The siGenome siRNAs (Dharmacon, Lafayette, CO) were used to target individual genes for inhibiting their expression as previously described (7 (link)). Cells were transfected with a negative control siRNA or a specific siRNA using DharmaFECT 4 reagent (Dharmacon, Lafayette, CO). A mixture of siRNA (25 nM final concentration) and DharmaFECT 4 reagent was incubated for 20 minutes at room temperate before being applied to the cells.