Effect of overexpression of Id2 or its mutants on the in vitro invasion of MCF-7 and SKOV-3 cells. The left panel is representative pictures of Transwell assays, performed for the indicated cells as described in "Methods". Each experiment 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 < 0.05; # P <0.01; N P > 0.05).