Background: Previous studies have implicated the GH/IGF-I axis in the pathogenesis of breast cancer and the development of tamoxifen resistance. IGF-I is a known proliferative and anti-apoptotic agent. In order to characterize the growth changes that occur when elements of the GH/IGF-I axis are disrupted we have used siRNA to transcriptionally silence the IGF-IR in the MCF-7 human breast cancer cell line.
Methods: MCF-7 cells were cultured in phenol red-free medium (RPMI 1640) with 10% fetal calf serum (FCS). A combination of four siRNA duplexes (SMARTpool siRNA, Dharmacon) designed to target IGF-IR mRNA was used. The transfection agent was oligofectamine (Invitrogen). MCF-7 cells (initial concentration 104 cells/well) were washed and incubated in 96 well plates with (i) serum free media (SFM) only (ii) SFM + siRNA (100nM) (iii) SFM + IGF-I (50ng/ml) (iv) SFM + siRNA + IGF-I. Cell proliferation was assessed at 24 and 48 hours using the colorimetric MTS assay. The results are the mean of three experiments.
Results: Cell numbers as a percentage of SFM only at 24 hours were SFM + IGF-I 101.4% (range 90.5-107.7), siRNA 58.% (range 50.3-67.3), siRNA + IGF-I 70.8% (range 55.7-83.4) and at 48 hours SFM + IGF-I 158.7% (range 95.8-219), siRNA 44.9% (range 36-62.1), siRNA + IGF-I 79.7% (range 44.5-111.4).
Conclusions: The decreased proliferation in response to siRNA against IGF-IR confirms the importance of IGF-I as a proliferative agent in breast cancer. The use of siRNA offers a valuable tool with which to manipulate the IGF-I axis.
22 - 24 Mar 2004
British Endocrine Societies