The MUC1 interfering RNA (siRNA) phenotype is rescued by stable transfection with MUC1. (a) MDA-MB-468 cells transfected with a full-length, siRNA-resistant MUC1 construct (468.MUC1Δ8) or empty vector (468.Neo); lysates were blotted for MUC1 extracellular (MUC1-EX) and cytoplasmic (MUC1-CT) domains, with actin as a loading control. The left panel shows untransfected cells; the right shows siRNA treatment of the stable transfectants and parental cells. (b) siRNA-transfected 468.Neo and 468.MUC1Δ8 cells were stained for expression of MUC1-EX 48 hours post-transfection and analyzed by flow cytometry. The black line represents isotype control, the green luciferase (Luc) siRNA, and the red MUC1 siRNA. Arrows point out the shaded regions that reflect the level of knockdown in each cell line. (c) Flow cytometric analysis of bromodeoxyuridine (BrdU) incorporation after 1.5 hours incubation with siRNA transfected cells. The number shown in each upper left quadrant reflects the percentage of BrdU-positive cells. A representative experiment is shown. (d) Total apoptosis is shown as the sum of early (propidium iodide (PI)-/annexin V+) and late (PI+/annexin V+) apoptotic populations for 468.Neo and 468.MUC1Δ8 cells trypsinized 24 hours post-transfection. A representative example is shown.