Dose response effect of β1 integrin siRNA on MMP-2 activation in MCF-7-MT1 cells. (A): Cells were plated and transfected with β1 integrin siRNA. Serial dilutions of β1/6 siRNA (2.5, 5, 10, 15 and 20 µM) were used in comparison with the 20 µM concentrations of β1/4 and β1/5 siRNAs. Protein concentrations were determined and equal amounts of lysates were electrophoresed with 10% SDS-PAGE under reducing conditions. Western Blot analysis was used to detect β1 integrin and MT1-MMP levels (B). (C): Serial dilutions of β1/6 siRNA (5, 10, and 20 µM) were used in comparison with the 20 µM concentrations of β1/4 and β1/5 siRNAs. Conditioned medium was collected and effects on MMP-2 activation were examined by zymography.