Glucose and Glutamine Deprivation Promotes Breast Cancer Lung Metastasis via BRD4-Dependent Enhancer Activation.

Nutrient deprivation in the tumor microenvironment drives metastatic progression. However, its role in breast cancer metastasis and underlying epigenetic mechanisms remain unclear. We identify an enhancer-driven transcriptional program that promotes breast cancer metastasis under nutrient deprivation. Transient glucose-glutamine deprivation in MCF7 and MDA-MB-231 cells induces the expression of genes involved in migration, invasion, and metastasis. Chromatin immunoprecipitation sequencing shows distinct enhancer activation, marked by increased histone H3 lysine 27 and bromodomain-containing protein 4 (BRD4) recruitment. Targeted enhancer acetylation using dCas9-p300 increases cognate gene expression. Motif and CUT&RUN analyses indicate the enrichment and direct binding of ATF3 and c-JUN at enhancers-essential for their activation. Transient transcriptome sequencing shows an increase in endothelin 1 (EDN1) enhancer RNA (eRNA) transcription to facilitate enhancer activation, which is reduced by treatment with eRNA-targeting antisense oligonucleotides (ASOs). In an orthotopic mouse model, BRD4 inhibition using JQ1 or MZ1 suppresses 4T1 cell metastasis. EDN1 enhancer acetylation with dCas9-p300 increases MCF7 tumor growth, which is reduced by BRD4 inhibition or ASO treatment. BRD4 and EDN1 expression is commonly upregulated in human breast metastasis. These findings define nutrient stress-responsive enhancers as epigenetic drivers of metastatic adaptation and highlight their therapeutic potential in breast cancer.