# Histone deacetylases (HDAC)

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

## TL;DR

Histone deacetylases tighten the packaging of DNA so that genes are switched off. Drugs that block them loosen the packaging and can wake up genes that make lymphoma cells stop growing or die.

## Summary

Histone deacetylases remove acetyl groups from lysines on histones and on non-histone proteins such as p53, HSP90 and tubulin, condensing chromatin and repressing transcription. Class I (HDAC1, 2, 3, 8) and class II (HDAC4 to 7, 9, 10) enzymes are the targets of approved inhibitors: vorinostat and romidepsin in cutaneous T-cell lymphoma, belinostat and romidepsin in peripheral T-cell lymphoma, and panobinostat (US approval withdrawn) in multiple myeloma. Responses are modest as single agents in solid tumours; combinations with immunotherapy and with hypomethylating agents are under study.

## Fields

- Kind: Target
- Last checked: 2026-09-10
- Tags: epigenetic
- Symbol: HDAC1, HDAC2, HDAC3, HDAC6
- Class: enzyme
- Biology: Inhibition causes histone hyperacetylation, cell-cycle arrest via p21 induction, apoptosis and reduced angiogenesis; class-related toxicities are fatigue, thrombocytopenia, diarrhoea and QT prolongation.
- Where found: Cutaneous T-cell lymphoma; Peripheral T-cell lymphoma; Multiple myeloma (panobinostat)

## Notes

- Prevalence not recorded as a positivity rate: HDACs are expressed in essentially all cells and HDAC inhibitors are not selected on target expression. Published series report continuous or cutoff-dependent expression rather than a positivity rate: Mithraprabhu 2014 found HDAC1 protein detectable in most myeloma trephines and compared >=90% with <=20% cell positivity for prognosis (doi:10.4161/15592294.2014.983367); Min 2012 graded HDAC1-3 expression in 13 PTCL-NOS and 78 DLBCL (doi:10.4132/KoreanJPathol.2012.46.2.142).

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Histone_deacetylase
- NCBI Gene HDAC1: https://www.ncbi.nlm.nih.gov/gene/3065

## Connected records

- cancers: [Multiple myeloma](https://onco.cc/cancers/multiple-myeloma/), [Peripheral T-cell lymphomas (including cutaneous T-cell lymphoma)](https://onco.cc/cancers/peripheral-t-cell-lymphoma/)
- drugs: [ABT-301](https://onco.cc/drugs/abt-301/), [Belinostat](https://onco.cc/drugs/belinostat/), [Resminostat](https://onco.cc/drugs/resminostat/), [Romidepsin](https://onco.cc/drugs/romidepsin/), [Vorinostat](https://onco.cc/drugs/vorinostat/)
- roadmaps: [Epigenetic therapy roadmap: loosening silenced genes → mutation-specific enzymes → editing the epigenome](https://onco.cc/roadmaps/epigenetics-roadmap/)
- companies: [4SC](https://onco.cc/companies/4sc/)

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