# Overexpression

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

## TL;DR

When a cell makes much more of a particular protein than normal cells do. Drugs that home in on that protein can then hit the tumour harder than healthy tissue.

## Summary

Overexpression can result from gene amplification, from a mutation in the gene's control region, or from signalling that keeps the gene switched on. It is what makes many antibody and ADC targets useful: TROP2, HER2, Nectin-4 and B7-H3 are all present at low levels on some normal cells but at far higher levels on particular tumours, so a targeted drug concentrates where the target is densest. Overexpression is scored by immunohistochemistry (0, 1+, 2+, 3+), and the threshold that counts as 'positive' can change as drugs improve, as happened with HER2-low.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: overexpressed; overexpresses; over-expression; over-expressed; overexpressing; over-expressing; abundant on; overexpress

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Gene_expression
- Wikipedia: https://en.wikipedia.org/wiki/Gene_expression

## Connected records

- terms: [Amplification](https://onco.cc/terms/amplification/), [Biomarker](https://onco.cc/terms/biomarker/), [Gene expression](https://onco.cc/terms/gene-expression/), [HER2-low and HER2-ultralow](https://onco.cc/terms/her2-low/), [Immunohistochemistry (IHC)](https://onco.cc/terms/ihc/)
- technologies: [Antibody-drug conjugate (ADC)](https://onco.cc/technologies/adc/)
- targets: [B7-H3](https://onco.cc/targets/b7h3/), [HER2](https://onco.cc/targets/her2/), [Nectin-4](https://onco.cc/targets/nectin4/), [TROP2](https://onco.cc/targets/trop2/)

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