APOE and Alzheimer disease: Notably, there were 5 differentially abundant proteins previously linked to CAA or AD either directly or by associated pathway involvement38–44: amyloid precursor protein (APP), serum amyloid P-component (APCS, also known as SAP), ApoE (APOE), fibrinogen alpha (FGA), olfactomedin-like protein 3 (OLFML3), and secreted frizzled related protein-3 (FRZB) (Figure 3C).