Specific inhibition of HER-2 expression in ovarian carcinoma cells by siRNA targeting HER-2

Objective: To investigate the effects of RNA interference (RNAi) targeting HER-2 gene on the biological traits of human ovarian carcinoma. Methods: siRNA specific to HER-2 gene was synthesized accord ing to the sequence in the GenBank. Human ovarian carcinoma cells of the line SKOV-3 were cultured and divided into 3 groups; control group; non-specific group, transfected with non-specific siRNA; and specific group, transfected with specific HER-2 siRNA. On the 5th day after transfection cisplatin was added into the culture fluid. The expression of HER-2 mRNA and the expression of protein both before and after transfection were detected by RT-PCR and Western blotting. The cell apoptosis was assessed by flow cytometry. The chemosensitivity of transfected cells to cisplatin was determined by MTT method. Results: S ince the 3rd day after transfection the expression of HER-2 mRNA of the HER-2 siRNA group was suppressed till 10 days later. On the 7th day after transfection the expression rate of HER-2 protein of the HER-2 siRNA group was (25.5 ± 0.8) % , significantly lower than those of the nonspecific siRNA group and control group, (95.7 ± 0.8) % and (96.6 ± 1.2) % respectively (both P < 0.001). On the 9th day after transfection no expression of HER-2 protein was found in the HER-2 siRNA group. The apoptosis rate of SKOV-3 cells increased time-dependently after transfection in the HER-2 siRNA group and reached the peak, (53.2 ± 1.0) % on the 6th day, significantly higher than those of the non-specific siRNA group and control group, (4.1 ± 0.3) % and (4.1 ± 0.3) % respectively (both P < 0. 001). After exposure to cisplatin for 24 hours, the survival rate of the HER-2 siRNA group was (58.4 ± 0.8) %, significantly higher than those of the nonspecific siRNA group and control group, (68.0 ± 0.6) % and (67.0 ± 0.3) % respectively (both P < 0.001). Conclusion: siRNA targeting HER-2 synthesized in vitro and tr ansfected into human ovarian carcinoma cells effectively suppresses the HER-2 expression, induces cell apoptosis, and increases the sensitivity to cisplatin of the cells. The successful application of HER-2 siRNA extends the list of available therapeutic modalities in the treatment of human ovarian cancer.