CDKN3 (cyclin dependent kinase inhibitor 3) is a dual-specificity phosphatase that plays a complex role in cell cycle regulation. The protein exhibits both protein serine/threonine and tyrosine phosphatase activity, dephosphorylating CDK2 at Thr-160 in a cyclin-dependent manner 123. CDKN3 expression fluctuates during the cell cycle, peaking in mitosis, which explains its frequent overexpression in rapidly growing tumors 4. Contrary to its name suggesting an inhibitory function, CDKN3 demonstrates oncogenic properties across multiple cancer types. It is significantly upregulated in most human cancers and correlates with poor overall survival 56. In hepatocellular carcinoma, gastric cancer, cervical cancer, ovarian cancer, and pancreatic cancer, CDKN3 overexpression promotes cell proliferation, invasion, and tumor growth while inhibiting apoptosis 7891011. The protein's oncogenic effects appear mediated through regulation of cell cycle checkpoints, mitotic spindle checkpoint, and chromosome 14 pathways, with associations to P53 and PI3K-AKT signaling 6. CDKN3 also correlates with immune cell infiltration in tumor tissues, suggesting additional roles in tumor microenvironment regulation 5.