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Galectin-3 binds to CD45 on diffuse large B cell lymphoma cells to regulate susceptibility to cell death

Mary C. Clark, Mabel Pang, Daniel K. Hsu, Fu-Tong Liu, Sven de Vos, Randy D. Gascoyne, Jonathan Said and Linda G. Baum

Abstract

Diffuse large B cell lymphoma (DLBCL) is the most common non-Hodgkin's lymphoma and an aggressive malignancy. Galectin-3 (gal-3), the only anti-apoptotic member of the galectin family, is overexpressed in DLBCL. While gal-3 can localize to intracellular sites, gal-3 is secreted by DLBCL cells and binds back to the cell surface in a carbohydrate-dependent manner. The major counterreceptor for gal-3 on DLBCL cells was identified as the transmembrane tyrosine phosphatase CD45. Removal of cell surface gal-3 from CD45 with the polyvalent glycan inhibitor GCS-100 rendered DLBCL cells susceptible to chemotherapeutic agents. Binding of gal-3 to CD45 modulated tyrosine phosphatase activity; removal of endogenous cell surface gal-3 from CD45 with GCS-100 increased phosphatase activity, while addition of exogenous gal-3 reduced phosphatase activity. Moreover, the increased susceptibility of DLBCL cells to chemotherapeutic agents after removal of gal-3 by GCS-100 required CD45 phosphatase activity. Gal-3 binding to a subset of highly glycosylated CD45 glycoforms was regulated by the C2GnT-1 glycosyltransferase, indicating that specific glycosylation of CD45 is important for regulation of gal-3-mediated signaling. These data identify a novel role for cell surface gal-3 and CD45 in DLBCL survival and suggest novel therapeutic targets to sensitize DLBCL cells to death.

  • Submitted June 20, 2012.
  • Accepted September 23, 2012.