Effect of cyclin D1 and Id1 on breast cancer cell protein expression and migration. Actively cycling MDA-MB-231 and ZR75-1 cells were monitored 20 h post-transfection with the indicated siRNA (cyclin D1/CDK4/6/Id1) or vector (Id1) for changes in gene or protein expression, and migration. Blots are representative, and plots are mean values from at least three independent experiments. Error bars represent standard deviation. MDA-MB-231 cells: (A) Microarray analysis. Left panel: CCND1 gene expression, right panel: ID1 gene expression (B) Western blot for cyclin d1, Id1 and Actin protein, (C) Cell migration as measured by Boyden chamber assay, dots indicate total number of migrated cells. (D) ChIP assay for Id1 promoter region following cyclin D1 pull down. ZR75-1: (E) Western blot for cyclin d1 and Actin protein (F) Cell migration- Boyden chamber assay. ***P ≥ 0.001, **P ≥ 0.01, *P ≥ 0.05 vs. control, two-tailed student's t-test.