(A) Effect of E-box mutagenesis on Id2-DBM-δHLH repression of E-cadherin promoter reporter activity. MCF-7 cells were transiently cotransfected with the indicated plasmids for luciferase assay as described in "Methods". Data are expressed as mean ± SEM for at least three separate determinations. (B) Effect of ectopic E-cadherin expression on Id2-DBM-δHLH-induced cell invasion potential. E-cadherin expression vector or the corresponding empty vector was transiently transfected into Id2-DBM-δHLH stably expressed or wild-type MCF-7 and SKOV-3 cells for immunoblotting analysis with the indicated antibodies (left panel) and Transwell assays (right panel). Data are expressed as the percentage of the control cells (mean ± SEM). (# P <0.01; N P > 0.05).