# ICOS

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

## TL;DR

ICOS (Inducible T-cell costimulator) is a gene. The public catalogues list it as a drug target, and clinical evidence ties its variants to diagnosis, prognosis or drug response.

## Summary

Stimulatory receptor expressed in activated or antigen-experienced T-cells that plays an important role in the immune response. Upon binding to its ligand ICOSL expressed on antigen presenting cells (APCs), delivers costimulatory signals that enhances all basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines including IL10, up-regulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B-cells. Also acts as a costimulatory receptor critical for the differentiation of T follicular regulatory cells upon immune challenges such as viral infection.

Open Targets scores its association with cancer at 0.61 (direct and indirect evidence; datatypes clinical 0.30, affected pathway 0.61, literature 0.97, genetic association 0.64, animal model 0.32).

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: inducible T cell costimulator; Inducible T-cell costimulator; AILIM; CD278
- Tags: cancer-genes-wave
- Symbol: ICOS
- Class: other
- Biology: Stimulatory receptor expressed in activated or antigen-experienced T-cells that plays an important role in the immune response. Upon binding to its ligand ICOSL expressed on antigen presenting cells (APCs), delivers costimulatory signals that enhances all basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines including IL10, up-regulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B-cells. Also acts as a costimulatory receptor critical for the differentiation of T follicular regulatory cells upon immune challenges such as viral infection. Mechanistically, potentiates TCR-induced calcium flux by augmenting PLCG1 activation and actin remodeling. In addition, activates PI3K signalling pathways independently of calcium flux. Essential both for efficient interaction between T and B-cells and for normal antibody responses to T-cell dependent antigens. Location: Cell membrane; Secreted (UniProt). Locus 2q33.2 (HGNC).

## 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: Open Targets known-drug datatype score 0.30. Evidence tier "clinical-evidence" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:5351: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:5351
- UniProt Q9Y6W8: https://www.uniprot.org/uniprotkb/Q9Y6W8/entry
- NCBI Gene 29851: https://www.ncbi.nlm.nih.gov/gene/29851
- Ensembl ENSG00000163600: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000163600

## Connected records

- collections: [Open Targets Platform](https://onco.cc/collections/open-targets/)

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