Evaluation of cell growth at different times after RB silencing. A) Decreased proliferation rates starting 48 h up to 7 days from transfection in RB/PLK1 and RB/AURORA-A co-depleted cells (double knock-down) in comparison with both untransfected and pRb-depleted cells. B) Western blot analysis showing increased Cyclin-E protein levels in pRb-depleted cells as well as in cells with knock-down of both RB and AURORA-A or PLK1, and increased Cyclin-A protein levels in RB/AURORA-A co-depleted cells. Cells with knock-down of both RB and AURORA-A or PLK1 but not with RB knock-down showed increased p21Cip1 levels. β-tubulin was used as a loading control of protein extracts.