PLATELET-LIKE PARTICLES RELEASED BY INHIBITION OF DNA SYNTHESIS IN THE HUMAN-MEGAKARYOBLASTIC LEUKEMIA CELL LINE, MEG-01s

Abstract

The human megakaryoblastic cell line, MEG-01s, released particles identified by a characteristic marginal microtubule bundle and by the localization of platelet-specific glycoprotein (GPIlb/Illa) in the plasma membrane, detected by an immunofluorescence method. The fluorescence image and size of these particles were similar to these features in human blood platelets. To analyze the regulation of particle release by MEG-01s, the effects of DNA synthesis inhibitors, tumor promoters, and protein kinase inhibitors on these cells were examined by an immunofluorescence method. The release of particles from MEG-Ols cells was enhanced by inhibitors of DNA synthesis : aphidicolin, 5-bromodeoxyuridine, 5-fluorodeoxyuridine, hydroxyurea, etoposide, and camptothecin. The particle release was specific to the MEG-01s cells, and did not occur in the myeloid leukemic cells, HL-60. These results suggest that the cessation of DNA synthesis may trigger terminal differentiation by synthesis of factors involving particle release by MEG-01s.