Objective  To construct eukaryotic expression vector of RNAi specific to nucleophosmin1 (NPM1) and investigate the effect of recombinant plasmid on NPM1 expression in K562 cells.   Methods  The expression level of NPM1 mRNA was detected by RT-PCR in leukemia cell lines (THP1 and K562)

bone marrow or blood samples from 5 patients with acute myelogenous leukemia (AML) and from 5 healthy subjects. A short hairpin RNA targeting NPM1 was synthesized and inserted into the plasmid pGenSil-1. After the recombinant plasmid was identified

the correct plasmid was transfected into K562 cells

then the expression level of NPM1 mRNA was detected by RT-PCR.   Results  NPM1 mRNA levels were higher in two leukemia cell lines and all AML samples than those in normal cells. The RNAi recombinant plasmid was constructed successfully. The NPM1 mRNA levels decreased by 64% in K562 cells after the recombinant plasmid transfection

but those were not inhibited in K562 cells transfected with empty plasmid and untransfected K562 cells.   Conclusion  NPM1 mRNA is overexpressed in leukemia cells. The RNAi recombinant targeting NPM1 suppresses the expression of NPM1 mRNA.