CDK6 is a serine/threonine kinase essential for G1/S phase cell cycle transition that phosphorylates retinoblastoma protein (Rb) and controls cell proliferation 1. CDK6 forms complexes with D-type G1 cyclins to regulate Rb-dependent cell cycle progression and is particularly important for hematopoietic and erythroid cell proliferation 2. Beyond canonical cell cycle control, CDK6 regulates glucose metabolism through SLC2A1/GLUT1 transcription 3 and exhibits distinct allosteric network properties compared to CDK4, with stronger cyclin-induced kinase activation despite structural similarity 4. In cancer biology, CDK4/6 inhibitors have revolutionized hormone receptor-positive breast cancer treatment by arresting cells in G1 phase 5, yet resistance emerges through multiple mechanisms including CDK6 overexpression and induction of Cyclin E/CDK2 activity 6. Notably, CDK6 expression level determines inhibitor sensitivity: tumors expressing both CDK4 and CDK6 preferentially rely on CDK6 for progression and show reduced inhibitor efficacy, particularly when CDK6 adopts a thermostable conformation resistant to drug binding 7. CDK4-selective inhibition may improve therapeutic efficacy by targeting tumor dependency on CDK4 while preserving CDK6's essential role in normal hematopoiesis 2. Pathogenic variants cause autosomal recessive microcephaly 12, highlighting CDK6's critical role in neurogenesis.