Objective To construct an expression vector of small interfering RNA （siRNA） against survivin and observe its effects on survivin expression and proliferation of human pancreatic cancer cell line PC-2 and breast cancer cell line MCF-7. Methods Constructed an expression vector of siRNA against survivin and transfected it into PC-2 and MCF-7 cells using lipofectamine

TM 2000.The expression of survivin was detected by semi-quantitive RT-PCR and immunohistochemistry

and its effects on proliferation of PC-2 and MCF-7 cells were detected by MTT assay. Results The introduction of sequence-specific siRNA could efficiently suppress survivin expression at both mRNA and protein levels in the two cancer cell lines. In PC-2 cells

the expression inhibition rates were 81.25% at mRNA level and 74.24% at protein level. In MCF-7 cells

the expression inhibition rates were 64.91% at mRNA level and 79.72% at protein level. The proliferation of PC-2 and MCF-7 cells was also suppressed

and 24 and 48 hours after the cells were reseeded

the proliferation inhibition rates of PC-2 cells were 28.00% and 33.38%

and that of MCF-7 cells were 31.58% and 33.02%

respectively. Conclusions The expression vector of siRNA against survivin can block survivin expression in PC-2 and MCF-7 cells efficiently and specifically. Down regulation of survivin expression can suppress proliferation of PC-2 and MCF-7 cells. Survivin RNAi may have potential value in gene therapy of human cancers.