Objective Nucleostemin (NS) is a GTP-conjugated protein located in the nucleoli of stem cells and some cancer cells,and maintains cell self-renewal.We aimed to evaluate NS as a potential target for lung carcinoma gene therapy by investigating NS gene expression and its effect on A549 cell proliferation.Methods NS mRNA and protein expression in A549,HepG2,SMMC-7721,HeLa,and U251 cells was analyzed by RT-PCR and western blotting following transfection of NS siRNAs and negative control siRNA (NC).The effect on cell proliferation was also analyzed by MTT assays.Results NS mRNA and protein were both expressed in A549 cells and four other tumor cell lines;the relative expression levels were similar in all five cell lines.The three pairs of NS siRNA,either transfected alone or cotransfected into A549 cells,could effectively inhibit the expression of NS mRNA and protein.Moreover,the interference ratio showed an obvious concentration-dependent relationship.NS siRNA treatment resulted in significant inhibition of A549 cell proliferation by 35.7%.Conclusion NS gene was not only highly expressed but also played an important role in A549 cell proliferation.Thus,targeting of NS may be a promising novel strategy for the treatment of lung carcinoma. Objective Nucleostemin (NS) is a GTP-conjugated protein located in the nucleoli of stem cells and some cancer cells, and maintains cell self-renewal. We aimed to evaluate NS as a potential target for lung carcinoma gene therapy by investigating NS gene expression and The effect on A549 cell proliferation. Methods NS mRNA and protein expression in A549, HepG2, SMMC-7721, HeLa, and U251 cells were analyzed by RT-PCR and western blotting following transfection of NS siRNAs and negative control siRNA (NC) effect on cell proliferation was also analyzed by MTT assays. Results NS mRNA and protein were both expressed in A549 cells and four other tumor cell lines; the relative expression levels were similar in all five cell lines. The three pairs of NS siRNA, either transfected alone or cotransfected into A549 cells, could effectively inhibit the expression of NS mRNA and protein. Moreover, the interference ratio showed an obvious concentration-dependent relationship. cant inhibition of A549 cell proliferation by 35.7% .Conclusion NS gene was not only highly expressed but also played an important role in A549 cell proliferation .hus, targeting of NS may be a promising novel strategy for the treatment of lung carcinoma.