Targeting ESR1 mutation-induced transcriptional addiction with BET inhibition
Ontology highlight
ABSTRACT: We investigated the therapeutic potential of BET inhibition to target ESR1 mutation-induced “transcriptional addiction” in ER-positive breast cancer. Our studies show that ESR1 mutant (Y537S and D538G) cells activate unique transcriptional programs that are targeted by OTX015, a BET inhibitor
Project description:Purpose: Breast cancers with ESR1 mutations are resistant to antiestrogen therapy. We aimed to investigate the association of ESR1 mutations with resistance to CDK4/6 inhibitors (CDK4/6i) using real-world data analysis and experimental validation. Patients and Methods: A total of 3,958 patients with estrogen receptor-positive (ER+) metastatic breast cancer with DNA sequencing data were analyzed. Breast tumor DNA and circulating tumor (ct) DNA were sequenced using the Tempus xT tumor assay and Tempus xF liquid biopsy, respectively. Patients were stratified into either treated with CDK4/6i (breast tumors: 1,070; ctDNA: 1,885) or CDK4/6i naïve (breast tumors: 750; ctDNA: 253). Engineered MCF7 cells carrying ESR1 Y537S or D538G knock-in mutations were used to study antitumor efficacy of the CDK4/6i, palbociclib in vitro and in vivo. Results: In both xF and xT assays, ESR1 mutations were the only somatic alterations significantly more frequent in those who received CDK4/6i than those who did not. Knock-in of ESR1 Y537S or ESR1 D538G in MCF7 cells resulted in upregulation of cell cycle-related gene signatures upon treatment with CDK4/6i ± antiestrogen compared to cells with non-mutant ESR1. MCF7 xenografts harboring ESR1 Y537S and D538G mutations established in nude mice were resistant to palbociclib. Conclusions: We report herein real-world and preclinical evidence that ESR1 mutations, particularly Y537S and D538G, can drive resistance to CDK4/6 inhibitors.
Project description:Purpose: Transcriptome analysis of ESR1 mutant cells was performed via sequencing total RNA in T47D and MCF7 cell lines containing Y537S and D538G mutations.
Project description:This study is designed to comprehensively characterize the FOXA1 cistromes of Y537S and D538G mutated ER versus WT ER in breast cancer cells.
Project description:Biotinylated 4xERE-containing DNA immobilized on streptavidin beads used to pulldown proteins recruited by unliganded WT ER-alpha versus Y537S, D538G, or ESR1-YAP1 fusion proteins from HeLa S3 human cell nuclear extracts.
Project description:Analysis of MCF7 cells transfected with ER mutants (S463P, Y537S and D538G) in phenol-red free, charcoal stripped FBS media and regular DMEM/F12 media. Results provide insight on the gene expression profiles induced by the various ER mutants. Total RNA extracted from transfected cells 48 hours after transfection 36 samples were analyzed, triplicates for each constructs (GFP vector control, WT, S463P, Y537S, D538G and S463P/D538G) for each type of media
Project description:Estrogen receptor-α (ERα) is an important driver of breast cancer and is the target for hormonal therapies, anti-estrogens and drugs that limit estrogen biosynthesis (aromatase inhibitors). Mutations in the ESR1 gene identified in metastatic breast cancer provide a potential mechanism for acquired resistance to hormone therapies. We have used CRISPR-Cas9 mediated genome editing in the MCF-7 breast cancer cell line, generating MCF-7-Y537S. MCF-7-Y537S cells encode a wild-type (tyrosine 537) and a mutant (serine 537) allele. Growth of the line is estrogen-independent and expression of ERα target genes is elevated in the absence of estrogen. ER ChIP-seq was carried out to map global ERα binding sites in the presence and absence of estrogen. RNA-seq following estrogen treatment was used for gene expression analysis. We show that expression of ER target genes and ER recruitment to ER binding regions is similar in MCF-7 and MCF-7-Y537S cells, except that ER recruitment to DNA and expression of ER target genes is frequently elevated in the absence of estrogen. Hormone depleted MCF7 Luc or Y537S cells were treated with 10nM E2 or ethanol, as vehicle control, for 8 hours, with 3 replicates (2 replicates for Y537S + E2). RNA-seq was carried out using Illumina Hiseq 2500.
Project description: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.
Project description:Estrogen receptor-α (ERα) is an important driver of breast cancer and is the target for hormonal therapies, anti-estrogens and drugs that limit estrogen biosynthesis (aromatase inhibitors). Mutations in the ESR1 gene identified in metastatic breast cancer provide a potential mechanism for acquired resistance to hormone therapies. We have used CRISPR-Cas9 mediated genome editing in the MCF-7 breast cancer cell line, generating MCF-7-Y537S. MCF-7-Y537S cells encode a wild-type (tyrosine 537) and a mutant (serine 537) allele. Growth of the line is estrogen-independent and expression of ERα target genes is elevated in the absence of estrogen. ER ChIP-seq was carried out to map global ERα binding sites in the presence and absence of estrogen. RNA-seq following estrogen treatment was used for gene expression analysis. We show that expression of ER target genes and ER recruitment to ER binding regions is similar in MCF-7 and MCF-7-Y537S cells, except that ER recruitment to DNA and expression of ER target genes is frequently elevated in the absence of estrogen Hormone depleted MCF-7 LUC /Y537S mutant cells were treated with estrogen (10nM) or ETOH as vehicle control for 45 mins. Erα Chip-seq was performed using Illumnia methodology