# Topoisomerase II alpha (TOP2A)

Source: https://onco.cc/targets/top2a/  
OnCo record `top2a` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The enzyme that cuts both DNA strands to untangle chromosomes before cell division. Etoposide and the anthracyclines hold it in the cut state, filling dividing cells with double-strand breaks.

## Summary

Topoisomerase II alpha passes one DNA double helix through a transient break in another, decatenating replicated chromosomes and relaxing supercoils; its expression peaks in proliferating cells. Etoposide and anthracyclines such as doxorubicin stabilise the covalent enzyme-DNA complex, converting a normal catalytic step into lasting double-strand breaks. Etoposide is central to small-cell lung cancer, germ cell tumour and lymphoma regimens; anthracyclines to breast cancer, lymphoma and sarcoma regimens. Therapy-related leukaemia with KMT2A rearrangement and anthracycline cardiotoxicity are the class hazards.

## Fields

- Kind: Target
- Last checked: 2026-09-04
- Symbol: TOP2A
- Class: enzyme
- Biology: Type IIA topoisomerase, proliferation-associated isoform; poisoned by etoposide and anthracyclines into a stable cleavage complex.
- Where found: Proliferating tumour cells; TOP2A amplification in a subset of HER2-positive breast cancers

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/TOP2A
- UniProt P11388: TOP2A: https://www.uniprot.org/uniprotkb/P11388/entry

## Connected records

- cancers: [Diffuse large B-cell lymphoma](https://onco.cc/cancers/dlbcl/), [Small-cell lung cancer](https://onco.cc/cancers/sclc/), [Testicular germ cell tumours](https://onco.cc/cancers/testicular/)
- drugs: [Aldoxorubicin](https://onco.cc/drugs/aldoxorubicin/), [Amrubicin](https://onco.cc/drugs/amrubicin/), [Amsacrine](https://onco.cc/drugs/amsacrine/), [Doxorubicin](https://onco.cc/drugs/doxorubicin/), [Etoposide](https://onco.cc/drugs/etoposide/), [Pirarubicin](https://onco.cc/drugs/pirarubicin/), [Pixantrone](https://onco.cc/drugs/pixantrone/), [Teniposide](https://onco.cc/drugs/teniposide/)

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JSON: https://onco.cc/api/v1/entities/top2a.json