Publications by authors named "Ivan Stamenkovic"

59 Publications

Ewing's Sarcoma.

N Engl J Med 2021 01;384(2):154-164

From the Institute of Pathology, Faculty of Biology and Medicine, University of Lausanne and Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland (N.R., I.S.); and the Department of Pathology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, and the Broad Institute of Harvard University and the Massachusetts Institute of Technology, Cambridge - both in Massachusetts (M.L.S.).

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http://dx.doi.org/10.1056/NEJMra2028910DOI Listing
January 2021

Opposing immune and genetic mechanisms shape oncogenic programs in synovial sarcoma.

Nat Med 2021 02 25;27(2):289-300. Epub 2021 Jan 25.

Broad Institute of Harvard and MIT, Cambridge, MA, USA.

Synovial sarcoma (SyS) is an aggressive neoplasm driven by the SS18-SSX fusion, and is characterized by low T cell infiltration. Here, we studied the cancer-immune interplay in SyS using an integrative approach that combines single-cell RNA sequencing (scRNA-seq), spatial profiling and genetic and pharmacological perturbations. scRNA-seq of 16,872 cells from 12 human SyS tumors uncovered a malignant subpopulation that marks immune-deprived niches in situ and is predictive of poor clinical outcomes in two independent cohorts. Functional analyses revealed that this malignant cell state is controlled by the SS18-SSX fusion, is repressed by cytokines secreted by macrophages and T cells, and can be synergistically targeted with a combination of HDAC and CDK4/CDK6 inhibitors. This drug combination enhanced malignant-cell immunogenicity in SyS models, leading to induced T cell reactivity and T cell-mediated killing. Our study provides a blueprint for investigating heterogeneity in fusion-driven malignancies and demonstrates an interplay between immune evasion and oncogenic processes that can be co-targeted in SyS and potentially in other malignancies.
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http://dx.doi.org/10.1038/s41591-020-01212-6DOI Listing
February 2021

The chromatin landscape of primary synovial sarcoma organoids is linked to specific epigenetic mechanisms and dependencies.

Life Sci Alliance 2021 02 23;4(2). Epub 2020 Dec 23.

Institute of Pathology, Centre Hospitalier Universitaire Vaudois, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland

Synovial sarcoma (SyS) is an aggressive mesenchymal malignancy invariably associated with the chromosomal translocation t(X:18; p11:q11), which results in the in-frame fusion of the BAF complex gene to one of three genes. Fusion of SS18 to SSX generates an aberrant transcriptional regulator, which, in permissive cells, drives tumor development by initiating major chromatin remodeling events that disrupt the balance between BAF-mediated gene activation and polycomb-dependent repression. Here, we developed SyS organoids and performed genome-wide epigenomic profiling of these models and mesenchymal precursors to define SyS-specific chromatin remodeling mechanisms and dependencies. We show that SS18-SSX induces broad BAF domains at its binding sites, which oppose polycomb repressor complex (PRC) 2 activity, while facilitating recruitment of a non-canonical (nc)PRC1 variant. Along with the uncoupling of polycomb complexes, we observed H3K27me3 eviction, H2AK119ub deposition and the establishment of de novo active regulatory elements that drive SyS identity. These alterations are completely reversible upon SS18-SSX depletion and are associated with vulnerability to USP7 loss, a core member of ncPRC1.1. Using the power of primary tumor organoids, our work helps define the mechanisms of epigenetic dysregulation on which SyS cells are dependent.
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http://dx.doi.org/10.26508/lsa.202000808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7768195PMC
February 2021

Attenuation of the pro-inflammatory signature of lung cancer-derived mesenchymal stromal cells by statins.

Cancer Lett 2020 08 8;484:50-64. Epub 2020 May 8.

Experimental Pathology Service, Institute of Pathology, CHUV, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 25, 1011, Lausanne, Switzerland.

Solid tumor growth triggers a dynamic host response, which recapitulates wound healing and defines the tumor microenvironment (TME). In addition to the action of the tumor cells themselves, the TME is maintained by a myriad of immune and stromal cell-derived soluble mediators and extracellular matrix components whose combined action supports tumor progression. However, therapeutic targeting of the TME has proven challenging because of incomplete understanding of the tumor-host crosstalk at the molecular level. Here, we investigated the crosstalk between mesenchymal stromal cells (MSCs) and primary cancer cells (PCCs) from human squamous cell lung carcinoma (SCC). We discovered that PCCs secrete CCL3 and stimulate IL-6, CCL2, ICAM-1 and VCAM-1 expression in MSCs and that the MSC-PCC crosstalk can be disrupted by the lipid-lowering drug simvastatin, which displays pleiotropic effects on cell metabolism and suppresses IL-6 and CCL2 production by MSCs and CCL3 secretion by PCCs. In addition, simvastatin inhibited spheroid formation by PCCs and negatively affected PCC survival. Our observations demonstrate that commonly used statins may be repurposed to target the TME in lung carcinoma.
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http://dx.doi.org/10.1016/j.canlet.2020.05.005DOI Listing
August 2020

LIN28B Underlies the Pathogenesis of a Subclass of Ewing Sarcoma LIN28B Control of EWS-FLI1 Stability.

Cell Rep 2020 03;30(13):4567-4583.e5

Experimental Pathology Service, Centre Hospitalier Universitaire Vaudois, University of Lausanne, 1011 Lausanne, Switzerland. Electronic address:

Ewing sarcoma (EwS) is associated with poor prognosis despite current multimodal therapy. Targeting of EWS-FLI1, the fusion protein responsible for its pathogenesis, and its principal downstream targets has not yet produced satisfactory therapeutic options, fueling the search for alternative approaches. Here, we show that the oncofetal RNA-binding protein LIN28B regulates the stability of EWS-FLI1 mRNA in ~10% of EwSs. LIN28B depletion in these tumors leads to a decrease in the expression of EWS-FLI1 and its direct transcriptional network, abrogating EwS cell self-renewal and tumorigenicity. Moreover, pharmacological inhibition of LIN28B mimics the effect of LIN28B depletion, suggesting that LIN28B sustains the emergence of a subset of EwS in which it also serves as an effective therapeutic target.
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http://dx.doi.org/10.1016/j.celrep.2019.12.053DOI Listing
March 2020

Mesenchymal stromal cells in cancer: a review of their immunomodulatory functions and dual effects on tumor progression.

J Pathol 2020 04 18;250(5):555-572. Epub 2019 Dec 18.

Laboratory of Experimental Pathology, Institute of Pathology, CHUV, Lausanne, Switzerland.

Mesenchymal stem or stromal cells (MSCs) are pluripotent cells implicated in a broad range of physiological events, including organogenesis and maintenance of tissue homeostasis as well as tissue regeneration and repair. Because their current definition is somewhat loose - based primarily on their ability to differentiate into a variety of mesenchymal tissues, adhere to plastic, and express, or lack, a handful of cell surface markers - MSCs likely encompass several subpopulations, which may have diverse properties. Their diversity may explain, at least in part, the pleiotropic functions that they display in different physiological and pathological settings. In the context of tissue injury, MSCs can respectively promote and attenuate inflammation during the early and late phases of tissue repair. They may thereby act as sensors of the inflammatory response and secrete mediators that boost or temper the response as required by the stage of the reparatory and regenerative process. MSCs are also implicated in regulating tumor development, in which they are increasingly recognized to play a complex role. Thus, MSCs can both promote and constrain tumor progression by directly affecting tumor cells via secreted mediators and cell-cell interactions and by modulating the innate and adaptive immune response. This review summarizes our current understanding of MSC involvement in tumor development and highlights the mechanistic underpinnings of their implication in tumor growth and progression. © 2020 Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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http://dx.doi.org/10.1002/path.5357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7217065PMC
April 2020

An Integrative Model of Cellular States, Plasticity, and Genetics for Glioblastoma.

Cell 2019 08 18;178(4):835-849.e21. Epub 2019 Jul 18.

Department of Pathology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02114, USA; Klarman Cell Observatory, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA. Electronic address:

Diverse genetic, epigenetic, and developmental programs drive glioblastoma, an incurable and poorly understood tumor, but their precise characterization remains challenging. Here, we use an integrative approach spanning single-cell RNA-sequencing of 28 tumors, bulk genetic and expression analysis of 401 specimens from the The Cancer Genome Atlas (TCGA), functional approaches, and single-cell lineage tracing to derive a unified model of cellular states and genetic diversity in glioblastoma. We find that malignant cells in glioblastoma exist in four main cellular states that recapitulate distinct neural cell types, are influenced by the tumor microenvironment, and exhibit plasticity. The relative frequency of cells in each state varies between glioblastoma samples and is influenced by copy number amplifications of the CDK4, EGFR, and PDGFRA loci and by mutations in the NF1 locus, which each favor a defined state. Our work provides a blueprint for glioblastoma, integrating the malignant cell programs, their plasticity, and their modulation by genetic drivers.
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http://dx.doi.org/10.1016/j.cell.2019.06.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6703186PMC
August 2019

Synovial sarcoma: when epigenetic changes dictate tumour development.

Swiss Med Wkly 2018 11 2;148:w14667. Epub 2018 Dec 2.

Experimental Pathology Service, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.

Synovial sarcoma is a highly aggressive soft tissue malignancy that often affects adolescents and young adults. It is associated with a unique chromosomal translocation that results in the formation and expression of the fusion gene SS18-SSX, which underlies its pathogenesis. Although SS18-SSX provides a potentially unique therapeutic target, all attempts to neutralise it have been unsuccessful thus far. When complete surgical removal of the tumour fails, therapy is limited to largely ineffective cytotoxic drug regimens. Nevertheless, recent discoveries about the mechanisms of SS18-SSX protein function have provided insight into potential alternative therapeutic strategies. SS18-SSX displays oncogenic activity through protein-protein interactions and participation in chromatin remodelling complexes. This review summarises our current understanding of the function of SS18-SSX and the mechanisms by which it alters the epigenetic landscape of permissive cells to induce transformation and the subsequent development of synovial sarcoma.
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http://dx.doi.org/10.4414/smw.2018.14667DOI Listing
November 2018

Epigenome editing of microsatellite repeats defines tumor-specific enhancer functions and dependencies.

Genes Dev 2018 08 24;32(15-16):1008-1019. Epub 2018 Jul 24.

Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.

Various types of repetitive sequences are dysregulated in cancer. In Ewing sarcoma, the oncogenic fusion protein EWS-FLI1 induces chromatin features typical of active enhancers at GGAA microsatellite repeats, but the function of these sites has not been directly demonstrated. Here, by combining nascent transcription profiling with epigenome editing, we found that a subset of GGAA microsatellite repeats is transcriptionally active in Ewing sarcoma and that silencing individual repeats abolishes local nascent transcription and leads to markedly reduced expression of putative target genes. Epigenome silencing of these repeat sites does not affect gene expression in unrelated cells, can prevent the induction of gene expression by EWS-FLI1, and, in the case of a GGAA repeat that controls expression from a distance of 470 kb, is sufficient to impair the growth of Ewing sarcoma xenografts. Using an experimental approach that is broadly applicable to testing different types of repetitive genomic elements, our study directly demonstrates that specific repeat microsatellites can have critical gene regulation functions in cancer and thus represent tumor-specific vulnerabilities that may be exploited to develop new therapies.
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http://dx.doi.org/10.1101/gad.315192.118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6075149PMC
August 2018

Reciprocal modulation of mesenchymal stem cells and tumor cells promotes lung cancer metastasis.

EBioMedicine 2018 Mar 23;29:128-145. Epub 2018 Feb 23.

Experimental Pathology Service, CHUV and University of Lausanne, 1011, Switzerland. Electronic address:

Metastasis is a multi-step process in which direct crosstalk between cancer cells and their microenvironment plays a key role. Here, we assessed the effect of paired tumor-associated and normal lung tissue mesenchymal stem cells (MSCs) on the growth and dissemination of primary human lung carcinoma cells isolated from the same patients. We show that the tumor microenvironment modulates MSC gene expression and identify a four-gene MSC signature that is functionally implicated in promoting metastasis. We also demonstrate that tumor-associated MSCs induce the expression of genes associated with an aggressive phenotype in primary lung cancer cells and selectively promote their dissemination rather than local growth. Our observations provide insight into mechanisms by which the stroma promotes lung cancer metastasis.
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http://dx.doi.org/10.1016/j.ebiom.2018.02.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5925622PMC
March 2018

Cancer Metastasis: A Reappraisal of Its Underlying Mechanisms and Their Relevance to Treatment.

Annu Rev Pathol 2018 01 25;13:117-140. Epub 2017 Oct 25.

Experimental Pathology Service, Centre Hospitalier Universitaire Vaudois, University of Lausanne, CH-1005 Lausanne, Switzerland; email:

Metastases are responsible for the vast majority of cancer-related deaths, but, despite intense efforts to understand their underlying mechanisms with the goal of uncovering effective therapeutic targets, treatment of metastatic cancer has progressed minimally. In this review, we examine the biological programs currently proposed to be key drivers of metastasis. On the basis of evidence from a growing body of research, we discuss to what extent the cellular and molecular mechanisms that are suggested to underlie cancer cell dissemination are specific to the metastatic process, as opposed to representing natural primary tumor progression. Our review highlights the contrast between the abundance of insight gained into the events that constitute the metastatic cascade and the paucity of therapeutic options.
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http://dx.doi.org/10.1146/annurev-pathol-020117-044127DOI Listing
January 2018

Tumor-Derived Mesenchymal Stem Cells Use Distinct Mechanisms to Block the Activity of Natural Killer Cell Subsets.

Cell Rep 2017 Sep;20(12):2891-2905

Experimental Pathology Service, Institute of Pathology, CHUV, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 25, 1011 Lausanne, Switzerland. Electronic address:

Mesenchymal stem cells (MSCs) display pleiotropic functions, which include secretion of soluble factors with immunosuppressive activity implicated in cancer progression. We compared the immunomodulatory effects on natural killer (NK) cells of paired intratumor (T)- and adjacent non-tumor tissue (N)-derived MSCs from patients with squamous cell lung carcinoma (SCC). We observed that T-MSCs were more strongly immunosuppressive than N-MSCs and affected both NK function and phenotype, as defined by CD56 expression. T-MSCs shifted NK cells toward the CD56 phenotype and differentially modulated CD56 subset functions. Whereas MSCs affected both degranulation and activating receptor expression in the CD56 subset, they primarily inhibited interferon-γ production in the CD56 subset. Pharmacological inhibition of prostaglandin E2 (PGE2) synthesis and, in some MSCs, interleukin-6 (IL-6) activity restored NK function, whereas NK cell stimulation by PGE2 alone mimicked T-MSC-mediated immunosuppression. Our observations provide insight into how stromal responses to cancer dampen NK cell activity in human lung SCC.
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http://dx.doi.org/10.1016/j.celrep.2017.08.089DOI Listing
September 2017

Cancer-Specific Retargeting of BAF Complexes by a Prion-like Domain.

Cell 2017 Sep 24;171(1):163-178.e19. Epub 2017 Aug 24.

Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA. Electronic address:

Alterations in transcriptional regulators can orchestrate oncogenic gene expression programs in cancer. Here, we show that the BRG1/BRM-associated factor (BAF) chromatin remodeling complex, which is mutated in over 20% of human tumors, interacts with EWSR1, a member of a family of proteins with prion-like domains (PrLD) that are frequent partners in oncogenic fusions with transcription factors. In Ewing sarcoma, we find that the BAF complex is recruited by the EWS-FLI1 fusion protein to tumor-specific enhancers and contributes to target gene activation. This process is a neomorphic property of EWS-FLI1 compared to wild-type FLI1 and depends on tyrosine residues that are necessary for phase transitions of the EWSR1 prion-like domain. Furthermore, fusion of short fragments of EWSR1 to FLI1 is sufficient to recapitulate BAF complex retargeting and EWS-FLI1 activities. Our studies thus demonstrate that the physical properties of prion-like domains can retarget critical chromatin regulatory complexes to establish and maintain oncogenic gene expression programs.
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http://dx.doi.org/10.1016/j.cell.2017.07.036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6791823PMC
September 2017

IMPs: an RNA-binding protein family that provides a link between stem cell maintenance in normal development and cancer.

Genes Dev 2016 11;30(22):2459-2474

Experimental Pathology Service, Centre Hospitalier Universitaire Vaudois/University of Lausanne, Lausanne CH-1011, Switzerland.

IMPs, also known as insulin-like growth factor 2 (IGF2) messenger RNA (mRNA)-binding proteins (IGF2BPs), are highly conserved oncofetal RNA-binding proteins (RBPs) that regulate RNA processing at several levels, including localization, translation, and stability. Three mammalian IMP paralogs (IMP1-3) have been identified that are expressed in most organs during embryogenesis, where they are believed to play an important role in cell migration, metabolism, and stem cell renewal. Whereas some IMP2 expression is retained in several adult mouse organs, IMP1 and IMP3 are either absent or expressed at very low levels in most tissues after birth. However, all three paralogs can be re-expressed upon malignant transformation and are found in a broad range of cancer types where their expression often correlates with poor prognosis. IMPs appear to resume their physiological functions in malignant cells, which not only contribute to tumor progression but participate in the establishment and maintenance of tumor cell hierarchies. This review summarizes our current understanding of the functions of IMPs during normal development and focuses on a series of recent observations that have provided new insight into how their physiological functions enable IMPs to play a potentially key role in cancer stem cell maintenance and tumor growth.
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http://dx.doi.org/10.1101/gad.287540.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5159662PMC
November 2016

The RNA Binding Protein IMP2 Preserves Glioblastoma Stem Cells by Preventing let-7 Target Gene Silencing.

Cell Rep 2016 05 12;15(8):1634-47. Epub 2016 May 12.

Division of Experimental Pathology, Institute of Pathology, CHUV, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 25, 1011 Lausanne, Switzerland. Electronic address:

Cancer stem cells (CSCs) can drive tumor growth, and their maintenance may rely on post-transcriptional regulation of gene expression, including that mediated by microRNAs (miRNAs). The let-7 miRNA family has been shown to induce differentiation by silencing stem cell programs. Let-7-mediated target gene suppression is prevented by LIN28A/B, which reduce let-7 biogenesis in normal embryonic and some cancer stem cells and ensure maintenance of stemness. Here, we find that glioblastoma stem cells (GSCs) lack LIN28 and express both let-7 and their target genes, suggesting LIN28-independent protection from let-7 silencing. Using photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP), we show that insulin-like growth factor 2 mRNA-binding protein 2 (IMP2) binds to let-7 miRNA recognition elements (MREs) and prevents let-7 target gene silencing. Our observations define the RNA-binding repertoire of IMP2 and identify a mechanism whereby it supports GSC and neural stem cell specification.
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http://dx.doi.org/10.1016/j.celrep.2016.04.086DOI Listing
May 2016

The fusion protein SS18-SSX1 employs core Wnt pathway transcription factors to induce a partial Wnt signature in synovial sarcoma.

Sci Rep 2016 Feb 24;6:22113. Epub 2016 Feb 24.

Institute of Pathology University of Lausanne and CHUV Lausanne, Switzerland.

Expression of the SS18/SYT-SSX fusion protein is believed to underlie the pathogenesis of synovial sarcoma (SS). Recent evidence suggests that deregulation of the Wnt pathway may play an important role in SS but the mechanisms whereby SS18-SSX might affect Wnt signaling remain to be elucidated. Here, we show that SS18/SSX tightly regulates the elevated expression of the key Wnt target AXIN2 in primary SS. SS18-SSX is shown to interact with TCF/LEF, TLE and HDAC but not β-catenin in vivo and to induce Wnt target gene expression by forming a complex containing promoter-bound TCF/LEF and HDAC but lacking β-catenin. Our observations provide a tumor-specific mechanistic basis for Wnt target gene induction in SS that can occur in the absence of Wnt ligand stimulation.
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http://dx.doi.org/10.1038/srep22113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4764983PMC
February 2016

Recruitment of Matrix Metalloproteinase-9 (MMP-9) to the Fibroblast Cell Surface by Lysyl Hydroxylase 3 (LH3) Triggers Transforming Growth Factor-β (TGF-β) Activation and Fibroblast Differentiation.

J Biol Chem 2015 May 30;290(22):13763-78. Epub 2015 Mar 30.

From the Division of Experimental Pathology, Institute of Pathology, CHUV, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 25, Lausanne CH1011, Switzerland

Solid tumor growth triggers a wound healing response. Similar to wound healing, fibroblasts in the tumor stroma differentiate into myofibroblasts (also referred to as cancer-associated fibroblasts) primarily, but not exclusively, in response to transforming growth factor-β (TGF-β). Myofibroblasts in turn enhance tumor progression by remodeling the stroma. Among proteases implicated in stroma remodeling, matrix metalloproteinases (MMPs), including MMP-9, play a prominent role. Recent evidence indicates that MMP-9 recruitment to the tumor cell surface enhances tumor growth and invasion. In the present work, we addressed the potential relevance of MMP-9 recruitment to and activity at the surface of fibroblasts. We show that recruitment of MMP-9 to the fibroblast cell surface occurs through its fibronectin-like (FN) domain and that the molecule responsible for the recruitment is lysyl hydroxylase 3 (LH3). Functional assays suggest that both pro- and active MMP-9 trigger α-smooth muscle actin expression in cultured fibroblasts, reflecting myofibroblast differentiation, possibly as a result of TGF-β activation. Moreover, the recombinant FN domain inhibited both MMP-9-induced TGF-β activation and α-smooth muscle actin expression by displacing MMP-9 from the fibroblast cell surface. Together our results uncover LH3 as a new docking receptor of MMP-9 on the fibroblast cell surface and demonstrate that the MMP-9 FN domain is essential for the interaction. They also show that the recombinant FN domain inhibits MMP-9-induced TGF-β activation and fibroblast differentiation, providing a potentially attractive therapeutic reagent toward attenuating tumor progression where MMP-9 activity is strongly implicated.
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http://dx.doi.org/10.1074/jbc.M114.622274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447954PMC
May 2015

EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma.

Cancer Cell 2014 Nov 30;26(5):668-681. Epub 2014 Oct 30.

Department of Pathology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.

The aberrant transcription factor EWS-FLI1 drives Ewing sarcoma, but its molecular function is not completely understood. We find that EWS-FLI1 reprograms gene regulatory circuits in Ewing sarcoma by directly inducing or repressing enhancers. At GGAA repeat elements, which lack evolutionary conservation and regulatory potential in other cell types, EWS-FLI1 multimers induce chromatin opening and create de novo enhancers that physically interact with target promoters. Conversely, EWS-FLI1 inactivates conserved enhancers containing canonical ETS motifs by displacing wild-type ETS transcription factors. These divergent chromatin-remodeling patterns repress tumor suppressors and mesenchymal lineage regulators while activating oncogenes and potential therapeutic targets, such as the kinase VRK1. Our findings demonstrate how EWS-FLI1 establishes an oncogenic regulatory program governing both tumor survival and differentiation.
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http://dx.doi.org/10.1016/j.ccell.2014.10.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4492343PMC
November 2014

Targeting cancer stem-like cells as an approach to defeating cellular heterogeneity in Ewing sarcoma.

Cancer Res 2014 Nov 26;74(22):6610-22. Epub 2014 Sep 26.

Experimental Pathology Service, CHUV and University of Lausanne, Lausanne, Switzerland.

Plasticity in cancer stem-like cells (CSC) may provide a key basis for cancer heterogeneity and therapeutic response. In this study, we assessed the effect of combining a drug that abrogates CSC properties with standard-of-care therapy in a Ewing sarcoma family tumor (ESFT). Emergence of CSC in this setting has been shown to arise from a defect in TARBP2-dependent microRNA maturation, which can be corrected by exposure to the fluoroquinolone enoxacin. In the present work, primary ESFT from four patients containing CD133(+) CSC subpopulations ranging from 3% to 17% of total tumor cells were subjected to treatment with enoxacin, doxorubicin, or both drugs. Primary ESFT CSC and bulk tumor cells displayed divergent responses to standard-of-care chemotherapy and enoxacin. Doxorubicin, which targets the tumor bulk, displayed toxicity toward primary adherent ESFT cells in culture but not to CSC-enriched ESFT spheres. Conversely, enoxacin, which enhances miRNA maturation by stimulating TARBP2 function, induced apoptosis but only in ESFT spheres. In combination, the two drugs markedly depleted CSCs and strongly reduced primary ESFTs in xenograft assays. Our results identify a potentially attractive therapeutic strategy for ESFT that combines mechanism-based targeting of CSC using a low-toxicity antibiotic with a standard-of-care cytotoxic drug, offering immediate applications for clinical evaluation.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-1106DOI Listing
November 2014

Imp2 controls oxidative phosphorylation and is crucial for preserving glioblastoma cancer stem cells.

Genes Dev 2012 Sep 16;26(17):1926-44. Epub 2012 Aug 16.

Experimental Pathology, Department of Laboratories, CHUV, University of Lausanne, Lausanne CH-1011, Switzerland.

Growth of numerous cancer types is believed to be driven by a subpopulation of poorly differentiated cells, often referred to as cancer stem cells (CSCs), that have the capacity for self-renewal, tumor initiation, and generation of nontumorigenic progeny. Despite their potentially key role in tumor establishment and maintenance, the energy requirements of these cells and the mechanisms that regulate their energy production are unknown. Here, we show that the oncofetal insulin-like growth factor 2 mRNA-binding protein 2 (IMP2, IGF2BP2) regulates oxidative phosphorylation (OXPHOS) in primary glioblastoma (GBM) sphere cultures (gliomaspheres), an established in vitro model for CSC expansion. We demonstrate that IMP2 binds several mRNAs that encode mitochondrial respiratory chain complex subunits and that it interacts with complex I (NADH:ubiquinone oxidoreductase) proteins. Depletion of IMP2 in gliomaspheres decreases their oxygen consumption rate and both complex I and complex IV activity that results in impaired clonogenicity in vitro and tumorigenicity in vivo. Importantly, inhibition of OXPHOS but not of glycolysis abolishes GBM cell clonogenicity. Our observations suggest that gliomaspheres depend on OXPHOS for their energy production and survival and that IMP2 expression provides a key mechanism to ensure OXPHOS maintenance by delivering respiratory chain subunit-encoding mRNAs to mitochondria and contributing to complex I and complex IV assembly.
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http://dx.doi.org/10.1101/gad.188292.112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435496PMC
September 2012

A TARBP2-dependent miRNA expression profile underlies cancer stem cell properties and provides candidate therapeutic reagents in Ewing sarcoma.

Cancer Cell 2012 Jun;21(6):807-21

Institute of Pathology, Centre Hospitalier Universitaire Vaudois, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.

We have recently demonstrated that human pediatric mesenchymal stem cells can be reprogrammed toward a Ewing sarcoma family tumor (ESFT) cancer stem cell (CSC) phenotype by mechanisms that implicate microRNAs (miRNAs). Here, we show that the miRNA profile of ESFT CSCs is shared by embryonic stem cells and CSCs from divergent tumor types. We also provide evidence that the miRNA profile of ESFT CSCs is the result of reversible disruption of TARBP2-dependent miRNA maturation. Restoration of TARBP2 activity and systemic delivery of synthetic forms of either of two of its targets, miRNA-143 or miRNA-145, inhibited ESFT CSC clonogenicity and tumor growth in vivo. Our observations suggest that CSC self-renewal and tumor maintenance may depend on deregulation of TARBP2-dependent miRNA expression.
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http://dx.doi.org/10.1016/j.ccr.2012.04.023DOI Listing
June 2012

Systematic identification of genomic markers of drug sensitivity in cancer cells.

Nature 2012 Mar 28;483(7391):570-5. Epub 2012 Mar 28.

Cancer Genome Project, Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK.

Clinical responses to anticancer therapies are often restricted to a subset of patients. In some cases, mutated cancer genes are potent biomarkers for responses to targeted agents. Here, to uncover new biomarkers of sensitivity and resistance to cancer therapeutics, we screened a panel of several hundred cancer cell lines--which represent much of the tissue-type and genetic diversity of human cancers--with 130 drugs under clinical and preclinical investigation. In aggregate, we found that mutated cancer genes were associated with cellular response to most currently available cancer drugs. Classic oncogene addiction paradigms were modified by additional tissue-specific or expression biomarkers, and some frequently mutated genes were associated with sensitivity to a broad range of therapeutic agents. Unexpected relationships were revealed, including the marked sensitivity of Ewing's sarcoma cells harbouring the EWS (also known as EWSR1)-FLI1 gene translocation to poly(ADP-ribose) polymerase (PARP) inhibitors. By linking drug activity to the functional complexity of cancer genomes, systematic pharmacogenomic profiling in cancer cell lines provides a powerful biomarker discovery platform to guide rational cancer therapeutic strategies.
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http://dx.doi.org/10.1038/nature11005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3349233PMC
March 2012

Let-7a is a direct EWS-FLI-1 target implicated in Ewing's sarcoma development.

PLoS One 2011 10;6(8):e23592. Epub 2011 Aug 10.

Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland.

Ewing's sarcoma family tumors (ESFT) are the second most common bone malignancy in children and young adults, characterized by unique chromosomal translocations that in 85% of cases lead to expression of the EWS-FLI-1 fusion protein. EWS-FLI-1 functions as an aberrant transcription factor that can both induce and suppress members of its target gene repertoire. We have recently demonstrated that EWS-FLI-1 can alter microRNA (miRNA) expression and that miRNA145 is a direct EWS-FLI-1 target whose suppression is implicated in ESFT development. Here, we use miRNA arrays to compare the global miRNA expression profile of human mesenchymal stem cells (MSC) and ESFT cell lines, and show that ESFT display a distinct miRNA signature that includes induction of the oncogenic miRNA 17-92 cluster and repression of the tumor suppressor let-7 family. We demonstrate that direct repression of let-7a by EWS-FLI-1 participates in the tumorigenic potential of ESFT cells in vivo. The mechanism whereby let-7a expression regulates ESFT growth is shown to be mediated by its target gene HMGA2, as let-7a overexpression and HMGA2 repression both block ESFT cell tumorigenicity. Consistent with these observations, systemic delivery of synthetic let-7a into ESFT-bearing mice restored its expression in tumor cells, decreased HMGA2 expression levels and resulted in ESFT growth inhibition in vivo. Our observations provide evidence that deregulation of let-7a target gene expression participates in ESFT development and identify let-7a as promising new therapeutic target for one of the most aggressive pediatric malignancies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023592PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3154507PMC
December 2011

Myeloid-derived suppressor cells are implicated in regulating permissiveness for tumor metastasis during mouse gestation.

J Clin Invest 2011 Jul 6;121(7):2794-807. Epub 2011 Jun 6.

Division of Experimental Pathology, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland.

Metastasis depends on the ability of tumor cells to establish a relationship with the newly seeded tissue that is conducive to their survival and proliferation. However, the factors that render tissues permissive for metastatic tumor growth have yet to be fully elucidated. Breast tumors arising during pregnancy display early metastatic proclivity, raising the possibility that pregnancy may constitute a physiological condition of permissiveness for tumor dissemination. Here we have shown that during murine gestation, metastasis is enhanced regardless of tumor type, and that decreased NK cell activity is responsible for the observed increase in experimental metastasis. Gene expression changes in pregnant mouse lung and liver were shown to be similar to those detected in premetastatic sites and indicative of myeloid cell infiltration. Indeed, myeloid-derived suppressor cells (MDSCs) accumulated in pregnant mice and exerted an inhibitory effect on NK cell activity, providing a candidate mechanism for the enhanced metastatic tumor growth observed in gestant mice. Although the functions of MDSCs are not yet understood in the context of pregnancy, our observations suggest that they may represent a shared mechanism of immune suppression occurring during gestation and tumor growth.
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http://dx.doi.org/10.1172/JCI41936DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3223816PMC
July 2011

Identification of prognostic molecular features in the reactive stroma of human breast and prostate cancer.

PLoS One 2011 18;6(5):e18640. Epub 2011 May 18.

Institute of Pathology, CHUV, and Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.

Primary tumor growth induces host tissue responses that are believed to support and promote tumor progression. Identification of the molecular characteristics of the tumor microenvironment and elucidation of its crosstalk with tumor cells may therefore be crucial for improving our understanding of the processes implicated in cancer progression, identifying potential therapeutic targets, and uncovering stromal gene expression signatures that may predict clinical outcome. A key issue to resolve, therefore, is whether the stromal response to tumor growth is largely a generic phenomenon, irrespective of the tumor type or whether the response reflects tumor-specific properties. To address similarity or distinction of stromal gene expression changes during cancer progression, oligonucleotide-based Affymetrix microarray technology was used to compare the transcriptomes of laser-microdissected stromal cells derived from invasive human breast and prostate carcinoma. Invasive breast and prostate cancer-associated stroma was observed to display distinct transcriptomes, with a limited number of shared genes. Interestingly, both breast and prostate tumor-specific dysregulated stromal genes were observed to cluster breast and prostate cancer patients, respectively, into two distinct groups with statistically different clinical outcomes. By contrast, a gene signature that was common to the reactive stroma of both tumor types did not have survival predictive value. Univariate Cox analysis identified genes whose expression level was most strongly associated with patient survival. Taken together, these observations suggest that the tumor microenvironment displays distinct features according to the tumor type that provides survival-predictive value.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0018640PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3097176PMC
September 2011

Securin and separase modulate membrane traffic by affecting endosomal acidification.

Traffic 2011 May 25;12(5):615-26. Epub 2011 Feb 25.

Division of Experimental Pathology, Faculty of Biology and Medicine, Institute of Pathology, CHUV, University of Lausanne, Rue du Bugnon 25, Lausanne CH1011, Switzerland.

Securin and separase play a key role in sister chromatid separation during anaphase. However, a growing body of evidence suggests that in addition to regulating chromosome segregation, securin and separase display functions implicated in membrane traffic in Caenorhabditis elegans and Drosophila. Here we show that in mammalian cells both securin and separase associate with membranes and that depletion of either protein causes robust swelling of the trans-Golgi network (TGN) along with the appearance of large endocytic vesicles in the perinuclear region. These changes are accompanied by diminished constitutive protein secretion as well as impaired receptor recycling and degradation. Unexpectedly, cells depleted of securin or separase display defective acidification of early endosomes and increased membrane recruitment of vacuolar (V-) ATPase complexes, mimicking the effect of the specific V-ATPase inhibitor Bafilomycin A1. Taken together, our findings identify a new functional role of securin and separase in the modulation of membrane traffic and protein secretion that implicates regulation of V-ATPase assembly and function.
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http://dx.doi.org/10.1111/j.1600-0854.2011.01169.xDOI Listing
May 2011

Synergistic effect of hyaluronate fragments in retinaldehyde-induced skin hyperplasia which is a Cd44-dependent phenomenon.

PLoS One 2010 Dec 16;5(12):e14372. Epub 2010 Dec 16.

Department of Dermatology, University of Geneva, Geneva, Switzerland.

Background: CD44 is a polymorphic proteoglycan and functions as the principal cell-surface receptor for hyaluronate (HA). Heparin-binding epidermal growth factor (HB-EGF) activation of keratinocyte erbB receptors has been proposed to mediate retinoid-induced epidermal hyperplasia. We have recently shown that intermediate size HA fragments (HAFi) reverse skin atrophy by a CD44-dependent mechanism.

Methodology And Principal Findings: Treatment of primary mouse keratinocyte cultures with retinaldehyde (RAL) resulted in the most significant increase in keratinocyte proliferation when compared with other retinoids, retinoic acid, retinol or retinoyl palmitate. RAL and HAFi showed a more significant increase in keratinocyte proliferation than RAL or HAFi alone. No proliferation with RAL was observed in CD44-/- keratinocytes. HA synthesis inhibitor, 4-methylumbelliferone inhibited the proliferative effect of RAL. HB-EGF, erbB1, and tissue inhibitor of MMP-3 blocking antibodies abrogated the RAL- or RAL- and HAFi-induced keratinocyte proliferation. Topical application of RAL or RAL and HAFi for 3 days caused a significant epidermal hyperplasia in the back skin of wild-type mice but not in CD44-/- mice. Topical RAL and HAFi increased epidermal CD44 expression, and the epidermal and dermal HA. RAL induced the expression of active HB-EGF and erbB1. However, treatment with RAL and HAFi showed a more significant increase in pro-HB-EGF when compared to RAL or HAFi treatments alone. We then topically applied RAL and HAFi twice a day to the forearm skin of elderly dermatoporosis patients. After 1 month of treatment, we observed a significant clinical improvement.

Conclusions And Significance: Our results indicate that (i) RAL-induced in vitro and in vivo keratinocyte proliferation is a CD44-dependent phenomenon and requires the presence of HA, HB-EGF, erbB1 and MMPs, (ii) RAL and HAFi show a synergy in vitro and in vivo in mouse skin, and (iii) the combination of RAL and HAFi seems to have an important therapeutic effect in dermatoporosis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014372PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002934PMC
December 2010

Transportin regulates nuclear import of CD44.

J Biol Chem 2010 Oct 27;285(40):30548-57. Epub 2010 Jul 27.

Division of Experimental Pathology, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne CH-1011, Switzerland.

CD44 is a facultative cell surface proteoglycan that serves as the principal cell surface receptor for hyaluronan (HA). Studies have shown that in addition to participating in numerous signaling pathways, CD44 becomes internalized upon engagement by ligand and that a portion of its intracellular domain can translocate to the nucleus where it is believed to play a functional role in cell proliferation and survival. However, the mechanisms whereby fragments of CD44 enter the nucleus have not been elucidated. Here we show that CD44 interacts with two import receptors of the importin β superfamily, importin β itself and transportin. Inhibition of importin β-dependent transport failed to block CD44 accumulation in the nucleus. By contrast, inhibition of the transportin-dependent pathway abrogated CD44 import. Mutagenesis of the intracellular domain of CD44 revealed that the 20 membrane-proximal residues contain sequences required for transportin-mediated nuclear transport. Our observations provide evidence that CD44 interacts with importin family members and identify the transportin-dependent pathway as the mechanism whereby full-length CD44 enters the nucleus.
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http://dx.doi.org/10.1074/jbc.M109.075838DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2945549PMC
October 2010