Stable suppression of HER-2 gene expression using siRNA increases the lysis of human ovarian carcinoma cells mediated by NK-92 cell line

The overexpression and amplification of HER-2 gene is associated with the malignant biological behavior of ovarian carcinoma and these tumor cells expressing elevated levels of HER-2 appear to be resistant to the cytolysis of NK-92. In this study, we analyzed the cytolysis effects of NK-92 on human ovarian carcinoma cells (SK-OV-3) after inhibition the expression of HER-2 mRNA by siRNA. Human ovarian carcinoma cell line SK-OV-3 was transfected with siRNA-hairpin expression retroviral vector (HER-2/siRNA) designed to target HER-2 mRNA. A negative control was established utilizing a vector lacking the antisense component (HER-2/negative). The expression levels of HER-2 gene in SK-OV-3/siRNA, and SK-OV-3/negative cell lines were evaluated by semi-quantitative RT-PCR and immunohistochemistry. The growth and the early apoptosis of these cells were assayed by MTT and flow cytometry, respectively. The cytotoxicity of NK-92 against target cells was investigated by LDH. SK-OV-3/siRNA and SK-OV-3 cells were injected subcutaneously into BALB/c nude mice respectively and NK-92 cells were intraperitoneally injected to examine the anti-tumor activity in vivo. The stable cell line (SK-OV-3/siRNA) with a persistent silence of HER-2 was established. The inhibited expression of HER-2 gene was exhibited by semi-quantitative RT-PCR and immunohistochemistry. The suppressed proliferation and the elicitation of early apoptosis cells were observed in SK-OV-3/siRNA cell line. NK-92 cell line can efficiently lyse the SK-OV-3/siRNA cells in vitro and significantly inhibit the growth of tumors xenografted with SK-OV-3/siRNA cells. Suppression of HER-2 gene expression using siRNA combined treatment of NK-92 presents a new strategy for NK-92 biological treatment on the HER-2 expression epithelial tumors.