PIN1 and Alzheimer disease: The findings that Pin1 is downregulated in degenerating neurons from AD patients (Liou et al., 2003) but its expression and activity is elevated in many cancers including those of the breast, prostate, brain, lung, and colon (Ryo et al., 2001; Wulf et al., 2001; Ayala et al., 2003; Bao et al., 2004), provides support for the argument that Pin1 can serve as a molecular switch.