GLYCOSPHINGOLIPIDS IN ONCOGENESIS AND DIFFERENTIATION

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Our previous work has focused on the structural characterization of human leukocyte and leukemia cell antigens. We have established that human leukocytes express lineage-specific glycosphingolipid antigens, and that several leukocyte-specific monoclonal antibodies bind to carbohydrate sequences carried by glycosphinoglipids. The complete structures of two complex myeloid-specific glycosphingolipid antigens recognized by these antibodies have recently been determined. Finally, the existence of a leukemia- associated glycosphingolipid antigen, GD3, has also been established. In the current proposal, we will extend this work by using biochemical and chemical techniques which include TLC immunostaining with carbohydrate sequence-specific monoclonal antibodies and fast atom bombardment mass spectrometry (FAB/MS), to determined the structure of other glycosphingolipid antigens that carry the epitope recognized by the myeloid-specific antibody, VIM-8. With these techniques and a procedure that combines the resolving power of thin-layer chromatography with the sensitivity of FAB/MS, we propose to obtain structural information on highly complex myeloid-specific (VIM-2) gangliosides. We also propose experiments to measure the activity and specificity of glycosyltransferases which synthesize the leukocyte, lineage- specific and leukemia-associated glycosphingolipid antigens that have previously been identified. A new antibody-based ELISA procedure will be used to determine the level of expression of these glycosyltransferases in normal human leukocytes and leukemia cells. These proposed experiments will (1) provide information on the structures of cell surface markers of normal human leukocytes and leukemia cells, and (2) establish the enzymatic basis for their biosynthesis. This fundamental information is needed to determine the mechanisms which lead to the expression of specific cell surface markers during normal differentiation and leukemogenesis.