GLYCOSPHINGOLIPIDS IN ONCOGENESIS AND DIFFERENTIATION

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The objectives of this project are to: (1) analyze the neutral glycosphingolipids and gangliosides from the leukocytes of normal donors and leukemic patients; (2) find a human leukemia cell line(s) to use as a model system to evaluate the regulation of neutral glycosphingolipids in human leukocytes; and (3) determine if the glycosphingolipids of human leukocytes are I,i antigens. We have completed structural characterization of the neutral glycosphingolipids and gangliosides of normal human leukocytes and leukemia cells. These studies have demonstrated that mature human leukocytes can be distinguished on the basis of their neutral glycosphingolipids (i.e., myeloid cells express neolacto compounds and lymphoid cells express globo compounds). We have also found that immature cells express both globo and neolacto compounds, suggesting a relationship between cell differentiation and glycolipid expression. We have evaluated the distribution of GD3 ganglioside among human leukocytes using an anti-GD3 monoclonal antibody and found that normal Ieukocytes and CML cells do not express this compound, whereas all other types of leukemic leukocytes have GD3. Therefore, GD3 appears to be restricted in its distribution to leukemic blast cells and chronic lymphocytic cells. Glycolipids carrying the i-antigen have been purified from CML cells and structurally characterized and detected by immunostaining with anti-i antibodies. We have purified 14C-galactose-labeled glycolipids from three myeloid leukemic cell lines and have structurally characterized them using glycosidases and HPLC of their perbenzolylated derivatives. The results of these analyses demonstrate that alterations in neutral glycosphingolipid expression occur after the myeloblastic stage of differentiation and before or at the promyelocyte stage. A comparison of the glycosphingolipids synthesized by untreated cells and cells treated with differentiating agents (butyrate, dimethyl sulfoxide, and phorbol diesters) will be made. The results from these studies will be useful in determining if there are variations in the classes of glycolipids synthesized by different leukemic cells and if chemically induced differentiation leads to alterations in glycolipid biosynthesis that are related to those occurring in freshly isolated leukocytes. (MI)