# Estrogen receptor (ERα)

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

## TL;DR

The hormone switch that drives most breast cancers. Blocking or destroying it is the oldest and most effective targeted therapy.

## Summary

Tamoxifen (SERM), aromatase inhibitors, fulvestrant (SERD), oral SERDs (elacestrant, imlunestrant, camizestrant), and the PROTAC degrader vepdegestrant (approved 2026 for ESR1-mutant disease) form the endocrine armamentarium. ESR1 mutations arise under aromatase-inhibitor pressure and are detected by ctDNA.

## Fields

- Kind: Target
- Last checked: 2026-09-04
- Tags: hormonal
- Symbol: ESR1
- Class: nuclear-receptor
- Biology: Ligand-activated nuclear receptor; ESR1 Y537S/D538G mutations render it ligand-independent.
- Where found: HR+ breast cancer (~70% of breast cancers); Endometrial; Ovarian (low-grade serous)

## Sources

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

## Connected records

- biomarkers: [ER status (oestrogen receptor by IHC)](https://onco.cc/biomarkers/er-status/), [ESR1 mutation (ligand-binding domain, usually in ctDNA)](https://onco.cc/biomarkers/esr1-mutation-ctdna/)
- cancers: [Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/), [Endometrial cancer](https://onco.cc/cancers/endometrial/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Male breast cancer](https://onco.cc/cancers/male-breast-cancer/), [Uterine sarcoma](https://onco.cc/cancers/uterine-sarcoma/)
- drugs: [Camizestrant](https://onco.cc/drugs/camizestrant/), [Diethylstilbestrol](https://onco.cc/drugs/diethylstilbestrol/), [Elacestrant](https://onco.cc/drugs/elacestrant/), [Exemestane](https://onco.cc/drugs/exemestane/), [Fluoroestradiol F-18 (FES PET)](https://onco.cc/drugs/fluoroestradiol-f18/), [Fulvestrant](https://onco.cc/drugs/fulvestrant/), [Giredestrant](https://onco.cc/drugs/giredestrant/), [Goserelin / leuprolide (ovarian function suppression)](https://onco.cc/drugs/goserelin/), [Guardant360 CDx](https://onco.cc/drugs/guardant360-cdx/), [Imlunestrant](https://onco.cc/drugs/imlunestrant/), [Letrozole (and other aromatase inhibitors)](https://onco.cc/drugs/letrozole/), [LNS8801](https://onco.cc/drugs/lns8801/), [Progestins (megestrol acetate, medroxyprogesterone, levonorgestrel IUD)](https://onco.cc/drugs/megestrol-progestins/), [Raloxifene](https://onco.cc/drugs/raloxifene/), [Tamoxifen](https://onco.cc/drugs/tamoxifen/), [Toremifene](https://onco.cc/drugs/toremifene/), [Vepdegestrant](https://onco.cc/drugs/vepdegestrant/)
- pathways: [Breast cancer (KEGG map)](https://onco.cc/pathways/breast-cancer-signalling/), [Chemical carcinogenesis - receptor activation](https://onco.cc/pathways/chemical-carcinogenesis-receptor-activation/), [Endometrial cancer (KEGG map)](https://onco.cc/pathways/endometrial-cancer-signalling/), [Lipid synthesis, uptake & cholesterol](https://onco.cc/pathways/lipid-metabolism-cancer/), [Oestrogen receptor signalling](https://onco.cc/pathways/er-signaling/), [Resistance routes: how a blocked pathway comes back](https://onco.cc/pathways/resistance-routes-map/), [The cell-cycle engine (cyclins & CDKs)](https://onco.cc/pathways/cell-cycle-engine-cdks/), [Transcriptional machinery & addiction](https://onco.cc/pathways/transcription-addiction/), [Ubiquitin-proteasome system & protein homeostasis](https://onco.cc/pathways/ubiquitin-proteasome-system/)
- trials: [EMBER-3](https://onco.cc/trials/ember-3/), [EMERALD](https://onco.cc/trials/emerald/), [evERA](https://onco.cc/trials/evera/), [lidERA](https://onco.cc/trials/lidera/), [MONALEESA-2](https://onco.cc/trials/monaleesa-2/), [SERENA-6](https://onco.cc/trials/serena-6/), [VERITAC-2](https://onco.cc/trials/veritac-2/)
- terms: [Agonist and antagonist](https://onco.cc/terms/agonist-antagonist/), [Chemoprevention (tamoxifen, anastrozole, raloxifene) and ER-negative breast cancer](https://onco.cc/terms/chemoprevention-and-er-negative-breast-cancer/), [Endocrine resistance](https://onco.cc/terms/endocrine-resistance/), [Endocrine therapy and endocrine resistance](https://onco.cc/terms/endocrine-therapy-resistance/), [ESR1 mutation](https://onco.cc/terms/esr1-mutation/), [Hormone receptor status (ER / PR)](https://onco.cc/terms/hormone-receptor-status/), [Hormone therapy](https://onco.cc/terms/hormone-therapy/), [Oral SERD](https://onco.cc/terms/oral-serd/), [Receptor](https://onco.cc/terms/receptor/), [Selective oestrogen receptor degrader (SERD)](https://onco.cc/terms/serd/)
- technologies: [CDK4/6 inhibitors](https://onco.cc/technologies/cdk46-inhibitor/), [Chemoprevention & risk-reducing surgery](https://onco.cc/technologies/chemoprevention/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/), [FES PET (oestrogen receptor imaging)](https://onco.cc/technologies/fes-pet/), [PROTACs & molecular glues (targeted protein degradation)](https://onco.cc/technologies/protac-degrader/)
- targets: [Progesterone receptor (PGR)](https://onco.cc/targets/pgr/)
- people: [Aditya Bardia](https://onco.cc/people/aditya-bardia/), [Debu Tripathy](https://onco.cc/people/debu-tripathy/), [François-Clément Bidard](https://onco.cc/people/francois-clement-bidard/), [Komal Jhaveri](https://onco.cc/people/komal-jhaveri/), [Massimo Cristofanilli](https://onco.cc/people/massimo-cristofanilli/), [Matthew P. Goetz](https://onco.cc/people/matthew-goetz/), [Mitch Dowsett](https://onco.cc/people/mitch-dowsett/), [Nicholas Turner](https://onco.cc/people/nicholas-turner/), [Seock-Ah Im](https://onco.cc/people/im-seock-ah/), [Stephen Johnston](https://onco.cc/people/stephen-johnston/)
- ideas: [Look for the resistant sub-population before the first dose](https://onco.cc/ideas/idea-bio1-baseline-ultradeep-resistant-clones/), [Low-dose tamoxifen for high-risk women, prescribed by pharmacists and nurses](https://onco.cc/ideas/idea-prev-low-dose-tamoxifen-uptake/), [Vaccinate against the resistance mutation before it takes over](https://onco.cc/ideas/idea-bio1-resistance-mutation-vaccine/)
- key papers: [IBIS-I: five years of tamoxifen keeps preventing breast cancer for at least 20 years](https://onco.cc/key-papers/paper-ibis-i-tamoxifen-lancet-oncol-2015/), [monarchE: two years of abemaciclib after surgery in high-risk, hormone-receptor-positive early breast cancer](https://onco.cc/key-papers/paper-monarche-jco-2020/), [NATALEE: three years of ribociclib after surgery in a broad population of hormone-receptor-positive early breast cancer](https://onco.cc/key-papers/paper-natalee-nejm-2024/), [The first PROTAC: a chimeric molecule that tags a protein for destruction](https://onco.cc/key-papers/paper-protac-concept-sakamoto-pnas-2001/)
- institutions: [Barbara Ann Karmanos Cancer Institute](https://onco.cc/institutions/karmanos/), [Beatson West of Scotland Cancer Centre / CRUK Scotland Institute](https://onco.cc/institutions/beatson-glasgow/), [Georgetown Lombardi Comprehensive Cancer Center](https://onco.cc/institutions/georgetown-lombardi/), [Tohoku University Hospital](https://onco.cc/institutions/tohoku-university-hospital/)
- companies: [Pathos AI](https://onco.cc/companies/pathos-ai/)

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JSON: https://onco.cc/api/v1/entities/estrogen-receptor.json