(A) Effect of Id2-specific siRNA transfection on the expression of the exogenous Id2-DBM protein in MCF-7 cells. The indicated siRNA oligonucleotides were transfected into the indicated MCF-7 cells. 48 h after transfection, total proteins were extracted and subjected to immunoblotting analysis with Id2-specific antibody. β-actin was used as the loading control. (B) Effect of knock down of exogenous Id2-DBM by RNA interference on in vitro invasion of MCF-7 cells. The indicated siRNA oligonucleotides were transfected as described in (A). 48 h after transfection, MCF-7 cells were subjected to performing Transwell experiments. The top panel shows representative pictures of Transwell assays, as described in "Methods". Each data was performed in triplicate and was repeated three times. Data are expressed as the percentage of the control cells (mean ± SEM, the bottom panel). (# P <0.01; N P > 0.05).