p21: tools to study the cell cycle mediator

Investigate p21 and its effectors with highly-cited tools.

​​We have put together the list of high impact products for your studies on the cyclin-dependent kinase (CDK) inhibitor p21 (also known as WAF1, CAP20, Cip1, and Sdi1). Browse the most-cited research targets and well-referenced products for better understanding p21 in cellular function.


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The p21 toolkit

TypeReagent nameDescriptionAbID

Anti-p21 antibody
Validated using a knockout cell line

Type: Rabbit monoclonal antibody
Reactivity: Hu
Applications: ICC/IF, Flow Cyt, WB, IP, IHC-P
Anti-p21 antibodyBiotin conjugatedab79467
Goat Anti-Rabbit IgG H&L Alexa Fluor® 488 conjugatedab150077
HRP conjugatedab205718
IRDye® 800CW (preadsorbed)ab216773

p21 SimpleStep ELISA® kit

Quantitatively measure p21 in human cell and tissue extracts. Get fast, reproducible results in 90 minutes.

Reactivity: Hu
Range: 62.5 pg/ml - 4000 pg/ml
Method: Colorimetric
ProteinRecombinant p21 proteinHuman p21 protein for use in WB and as control1.ab56278
Small molecule compoundUC2288 (inhibitor)
Selective p21 inhibitor structurally related to Sorafenib (ab141966). Inhibits cytosolic p21 (IC50 = 10 µM) and functions independently of p53 2 3.ab146969
Tenovin-1 (activator)p21 activator and inducer of cell cycle arrest4.ab120889

Activation of p53-p21 pathway 

DNA damaging agents activate the p53-p21 pathway causing cell cycle arrest and DNA repair5. This mechanism is exploited by chemotherapeutic agents that induce p21 as a means of inhibiting cancer progression. Investigating p21 regulation in a p53-dependent or -independent manner can form a key basis of tumor suppression6, 7.

OxaliplatinInducer, inhibitorExhibits dual role in p53-dependent and -independent pathways. Causes G0-G1 arrest in p53 wild type cells and p21 degradation in p53 mutants8.ab141054
NocodazoleInducerp21 inducer that increases expression of p21 in a p53-dependent fashion in absence of DNA damage9, 10.ab120630
Cycloheximide (CHX)ModulatorInduction of p21 during serum stimulation (indicating serum contains a p21 blocking element)7. CHX traditionally acts as a p21 inhibitor promoting apoptosis in serum-starved cells11.ab120093
PMAInducerp53-independent p21 induction via Sp1 binding sites within p21 promoter12.

Okadaic acidab120375

Click here for full list of p21 inducers and inhibitors


  1. Sun, Z. et al. Increased SHP-1 expression results in radioresistance, inhibition of cellular senescence, and cell cycle redistribution in nasopharyngeal carcinoma cells. Radiat. Oncol. 10, 152 (2015). Read more
  2. Wettersten, H. I. et al. A novel p21 attenuator which is structurally related to sorafenib. Cancer Biol. Ther. 14, 278–285 (2013). Read more
  3. Liu, R., Wettersten, H. I., Park, S.-H. & Weiss, R. H. Small-molecule inhibitors of p21 as novel therapeutics for chemotherapy-resistant kidney cancer. Future Med. Chem. 5, 991–4 (2013). Read more
  4. Wilking, M. J., Singh, C., Nihal, M., Zhong, W. & Ahmad, N. SIRT1 deacetylase is overexpressed in human melanoma and its small molecule inhibition imparts anti-proliferative response via p53 activation. Arch. Biochem. Biophys. 563, 94–100 (2014). Read more
  5. He, G. et al. Induction of p21 by p53 following DNA damage inhibits both Cdk4 and Cdk2 activities. Oncogene 24, 2929–2943 (2005). Read more
  6. Galanos, P. et al. Chronic p53-independent p21 expression causes genomic instability by deregulating replication licensing. Nat. Cell Biol. 18, 777 (2016). Read more
  7. Macleod, K. F. et al. p53-dependent and independent expression of p21 during cell growth, differentiation, and DNA damage. Genes Dev. 9, 935–44 (1995).​ Read more
  8. Hata, T. et al. Role of p21waf1/cip1 in effects of oxaliplatin in colorectal cancer cells. Mol. Cancer Ther. 4, 1585–1594 (2005). Read more
  9. Lanni, J. S. & Jacks, T. Characterization of the p53-Dependent Postmitotic Checkpoint following Spindle Disruption. Mol. Cell. Biol. 18, 1055–1064 (1998).​ Read more
  10. Linke, S. P., Clarkin, K. C., Di Leonardo, A., Tsou, A. & Wahl, G. M. A reversible, p53-dependent G0/G1 cell cycle arrest induced by ribonucleotide depletion in the absence of detectable DNA damage. Genes Dev. 10, 934–947 (1996). Read more
  11. Arbel-Goren, R., Levy, Y., Ronen, D. & Zick, Y. Cyclin-dependent kinase inhibitors and JNK act as molecular switches, regulating the choice between growth arrest and apoptosis induced by galectin-8. J. Biol. Chem. 280, 19105–19114 (2005).​ Read more
  12. Kennett, S. Sp3 encodes multiple proteins that differ in their capacity to stimulate or repress transcription. Nucleic Acids Res. 25, 3110–3117 (1997). Read more


Alexa Fluor® is a registered trademark of Life Technologies. Alexa Fluor®dye conjugates contain(s) technology licensed to Abcam by Life Technologies.

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