Project description:Approximately 75% of breast cancers are driven by the estrogen receptor alpha (ER), and despite the advent of endocrine therapy to block ER signaling pathways, a significant portion of women develop resistance to these drugs. The pioneer factor FOXA1 has been shown to facilitate nearly all DNA-binding events of ER in response to estrogen in ER+ breast cancer (ER+BC). Notably, up-regulation of FOXA1 is a hallmark of endocrine-resistant phenotypes and has been shown to reprogram enhancer elements, leading to an altered transcriptome. However, FOXA1 is a critical pioneer factor for multiple nuclear hormone receptors aside from ER and is implicated in regulation of important factors such as HER2 and the androgen receptor (AR). With the diverse array of breast cancer molecular subtypes displaying complex interplay between ER, HER2, AR, PR, and other hormone receptors, describing the complete ensemble of FOXA1 binding partners in various contexts, such as endocrine-resistant tumors, is of increasing importance. To classify FOXA1 interactors, we generated MCF-7 cell lines stably expressing the biotin ligase miniTurbo fused to the N- or C-terminus of FOXA1. Using proximity labeling (PL) coupled with LC-MS/MS, we have comprehensively cataloged interactors of FOXA1, including expected proteins such as ER, AR, MLL3, YAP1, and GATA-3. Moreover, we have discovered 157 previously unpublished interactors of FOXA1. Importantly, poorer prognosis for relapse-free survival among ER+BC patients is associated with several of these novel interactors, including NR2C2, an orphan nuclear receptor previously shown to regulate various nuclear hormone receptor signaling but whose roles in breast cancer remain unclear. NR2C2 ChIP-seq in MCF-7 cells under control or FOXA1-depleted conditions revealed multiple NR2C2 binding mechanisms in relation to FOXA1 levels and binding, suggesting possible coordinate regulation of key loci. Integrating proteomic and genomic approaches, we have potentially highlighted new mechanisms of FOXA1 that could have future clinical impacts.
Project description:Estrogen Receptor-a (ER) is the key feature in the majority of breast cancers and ER binding to the genome correlates with the Forkhead protein FOXA1 (HNF3a), but mechanistic insight is lacking. We now show that FOXA1 is the defining factor that governs differential ER-chromatin interactions. We show that almost all ER-chromatin interactions and gene expression changes are dependent on the presence of FOXA1 and that FOXA1 dictates genome-wide chromatin accessibility. Furthermore, we show that CTCF is an upstream negative regulator of FOXA1-chromatin interactions. In ER responsive breast cancer cells, the dependency on FOXA1 for tamoxifen-ER activity is absolute and in tamoxifen resistant cells, ER binding occurs independently of ligand, but in a FOXA1 dependent manner. Importantly, expression of FOXA1 in non-breast cancer cells is sufficient to alter ER binding and response to endocrine treatment. As such, FOXA1 is the primary determinant that regulates estrogen-ER activity and endocrine response in breast cancer cells and is sufficient to program ER functionality in non-breast cancer contexts. FoxA1 silenced breast cancer MCF-7 cell lines or control siRNA in the presence of Estrogen or a vehicle. MCF-7 cells were hormone-depleted for 3 d and treated with 100 nM estrogen for 6 h. There were three biological replicates for each of the four different groups.
Project description:Estrogen Receptor-a (ER) is the key feature in the majority of breast cancers and ER binding to the genome correlates with the Forkhead protein FOXA1 (HNF3a), but mechanistic insight is lacking. We now show that FOXA1 is the defining factor that governs differential ER-chromatin interactions. We show that almost all ER-chromatin interactions and gene expression changes are dependent on the presence of FOXA1 and that FOXA1 dictates genome-wide chromatin accessibility. Furthermore, we show that CTCF is an upstream negative regulator of FOXA1-chromatin interactions. In ER responsive breast cancer cells, the dependency on FOXA1 for tamoxifen-ER activity is absolute and in tamoxifen resistant cells, ER binding occurs independently of ligand, but in a FOXA1 dependent manner. Importantly, expression of FOXA1 in non-breast cancer cells is sufficient to alter ER binding and response to endocrine treatment. As such, FOXA1 is the primary determinant that regulates estrogen-ER activity and endocrine response in breast cancer cells and is sufficient to program ER functionality in non-breast cancer contexts. breast cancer MCF-7 cell lines were treaated in the presence of Estrogen, Estrogen plus Tamoxifen, Tamoxifen or a vehicle. MCF-7 cells were hormone-depleted for 3 d and treated with 100 nM estrogen or 1 microM Tamoxifen for 6 h. There were four biological replicates for each of the four different groups.
Project description:Estrogen Receptor-a (ER) is the key feature in the majority of breast cancers and ER binding to the genome correlates with the Forkhead protein FOXA1 (HNF3a), but mechanistic insight is lacking. We now show that FOXA1 is the defining factor that governs differential ER-chromatin interactions. We show that almost all ER-chromatin interactions and gene expression changes are dependent on the presence of FOXA1 and that FOXA1 dictates genome-wide chromatin accessibility. Furthermore, we show that CTCF is an upstream negative regulator of FOXA1-chromatin interactions. In ER responsive breast cancer cells, the dependency on FOXA1 for tamoxifen-ER activity is absolute and in tamoxifen resistant cells, ER binding occurs independently of ligand, but in a FOXA1 dependent manner. Importantly, expression of FOXA1 in non-breast cancer cells is sufficient to alter ER binding and response to endocrine treatment. As such, FOXA1 is the primary determinant that regulates estrogen-ER activity and endocrine response in breast cancer cells and is sufficient to program ER functionality in non-breast cancer contexts.
Project description:Estrogen Receptor-a (ER) is the key feature in the majority of breast cancers and ER binding to the genome correlates with the Forkhead protein FOXA1 (HNF3a), but mechanistic insight is lacking. We now show that FOXA1 is the defining factor that governs differential ER-chromatin interactions. We show that almost all ER-chromatin interactions and gene expression changes are dependent on the presence of FOXA1 and that FOXA1 dictates genome-wide chromatin accessibility. Furthermore, we show that CTCF is an upstream negative regulator of FOXA1-chromatin interactions. In ER responsive breast cancer cells, the dependency on FOXA1 for tamoxifen-ER activity is absolute and in tamoxifen resistant cells, ER binding occurs independently of ligand, but in a FOXA1 dependent manner. Importantly, expression of FOXA1 in non-breast cancer cells is sufficient to alter ER binding and response to endocrine treatment. As such, FOXA1 is the primary determinant that regulates estrogen-ER activity and endocrine response in breast cancer cells and is sufficient to program ER functionality in non-breast cancer contexts.
Project description:Breast cancer is a heterogeneous disease comprised of at least five major subtypes. Luminal subtype tumors confer a more favourable patient prognosis, which is in part, attributed to the Estrogen Receptor-alpha (ER) positivity and anti-hormone responsiveness of these tumors. Expression of the forkhead box transcription factor, FOXA1, also correlates with the luminal subtype and patient survival, but is present in a subset of ER-negative tumors. Similarly, FOXA1 is consistently expressed in luminal breast cancer cell lines even in the absence of ER. In contrast, basal breast cancer cell lines do not express FOXA1, and loss of FOXA1 in luminal cells increases migration and invasion, characteristics of the basal subtype. To delineate an ER-independent role for FOXA1 in maintaining the luminal phenotype, and hence a more favourable prognosis, we performed cDNA microarray analyses on luminal FOXA1-positive, ER-positive (MCF7, T47D) and FOXA1-positive, ER-negative (MDA-MB-453, SKBR3) cell lines in the presence or absence of transient FOXA1 silencing. This resulted in three FOXA1 transcriptomes: (1) a luminal-signature (consistent across cell lines), (2) an ER-positive signature (restricted to MCF7 and T47D) and (3) an ER-negative signature (restricted to MDA-MB-453 and SKBR3). Use of Gene Set Enrichment Analyses (GSEA) as a phenotyping tool revealed that FOXA1 silencing resulted in a transcriptome shift from luminal to basal gene expression signatures. FOXA1 binds to both luminal and basal genes within luminal breast cancer cells, suggesting that it not only transactivates luminal genes, but also represses basal-associated genes. From these results we conclude that FOXA1 controls plasticity between basal and luminal cells, playing a dominant role in repressing the basal phenotype, and thus tumor aggressiveness, in luminal breast cancer cells. Although it has been proposed that FOXA1-targeting agents may be useful for treating luminal tumors, these data suggest that this approach may promote transitions toward a more aggressive cancer. FOXA1 siRNA treated breast cell lines compared directly to nonspecific siRNA treated cell lines using Agilent 4X44 microarrays.
Project description:The ets transcription factor ELF5 specifies the differentiation of mammary progenitor cells to establish the milk-secreting lineage. ER- and poor prognosis basal breast cancers arise from this progenitor cell and these cancers express high levels of Elf5. Knockdown of ELF5 expression in basal breast cancer cell lines, or forced expression in luminal breast cancer cell lines, resulted in reduced cell proliferation. Transcript profiling and chromatin immunoprecipitation revealed that the transcriptional activity of ELF5 specified the gene expression patterns that distinguish basal from luminal breast cancer, including suppression of FOXA1, GATA3 and ER, key estrogen-action genes. Tamoxifen treatment of luminal MCF7 cells upregulated Elf5 expression and cells that acquired resistance to Tamoxifen became dependent on ELF5 for proliferation. ELF5 is a regulator of breast cancer cell proliferation, transcriptionally specifies the basal molecular subtype and is utilised by ER+ breast cancer cells to escape proliferative arrest caused by Tamoxifen. ChIP-Seq using an antibody to ELF5, in T47D breast carcinoma cell lines
Project description:Forkhead box protein A1 (FOXA1) has been shown to have critical functions in prostate and ER alpha positive breast cancer. As a pioneering transcriptional factor, FOXA1 regulates DNA accessibility for the androgen receptor in prostate and the estrogen receptor alpha in ER positive breast cancer, respectively. FOXA1 is also expressed in human epidermal growth factor receptor-2 (HER2/ErbB2) positive breast cancers, but its functions in HER2 positive breast cancer are unclear. The loss of FOXA1 results in a decrease in the viability of HER2 positive and HER2 amplified cell lines suggesting that FOXA1 may have an important role in HER2 positive breast cancers. In this report, we examined patient-derived single-cell RNA sequencing and spatial transcriptomics data and demonstrated that FOXA1 is co-expressed with ErbB2 in HER2 positive breast cancers. Knocking down FOXA1 expression led to the reduction of HER2 expression and signaling. Chromatin Immunoprecipitation Sequencing (ChIP-seq) and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) identified FOXA1 binding motifs in the ErbB2 promoter and regulatory element regions, which controlled ErbB2 gene expression. Interestingly, the knockdown of FOXA1 increased Epithelial Mesenchymal Transition (EMT) signaling and inhibited luminal tumor differentiation. Furthermore, FOXA1 and TRPS1 regulated TEAD/YAP-TAZ activity. Taken together, our data demonstrate that FOXA1 is required for HER2 expression and luminal identity in HER2+ breast cancer.
Project description:Forkhead box protein A1 (FOXA1) has been shown to have critical functions in prostate and ER alpha positive breast cancer. As a pioneering transcriptional factor, FOXA1 regulates DNA accessibility for the androgen receptor in prostate and the estrogen receptor alpha in ER positive breast cancer, respectively. FOXA1 is also expressed in human epidermal growth factor receptor-2 (HER2/ErbB2) positive breast cancers, but its functions in HER2 positive breast cancer are unclear. The loss of FOXA1 results in a decrease in the viability of HER2 positive and HER2 amplified cell lines suggesting that FOXA1 may have an important role in HER2 positive breast cancers. In this report, we examined patient-derived single-cell RNA sequencing and spatial transcriptomics data and demonstrated that FOXA1 is co-expressed with ErbB2 in HER2 positive breast cancers. Knocking down FOXA1 expression led to the reduction of HER2 expression and signaling. Chromatin Immunoprecipitation Sequencing (ChIP-seq) and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) identified FOXA1 binding motifs in the ErbB2 promoter and regulatory element regions, which controlled ErbB2 gene expression. Interestingly, the knockdown of FOXA1 increased Epithelial Mesenchymal Transition (EMT) signaling and inhibited luminal tumor differentiation. Furthermore, FOXA1 and TRPS1 regulated TEAD/YAP-TAZ activity. Taken together, our data demonstrate that FOXA1 is required for HER2 expression and luminal identity in HER2+ breast cancer.