# CTSS

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

## TL;DR

CTSS (Cathepsin S) is an enzyme. In the public catalogues the evidence so far is association rather than a proven role. Tied to Skin cancer and Basal cell carcinoma.

## Summary

Thiol protease. Key protease responsible for the removal of the invariant chain from MHC class II molecules and MHC class II antigen presentation. The bond-specificity of this proteinase is in part similar to the specificities of cathepsin L.

Open Targets scores its association with cancer at 0.57 (direct and indirect evidence; datatypes literature 0.98, genetic association 0.71).

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: cathepsin S; Cathepsin S
- Tags: cancer-genes-wave
- Symbol: CTSS
- Class: enzyme
- Biology: Thiol protease. Key protease responsible for the removal of the invariant chain from MHC class II molecules and MHC class II antigen presentation. The bond-specificity of this proteinase is in part similar to the specificities of cathepsin L. Elicits itch by mediating cleavage and activation of MRGPRX1. Location: Lysosome; Secreted; Cytoplasmic vesicle, phagosome (UniProt). Locus 1q21.3 (HGNC).
- Where found: Skin cancer: Open Targets association 0.50 with skin cancer (MONDO_0002898); Basal cell carcinoma: Open Targets association 0.52 with basal cell carcinoma (MONDO_0020804)

## 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: none stated by the sources. Evidence tier "association-only" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:2545: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:2545
- UniProt P25774: https://www.uniprot.org/uniprotkb/P25774/entry
- NCBI Gene 1520: https://www.ncbi.nlm.nih.gov/gene/1520
- Ensembl ENSG00000163131: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000163131

## Connected records

- collections: [Open Targets Platform](https://onco.cc/collections/open-targets/)
- cancers: [Basal cell carcinoma](https://onco.cc/cancers/basal-cell-carcinoma/), [Skin cancer (all types)](https://onco.cc/cancers/skin-cancer/)

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