Objective       To construct an expression vector of P75 small interfering RNA (siRNA)

and to determine its effects on the cell proliferation and apoptosis in breast cancer cells SKBR3 induced by nerve growth factor (NGF).       Methods       According to the mRNA complete sequence of P75 gene in GenB

ank

3 pairs of DNA sequence transcribing short hairpin RNAs of P75 were selected and designed

and then constructed with the vector of pSilencer™4.1-CMV neo plasmid. After the vectors were transfected into SKBR3 cells

the strongest interference effect of them was chosen by fluorescent quantitation PCR and Western blotting. Then the obtained vector was transfected into SKBR3 cells after confirmed by sequencing. The stable cell line expressing P75 siRNA was selected by G418 assay. MTT assay was performed to assess the cell proliferation induced by NGF after P75 interference and the cell apoptosis was evaluated by flow cytometry (FCM). The mouse model of transplanted breast carcinoma was constructed by SKBR3 cells. The effect of P75 siRNA on the growth of the tumor and the expression of apoptosis relevant proteins were observed on the tumor-bearing mice.       Results       The expressing vector of P75 siRNA was successfully constructed. The mRNA and protein levels of P75 were decreased after P75 interference

especially with the vector of P75 2-siRNA. MTT assay showed that NGF significantly stimulated the proliferation of SKBR3 cells and the proliferation was more significant when combined with P75-siRNA in comparison with blank control（

P

0.05）. The apoptotic rate was obviously lower in the cells treated by NGF+P75-siRNA and NGF along compared with the cells transfected with blank vector（

P

0.05）. Those cells after NGF+P75-siRNA treatment had the lowest apoptotic rate （

P

0.05）. In the mouse model of transplanted breast cancer

tumor growth in P75-interfering group was more obvious than un-transfection group and blank carrier transfection group（

P

0.05）as well as a decrease in Caspase-3 and Bax expression and an increase in Bcl-2 expression.       Conclusion       The vector of P75 siRNA decreases the expression of P75 in SKBR3 cells effectively

and enhances the cell proliferation and anti-apoptosis of NGF. So it leads to tumor grow more obviously.