CDK6 is negatively regulated by binding to certain inhibitors that can be classified in two groups;[REF] CKIs or CIP/KIP family members like the protein p21[REF] and p27 act blocking and inhibiting the assembled C-CDKs binding complex enzymes[REF] in their catalytic domain [REF].
Furthermore, inhibitors of the INK4 family members like p15, p16, p18 and p19 inhibit the monomer of CDK6, preventing the complex formation [REF].