[Growth of breast cancer cells is inhibited in vitro by cyclin E-siRNA].

Objective: To investigate the changes of biological characteristics of breast cancer cell line by cyclin E expression.

Methods: Human breast cancer cell line MCF-7 was transfected with cyclin E siRNA vector pEGFP/CCNE2. siRNA-induced silencing of cyclin E was determined by RT-PCR at RNA level and Western blot at protein level. The proliferation of MCF-7 cells and their sensitivity to chemotherapy was measured by CCK-8 assay. The cells were examined by FCM. The cell line was injected into nude mice and the tumor size was measured.

Results: The expression of cyclin E was inhibited in the MCF-7 cells. The relative expression level of cyclin E mRNA was 0.23 +/- 0.05, and that of cyclin E protein was 0.24 +/- 0.05. The cell growth was inhibited by 68.56% +/- 0.08%, and their sensitivity to chemotherapy was increased. Most cells were blocked at G(1) (77.38%), their tumorigenic ability in nude mice was reduced, and the size of tumor formed in mice of the experimental group was decreased than that of controls.

Conclusion: Inhibition of cyclin E expression in breast cancer cells can block their cell cycle at G(1) phase, reduce their cell growth, differentiation and proliferation, and increase their sensitivity to chemotherapy.