Human Leukemic Myeloblasts and Myeloblastoid Cells Contain the Enzyme Cytidine 5-Monophosphate-N-acetylneuraminic Acid: Gal β l-3GalNAcα(2–3)-sialyltransferase

We have examined the role of CMP-NeuAc: Ga101-3GaINAc-R a{2–3)-sialyltransferase in fresh leukemia cells and leukemia-derived cell lines. Enzyme activity in normal granulocytes using Gal β 1-3Ga1NAcα-o-nitrophenyl as substrate was 1.5 ± 0.7 nmol/mg/h whereas activity in morphologically mature granulocytes from 6 patients with chronic myelogenous leukemia (CML) was 4.2 ±1.6 nmol/mg/h (P < 0.0S). Myeloblasts from 5 patients with CML in blast crisis showed enzyme activity levels of 6.5 ± 2.5 nmol/mg/h. From 2 patients with CML, both blasts and granulocytes were obtained, with higher enzyme activity in the patients9 blasts (7.1 nmol/mg/h) than in their granulocytes (4.9 nmol/mg/h) in both cases, suggesting that the increase in enzyme activity is related to the differentiation or proliferation status of the CML cells. However, similarly high enzyme levels were also seen in myeloblasts from acute myeloblastic leukemia patients (5.6 ±1.4 nmol/mg/h) and in some acute myeloblastic leukemia-derived cell lines (KGla and HL60), suggesting that increased levels of this enzyme are not directly correlated with the presence of the Ph1 chromosome. This α(2–3)-sialyltransferase activity can also be detected in normal peripheral blood lymphocytes and exhibits increased activity in chronic lymphocytic leukemia cells and acute lymphoblastic leukemia. These data suggest that the level of enzyme activity may vary with growth rate and maturation status in myeloid and lymphoid hemopoietic cells. Finally, we have identified a glycoprotein in acute myeloblastic leukemia cells that serves as a substrate for the α(2–3)-sialyltransferase. The desialylated form of the glycoprotein was resialylated in vitro by the purified placental form of this a(2–3)-sialyltransferase and exhibits a molecular weight of about 150, 000.