PPIH (peptidylprolyl isomerase H) is a nuclear cyclophilin that functions as both a peptidyl-prolyl isomerase and molecular chaperone 1. As a core spliceosomal component, PPIH participates in pre-mRNA splicing by directly interacting with PRPF4 through bi-partite binding sites and integrating into the U4/U5/U6 tri-snRNP complex 2. The protein exhibits chaperone activity that prevents tau aggregation, demonstrating protective roles in protein homeostasis 3. PPIH is significantly overexpressed in multiple cancer types, including hepatocellular carcinoma and cholangiocarcinoma, where elevated expression correlates with poor prognosis, advanced tumor stage, and TP53 mutations 45. Multi-omics analyses reveal PPIH promotes cancer cell proliferation, migration, and invasion while influencing the tumor microenvironment through immune cell interactions 6. The protein shows strong diagnostic value across various malignancies and may serve as both a prognostic biomarker and potential therapeutic target 65. PPIH's dual roles in essential cellular processes like splicing and protein folding, combined with its dysregulation in cancer, highlight its importance in both normal cellular function and disease pathogenesis.