Among the macromolecular components of the cell membrane which change during differentiation of a variety of cell types are glycosaminoglycans. These long-chain polyanionic carbohydrates have been correlated with discrete maturational stages of development of many embryonic systems and of the developing human leukocyte. While previous studies in this laboratory have demonstrated a decrease in precursor incorporation into these highly-charged carbohydrates associated with leukemic cell differentiation, the importance of an alteration of these macromolecules in the regulation and expression of the maturation process has not been fully delineated. Since previous studies have suggested that glycosaminoglycan degradation is intimately associated with cell differentiation, we will measure the degradation of radiolabeled glycosaminoglycans by HL-60 human acute promyelocytic leukemia cells which have been treated with differentiation inducers for various periods of time. The relationship of glycosaminoglycan metabolism and cellular commitment to differentiate will also be explored by exposing cells to an inducer for a very short period of time before irreversible commitment occurs, and analyzing glycosaminoglycan production. With the aid of mutant HL-60 cell lines resistant to the induction of differentiation, we will determine if cellular glycosaminoglycan levels correlate with sensitivity to an inducer. We will also determine the effect on differentiation of compounds which alter glycosaminoglycan production. Quantitation of glycosaminoglycans by precipitation reactions and spectrophotometric analyses, as well as characterization by specific enzyme degradation, ion-exchange chromatography, and gel permeation chromatography will be performed. Preliminary results suggest that pretreatment with such compounds alters response to differentiation inducers. These assays will be performed in cell culture studies of differentiation induction. Serum glycosaminoglycan analyses of patients with subacute leukemia receiving 5-azacytidine for differentiation induction will also be performed to assess glycosaminoglycan levels as a marker of disease and to correlate levels with chemotherapeutic responsiveness. A better understanding of the role of glycosaminoglycans during leukemic cell differentiation may be of importance diagnostically, and aid in the development of clinically useful differentiation inducers.
