Cyclin-dependent kinase inhibitor 1 (CDKN1A) (CDKN1A)

Cyclin-dependent kinase inhibitor 1, commonly known as p21 (CDKN1A), is a potent cyclin-dependent kinase inhibitor (CKI) that binds to and inhibits the activity of cyclin-CDK2, -CDK1, and -CDK4/6 complexes (UniProt P38936). It acts as a critical mediator of cell cycle arrest in the G1 and S phases, primarily functioning downstream of the p53 tumor suppressor protein in response to DNA damage (PubMed: 25484732). Beyond its role in cell cycle control, p21 is involved in regulating apoptosis, DNA repair, and the induction of cellular senescence (NCBI Gene: 1026). In oncology, the loss or downregulation of p21 is frequently observed and contributes to uncontrolled cell proliferation, making its restoration a therapeutic goal (PubMed: 28883112). Pharmacological strategies often focus on inducing p21 expression through MDM2 inhibitors, such as Idasanutlin, which stabilize p53, or through HDAC inhibitors like Vorinostat that modify the CDKN1A promoter (PubChem CID 11626560; PubMed: 17446443). Additionally, experimental small molecules like UC2288 have been developed to directly modulate p21 activity, highlighting its potential as a direct therapeutic target in specific contexts (PubMed: 24631431).

Other names

p21CIP1WAF1CAP20CDKN1p21Cip1/Waf1

Induction of CDKN1A expression through p53 stabilization or HDAC inhibition, leading to the inhibition of cyclin-CDK complexes and subsequent cell cycle arrest.