CDK3 (cyclin-dependent kinase 3) is a serine/threonine protein kinase that plays a critical role in cell cycle regulation, particularly during G0-G1 and G1-S transitions 1. CDK3 drives retinoblastoma (Rb) phosphorylation during the G0/G1 transition and early G1 phase, preceding the effects of other CDKs, and can directly regulate E2F activity independently of Rb 1. The protein forms complexes with cyclin C and cyclin E2, with cyclin E2 specifically activating both CDK2 and CDK3 2. CDK3 expression is extremely low in normal human tissues but significantly upregulated in various cancers, including nasopharyngeal carcinoma and colorectal cancer, where it correlates with disease progression and metastasis 134. In colorectal cancer, CDK3 promotes epithelial-mesenchymal transition through phosphorylating c-Jun and activating AP-1 signaling 4. CDK3 is regulated by microRNAs, particularly miR-150, miR-873, and miR-125a-3p, which suppress its expression and exhibit tumor suppressor functions 56. Recent studies have identified CDK3 as a driver of neurodegeneration in Alzheimer's disease, where elevated levels induce neuronal death through cell cycle reentry mechanisms 7.