Reduction of APP expression is associated with the apoptotic induction in breast cancer cells. (A) A series of MCF-10A cells were infected with lentivirus encoding control (shluc) or APP shRNA (shAPP-7) and then tested for APP expression by immunoblotting. Under this condition, alteration of apoptotic indicators such as cleaved PARP and cleaved Caspase-3 were compared. (B) MDA-MB-231 cells were infected with lentivirus encoding shluc, shAPP-5, or shAPP-7. Each cell line was treated with TRAIL (10 ng/ml) or 5-FU (200 μM) for 24 hours. (C, D) The on-going early apoptotic events were compared by staining for extracellular Annexin V and cell viability with propidium iodide (PI). The apoptotic cell populations with Annexin V high and PI low were indicated as percentage.