Targeting ESR1 mutation–induced transcriptional addiction in breast cancer with BET inhibition

Sm N. Udden, Qian Wang, Sunil Kumar, Venkat Malladi, Shwu-Yuan Wu, Shuguang Wei, Bruce A. Posner, Sophie Geboers, Noelle S Williams, Yulun Liu, Jayesh K. Sharma, Ram S Mani, Srinivas Malladi, Karla Parra, Mia Hofstad, Ganesh V. Raj, Jose M. Larios, Reshma Jagsi, Max S. Wicha, Ben Ho ParkGaorav P. Gupta, Arul M. Chinnaiyan, Cheng-Ming Chiang, Prasanna G. Alluri

Research output: Contribution to journalArticlepeer-review

Abstract

Acquired mutations in the ligand-binding domain (LBD) of the gene encoding estrogen receptor α (ESR1) are common mechanisms of endocrine therapy resistance in patients with metastatic ER+ breast cancer. The ESR1 Y537S mutation, in particular, is associated with development of resistance to most endocrine therapies used to treat breast cancer. Employing a high-throughput screen of nearly 1,200 Federal Drug Administration–approved (FDA-approved) drugs, we show that OTX015, a bromodomain and extraterminal domain (BET) inhibitor, is one of the top suppressors of ESR1 mutant cell growth. OTX015 was more efficacious than fulvestrant, a selective ER degrader, in inhibiting ESR1 mutant xenograft growth. When combined with abemaciclib, a CDK4/6 inhibitor, OTX015 induced more potent tumor regression than current standard-of-care treatment of abemaciclib + fulvestrant. OTX015 has preferential activity against Y537S mutant breast cancer cells and blocks their clonal selection in competition studies with WT cells. Thus, BET inhibition has the potential to both prevent and overcome ESR1 mutant–induced endocrine therapy resistance in breast cancer.

Original languageEnglish (US)
Article numbere151851
JournalJCI Insight
Volume7
Issue number17
DOIs
StatePublished - Sep 8 2022

ASJC Scopus subject areas

  • Medicine(all)

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