Publications by authors named "Robert J Norgard"

17 Publications

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MYC levels regulate metastatic heterogeneity in pancreatic adenocarcinoma.

Cancer Discov 2021 Sep 22. Epub 2021 Sep 22.

Ontario Institute for Cancer Research.

The degree of metastatic disease varies widely amongst cancer patients and impacts clinical outcomes. However, the biological and functional differences that drive the extent of metastasis are poorly understood. We analyzed primary tumors and paired metastases using a multi-fluorescent lineage-labeled mouse model of pancreatic ductal adenocarcinoma (PDAC) - a tumor type where most patients present with metastases. Genomic and transcriptomic analysis revealed an association between metastatic burden and gene amplification or transcriptional upregulation of MYC and its downstream targets. Functional experiments showed that MYC promotes metastasis by recruiting tumor associated macrophages (TAMs), leading to greater bloodstream intravasation. Consistent with these findings, metastatic progression in human PDAC was associated with activation of MYC signaling pathways and enrichment for MYC amplifications specifically in metastatic patients. Collectively, these results implicate MYC activity as a major determinant of metastatic burden in advanced PDAC.
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http://dx.doi.org/10.1158/2159-8290.CD-20-1826DOI Listing
September 2021

Calcium signaling induces a partial EMT.

EMBO Rep 2021 Sep 29;22(9):e51872. Epub 2021 Jul 29.

Abramson Family Cancer Research Institute and Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Epithelial plasticity, or epithelial-to-mesenchymal transition (EMT), is a well-recognized form of cellular plasticity, which endows tumor cells with invasive properties and alters their sensitivity to various agents, thus representing a major challenge to cancer therapy. It is increasingly accepted that carcinoma cells exist along a continuum of hybrid epithelial-mesenchymal (E-M) states and that cells exhibiting such partial EMT (P-EMT) states have greater metastatic competence than those characterized by either extreme (E or M). We described recently a P-EMT program operating in vivo by which carcinoma cells lose their epithelial state through post-translational programs. Here, we investigate the underlying mechanisms and report that prolonged calcium signaling induces a P-EMT characterized by the internalization of membrane-associated E-cadherin (ECAD) and other epithelial proteins as well as an increase in cellular migration and invasion. Signaling through Gαq-associated G-protein-coupled receptors (GPCRs) recapitulates these effects, which operate through the downstream activation of calmodulin-Camk2b signaling. These results implicate calcium signaling as a trigger for the acquisition of hybrid/partial epithelial-mesenchymal states in carcinoma cells.
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http://dx.doi.org/10.15252/embr.202051872DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8419705PMC
September 2021

Single-cell lineage tracing of metastatic cancer reveals selection of hybrid EMT states.

Cancer Cell 2021 Aug 10;39(8):1150-1162.e9. Epub 2021 Jun 10.

Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Cell & Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, USA. Electronic address:

The underpinnings of cancer metastasis remain poorly understood, in part due to a lack of tools for probing their emergence at high resolution. Here we present macsGESTALT, an inducible CRISPR-Cas9-based lineage recorder with highly efficient single-cell capture of both transcriptional and phylogenetic information. Applying macsGESTALT to a mouse model of metastatic pancreatic cancer, we recover ∼380,000 CRISPR target sites and reconstruct dissemination of ∼28,000 single cells across multiple metastatic sites. We find that cells occupy a continuum of epithelial-to-mesenchymal transition (EMT) states. Metastatic potential peaks in rare, late-hybrid EMT states, which are aggressively selected from a predominately epithelial ancestral pool. The gene signatures of these late-hybrid EMT states are predictive of reduced survival in both human pancreatic and lung cancer patients, highlighting their relevance to clinical disease progression. Finally, we observe evidence for in vivo propagation of S100 family gene expression across clonally distinct metastatic subpopulations.
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http://dx.doi.org/10.1016/j.ccell.2021.05.005DOI Listing
August 2021

PTHrP Drives Pancreatic Cancer Growth and Metastasis and Reveals a New Therapeutic Vulnerability.

Cancer Discov 2021 Jul 15;11(7):1774-1791. Epub 2021 Feb 15.

Herbert Irving Comprehensive Cancer Center, Division of Digestive and Liver Diseases, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, New York.

Pancreatic cancer metastasis is a leading cause of cancer-related deaths, yet very little is understood regarding the underlying biology. As a result, targeted therapies to inhibit metastasis are lacking. Here, we report that the parathyroid hormone-related protein (PTHrP encoded by ) is frequently amplified as part of the amplicon in patients with pancreatic cancer. PTHrP upregulation drives the growth of both primary and metastatic tumors in mice and is highly enriched in pancreatic ductal adenocarcinoma metastases. Loss of PTHrP-either genetically or pharmacologically-dramatically reduces tumor burden, eliminates metastasis, and enhances overall survival. These effects are mediated in part through a reduction in epithelial-to-mesenchymal transition, which reduces the ability of tumor cells to initiate metastatic cascade. , which encodes osteopontin, is revealed to be a downstream effector of PTHrP. Our results establish a new paradigm in pancreatic cancer whereby PTHrP is a driver of disease progression and emerges as a novel therapeutic vulnerability. SIGNIFICANCE: Pancreatic cancer often presents with metastases, yet no strategies exist to pharmacologically inhibit this process. Herein, we establish the oncogenic and prometastatic roles of , a novel amplified gene in pancreatic ductal adenocarcinoma. We demonstrate that blocking PTHrP activity reduces primary tumor growth, prevents metastasis, and prolongs survival in mice..
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http://dx.doi.org/10.1158/2159-8290.CD-20-1098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8292165PMC
July 2021

Epigenetic and Transcriptional Control of the Epidermal Growth Factor Receptor Regulates the Tumor Immune Microenvironment in Pancreatic Cancer.

Cancer Discov 2021 Mar 6;11(3):736-753. Epub 2020 Nov 6.

Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.

Although immunotherapy has revolutionized cancer care, patients with pancreatic ductal adenocarcinoma (PDA) rarely respond to these treatments, a failure that is attributed to poor infiltration and activation of T cells in the tumor microenvironment (TME). We performed an CRISPR screen and identified lysine demethylase 3A (KDM3A) as a potent epigenetic regulator of immunotherapy response in PDA. Mechanistically, KDM3A acts through Krueppel-like factor 5 (KLF5) and SMAD family member 4 (SMAD4) to regulate the expression of the epidermal growth factor receptor (EGFR). Ablation of KDM3A, KLF5, SMAD4, or EGFR in tumor cells altered the immune TME and sensitized tumors to combination immunotherapy, whereas treatment of established tumors with an EGFR inhibitor, erlotinib, prompted a dose-dependent increase in intratumoral T cells. This study defines an epigenetic-transcriptional mechanism by which tumor cells modulate their immune microenvironment and highlights the potential of EGFR inhibitors as immunotherapy sensitizers in PDA. SIGNIFICANCE: PDA remains refractory to immunotherapies. Here, we performed an CRISPR screen and identified an epigenetic-transcriptional network that regulates antitumor immunity by converging on EGFR. Pharmacologic inhibition of EGFR is sufficient to rewire the immune microenvironment. These results offer a readily accessible immunotherapy-sensitizing strategy for PDA..
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http://dx.doi.org/10.1158/2159-8290.CD-20-0519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7933070PMC
March 2021

Isolation and Identification of EMT Subtypes.

Methods Mol Biol 2021 ;2179:315-326

Abramson Family Cancer Research Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.

Metastasis and chemoresistance, the most lethal features of cancer progression, are strongly associated with a form of cellular plasticity known as the epithelial-to-mesenchymal transition (EMT). Carcinoma cells undergoing EMT lose their epithelial morphology and become more mobile, allowing them to invade and migrate more efficiently. This shift is also associated with a change in vulnerability to chemotherapeutic agents. Importantly, EMT does not involve a single mechanism, but rather encompasses a spectrum of phenotypes with differing degrees of epithelial and mesenchymal characteristics. These hybrid/partial epithelial-mesenchymal states are associated with other important aspects of tumor biology, such as distinct modes of cellular invasion and drug resistance, illustrating the need to further characterize this phenomenon in tumor cells. Although simple in theory, the identification of tumor cells that have undergone EMT in vivo has proven difficult due to their high similarity to other mesenchymal cells that populate tumor stroma, such as cancer-associated fibroblasts. This protocol describes two methods for isolating epithelial and EMT cancer cell populations from primary murine tumors and cultured cancer cells to identify different EMT subtypes. These populations can then be used for several applications, including, but not limited to, functional studies of motility or invasion, gene expression analysis (RNA sequencing and RT-qPCR), DNA sequencing, epigenetic analysis, tumor subtyping, western blotting, immunohistochemistry, etc. Finally, we describe a flow cytometry-based approach to identify and study tumors cells that are undergoing partial EMT.
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http://dx.doi.org/10.1007/978-1-0716-0779-4_24DOI Listing
March 2021

Pharmacologic Activation of the G Protein-Coupled Estrogen Receptor Inhibits Pancreatic Ductal Adenocarcinoma.

Cell Mol Gastroenterol Hepatol 2020 4;10(4):868-880.e1. Epub 2020 May 4.

Perelman School of Medicine, Department of Dermatology, University of Pennsylvania, Philadelphia. Electronic address:

Background & Aims: Female sex is associated with lower incidence and improved clinical outcomes for most cancer types including pancreatic ductal adenocarcinoma (PDAC). The mechanistic basis for this sex difference is unknown. We hypothesized that estrogen signaling may be responsible, despite the fact that PDAC lacks classic nuclear estrogen receptors.

Methods: Here we used murine syngeneic tumor models and human xenografts to determine that signaling through the nonclassic estrogen receptor G protein-coupled estrogen receptor (GPER) on tumor cells inhibits PDAC.

Results: Activation of GPER with the specific, small molecule, synthetic agonist G-1 inhibited PDAC proliferation, depleted c-Myc and programmed death ligand 1 (PD-L1), and increased tumor cell immunogenicity. Systemically administered G-1 was well-tolerated in PDAC bearing mice, induced tumor regression, significantly prolonged survival, and markedly increased the efficacy of PD-1 targeted immune therapy. We detected GPER protein in a majority of spontaneous human PDAC tumors, independent of tumor stage.

Conclusions: These data, coupled with the wide tissue distribution of GPER and our previous work showing that G-1 inhibits melanoma, suggest that GPER agonists may be useful against a range of cancers that are not classically considered sex hormone responsive and that arise in tissues outside of the reproductive system.
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http://dx.doi.org/10.1016/j.jcmgh.2020.04.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7578406PMC
May 2020

Senescence-Induced Vascular Remodeling Creates Therapeutic Vulnerabilities in Pancreas Cancer.

Cell 2020 04 31;181(2):424-441.e21. Epub 2020 Mar 31.

Department of Cancer Biology and Genetics, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA. Electronic address:

KRAS mutant pancreatic ductal adenocarcinoma (PDAC) is characterized by a desmoplastic response that promotes hypovascularity, immunosuppression, and resistance to chemo- and immunotherapies. We show that a combination of MEK and CDK4/6 inhibitors that target KRAS-directed oncogenic signaling can suppress PDAC proliferation through induction of retinoblastoma (RB) protein-mediated senescence. In preclinical mouse models of PDAC, this senescence-inducing therapy produces a senescence-associated secretory phenotype (SASP) that includes pro-angiogenic factors that promote tumor vascularization, which in turn enhances drug delivery and efficacy of cytotoxic gemcitabine chemotherapy. In addition, SASP-mediated endothelial cell activation stimulates the accumulation of CD8 T cells into otherwise immunologically "cold" tumors, sensitizing tumors to PD-1 checkpoint blockade. Therefore, in PDAC models, therapy-induced senescence can establish emergent susceptibilities to otherwise ineffective chemo- and immunotherapies through SASP-dependent effects on the tumor vasculature and immune system.
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http://dx.doi.org/10.1016/j.cell.2020.03.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7278897PMC
April 2020

Tumor Cell-Intrinsic USP22 Suppresses Antitumor Immunity in Pancreatic Cancer.

Cancer Immunol Res 2020 03 23;8(3):282-291. Epub 2019 Dec 23.

Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.

Although immune checkpoint blockade (ICB) improves clinical outcome in several types of malignancies, pancreatic ductal adenocarcinoma (PDA) remains refractory to this therapy. Preclinical studies have demonstrated that the relative abundance of suppressive myeloid cells versus cytotoxic T cells determines the efficacy of combination immunotherapies, which include ICB. Here, we evaluated the role of the ubiquitin-specific protease 22 (USP22) as a regulator of the immune tumor microenvironment (TME) in PDA. We report that deletion of USP22 in pancreatic tumor cells reduced the infiltration of myeloid cells and promoted the infiltration of T cells and natural killer (NK) cells, leading to an improved response to combination immunotherapy. We also showed that ablation of tumor cell-intrinsic USP22 suppressed metastasis of pancreatic tumor cells in a T-cell-dependent manner. Finally, we provide evidence that USP22 exerted its effects on the immune TME by reshaping the cancer cell transcriptome through its association with the deubiquitylase module of the SAGA/STAGA transcriptional coactivator complex. These results indicated that USP22 regulates immune infiltration and immunotherapy sensitivity in preclinical models of pancreatic cancer.
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http://dx.doi.org/10.1158/2326-6066.CIR-19-0661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173406PMC
March 2020

A biomimetic pancreatic cancer on-chip reveals endothelial ablation via ALK7 signaling.

Sci Adv 2019 08 28;5(8):eaav6789. Epub 2019 Aug 28.

Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, lethal malignancy that invades adjacent vasculatures and spreads to distant sites before clinical detection. Although invasion into the peripancreatic vasculature is one of the hallmarks of PDAC, paradoxically, PDAC tumors also exhibit hypovascularity. How PDAC tumors become hypovascular is poorly understood. We describe an organotypic PDAC-on-a-chip culture model that emulates vascular invasion and tumor-blood vessel interactions to better understand PDAC-vascular interactions. The model features a 3D matrix containing juxtaposed PDAC and perfusable endothelial lumens. PDAC cells invaded through intervening matrix, into vessel lumen, and ablated the endothelial cells, leaving behind tumor-filled luminal structures. Endothelial ablation was also observed in in vivo PDAC models. We also identified the activin-ALK7 pathway as a mediator of endothelial ablation by PDAC. This tumor-on-a-chip model provides an important in vitro platform for investigating the process of PDAC-driven endothelial ablation and may provide a mechanism for tumor hypovascularity.
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http://dx.doi.org/10.1126/sciadv.aav6789DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6713506PMC
August 2019

Cellular Plasticity in Cancer.

Cancer Discov 2019 07 16;9(7):837-851. Epub 2019 Apr 16.

Abramson Family Cancer Research Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.

During cancer progression, tumor cells undergo molecular and phenotypic changes collectively referred to as cellular plasticity. Such changes result from microenvironmental cues, stochastic genetic and epigenetic alterations, and/or treatment-imposed selective pressures, thereby contributing to tumor heterogeneity and therapy resistance. Epithelial-mesenchymal plasticity is the best-known case of tumor cell plasticity, but recent work has uncovered other examples, often with functional consequences. In this review, we explore the nature and role(s) of these diverse cellular plasticity programs in premalignant progression, tumor evolution, and adaptation to therapy and consider ways in which targeting plasticity could lead to novel anticancer treatments. SIGNIFICANCE: Changes in cell identity, or cellular plasticity, are common at different stages of tumor progression, and it has become clear that cellular plasticity can be a potent mediator of tumor progression and chemoresistance. Understanding the mechanisms underlying the various forms of cell plasticity may deliver new strategies for targeting the most lethal aspects of cancer: metastasis and resistance to therapy.
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http://dx.doi.org/10.1158/2159-8290.CD-19-0015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6606363PMC
July 2019

Acetyl-CoA Metabolism Supports Multistep Pancreatic Tumorigenesis.

Cancer Discov 2019 03 9;9(3):416-435. Epub 2019 Jan 9.

Department of Cancer Biology, Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.

Pancreatic ductal adenocarcinoma (PDA) has a poor prognosis, and new strategies for prevention and treatment are urgently needed. We previously reported that histone H4 acetylation is elevated in pancreatic acinar cells harboring mutations prior to the appearance of premalignant lesions. Because acetyl-CoA abundance regulates global histone acetylation, we hypothesized that altered acetyl-CoA metabolism might contribute to metabolic or epigenetic alterations that promote tumorigenesis. We found that acetyl-CoA abundance is elevated in -mutant acinar cells and that its use in the mevalonate pathway supports acinar-to-ductal metaplasia (ADM). Pancreas-specific loss of the acetyl-CoA-producing enzyme ATP-citrate lyase (ACLY) accordingly suppresses ADM and tumor formation. In PDA cells, growth factors promote AKT-ACLY signaling and histone acetylation, and both cell proliferation and tumor growth can be suppressed by concurrent BET inhibition and statin treatment. Thus, KRAS-driven metabolic alterations promote acinar cell plasticity and tumor development, and targeting acetyl-CoA-dependent processes exerts anticancer effects. SIGNIFICANCE: Pancreatic cancer is among the deadliest of human malignancies. We identify a key role for the metabolic enzyme ACLY, which produces acetyl-CoA, in pancreatic carcinogenesis. The data suggest that acetyl-CoA use for histone acetylation and in the mevalonate pathway facilitates cell plasticity and proliferation, suggesting potential to target these pathways...
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http://dx.doi.org/10.1158/2159-8290.CD-18-0567DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6643997PMC
March 2019

Tumor Cell-Intrinsic Factors Underlie Heterogeneity of Immune Cell Infiltration and Response to Immunotherapy.

Immunity 2018 07 26;49(1):178-193.e7. Epub 2018 Jun 26.

Abramson Family Cancer Research Institute, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA; Department of Medicine, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA; Abramson Cancer Center, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA; Parker Institute for Cancer Immunotherapy, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA. Electronic address:

The biological and functional heterogeneity between tumors-both across and within cancer types-poses a challenge for immunotherapy. To understand the factors underlying tumor immune heterogeneity and immunotherapy sensitivity, we established a library of congenic tumor cell clones from an autochthonous mouse model of pancreatic adenocarcinoma. These clones generated tumors that recapitulated T cell-inflamed and non-T-cell-inflamed tumor microenvironments upon implantation in immunocompetent mice, with distinct patterns of infiltration by immune cell subsets. Co-injecting tumor cell clones revealed the non-T-cell-inflamed phenotype is dominant and that both quantitative and qualitative features of intratumoral CD8 T cells determine response to therapy. Transcriptomic and epigenetic analyses revealed tumor-cell-intrinsic production of the chemokine CXCL1 as a determinant of the non-T-cell-inflamed microenvironment, and ablation of CXCL1 promoted T cell infiltration and sensitivity to a combination immunotherapy regimen. Thus, tumor cell-intrinsic factors shape the tumor immune microenvironment and influence the outcome of immunotherapy.
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http://dx.doi.org/10.1016/j.immuni.2018.06.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6707727PMC
July 2018

EMT Subtype Influences Epithelial Plasticity and Mode of Cell Migration.

Dev Cell 2018 06;45(6):681-695.e4

Department of Medicine, Gastroenterology Division, Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, 421 Curie Blvd, 512 BRB II/III, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

Epithelial-mesenchymal transition (EMT) is strongly implicated in tumor cell invasion and metastasis. EMT is thought to be regulated primarily at the transcriptional level through the repressive activity of EMT transcription factors. However, these classical mechanisms have been parsed out almost exclusively in vitro, leaving questions about the programs driving EMT in physiological contexts. Here, using a lineage-labeled mouse model of pancreatic ductal adenocarcinoma to study EMT in vivo, we found that most tumors lose their epithelial phenotype through an alternative program involving protein internalization rather than transcriptional repression, resulting in a "partial EMT" phenotype. Carcinoma cells utilizing this program migrate as clusters, contrasting with the single-cell migration pattern associated with traditionally defined EMT mechanisms. Moreover, many breast and colorectal cancer cell lines utilize this alternative program to undergo EMT. Collectively, these results suggest that carcinoma cells have different ways of losing their epithelial program, resulting in distinct modes of invasion and dissemination.
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http://dx.doi.org/10.1016/j.devcel.2018.05.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014628PMC
June 2018

Metastatic progression is associated with dynamic changes in the local microenvironment.

Nat Commun 2016 09 15;7:12819. Epub 2016 Sep 15.

Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

Most cancer-associated deaths result from metastasis. However, it remains unknown whether the size, microenvironment or other features of a metastatic lesion dictate its behaviour or determine the efficacy of chemotherapy in the adjuvant (micrometastatic) setting. Here we delineate the natural history of metastasis in an autochthonous model of pancreatic ductal adenocarcinoma (PDAC), using lineage tracing to examine the evolution of disseminated cancer cells and their associated microenvironment. With increasing size, lesions shift from mesenchymal to epithelial histology, become hypovascular and accumulate a desmoplastic stroma, ultimately recapitulating the primary tumours from which they arose. Moreover, treatment with gemcitabine and nab-paclitaxel significantly reduces the overall number of metastases by inducing cell death in lesions of all sizes, challenging the paradigm that PDAC stroma imposes a critical barrier to drug delivery. These results illuminate the cellular dynamics of metastatic progression and suggest that adjuvant chemotherapy affords a survival benefit by directly targeting micrometastases.
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http://dx.doi.org/10.1038/ncomms12819DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027614PMC
September 2016

Dormancy and growth of metastatic breast cancer cells in a bone-like microenvironment.

Clin Exp Metastasis 2015 Apr 8;32(4):335-44. Epub 2015 Mar 8.

Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 428 S. Frear Laboratory, University Park, PA, 16802, USA.

Breast cancer can reoccur, often as bone metastasis, many years if not decades after the primary tumor has been treated. The factors that stimulate dormant metastases to grow are not known, but bone metastases are often associated with skeletal trauma. We used a dormancy model of MDA-MB-231BRMS1, a metastasis-suppressed human breast cancer cell line, co-cultured with MC3T3-E1 osteoblasts in a long term, three dimensional culture system to test the hypothesis that bone remodeling cytokines could stimulate dormant cells to grow. The cancer cells attached to the matrix produced by MC3T3-E1 osteoblasts but grew slowly or not at all until the addition of bone remodeling cytokines, TNFα and IL-β. Stimulation of cell proliferation by these cytokines was suppressed with indomethacin, an inhibitor of cyclooxygenase and of prostaglandin production, or a prostaglandin E2 (PGE2) receptor antagonist. Addition of PGE2 directly to the cultures also stimulated cell proliferation. MCF-7, non-metastatic breast cancer cells, remained dormant when co-cultured with normal human osteoblast and fibroblast growth factor. Similar to the MDA-MB-231BRMS1 cells, MCF-7 proliferation increased in response to TNFα and IL-β. These findings suggest that changes in the bone microenvironment due to inflammatory cytokines associated with bone repair or excess turnover may trigger the occurrence of latent bone metastasis.
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http://dx.doi.org/10.1007/s10585-015-9710-9DOI Listing
April 2015
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