Background:It has been reported that the expression of SPP1

the mRNA for osteopontin （OPN）

is increased in a number of transformed cell lines and some tumors. Increased serum and plasma OPN levels were associated with advanced-stage carcinomas of the lung

breast

colon and prostate. The extent of OPN expression may be correlated with the malignancy degree of gliomas

but the specific role of OPN in the malignancy of gliomas remains to be clarified. Methods:In this study

we used a lentiviral system

which could induce a long-lasting down-regulation of gene expression

to knock down the OPN gene in human glioma cell line U251. And then we observed the proliferation and apoptosis of glioma cells. Results:OPN mRNA and protein were successfully knocked down in U251 cells

and the expression of caspase-3 and caspase-9 were increased about by 2 folds in OPN down-regulated U251 cells. 3-[4

5-dimethylthiazol-2-yl]-2

5-diphenyltetrazolium （MTT） assay showed that OPN down-regulation did not affect the proliferation of U251 cells. Conclusion:Our findings indicate that OPN might play a role in apoptosis

but not in cell proliferation in U251 glioma cells.