Objective    To study the mechanisms by which the RNA targeting Livin regulates the proliferation and apoptosis of MDA-MB-231 cells.     Methods    Three siRNA eukaryotic expression vectors targeting Livin were constructed and transfected into breast cancer MDA-MB-231 cells. The changes of Livin

Caspase-3 and Smac/DIABLO expressions in MDA-MB-231 cells with or without RNAi transfection were detected by quantitative

Real-Time PCR and Western blotting. The proliferation of MDA-MB-231 cells was detected by MTT assay

their cell cycles by flow cytometry and their apoptosis by TUNEL assay and their morphological changes observed by optical microscope and electron microscope.     Results    Three specific siRNA eukaryotic expression vectors targeting Livin were successfully constructed. They all could inhibit the expressions of Livin mRNA and protein to different degree

of which si-Livin2 showed the highest inhibition rate. Forty-eight hours after si-Livin2 transfection

the proliferation of MDA-MB-231 cells was strongly inhibited

with the inhibition rate of 36.1%. The cell percentage of the G

0

/G

1

phase was increased and that of the S phase was decreased. The apoptosis rate of MDA-MB-231 cells increased and the typical apoptosis was observed under electron microscope. The mRNA and protein expressions of Caspase-3 and Smac/DIABL were all increased.     Conclusion    Through upregulating the expressions of Caspase-3 and Smac/DIABLO

RNAi targeting Livin inhibits the proliferation and induces the apoptosis of MDA-MB-231 cells.