Objective  To study the function of heat shock protein 70 (HSP70) on proliferation and apoptosis of HeLa cells by observing the effect of its small interfering RNA (siRNA) on them in vitro.   Methods  siRNA targeting HSP70 gene was designed and cloned into the vector pTZU6+1(pHSP70siRNA) and transformed into DH5a followed by extraction of plasmid DNA. pHSP70siRNA wa

s identified by restriction enzyme digestion and sequencing for analysis and transfected into HeLa cells with Lipofectamine

TM

2000. The transfected pTZU6+1 was used as a negative control and the non-transfected pTZU6 +1 served as a blank control.  After 48 hours of transfection

the expression levels of HSP70 mRNA and protein were measured by semi-quantity RT-PCR and Western blotting

respectively. The  growth inhibition ratio of HeLa cells was determined by MTT. AO/EB staining was used for observation of morphologic changes in HeLa cells. The apoptosis rate and cell cycle were detected by flow cytometry.   Results  The expression levels of HSP70 mRNA and protein were significantly lower while the cell growth inhibition rate was significantly higher in HeLa cells than in negative controls (P0.01

0.05). Apoptotic morphology was observed in HeLa cells under a fluorescence microscope. Flow cytometry showed that the apoptosis rate was significantly higher in pHSP70-siRNA than in controls with the cells arrested mainly in G2/M phase.   Conclusion  HSP70-siRNA can effectively inhibit the proliferation and promote the apoptosis of HeLa cells

and may thus become a new target of gene therapy for cervical cancer.