Neutrophilic differentiation of promyelocytic HL-60 cells is associated with increased expression of terminal galactose residues on the cell surface.

An important hallmark of cancer cells is altered glycosylation of cell surface molecules in comparison with normal or differentiated cells. Terminal galactose residues represent important elements of cellular glycocalyx, but their regulation and functions remain not fully elucidated. Here, we used lectin-induced aggregation assay to analyze changes in the expression of galactose residues on the surface of live human leukemia HL-60 cells in association with their neutrophilic differentiation induced by all-trans retinoic acid (ATRA). We found that live HL-60 in suspension expressed multiple types of glycans on the cell surface recognized by plant lectins with different glycan-binding specificity. Detailed analysis of cell aggregation responses induced by the galactose-binding Ricinus communis agglutinin (RCA) demonstrated that this activity was enhanced by a sialyltransferase inhibitor P-3FAX-Neu5Ac and suppressed by an inhibitor of N-glycosylation tunicamycin. Following the ATRA-induced differentiation (1 μM ATRA, 3 days), RCA-induced aggregation was elevated, implying the increase in the level of terminal galactose residues on the cell surface. Bioinformatics analysis of available GEO datasets showed that this change might be associated with the metabolic reprogramming of sialyltransferases and neuraminidases, both controlling the availability of galactose-terminated glycans in cells. Collectively, these findings demonstrate that ATRA-induced neutrophilic differentiation of promyelocytic leukemia HL-60 cells is accompanied by elevated cell surface galactosylation, suggesting new directions for future investigations into the cell biological mechanisms of cancer differentiation therapy.