APP and neuroblastoma: Retinoic acid causes PI3K and PKC-dependent upregulation of 2 putative α-secretases and the disintegrin metalloproteinases ADAM10 and TACE, stimulates α-secretase processing of amyloid precursor protein (APP), and down regulates β-secretase cleavage thereby leading to suppression of amyloid-β formation in human neuroblastoma SH-SY5Y cells (Figure 3).