Project description:The estrogen receptor alpha (ERa) drives the growth of two-thirds of all breast cancers. Endocrine therapy impinges on estrogen-induced ERa activation to block tumor growth. However, half of ERa-positive breast cancers are tolerant or acquire endocrine therapy resistance. Here we demonstrate that breast cancer cells undergo genome-wide reprogramming of their chromatin landscape, defined by epigenomic maps and chromatin openness, as they acquire resistance to endocrine therapy. This reveals a role for the Notch pathway while excluding classical ERa signaling. In agreement, blocking Notch signaling, using gamma-secretase inhibitors, or targeting its downstream gene PBX1 abrogates growth of endocrine therapy-resistant breast cancer cells. Moreover Notch signaling through PBX1 directs a transcriptional program predictive of tumor outcome and endocrine therapy response. Comparing histone modifications (H3K4me2 and H3K36me3), chromatin openness (FAIRE) and PBX1 binding between endocrine therapy sensitive MCF7 and resistant MCF7-LTED cells.
Project description:The estrogen receptor alpha (ERa) drives the growth of two-thirds of all breast cancers. Endocrine therapy impinges on estrogen-induced ERa activation to block tumor growth. However, half of ERa-positive breast cancers are tolerant or acquire endocrine therapy resistance. Here we demonstrate that breast cancer cells undergo genome-wide reprogramming of their chromatin landscape, defined by epigenomic maps and chromatin openness, as they acquire resistance to endocrine therapy. This reveals a role for the Notch pathway while excluding classical ERa signaling. In agreement, blocking Notch signaling, using gamma-secretase inhibitors, or targeting its downstream gene PBX1 abrogates growth of endocrine therapy-resistant breast cancer cells. Moreover Notch signaling through PBX1 directs a transcriptional program predictive of tumor outcome and endocrine therapy response.
Project description:Expression of estrogen receptor (ESR1) determines whether a breast cancer patient receives endocrine therapy as part of their adjuvant care, but does not guarantee patient response. However, the molecular factors that define endocrine response in ESR1-positive breast cancer patients remain poorly understood. Here, we characterize the DNA methylome of endocrine sensitivity and demonstrate the potential impact of differential DNA methylation on endocrine response in breast cancer. We show that DNA hypermethylation occurs predominantly at estrogen-responsive enhancers and is associated with reduced ESR1 binding and decreased gene expression of key regulators of ESR1-activity; thus providing a novel mechanism by which endocrine response is abated in ESR1-positive breast cancers. Conversely, we delineate that ESR1-responsive enhancer hypomethylation is critical in transition from normal mammary epithelial cells to endocrine responsive ESR1-positive cancer. Cumulatively these novel insights highlight the potential of ESR1-responsive enhancer methylation to both predict ESR1-positive disease and stratify ESR1-positive breast cancer patients as responders to endocrine therapy. Methylation profiling with Illumina's HumanMethylation450K array was performed on ESR1-positive hormone sensitive MCF7 cells, and three different well characterised endocrine resistant MCF7-derived cell lines; tamoxifen-resistant (TAMR), fulvestrant-resistant (FASR) and estrogen deprivation resistant (MCF7X) cells. For each cell line two biological replicates were profiled bringing the number of samples to eight.
Project description:Expression profile of the endocrine therapy resistant breast cancer cells LTED depleted of PBX1 or treated with the gamma-secretase inhibitor MRK003
Project description:Analysis of the response to PBX1 deprivation either using an siRNA approach or using a chemicalcompound indirectly targeting it. Deprivation of PBX1 is hypothesized to be essential for the growth of endocrine therapy resistant breast cancer cells (LTED)
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:Analysis of the response to PBX1 deprivation either using an siRNA approach or using a chemicalcompound indirectly targeting it. Deprivation of PBX1 is hypothesized to be essential for the growth of endocrine therapy resistant breast cancer cells (LTED) Total RNA was obtained from cells treated with siPBX1 or a control siRNA. The second set contains RNA from cells treated with MRK003 or a control (DMSO).
Project description:Effect of PBX1 silencing on global gene expression of MCF7 cells stimulated with EGF. The hypothesis tested was that PBX1 is essential for EGF signaling in ERa positive breast cancer cells.
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:Estrogen receptor alpha plays a critical role in breast cancer and is a major target in endocrine therapy. HIF-1 alpha have been associated with ER alpha and predict a worse outcome. Recent studies indicate that histone demethylase JMJD2B is a HIF-1 alpha target. However, little is known about the biological functions of JMJD2B, especially in breast cancer. To elucidate the mechanism by which JMJD2B reguates gene expression in normoxia and hypoxia, MCF-7 breast cancer cells were depleted forJMJD2B in normoxia and hypoxia. Our results provide insight into JMJD2B regulation of gene expression in breast cancer cells in normoxia and hypoxia. MCF7 cells were subjected to transfection with siRNA controls and two different siRNA oligos against JMJD2B for 24 hours. Cells were treated in normoxia and hypoxia for another 16 hours.
