Project description:Approximately 20% of early-stage breast cancers display amplification or overexpression of the ErbB2/HER2 oncogene, conferring poor prognosis and resistance to endocrine therapy. Targeting HER2+ tumors with trastuzumab or the receptor tyrosine kinase (RTK) inhibitor lapatinib significantly improves survival, yet tumor resistance and progression of metastatic disease can develop over time. While the mechanisms of cytosolic HER2 signaling are well studied, nuclear signaling components and gene regulatory networks that bestow therapeutic resistance and limitless proliferative potential are incompletely understood. Here, we use biochemical and bioinformatics approaches to identify effectors and targets of HER2 transcriptional signaling in human breast cancer. Phosphorylation and activity of the Steroid Receptor Coactivator-3 (SRC-3) is reduced upon HER2 inhibition, and recruitment of SRC-3 to regulatory elements of endogenous genes is altered. Transcripts regulated by HER2 signaling are highly enriched with E2F1 binding sites and define a gene signature associated with proliferative breast tumor subtypes, cell cycle progression, and G1 to S phase transition. We show that HER2 signaling drives proliferation in breast cancer cells through regulation of E2F1-driven DNA metabolism and replication genes together with phosphorylation and activity of the transcriptional coactivator SRC-3. Furthermore, our analyses identified a cyclin dependent kinase (CDK) signaling node that, when targeted using the CDK4/6 inhibitor Palbociclib, defines cooperative signaling pathways for expression of tumorigenic gene networks. Our findings suggest this proliferative gene signature is amendable to pharmacological targeting. These results have implications for rational discovery of pharmacological combinations in pre-clinical models of adjuvant treatment and therapeutic resistance
Project description:The Epidermal Growth Factor Receptor 2 (ERBB2 or HER2) is amplified and overexpressed in approximately 20% of invasive breast cancers and is associated with metastasis and poor prognosis. Here we describe the role of a constitutively active splice variant of HER2 (Delta-HER2) in human mammary epithelial cells. Overexpression of Delta-HER2 in human mammary cells decreased apoptosis and increased proliferation and expression of epithelial-to-mesenchymal markers. It also induced invasion in three-dimensional cultures and promoted tumorigenicity and metastasis in vivo. In contrast, similar overexpression of wild-type HER2 failed to evoke the same effects. Unbiased protein-tyrosine phosphorylation profiling revealed a significant increase in phosphorylation of several key signaling proteins upon Delta-HER2 expression, some of which not previously shown to belong to the HER2 pathway. In addition, microarray analysis revealed the expression of a set of genes specifically associated with Delta-HER2 expression. We found those genes to be highly expressed in ER-negative, high grade and metastatic primary breast tumors. Altogether, these results provide new insights into the function of a tumorigenic splice variant of HER2 and the signaling cascade deriving from its activity RNA was extracted from MCF10A expressing empty vector, WT-HER2 or Delta-HER2 (n=3).
Project description:The E2F family consists of transcriptional repressors and activators that control cell proliferation. In the classic paradigm of cell cycle regulation, the three activators, E2F1, E2F2 and E2F3, are invariably depicted as the final components of a CDK/Rb signaling cascade that executes the transcriptional program necessary to commit cells to enter S phase. Unexpectedly, we find through analysis of Affymetrix expression array data that mature lens epithelial cells deficient for E2F1-3 fail to repress cell cycle-regulated genes (and other targets of E2F) and that this corresponds with subsequent apoptosis and cellular collapse in the lens. Murine lenses were collected at two stages of development for RNA extraction and hybridization on Affymetrix microarrays. Our aim was to determine key events that lead to cellular collapse of lenses triply deficient for E2F1, E2F2, and E2F3 in neonates.
Project description:The steroid co-activator protein SRC-1 plays an important role in endocrine therapy resistant breast cancer. Its expression is associated with large high grade tumours, HER2 positivity, disease recurrence and resistance to endocrine therapy. SRC-1's role in affecting the transcriptome of the breast cancer endocrine resistant setting is uncovered through this RNA-seq analysis of LY2 cells grown with or without the presence of SRC-1
Project description:<p>The HER pathway is the driving force behind 30% of human breast cancers. It is important to understand how targeted therapies block different cellular pathways, and mechanisms of escape from this blockage. Therapies directed at HER2 establish a successful treatment paradigm, but de novo and acquired resistance exist. The HER signaling system is a complex network with four receptors and eleven ligands, a phosphorylation signaling cascade, and many transcription factors, all complicated by both positive and negative feedback circuits. Analysis of genomes, exomes and transcriptomes by next generation sequencing is aimed at uncovering the genetic factors responsible for patient responses to HER2-directed therapies.</p> <p>We are sequencing HER2-overexpressing cancers, in order to identify potential somatic changes that may better select patients who will benefit from therapy, to determine new targets that may overcome resistance, and to improve outcomes with known current HER2-targeted therapies. Whole exome capture sequencing will determine somatic mutation profiles in HER2-overexpressing tumors, to comprehensively characterize the somatic alterations, with the goal of identifying those patients most likely to respond, as well as discovering new targets that may overcome resistance to HER2-directed therapy. We augment the whole exome data with RNA-seq data to determine expression levels of somatic mutations we discover. </p>
Project description:The Epidermal Growth Factor Receptor 2 (ERBB2 or HER2) is amplified and overexpressed in approximately 20% of invasive breast cancers and is associated with metastasis and poor prognosis. Here we describe the role of a constitutively active splice variant of HER2 (Delta-HER2) in human mammary epithelial cells. Overexpression of Delta-HER2 in human mammary cells decreased apoptosis and increased proliferation and expression of epithelial-to-mesenchymal markers. It also induced invasion in three-dimensional cultures and promoted tumorigenicity and metastasis in vivo. In contrast, similar overexpression of wild-type HER2 failed to evoke the same effects. Unbiased protein-tyrosine phosphorylation profiling revealed a significant increase in phosphorylation of several key signaling proteins upon Delta-HER2 expression, some of which not previously shown to belong to the HER2 pathway. In addition, microarray analysis revealed the expression of a set of genes specifically associated with Delta-HER2 expression. We found those genes to be highly expressed in ER-negative, high grade and metastatic primary breast tumors. Altogether, these results provide new insights into the function of a tumorigenic splice variant of HER2 and the signaling cascade deriving from its activity
Project description:The E2F family consists of transcriptional repressors and activators that control cell proliferation. In the classic paradigm of cell cycle regulation, the three activators, E2F1, E2F2 and E2F3, are invariably depicted as the final components of a CDK/Rb signaling cascade that executes the transcriptional program necessary to commit cells to enter S phase. Unexpectedly, we find through analysis of Affymetrix expression array data that mature lens epithelial cells deficient for E2F1-3 fail to repress cell cycle-regulated genes (and other targets of E2F) and that this corresponds with subsequent apoptosis and cellular collapse in the lens.
Project description:Upon G1-S transition, cyclin-dependent kinases (CDKs) phosphorylate the retinoblastoma tumor suppressor protein (pRB) to release E2F transcription factors, which activate transcriptional programs, required for S-phase entry. Beyond the G1-S transition, pRB activity remains poorly understood. Our lab has discovered that pRB retains exclusive binding to E2F1 through an alternate E2F1-‘specific’ binding site at the pRB c-terminus independent of CDK phosphorylation. We have developed a gene-targeted mouse model that is defective for the E2F1-‘specific’ interaction. We are exploring the function of this complex through genome-wide binding and expression profiling. Overall, this work suggests an alternate pRB-E2F1 complex persists independent of CDK phosphorylation to establish regions of constitutive heterochromatin.
Project description:Upon G1-S transition, cyclin-dependent kinases (CDKs) phosphorylate the retinoblastoma tumor suppressor protein (pRB) to release E2F transcription factors, which activate transcriptional programs, required for S-phase entry. Beyond the G1-S transition, pRB activity remains poorly understood. Our lab has discovered that pRB retains exclusive binding to E2F1 through an alternate E2F1-‘specific’ binding site at the pRB c-terminus independent of CDK phosphorylation. We have developed a gene-targeted mouse model that is defective for the E2F1-‘specific’ interaction. We are exploring the function of this complex through genome-wide binding and expression profiling. Overall, this work suggests an alternate pRB-E2F1 complex persists independent of CDK phosphorylation to establish regions of constitutive heterochromatin