PIN1 is a peptidylprolyl cis/trans isomerase that catalyzes conformational changes in phosphorylated Ser/Thr-Pro motifs, acting as a molecular switch regulating multiple cellular processes 1. Through this mechanism, PIN1 controls cell cycle progression, protein degradation, and cellular signaling 1. PIN1 regulates RAF1 dephosphorylation after mitogen activation 2, targets PML and BCL6 for degradation 3, and modulates JNK signaling by destabilizing FBXW7 4. Under hypoxia, PIN1 isomerizes phosphorylated PGK1 to promote mitochondrial targeting 5. PIN1 overexpression is prevalent in multiple cancers, correlating with poor prognosis. Cytoplasmic PIN1 elevation occurs progressively from normal nevi to metastatic melanoma, predicting worse survival 6. PIN1 promotes bladder cancer through SREBP2-mediated cholesterol biosynthesis 7 and maintains glioblastoma telomeres and NF-κB signaling 8. Conversely, PIN1 dysfunction contributes to Alzheimer's disease pathogenesis; reduced PIN1 activity is observed in mild cognitive impairment and AD brains with oxidative modification 910. Additionally, PIN1 downregulation associates with vascular smooth muscle cell senescence in atherosclerosis 11. PIN1 genetic polymorphisms influence cancer susceptibility, with protective effects in breast and lung cancers but increased risk for nasopharyngeal carcinoma 12.