To date we have characterized the decrease in steady state mRNA levels mediated by synthetic siRNAs corresponding to 35 genes associated directly with or down stream of IGF-1R and its related receptors. RNA analysis was used to characterize all of the RNAi effectors, with quantitative Western blot analysis used to analyze the decrease in protein levels of some of the target proteins. In all cases at least one synthetic siRNA was identified that reduced steady-state mRNA levels of the corresponding gene significantly, and where studied this was matched with a significant decrease in protein levels that was sustained at least 96 hours. To investigate the functional consequence of the knockdown of some of the genes associated with the IGF pathway we have investigated the effect of RNAi against 32 genes associated with the pathway members in multiple cell lines with a focus on mammary epithelial and breast cancer cell lines. An RNAi profile for these cell lines has been established and follow up work is now being conducted as part of collaborative effort with the Molecular Target Development Program, CCR, NCI.