Deletion or antagonists of the PGE2 receptors EP2 and EP4, both in cultured cells expressing mutant amyloid precursor protein (APP) [64,65] and in vivo [64], resulted in a significant reduction of beta-amyloid plaques, further confirming that Aβ and PGE2 synthesis are part of a positive feedback loop contributing to AD pathology. This evidence concerns the gene APP and Alzheimer disease.