Inhibitory Effect of Small Interfering RNA Targeting Insulin-Like Growth Factor-I Receptor in Ovarian Cancer OVCAR3 Cells

Aim: Insulin-like growth factor-I receptor (IGF-IR) is widely overexpressed in a variety of human cancers including ovarian cancer. It plays an important role in cancer cell proliferation and tumor growth. In this study, small interfering RNA (siRNA) was used to silence IGF-IR gene expression in the human ovarian cancer cell line OVCAR3 and then its effects on proliferation, apoptosis, angiogenesis, and the growth of tumor cells in vitro and in nude mice were evaluated. Methods: Three siRNA sequences for the IGF-IR gene were cloned into expression plasmids and transfected into OVCAR3 cells. The downregulation of IGF-IR expression at both mRNA and protein levels were detected by real-time polymerase chain reaction and western blot analysis. Cell proliferation inhibition rates were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Nude mice (n = 6 per group) were subcutaneously xenografted with 2 x 10(6) OVCAR3 cancer cells. Tumor growth, cellular proliferation (Ki-67 immunohistochemistry), apoptosis, and angiogenesis (CD31 immunohistochemistry) were compared for mice administered either IGF-IR-specific or negative control siRNA over 5 weeks. Results: The mRNA and protein expression of IGF-IR was significantly decreased at 48 hours after transfection, leading to a potent suppression of tumor cell proliferation in vitro. The IGF-IR-specific siRNA dramatically suppressed tumor growth and cellular proliferation, as well as promoted tumor cellular apoptosis and inhibited angiogenesis in an OVCAR3 s.c. xenograft model. Conclusions: The siRNA targeting of IGF-IR can effectively inhibit the growth of ovarian cancer cells and may be used as a potent therapy.