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Effect of knockdown of CtBP proteins on gene expression in MCF7 breast cancer cells, under normoxia and hypoxia

ABSTRACT: Regulation of gene expression by the CtBP family of NADH-sensitive transcriptional regulators, in MCF7 cells under normoxia and hypoxia. To determine the effect of CtBP knockdown on gene expression in MCF7 we transfected cells with an siRNA (5′-GGGAGGACCUGGAGAAGUUdTdT-3′/3′-dTdTCCCUCCUGGACCUCUUCAA-5′, obtained from Ambion) targetting both CtBP1 and CtBP2 (versus control siRNA). After 48 hours cells were either transferred to a hypoxic chamber (1% oxygen), or maintained in normoxia, for 18 hours.

ORGANISM(S): Homo sapiens

PROVIDER: GSE111259 | GEO | 2021/02/01

REPOSITORIES: GEO

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Project description:Pancreatic ductal adenocarcinoma (PDAC) remains among the most lethal of human cancers underscoring the need to identify new therapeutic vulnerabilities. Previously, we reported high expression of transcriptional co-regulators C-terminal binding proteins (CtBP) 1 and 2 in human PDAC, however their precise role in PDAC formation or progression remains unclear. Here, we have studied PDAC tumor dependency on CtBPs for growth and metastasis using an orthotopic syngeneic pancreatic tumor mouse model. CRISPR-based homozygous deletion of Ctbp2 dramatically decreased PDAC tumor growth, drastically reduced metastatic potential, and significantly prolonged survival. Interrogating differential gene expression of the orthotopic PDAC tumors from CtBP2 WT vs. CtBP2 KO cohorts, we identified significant downregulation of the EGFR-superfamily receptor ErbB3 in CtBP2 KO tumors, and further determined that CtBP regulates expression of both the ErbB2 and 3 EGFR superfamily genes in PDAC cells. We therefore hypothesized that CtBP regulation of physiologic ErbB2/3 signaling contributes, in part, to PDAC growth and metastasis. Indeed, we observed that CtBP2 KO cells exhibited severely attenuated activation of phospho-Akt after neuregulin stimulation of ErbB2/3, and we demonstrate that human PDAC cells also show CtBP dependence of ErbB2/3 expression. Our results suggest that a subset of PDAC tumors is dependent on physiologic ErbB2/3 signaling and could be targeted by pharmacologic inhibitors of ErbB2 and/or ErbB3. Providing proof of concept, the ErbB2-targeted multikinase inhibitor lapatinib, but not the ErbB1/EGFR targeted agent erlotinib, effectively killed ErbB3 expressing PDAC cells, while CtBP2 KO cells where ErbB3 expression was extinguished, were resistant to lapatinib. Taken together, our data suggests that ErBb2/3 targeted therapeutics can effectively target a critical PDAC dependency on physiologic ErbB2/3 signaling which is the result of CtBP’s oncogenic transcriptional program that drives PDAC tumor progression.

Project description:Branching from conduits is a defining feature of the gas delivery systems of invertebrates (tracheae built from epithelial cells) and vertebrates (vasculature lined by endothelial cells). Here, we show that the vertebrate transcriptional repressor Tel plays an evolutionarily conserved role in angiogenesis: it is indispensable for sprouting of primary human endothelial cells and for the normal development of the Danio rerio embryo blood circulatory system. Tel controls endothelial sprouting via binding to the generic co-repressor C-terminal binding protein (CtBP). In endothelial cells, the Tel:CtBP complex temporally restricts a VEGF-mediated pulse of dll4 expression and consequently integrates VEGFR intracellular signaling and intercellular Notch-Dll4 signaling. It further refines branching by regulating expression of other factors that constrain angiogenesis such as sprouty family members and ve-cadherin. Thus, the Tel:CtBP complex moderates the balance between positive and antagonistic angiogenesis cues and thereby conditions endothelial cells for angiogenesis. Since the activity of CtBP is attuned to intracellular NADH levels, our results raise the possibility that Tel-mediated sprouting could be sensitized to the metabolic status of the tissue. Tel control of branching appears to be evolutionarily conserved since Yan, the invertebrate orthologue of Tel, is similarly required for branching morphogenesis of the invertebrate tracheae. Collectively, our work suggests that Tel is a central regulator of angiogenesis and highlights Tel and its associated networks as potential targets for the development of therapeutic strategies to inhibit pathological angiogenesis. 2 independent screens were performed testing effects of knockdown of Tel or CtBP (screen 1) or effects of VEGF-A (screen 2) on Human Umbilical Vein Endothelial Cells (HUVECs). For screen 1 we tested 3 different conditions. We established stable HUVEC cell lines which were either infected with control lentivirus (Mock), or lentivirus expressing short hairpin RNA constructs for the specific knockdown of Tel(Teli) or CtBP2 (CtBP2i). Expression in the Teli and CtBP2i cell lines was compared to expression in the Mock cell line for screen 1. For screen 2 we tested 2 conditions. We exposed HUVECs to VEGF (50ng/mL) for 30 minutes (samplename: VEGF30) and compared the transcriptome of these cells to untreated HUVECs (VEGF0). For each condition 2 independent repeats were analyzed and expression of genes was averaged for each repeat. HUVECs were grown under standard conditions (37degrees Celsius, 5% CO2) in EGM2 medium (Lonza).

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Effect of knockdown of CtBP proteins on gene expression in MCF7 breast cancer cells, under normoxia and hypoxia

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