Involvement of nucleophosmin/B23 in TPA-induced megakaryocytic differentiation of K562 cells

Abstract

Human myelogenous leukaemia K562 cells were induced to undergo megakaryocytic differentiation by treatment with phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (20 nM, 24 -72 h). The steady-state level of nucleophosmin/B23 mRNA decreased during the TPA-induced differentiation. There was also decrease in the level of cellular nucleophosmin/B23 protein and appearance of its degraded product (25 kDa) during the TPA-induced differentiation. Furthermore, K562/B23 (wild type), K562/D1 (D280 -294) and K562/D2 (D263 -294) cells were less, while K562/D3 (D244 -294) cells were more responsive to TPA-induced differentiation as compared to K562/vector or parental K562 cells. Activation of the ERK/MAPK was observed in parental K562 cells upon TPA treatment (5 nM, 5 -30 min). As compared to K562/vector cells, less activation of ERK/MAPK was observed in K562/D2 cells, while ERK/MAPK was highly activated in K562/D3 cells upon TPA treatment. Our results indicate that nucleophosmin/B23 plays an important role in TPA-induced differentiation of K562 cells and the amino acids 244 -294 at C-terminal of nucleophosmin/B23 could be an important site for regulation of cellular response to differentiation.

Prevalence and prognostic impact of NPM1 mutations in 1485 adult patients with acute myeloid leukemia (AML)

“…Hsu and Yung showed that K562 cells transfected with a C-terminal NPM1 mutant have an increased ability for megakaryocytic differentiation. 41 This might imply that blasts with NPM1 mutations retain a certain capacity for thrombocytic differentiation. A novel aspect was the highly significant increase of NPM1 mutations in female patients (33% versus 22%; P Ͻ .001).…”

Identification of Proteins Cleaved Downstream of Caspase Activation in Monocytes Undergoing Macrophage Differentiation

“…This 38-kDa phosphoprotein regulates various cellular functions, including centrosome duplication, gene transcription, and cell proliferation (57,58). Its overexpression prevents retinoic acid-induced granulocytic differentiation of HL-60 leukemic cells (59), whereas the protein is cleaved in K562 leukemic cells undergoing TPAinduced megakaryocytic differentiation (60). The npm gene is involved in various chromosome translocations that characterize malignant hematopoietic diseases (61,62), npm mutations that cause aberrant cytoplasmic localization of the protein are found with a high frequency in acute myelogenous leukemias (63), and npm ϩ/Ϫ mice demonstrate features of human myelodysplatic syndromes (64).…”

Mutated nucleophosmin detects clonal multilineage involvement in acute myeloid leukemia: impact on WHO classification

“…In cases showing erythroid involvement, NPM cytoplasmic positivity was strongest in proerythoblasts than in any other leukemic cell ( Figure 2B, G/NPM and NPM); more mature erythroid precursors were usually weakly positive or negative ( Figure 2B, G/NPM), in line with NPM down-regulation during differentiation of erythroid and other hemopoietic progenitors. [34][35][36][37] NPMc ϩ erythroid cells ranged from isolated (best identified by double glycophorin A/NPM staining) ( Figure 2B, G/NPM) through variably sized clusters to most marrow cells (M6 cases). Strongly NPMc ϩ /glycophorin A-negative proerythroblasts were occasionally observed (not shown), unsurprisingly, because glycophorin A may be weakly expressed or absent in most immature erythroid precursors.…”