DECREASE IN NUCLEOSIDE DIPHOSPHATE KINASE (NDPK NM23) EXPRESSION DURING HEMATOPOIETIC MATURATION/

The nucleoside diphosphate kinase (NDPK/nm23) isoforms H1 and H2 were localized in hematopoietic tissues. Flow cytometric analysis and enzym atic assays were used to quantify the intracellular and extracellular concentrations of NDPK. Bone marrow CD34(+) progenitors contained the highest intracellular levels of both nm23-H1 and nm23-H2. Lower levels were measured in more mature bone marrow cells, whereas peripheral bl ood leukocytes had the lowest expression of nm23. These data suggest a function of NDPK in early hematopoiesis and a down-regulation of NDPK upon differentiation. In addition, an up-regulation of nm23 expressio n was observed in lymphocytes after induction of proliferation with ph ytohemagglutinin. Multiparameter flow cytometry demonstrated that this up-regulation occurred during the G(0)/G(1)-transition. Flow cytometr ic analysis also revealed a weak surface expression of nm23 on a numbe r of hematopoietic cell lines, which was not detected on normal hemato poietic cells. Our data also demonstrated the presence of NDPK in huma n plasma, probably due to a limited in vivo lysis of red blood cells.