# CDKN1A

Source: https://onco.cc/targets/cdkn1a/  
OnCo record `cdkn1a` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

CDKN1A (Cyclin-dependent kinase inhibitor 1) is a gene whose normal job is to hold cell growth in check. The public catalogues list it as a drug target, an oncogene driver, a tumour suppressor and a biomarker, and clinical evidence ties its variants to diagnosis, prognosis or drug response. Tied to Bladder & urothelial cancer, Hepatocellular carcinoma, Colorectal cancer and 4 more.

## Summary

Plays an important role in controlling cell cycle progression and DNA damage-induced G2 arrest. Involved in p53/TP53 mediated inhibition of cellular proliferation in response to DNA damage. Also involved in p53-independent DNA damage-induced G2 arrest mediated by CREB3L1 in astrocytes and osteoblasts.

CIViC holds 4 clinical evidence items and 0 assertions across 4 variants, naming Fluorouracil. Open Targets scores its association with cancer at 0.72 (direct and indirect evidence; datatypes affected pathway 0.76, literature 1.00, genetic association 0.62, somatic mutation 0.80, animal model 0.53). IntOGen calls it a driver in 9 cohorts (2 activating, 7 loss-of-function), covering Bladder Urothelial Carcinoma, Chromophobe Renal Cell Carcinoma, Hepatocellular Carcinoma.

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: cyclin dependent kinase inhibitor 1A; Cyclin-dependent kinase inhibitor 1; P21; CIP1; WAF1; SDI1; CAP20; p21CIP1; p21Cip1/Waf1; p21; CDKN1
- Tags: cancer-genes-wave
- Symbol: CDKN1A
- Class: tumor-suppressor
- Biology: Plays an important role in controlling cell cycle progression and DNA damage-induced G2 arrest. Involved in p53/TP53 mediated inhibition of cellular proliferation in response to DNA damage. Also involved in p53-independent DNA damage-induced G2 arrest mediated by CREB3L1 in astrocytes and osteoblasts. Binds to and inhibits cyclin-dependent kinase activity, preventing phosphorylation of critical cyclin-dependent kinase substrates and blocking cell cycle progression. Functions in the nuclear localisation and assembly of cyclin D-CDK4 complex and promotes its kinase activity towards RB1. At higher stoichiometric ratios, inhibits the kinase activity of the cyclin D-CDK4 complex. Location: Cytoplasm; Nucleus (UniProt). Locus 6p21.2 (HGNC).
- Where found: Bladder & urothelial cancer: Open Targets association 0.64 with urinary bladder cancer (MONDO_0001187); IntOGen driver in 5 cohorts (BLCA); Hepatocellular carcinoma: IntOGen driver in 3 cohorts (HCC); Colorectal cancer: CIViC evidence names this disease; Renal cell carcinoma: IntOGen driver in 1 cohort (CHRCC); Breast cancer: Open Targets association 0.51 with breast cancer (MONDO_0007254); Retinoblastoma: CIViC evidence names this disease

## Notes

- Written by scripts/fetch-cancer-genes.ts from CIViC, Open Targets, IntOGen, HGNC and UniProt; the function text is UniProt's, condensed and in UK spelling. Roles: CIViC lists 1 therapies; IntOGen calls it an activating (Act) driver in 2 cohorts; IntOGen calls it a loss-of-function (LoF) driver in 7 cohorts; CIViC holds 4 clinical evidence items on its variants. Evidence tier "clinical-evidence" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:1784: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:1784
- UniProt P38936: https://www.uniprot.org/uniprotkb/P38936/entry
- NCBI Gene 1026: https://www.ncbi.nlm.nih.gov/gene/1026
- Ensembl ENSG00000124762: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000124762

## Connected records

- collections: [CIViC](https://onco.cc/collections/civic/), [IntOGen](https://onco.cc/collections/intogen/), [Open Targets Platform](https://onco.cc/collections/open-targets/)
- cancers: [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/), [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Chromophobe renal cell carcinoma](https://onco.cc/cancers/chromophobe-rcc/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Hepatocellular carcinoma](https://onco.cc/cancers/hcc/), [Renal cell carcinoma](https://onco.cc/cancers/rcc/), [Retinoblastoma](https://onco.cc/cancers/retinoblastoma/)
- pathways: [Cellular senescence](https://onco.cc/pathways/senescence/), [p53 / RB / cell-cycle checkpoint](https://onco.cc/pathways/p53-cell-cycle/), [The cell-cycle engine (cyclins & CDKs)](https://onco.cc/pathways/cell-cycle-engine-cdks/), [The p53 network (guardian of the genome)](https://onco.cc/pathways/p53-mdm2-axis/)

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JSON: https://onco.cc/api/v1/entities/cdkn1a.json