APP and neuroblastoma: Using human neuroblastoma (SH-SY5Y) cells stably overexpressing APP or BACE1 (Fig. 3a), we measured secreted levels of Aβ34, Aβ38, Aβ40, and Aβ42 in the supernatants using the ultra-sensitive 4-plex assay, whereas sAPPβ and sAPPtotal were detected by western blot (Fig. 3a–h).