CCNI2 (cyclin I family member 2) is a CDK5 activator that functions as a cyclin-dependent kinase regulator involved in cell cycle progression 1. Unlike its homolog CCNI, CCNI2 primarily retains CDK5 in the cytoplasm and cell membrane rather than the nucleus, and CCNI2 depletion affects cell cycle progression and proliferation 1. CCNI2 is aberrantly elevated in multiple cancer types including pancreatic, colorectal, gastric, and hepatocellular carcinoma, where elevated expression correlates with poor overall survival and advanced pathological stage 2345. Functionally, CCNI2 promotes cancer progression through multiple mechanisms: in pancreatic cancer, it activates the PI3K/AKT signaling pathway to enhance cell proliferation and migration 2; in gastric cancer, it works through hepatoma-derived growth factor (HDGF) to increase proliferation and migration while suppressing apoptosis 4; and in colorectal cancer, CCNI2 knockdown arrests cells in G2 phase and promotes apoptosis 3. CCNI2 peptides show altered plasma levels in ovarian cancer patients 6. These findings establish CCNI2 as a potential prognostic marker and therapeutic target across multiple malignancies.