BIPHASIC MODULATION OF CELL-GROWTH BY RECOMBINANT HUMAN GALECTIN-1

Human soluble galactose-binding lectin (galectin-1) has been expressed as an Escherichia coli fusion protein, following the amplification by polymerase chain reaction of cDNA prepared from a human osteosarcoma cell line. The fusion protein is a functional beta-galactoside-binding lectin, as is the recombinant galectin when purified from the cleaved fusion protein. The recombinant galectin has a biphasic effect on cel l proliferation. Unlike the fusion protein, it functions as a human ce ll growth inhibitor, confirming earlier findings with natural human ga lectin-1, though it is less effective than the natural galectin. This reaction is not significantly inhibited by lactose, and is thus largel y independent of the beta-galactoside-binding site. At lower concentra tions, recombinant galectin-1 is mitogenic, this activity being suscep tible to inhibition by lactose, and thus attributable to the beta-gala ctoside-binding ability of the protein. Some tumour cells are suscepti ble to the growth-inhibitory effect, and the galectin-1 gene is expres sed in both normal and tumour cells.