(A) Effect of overexpression of Id2 or its mutants on E-cadherin protein expression. Total proteins were extracted from the indicated cells for analysis of E-cadherin protein by western blot. (B) Effect of overexpression of Id2 or its mutants on the transactivation of E-cadherin gene promoter. The indicated 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.