Project description:Effect of PBX1 silencing on global gene expression of MCF7 cells stimulated with estradiol. The hypothesis tested was that PBX1 is essential for estrogen signaling in ERa positive breast cancer cells. Total RNA was obtained from MCF7 cells treated with siRNA directed at PBX1 or an siControl for 72h. Cells were then stimulated with estradiol (E2) for 3h prior to RNA extraction.
Project description:This SuperSeries is composed of the following subset Series: GSE28006: The pioneer factor PBX1 guides a distinct ERa signaling in breast cancer [mRNA profiling] GSE28007: The pioneer factor PBX1 guides a distinct ERa signaling in breast cancer [ChIP-seq] Refer to individual Series
Project description:Effect of PBX1 silencing on global gene expression of MCF7 cells stimulated with estradiol. The hypothesis tested was that PBX1 is essential for estrogen signaling in ERa positive breast cancer cells. Total RNA was obtained from MCF7 cells treated with siRNA directed at PBX1 or an siControl for 72h. Cells were then stimulated with estradiol (E2) for 3h prior to RNA extraction.
Project description:We profiled global PBX1 binding in MCF7 cells. The hypothesis tested was that PBX1 binds regions that recruit ERa following estradiol stimulation. Profiling of PBX1 cistrome in MCF7 breast cancer cells
Project description:We profiled global PBX1 binding in MCF7 cells. The hypothesis tested was that PBX1 binds regions that recruit ERa following estradiol stimulation.
Project description:Effect of PBX1 silencing on global gene expression of MCF7 cells stimulated with estradiol. The hypothesis tested was that PBX1 is essential for estrogen signaling in ERa positive breast cancer cells.
Project description:Altered transcriptional programs are a hallmark of diseases, yet how these are established is still ill-defined. PBX1 is a TALE homeodomain protein involved in the development of different types of cancers. The estrogen receptor alpha (ER?) is central to the development of two-thirds of all breast cancers. Here we demonstrate that PBX1 acts as a pioneer factor and is essential for the ER?-mediated transcriptional response driving aggressive tumors in breast cancer. Indeed, PBX1 expression correlates with ER? in primary breast tumors, and breast cancer cells depleted of PBX1 no longer proliferate following estrogen stimulation. Profiling PBX1 recruitment and chromatin accessibility across the genome of breast cancer cells through ChIP-seq and FAIRE-seq reveals that PBX1 is loaded and promotes chromatin openness at specific genomic locations through its capacity to read specific epigenetic signatures. Accordingly, PBX1 guides ER? recruitment to a specific subset of sites. Expression profiling studies demonstrate that PBX1 controls over 70% of the estrogen response. More importantly, the PBX1-dependent transcriptional program is associated with poor-outcome in breast cancer patients. Correspondingly, PBX1 expression alone can discriminate a priori the outcome in ER?-positive breast cancer patients. These features are markedly different from the previously characterized ER?-associated pioneer factor FoxA1. Indeed, PBX1 is the only pioneer factor identified to date that discriminates outcome such as metastasis in ER?-positive breast cancer patients. Together our results reveal that PBX1 is a novel pioneer factor defining aggressive ER?-positive breast tumors, as it guides ER? genomic activity to unique genomic regions promoting a transcriptional program favorable to breast cancer progression.
Project description:Over 30% of ERα breast cancer patients develop relapses and progress to metastatic disease despite treatment with endocrine therapies. The pioneer factor PBX1 translates epigenetic cues and mediates estrogen induced ERα binding. Here we demonstrate that PBX1 plays a central role in regulating the ERα transcriptional response to epidermal growth factor (EGF) signaling. PBX1 regulates a subset of EGF-ERα genes highly expressed in aggressive breast tumours. Retrospective stratification of luminal patients using PBX1 protein levels in primary cancer further demonstrates that elevated PBX1 protein levels correlate with earlier metastatic progression. In agreement, PBX1 protein levels are significantly upregulated during metastatic progression in ERα-positive breast cancer patients. Finally we reveal that PBX1 upregulation in aggressive tumours is partly mediated by genomic amplification of the PBX1 locus. Correspondingly, ERα-positive breast cancer patients carrying PBX1 amplification are characterized by poor survival. Notably, we demonstrate that PBX1 amplification can be identified in tumor derived-circulating free DNA of ERα-positive metastatic patients. Metastatic patients with PBX1 amplification are also characterized by shorter relapse-free survival. Our data identifies PBX1 amplification as a functional hallmark of aggressive ERα-positive breast cancers. Mechanistically, PBX1 amplification impinges on several critical pathways associated with aggressive ERα-positive breast cancer.