Selectins and Anti-CD15 (Lewis X/a) Antibodies Transmit Activation Signals in Hodgkin's Lymphoma-derived Cell Lines

Objective: The CD15 (Lewis x) cell surface oligosaccharide moiety is expressed in a variety of normal and tumor cells and recognized by selectins. The detection of CD15 on malignant Hodgkin-Reed-Sternberg (HRS) cells serves as a diagnostic marker of Hodgkin's lymphoma (HL). Retrospective studies suggest that the expression of nonsialylated CD15 molecules on HRS cells has a positive prognostic value while presence of sialylated CD15 may correlate with a poor outcome. However, the relevance of the CD15 antigen expression to the pathobiology of the disease is not clear. In this work, we studied the contribution of CD15 to cell adhesion and the activation of signaling cascades in two HL-derived cell lines, KMH-2 and L428.

Methods: Immobilized anti-CD15 monoclonal antibodies and recombinant E- and P-selectins were used to activate KMH-2 and L428 cells. Immunoblotting, immunoprecipitation, and the electrophoretic mobility shift assay were performed to detect tyrosine phosphorylation of c-Cbl, c-Jun nuclear translocation, and AP-1 DNA binding.

Results: Treatment of cells with antibodies against the sialylated and nonsialylated forms of CD15, or with immobilized selectins, induced changes in cell morphology. Tyrosine phosphorylation of c-Cbl, together with tyrosine phosphorylation of multiple protein substrates, was also induced. In addition, binding of the CD15 molecules induced nuclear translocation of c-Jun and an increase in AP-1 DNA binding activity.

Conclusions: We suggest that CD15 has a dual physiological role, both as an adhesion molecule recognized by selectins and as a regulatory molecule upstream to specific intracellular signaling cascades with implications to the pathogenesis of HL.