScreen technology in a competitive binding configuration. Our efforts were hampered by the weak binding affinities of galectin-1 for its binding ligands (μM range). Consequently, the AlphaScreen assay could not have been developed at the level that would satisfy the guidelines from the National Chemical Genomics Center. Nevertheless, we have optimized the AlphaScreen assay for galectin-3, another member of galectin family, and screened an FDA approved oncology drug library (n = 101) from the NIH. We identified three possible inhibitors of galectin-3. These compounds showed a positive activity in dose response experiments: bleomycin (IC50 = 25.7 nM), cisplatin (IC50 = 127 nM), and mitoxantrone HCl (IC50 = 662 nM).