Tumor protein p53–p21 signaling pathway

The “Tumor protein p53–p21 signaling pathway” represents a molecular signaling axis rather than a single molecule or receptor. The p53 protein is a highly studied transcription factor and canonical tumor suppressor frequently mutated or inactivated in cancer[2][4][6]. Upon cellular stress such as DNA damage, p53 is stabilized and activated, leading to the transcriptional upregulation of the CDKN1A gene, which encodes p21 (also called WAF1/CIP1)[1][3][5]. p21 functions as a cyclin-dependent kinase inhibitor, blocking cyclin-CDK complexes and enforcing cell cycle arrest, primarily at the G1/S checkpoint, to enable DNA repair or trigger senescence or apoptosis[1][2][3][5]. Disruption of either p53 or p21 undermines this checkpoint, fostering uncontrolled proliferation and tumorigenesis[2][6]. This pathway is instrumental for maintaining genomic integrity and acts as a critical defense against oncogenic transformation[2][3][4]. **Important clarification:** - This query refers to a **signaling pathway**, not an individual molecular target suitable for direct therapeutic targeting such as a receptor, enzyme, or transporter[2][3][4]. - Therapeutic agents may target individual proteins within the pathway (e.g., p53 reactivators, MDM2 inhibitors) rather than the entire pathway as a single “target.”[5][6] - p53 (gene symbol: TP53) is the canonical protein and is often the direct target in research and drug discovery, not the broader signaling axis.

Other names

p53 pathwayp53–p21–RB pathwayp53–CDKN1A pathwayp53 signaling pathway