[Effects of NPM1 gene expression on acute myeloid leukemia cell lines and its mechanism]

Objective: To investigate the impact and mechanism of NPM1 gene expression on acute myeloid leukemia (AML) cell lines. Methods: Human AML cell line U937 and HL-60 cells were transfected with NPM1 plasmid to establish stable clones, and the high NPM1 protein expression (NPM1(hi)) clones were screened by Western blot. The cell proliferation was assayed by methylthiazolyl tetrazolium bromide (MTT) , cell cycle and cell apoptosis by flow cytometric, cell colony formation by microscope count, the molecular pathways related to cell cycle by Western blot. The expression of NPM1 gene in primary AML bone marrow mononuclear cells (BMMC) was investigated by RQ-PCR. Results: ①The proliferation of NPM1(hi) U937 and HL-60 cells was similar with that of control cells (4.68±1.28 vs 3.89±0.81, 3.34±0.37 vs 2.68±0.29, P>0.05) . ②The percentage of S phase in NPM1(hi) U937 and HL-60 cells was higher than that in control cells[ (50.22±3.42) % vs (39.78±3.80) %, (59.01±3.27) % vs (43.94±2.08) %, P<0.05]. ③The anti-apoptosis capacity and colony formation abilities of NPM1(hi) U937 cells increased than that of control cells[ (68.8±10.2) % vs (48.7±3.22) %, and (772.7±24.0) vs (652.3±16.5) , P<0.05], but the above abilities of NPM1(hi) HL60 cells were similar with that of control cells. ④ The expressions of CDK4, Cyclin D1, Cyclin D2 and Cyclin E in NPM1(hi) leukemia cells were higher than that of control cells, but the expression of Cyclin D3 was lower. ⑤The NPM1 expression levels in AML patients with favorable cytogenetic prognosis were lower than that of patients with intermediate prognosis. Conclusions: NPM1 protein could promote more cells to enter S phase, enhance the ability of antiapoptosis and colony formation in AML cell lines. The quantitative level of NPM1 may predict the cytogenetic risk of AML patients.