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Iloki Assanga SB, Lewis Luján LM, McCarty MF. Targeting beta-catenin signaling for prevention of colorectal cancer - Nutraceutical, drug, and dietary options. Eur J Pharmacol 2023; 956:175898. [PMID: 37481200 DOI: 10.1016/j.ejphar.2023.175898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 06/09/2023] [Accepted: 06/29/2023] [Indexed: 07/24/2023]
Abstract
Progressive up-regulation of β-catenin signaling is very common in the transformation of colorectal epithelium to colorectal cancer (CRC). Practical measures for opposing such signaling hence have potential for preventing or slowing such transformation. cAMP/PKA activity in colon epithelium, as stimulated by COX-2-generated prostaglandins and β2-adrenergic signaling, boosts β-catenin activity, whereas cGMP/PKG signaling has the opposite effect. Bacterial generation of short-chain fatty acids (as supported by unrefined high-carbohydrate diets, berberine, and probiotics), dietary calcium, daily aspirin, antioxidants opposing cox-2 induction, and nicotine avoidance, can suppress cAMP production in colonic epithelium, whereas cGMP can be boosted via linaclotides, PDE5 inhibitors such as sildenafil or icariin, and likely high-dose biotin. Selective activation of estrogen receptor-β by soy isoflavones, support of adequate vitamin D receptor activity with UV exposure or supplemental vitamin D, and inhibition of CK2 activity with flavanols such as quercetin, can also oppose β-catenin signaling in colorectal epithelium. Secondary bile acids, the colonic production of which can be diminished by low-fat diets and berberine, can up-regulate β-catenin activity by down-regulating farnesoid X receptor expression. Stimulation of PI3K/Akt via insulin, IGF-I, TLR4, and EGFR receptors boosts β-catenin levels via inhibition of glycogen synthase-3β; plant-based diets can down-regulate insulin and IGF-I levels, exercise training and leanness can keep insulin low, anthocyanins and their key metabolite ferulic acid have potential for opposing TLR4 signaling, and silibinin is a direct antagonist for EGFR. Partially hydrolyzed phytate can oppose growth factor-mediated down-regulation of β-catenin by inhibiting Akt activation. Multifactorial strategies for safely opposing β-catenin signaling can be complemented with measures that diminish colonic mutagenesis and DNA hypomethylation - such as avoidance of heme-rich meat and charred or processed meats, consumption of phase II-inductive foods and nutraceuticals (e.g., Crucifera), and assurance of adequate folate status.
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Affiliation(s)
- Simon Bernard Iloki Assanga
- Departamento de Ciencias Químico Biológicas, Universidad de Sonora, Blvd Luis Encinas y Rosales S/N Col. Centro, Hermosillo, Sonora, C.P. 83000, Mexico.
| | - Lidianys María Lewis Luján
- Technological Institute of Hermosillo (ITH), Ave. Tecnológico y Periférico Poniente S/N, Col. Sahuaro, Hermosillo, Sonora, C.P. 83170, México.
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2
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Pompili S, Latella G, Gaudio E, Sferra R, Vetuschi A. The Charming World of the Extracellular Matrix: A Dynamic and Protective Network of the Intestinal Wall. Front Med (Lausanne) 2021; 8:610189. [PMID: 33937276 PMCID: PMC8085262 DOI: 10.3389/fmed.2021.610189] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 03/22/2021] [Indexed: 02/06/2023] Open
Abstract
The intestinal extracellular matrix (ECM) represents a complex network of proteins that not only forms a support structure for resident cells but also interacts closely with them by modulating their phenotypes and functions. More than 300 molecules have been identified, each of them with unique biochemical properties and exclusive biological functions. ECM components not only provide a scaffold for the tissue but also afford tensile strength and limit overstretch of the organ. The ECM holds water, ensures suitable hydration of the tissue, and participates in a selective barrier to the external environment. ECM-to-cells interaction is crucial for morphogenesis and cell differentiation, proliferation, and apoptosis. The ECM is a dynamic and multifunctional structure. The ECM is constantly renewed and remodeled by coordinated action among ECM-producing cells, degrading enzymes, and their specific inhibitors. During this process, several growth factors are released in the ECM, and they, in turn, modulate the deposition of new ECM. In this review, we describe the main components and functions of intestinal ECM and we discuss their role in maintaining the structure and function of the intestinal barrier. Achieving complete knowledge of the ECM world is an important goal to understand the mechanisms leading to the onset and the progression of several intestinal diseases related to alterations in ECM remodeling.
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Affiliation(s)
- Simona Pompili
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Giovanni Latella
- Department of Life, Health and Environmental Sciences, Gastroenterology Unit, University of L'Aquila, L'Aquila, Italy
| | - Eugenio Gaudio
- Department of Anatomical, Histological, Forensic Medicine, and Orthopedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Roberta Sferra
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Antonella Vetuschi
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
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3
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Lawrance IC, Rogler G, Bamias G, Breynaert C, Florholmen J, Pellino G, Reif S, Speca S, Latella G. Cellular and Molecular Mediators of Intestinal Fibrosis. J Crohns Colitis 2017. [PMID: 25306501 DOI: 10.1016/j.crohns.2014.09.00] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.
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Affiliation(s)
- Ian C Lawrance
- Centre for Inflammatory Bowel Diseases, Fremantle Hospital, Fremantle, WA, Australia.,University Department of Medicine and Pharmacology, University of Western Australia, Fremantle Hospital, Freemantle, WA, Australia
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital of Zurich, Zurich, Switzerland
| | - Giorgos Bamias
- Academic Department of Gastroenterology, Ethnikon and Kapodistriakon University of Athens, Laikon Hospital, Athens, Greece
| | - Christine Breynaert
- Department of Immunology and Microbiology, Laboratory of Clinical Immunology, KU Leuven, Leuven, Belgium.,Department of General Internal Medicine, University Hospitals Leuven, Leuven, Belgium
| | - Jon Florholmen
- Research Group of Gastroenterology and Nutrition, Institute of Clinical Medicine, Artic University of Norway and University Hospital of Northern Norway, Tromsø, Norway
| | - Gianluca Pellino
- General Surgery Unit, Second University of Naples, Naples, Italy
| | - Shimon Reif
- Department of Pediatrics, Tel-Aviv Souraski Medical Center, Tel-Aviv, Israel
| | - Silvia Speca
- National Institute of Health and Medical Research-INSERM, Unit U995, Lille, France
| | - Giovanni Latella
- Department of Life, Health and Environmental Sciences, Gastroenterology Unit, University of L'Aquila, L'Aquila, Italy
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4
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Lawrance IC, Rogler G, Bamias G, Breynaert C, Florholmen J, Pellino G, Reif S, Speca S, Latella G. Cellular and Molecular Mediators of Intestinal Fibrosis. J Crohns Colitis 2017; 11:1491-1503. [PMID: 25306501 PMCID: PMC5885809 DOI: 10.1016/j.crohns.2014.09.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.
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Affiliation(s)
- Ian C Lawrance
- Centre for Inflammatory Bowel Diseases, Fremantle Hospital, Fremantle, WA, Australia
- University Department of Medicine and Pharmacology, University of Western Australia, Fremantle Hospital, Freemantle, WA, Australia
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital of Zurich, Zurich, Switzerland
| | - Giorgos Bamias
- Academic Department of Gastroenterology, Ethnikon and Kapodistriakon University of Athens, Laikon Hospital, Athens, Greece
| | - Christine Breynaert
- Department of Immunology and Microbiology, Laboratory of Clinical Immunology, KU Leuven, Leuven, Belgium
- Department of General Internal Medicine, University Hospitals Leuven, Leuven, Belgium
| | - Jon Florholmen
- Research Group of Gastroenterology and Nutrition, Institute of Clinical Medicine, Artic University of Norway and University Hospital of Northern Norway, Tromsø, Norway
| | - Gianluca Pellino
- General Surgery Unit, Second University of Naples, Naples, Italy
| | - Shimon Reif
- Department of Pediatrics, Tel-Aviv Souraski Medical Center, Tel-Aviv, Israel
| | - Silvia Speca
- National Institute of Health and Medical Research-INSERM, Unit U995, Lille, France
| | - Giovanni Latella
- Department of Life, Health and Environmental Sciences, Gastroenterology Unit, University of L'Aquila, L'Aquila, Italy
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Powell RH, Behnke MS. WRN conditioned media is sufficient for in vitro propagation of intestinal organoids from large farm and small companion animals. Biol Open 2017; 6:698-705. [PMID: 28347989 PMCID: PMC5450310 DOI: 10.1242/bio.021717] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Recent years have seen significant developments in the ability to continuously propagate organoids derived from intestinal crypts. These advancements have been applied to mouse and human samples providing models for gastrointestinal tissue development and disease. We adapt these methods for the propagation of intestinal organoids (enteroids) from various large farm and small companion (LF/SC) animals, including cat, dog, cow, horse, pig, sheep and chicken. We show that LF/SC enteroids propagate and expand in L-WRN conditioned media containing signaling factors Wnt3a, R-spondin-3, and Noggin (WRN). Multiple successful isolations were achieved for each species, and the growth of LF/SC enteroids was maintained to high passage number. LF/SC enteroids expressed crypt stem cell marker LGR5 and low levels of mesenchymal marker VIM. Labeling with EdU also showed distinct regions of cell proliferation within the enteroids marking crypt-like regions. The ability to grow and maintain LF/SC enteroid cell lines provides additional models for the study of gastrointestinal developmental biology as well as platforms for the study of host-pathogen interactions between intestinal cells and zoonotic enteric pathogens of medical importance. Summary: Culturing methods for the propagation of crypt-derived mouse and human enteroids are applicable to large farm and small companion animals, demonstrating conservation of the crypt signaling microenvironment.
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Affiliation(s)
- Robin H Powell
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Michael S Behnke
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
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Tang CY, Man XF, Guo Y, Tang HN, Tang J, Zhou CL, Tan SW, Wang M, Zhou HD. IRS-2 Partially Compensates for the Insulin Signal Defects in IRS-1 -/- Mice Mediated by miR-33. Mol Cells 2017; 40:123-132. [PMID: 28190325 PMCID: PMC5339503 DOI: 10.14348/molcells.2017.2228] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 12/23/2016] [Accepted: 01/04/2017] [Indexed: 01/06/2023] Open
Abstract
Insulin signaling is coordinated by insulin receptor substrates (IRSs). Many insulin responses, especially for blood glucose metabolism, are mediated primarily through Irs-1 and Irs-2. Irs-1 knockout mice show growth retardation and insulin signaling defects, which can be compensated by other IRSs in vivo; however, the underlying mechanism is not clear. Here, we presented an Irs-1 truncated mutated mouse (Irs-1-/-) with growth retardation and subcutaneous adipocyte atrophy. Irs-1-/- mice exhibited mild insulin resistance, as demonstrated by the insulin tolerance test. Phosphatidylinositol 3-kinase (PI3K) activity and phosphorylated Protein Kinase B (PKB/AKT) expression were elevated in liver, skeletal muscle, and subcutaneous adipocytes in Irs-1 deficiency. In addition, the expression of IRS-2 and its phosphorylated version were clearly elevated in liver and skeletal muscle. With miRNA microarray analysis, we found miR-33 was down-regulated in bone marrow stromal cells (BMSCs) of Irs-1-/- mice, while its target gene Irs-2 was up-regulated in vitro studies. In addition, miR-33 was down-regulated in the presence of Irs-1 and which was up-regulated in fasting status. What's more, miR-33 restored its expression in re-feeding status. Meanwhile, miR-33 levels decreased and Irs-2 levels increased in liver, skeletal muscle, and subcutaneous adipocytes of Irs-1-/- mice. In primary cultured liver cells transfected with an miR-33 inhibitor, the expression of IRS-2, PI3K, and phosphorylated-AKT (p-AKT) increased while the opposite results were observed in the presence of an miR-33 mimic. Therefore, decreased miR-33 levels can up-regulate IRS-2 expression, which appears to compensate for the defects of the insulin signaling pathway in Irs-1 deficient mice.
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Affiliation(s)
- Chen-Yi Tang
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Xiao-Fei Man
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Yue Guo
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Hao-Neng Tang
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Jun Tang
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Ci-La Zhou
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Shu-Wen Tan
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
| | - Min Wang
- Department of Endocrinology, Xiangya Hospital, Central South University, Changsha, Hunan 410008,
China
| | - Hou-De Zhou
- Department of Endocrinology and Metabolism, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011,
China
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7
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Milk growth factors and expression of small intestinal growth factor receptors during the perinatal period in mice. Pediatr Res 2016; 80:759-765. [PMID: 27603563 DOI: 10.1038/pr.2016.150] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/26/2016] [Indexed: 01/23/2023]
Abstract
BACKGROUND Growth factors (GFs) are milk bioactive components contributing to the regulation of neonatal small intestinal maturation, and their receptors on the small intestinal epithelium play essential roles in mediating the functions of GFs. There is limited data correlating milk GFs and their receptors in the neonatal small intestine during the perinatal period. METHODS Small intestines of C57BL/6N mouse pups were collected at regular intervals during fetal life and up to postnatal day (PD) 60. Gene expression of GF receptors was determined by real-time qPCR. Milk GF concentrations up to PD21 were analyzed by enzyme-linked immunosorbent assay. RESULTS The majority of GF receptors showed significantly greater expression in the fetus than in postnatal life, and a sharp decrease occurred from PD14 extending to PD60; solid food restriction (PD14 and PD18) did not affect this decrease. Concentrations of five detected milk GFs demonstrated that GFs and the corresponding small intestinal receptors exhibited different correlations, with only milk transforming growth factor β1 (TGF-β1) having a significant positive correlation with TGF-β receptor 1 mRNA. CONCLUSION Gene expression of small intestinal GF receptors is likely a process of neonatal intestinal maturation that is affected concurrently by milk GFs and additional endogenous factors.
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Merker SR, Weitz J, Stange DE. Gastrointestinal organoids: How they gut it out. Dev Biol 2016; 420:239-250. [PMID: 27521455 DOI: 10.1016/j.ydbio.2016.08.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 07/09/2016] [Accepted: 08/10/2016] [Indexed: 02/06/2023]
Abstract
The gastrointestinal tract is characterized by a self-renewing epithelium fueled by adult stem cells residing at the bottom of the intestinal crypt and gastric glands. Their activity and proliferation is strongly dependent on complex signaling pathways involving other crypt/gland cells as well as surrounding stromal cells. In recent years organoids are becoming increasingly popular as a new and powerful tool to study developmental or other biological processes. Organoids retain morphological and molecular patterns of the tissue they are derived from, are self-organizing, relatively simple to handle and accessible to genetic engineering. This review focuses on the developmental processes and signaling molecules involved in epithelial homeostasis and how a profound knowledge of these mechanisms allowed the establishment of a three dimensional organoid culture derived from adult gastrointestinal stem cells.
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Affiliation(s)
- Sebastian R Merker
- Department of Gastrointestinal, Thoracic and Vascular Surgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
| | - Jürgen Weitz
- Department of Gastrointestinal, Thoracic and Vascular Surgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
| | - Daniel E Stange
- Department of Gastrointestinal, Thoracic and Vascular Surgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany.
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9
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Santoro MA, Blue RE, Andres SF, Mah AT, Van Landeghem L, Lund PK. Obesity and intestinal epithelial deletion of the insulin receptor, but not the IGF 1 receptor, affect radiation-induced apoptosis in colon. Am J Physiol Gastrointest Liver Physiol 2015; 309:G578-89. [PMID: 26251471 PMCID: PMC4593818 DOI: 10.1152/ajpgi.00189.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/31/2015] [Indexed: 01/31/2023]
Abstract
Current views suggest that apoptosis eliminates genetically damaged cells that may otherwise form tumors. Prior human studies link elevated insulin and reduced apoptosis to risk of colorectal adenomas. We hypothesized that hyperinsulinemia associated with obesity would lead to reduced colon epithelial cell (CEC) apoptosis after radiation and that this effect would be altered by deletion of the insulin-like growth factor (IGF) 1 receptor (IGF1R) or the insulin receptor (IR). Mice with villin-Cre-mediated IGF1R or IR deletion in CECs and floxed littermates were fed a high-fat diet to induce obesity and hyperinsulinemia or control low-fat chow. Mice were exposed to 5-Gy abdominal radiation to induce DNA damage and euthanized 4 h later for evaluation of apoptosis by localization of cleaved caspase-3. Obese mice exhibited decreased apoptosis of genetically damaged CECs. IGF1R deletion did not affect CEC apoptosis in lean or obese animals. In contrast, IR loss increased CEC apoptosis in both diet groups but did not prevent antiapoptotic effects of obesity. Levels of p53 protein were significantly reduced in CECs of obese mice with intact IR but increased in both lean and obese mice without IR. Levels of mRNAs encoding proapoptotic Perp and the cell cycle inhibitor Cdkn1b/p27 were reduced in CECs of obese mice and increased in lean mice lacking IR. Together, our studies provide novel evidence for antiapoptotic roles of obesity and IR, but not IGF1R, in colonic epithelium after DNA damage. However, neither IR nor IGF1R deletion prevented a reduction in radiation-induced CEC apoptosis during obesity and hyperinsulinemia.
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Affiliation(s)
- M. Agostina Santoro
- 1Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and
| | - R. Eric Blue
- 1Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and
| | - Sarah F. Andres
- 1Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and
| | - Amanda T. Mah
- 2Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Laurianne Van Landeghem
- 1Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and
| | - P. Kay Lund
- 1Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and
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Danielsen SA, Eide PW, Nesbakken A, Guren T, Leithe E, Lothe RA. Portrait of the PI3K/AKT pathway in colorectal cancer. Biochim Biophys Acta Rev Cancer 2014; 1855:104-21. [PMID: 25450577 DOI: 10.1016/j.bbcan.2014.09.008] [Citation(s) in RCA: 173] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 09/07/2014] [Indexed: 12/16/2022]
Abstract
PI3K/AKT signaling leads to reduced apoptosis, stimulates cell growth and increases proliferation. Under normal conditions, PI3K/AKT activation is tightly controlled and dependent on both extracellular growth signals and the availability of amino acids and glucose. Genetic aberrations leading to PI3K/AKT hyper-activation are observed at considerable frequency in all major nodes in most tumors. In colorectal cancer the most commonly observed pathway changes are IGF2 overexpression, PIK3CA mutations and PTEN mutations and deletions. Combined, these alterations are found in about 40% of large bowel tumors. In addition, but not mutually exclusive to these, KRAS mutations are observed at a similar frequency. There are however additional, less frequent and more poorly understood events that may also push the PI3K/AKT pathway into overdrive and thus promote malignant growth. Here we discuss aberrations of components at the genetic, epigenetic, transcriptional, post-transcriptional, translational and post-translational level where perturbations may drive excessive PI3K/AKT signaling. Integrating multiple molecular levels will advance our understanding of this cancer critical circuit and more importantly, improve our ability to pharmacologically target the pathway in view of clonal development, tumor heterogeneity and drug resistance mechanisms. In this review, we revisit the PI3K/AKT pathway cancer susceptibility syndromes, summarize the known aberrations at the different regulatory levels and the prognostic and predictive values of these alterations in colorectal cancer.
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Affiliation(s)
- Stine Aske Danielsen
- Department of Cancer Prevention, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway
| | - Peter Wold Eide
- Department of Cancer Prevention, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway
| | - Arild Nesbakken
- K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway; Department of Gastrointestinal Surgery, Oslo University Hospital, Oslo, Norway
| | - Tormod Guren
- K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway; Department of Oncology, Oslo University Hospital, Oslo, Norway
| | - Edward Leithe
- Department of Cancer Prevention, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway
| | - Ragnhild A Lothe
- Department of Cancer Prevention, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; K.G. Jebsen Colorectal Cancer Research Centre, Oslo University Hospital, Oslo, Norway.
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11
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Santoro MA, Andres SF, Galanko JA, Sandler RS, Keku TO, Lund PK. Reduced insulin-like growth factor I receptor and altered insulin receptor isoform mRNAs in normal mucosa predict colorectal adenoma risk. Cancer Epidemiol Biomarkers Prev 2014; 23:2093-100. [PMID: 25017244 DOI: 10.1158/1055-9965.epi-14-0177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Hyperinsulinemia resulting from obesity and insulin resistance is associated with increased risk of many cancers, but the biology underlying this risk is unclear. We hypothesized that increased mRNA levels of the insulin-like growth factor I receptor (IGFIR) versus the insulin receptor (IR) or elevated ratio of IR-A:IR-B isoforms in normal rectal mucosa would predict adenoma risk, particularly in individuals with high body mass index (BMI) or plasma insulin. METHODS Biopsies from normal rectal mucosa were obtained from consenting patients undergoing routine colonoscopy at University of North Carolina Hospitals (Chapel Hill, NC). Subjects with colorectal adenomas were classified as cases (n = 100) and were matched to adenoma-free controls (n = 98) based on age, sex, and BMI. IGFIR and IR mRNA levels were assessed by qRT-PCR, and IR-A:IR-B mRNA ratios by standard PCR. Plasma insulin and crypt apoptosis were measured by ELISA and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), respectively. Logistic regression models examined relationships between receptor mRNAs, BMI, plasma insulin, and adenoma risk. RESULTS Unexpectedly, cases were significantly more likely to have lower IGFIR mRNA levels than controls. No overall differences in total IR mRNA or IR-A:IR-B ratios were observed between cases and controls. Interestingly, in patients with high plasma insulin, increased IR-A:IR-B ratio was associated with increased likelihood of having adenomas. CONCLUSIONS Our work shows novel findings that reduced IGFIR mRNA and, during high plasma insulin, increased IR-A:IR-B ratios in normal rectal mucosa are associated with colorectal adenoma risk. IMPACT Our work provides evidence supporting a link between IGFIR and IR isoform expression levels and colorectal adenoma risk.
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Affiliation(s)
- M Agostina Santoro
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Sarah F Andres
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Joseph A Galanko
- Department of Medicine and Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Robert S Sandler
- Department of Medicine and Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Temitope O Keku
- Department of Medicine and Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - P Kay Lund
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
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12
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Reynolds A, Wharton N, Parris A, Mitchell E, Sobolewski A, Kam C, Bigwood L, El Hadi A, Münsterberg A, Lewis M, Speakman C, Stebbings W, Wharton R, Sargen K, Tighe R, Jamieson C, Hernon J, Kapur S, Oue N, Yasui W, Williams MR. Canonical Wnt signals combined with suppressed TGFβ/BMP pathways promote renewal of the native human colonic epithelium. Gut 2014; 63:610-21. [PMID: 23831735 PMCID: PMC3963552 DOI: 10.1136/gutjnl-2012-304067] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND A defining characteristic of the human intestinal epithelium is that it is the most rapidly renewing tissue in the body. However, the processes underlying tissue renewal and the mechanisms that govern their coordination have proved difficult to study in the human gut. OBJECTIVE To investigate the regulation of stem cell-driven tissue renewal by canonical Wnt and TGFβ/bone morphogenetic protein (BMP) pathways in the native human colonic epithelium. DESIGN Intact human colonic crypts were isolated from mucosal tissue samples and placed into 3D culture conditions optimised for steady-state tissue renewal. High affinity mRNA in situ hybridisation and immunohistochemistry were complemented by functional genomic and bioimaging techniques. The effects of signalling pathway modulators on the status of intestinal stem cell biology, crypt cell proliferation, migration, differentiation and shedding were determined. RESULTS Native human colonic crypts exhibited distinct activation profiles for canonical Wnt, TGFβ and BMP pathways. A population of intestinal LGR5/OLFM4-positive stem/progenitor cells were interspersed between goblet-like cells within the crypt-base. Exogenous and crypt cell-autonomous canonical Wnt signals supported homeostatic intestinal stem/progenitor cell proliferation and were antagonised by TGFβ or BMP pathway activation. Reduced Wnt stimulation impeded crypt cell proliferation, but crypt cell migration and shedding from the crypt surface were unaffected and resulted in diminished crypts. CONCLUSIONS Steady-state tissue renewal in the native human colonic epithelium is dependent on canonical Wnt signals combined with suppressed TGFβ/BMP pathways. Stem/progenitor cell proliferation is uncoupled from crypt cell migration and shedding, and is required to constantly replenish the crypt cell population.
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Affiliation(s)
- Amy Reynolds
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Natalia Wharton
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Alyson Parris
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Esther Mitchell
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Anastasia Sobolewski
- Department of Gut Health and Food Safety, Institute Strategic Programme, Institute of Food Research, Colney, Norwich Research Park, Norwich, Norfolk, UK
| | - Christy Kam
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Loren Bigwood
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Ahmed El Hadi
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Andrea Münsterberg
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
| | - Michael Lewis
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Christopher Speakman
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - William Stebbings
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Richard Wharton
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Kevin Sargen
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Richard Tighe
- Department of Gastroenterology, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Crawford Jamieson
- Department of Gastroenterology, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - James Hernon
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Sandeep Kapur
- Department of Surgery, Norfolk and Norwich University Hospitals Trust, Colney Lane, Norwich Research Park, Norwich, Norfolk, UK
| | - Naohide Oue
- Department of Molecular Pathology, Hiroshima University Institute of Biomedical and Health Sciences, Hiroshima, Japan
| | - Wataru Yasui
- Department of Molecular Pathology, Hiroshima University Institute of Biomedical and Health Sciences, Hiroshima, Japan
| | - Mark R Williams
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk, UK
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Riehl TE, Ee X, Stenson WF. Hyaluronic acid regulates normal intestinal and colonic growth in mice. Am J Physiol Gastrointest Liver Physiol 2012; 303:G377-88. [PMID: 22556141 PMCID: PMC3423109 DOI: 10.1152/ajpgi.00034.2012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 04/29/2012] [Indexed: 01/31/2023]
Abstract
Hyaluronic acid (HA), a component of the extracellular matrix, affects gastrointestinal epithelial proliferation in injury models, but its role in normal growth is unknown. We sought to determine the effects of exogenous HA on intestinal and colonic growth by intraperitoneal injection of HA twice a week into C57BL/6 mice from 3 to 8 wk of age. Similarly, to determine the effects of endogenous HA on intestinal and colonic growth, we administered PEP-1, a peptide that blocks the binding of HA to its receptors, on the same schedule. In mice treated with exogenous HA, villus height and crypt depth in the intestine, crypt depth in the colon, and epithelial proliferation in the intestine and colon were increased. In mice treated with PEP-1, intestinal and colonic length were markedly decreased and crypt depth and villus height in the intestine, crypt depth in the colon, and epithelial proliferation in the intestine and colon were decreased. Administration of HA was associated with increased levels of EGF (intestine) and IGF-I (colon), whereas administration of PEP-1 was associated with decreased levels of IGF-I (intestine) and epiregulin (colon). Exogenous HA increases intestinal and colonic epithelial proliferation, resulting in hyperplasia. Blocking the binding of endogenous HA to its receptors results in decreased intestinal and colonic length and a mucosal picture of hypoplasia, suggesting that endogenous HA contributes to the regulation of normal intestinal and colonic growth.
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Affiliation(s)
- Terrence E Riehl
- Division of Gastroenterology, Washington University, St. Louis, Missouri, USA
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Speca S, Giusti I, Rieder F, Latella G. Cellular and molecular mechanisms of intestinal fibrosis. World J Gastroenterol 2012; 18:3635-61. [PMID: 22851857 PMCID: PMC3406417 DOI: 10.3748/wjg.v18.i28.3635] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Revised: 03/26/2012] [Accepted: 04/09/2012] [Indexed: 02/06/2023] Open
Abstract
Fibrosis is a chronic and progressive process characterized by an excessive accumulation of extracellular matrix (ECM) leading to stiffening and/or scarring of the involved tissue. Intestinal fibrosis may develop in several different enteropathies, including inflammatory bowel disease. It develops through complex cell, extracellular matrix, cytokine and growth factor interactions. Distinct cell types are involved in intestinal fibrosis, such as resident mesenchymal cells (fibroblasts, myofibroblasts and smooth muscle cells) but also ECM-producing cells derived from epithelial and endothelial cells (through a process termed epithelial- and endothelial-mesenchymal transition), stellate cells, pericytes, local or bone marrow-derived stem cells. The most important soluble factors that regulate the activation of these cells include cytokines, chemokines, growth factors, components of the renin-angiotensin system, angiogenic factors, peroxisome proliferator-activated receptors, mammalian target of rapamycin, and products of oxidative stress. It soon becomes clear that although inflammation is responsible for triggering the onset of the fibrotic process, it only plays a minor role in the progression of this condition, as fibrosis may advance in a self-perpetuating fashion. Definition of the cellular and molecular mechanisms involved in intestinal fibrosis may provide the key to developing new therapeutic approaches.
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The insulin receptor substrate 1 (IRS1) in intestinal epithelial differentiation and in colorectal cancer. PLoS One 2012; 7:e36190. [PMID: 22558377 PMCID: PMC3338610 DOI: 10.1371/journal.pone.0036190] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 04/01/2012] [Indexed: 12/13/2022] Open
Abstract
Colorectal cancer (CRC) is associated with lifestyle factors that affect insulin/IGF signaling, of which the insulin receptor substrate 1 (IRS1) is a key transducer. We investigated expression, localization and pathologic correlations of IRS1 in cancer-uninvolved colonic epithelium, primary CRCs with paired liver metastases and in vitro polarizing Caco2 and HT29 cells. IRS1 mRNA and protein resulted higher, relative to paired mucosa, in adenomas of familial adenomatous polyposis patients and in CRCs that overexpressed c-MYC, ß-catenin, InsRß, and IGF1R. Analysis of IRS1 immunostaining in 24 cases of primary CRC with paired colonic epithelium and hepatic metastasis showed that staining intensity was significantly higher in metastases relative to both primary CRC (P<0.01) and colonic epithelium (P<0.01). Primary and metastatic CRCs, compared to colonic epithelium, contained significantly higher numbers of IRS1-positive cells (P = 0.013 and P = 0.014, respectively). Pathologic correlations in 163 primary CRCs revealed that diffuse IRS1 staining was associated with tumors combining differentiated phenotype and aggressive markers (high Ki67, p53, and ß-catenin). In Caco 2 IRS1 and InsR were maximally expressed after polarization, while IGF1R was highest in pre-polarized cells. No nuclear IRS1 was detected, while, with polarization, phosphorylated IRS1 (pIRS1) shifted from the lateral to the apical plasma membrane and was expressed in surface cells only. In HT29, that carry mutations constitutively activating survival signaling, IRS1 and IGF1R decreased with polarization, while pIRS1 localized in nuclear spots throughout the course. Overall, these data provide evidence that IRS1 is modulated according to CRC differentiation, and support a role of IRS1 in CRC progression and liver metastatization.
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Affiliation(s)
- Rao N. Jaladanki
- University of Maryland School of Medicine and Baltimore Veterans Affairs Medical Center
| | - Jian-Ying Wang
- University of Maryland School of Medicine and Baltimore Veterans Affairs Medical Center
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Stanzel RDP, Lourenssen S, Nair DG, Blennerhassett MG. Mitogenic factors promoting intestinal smooth muscle cell proliferation. Am J Physiol Cell Physiol 2010; 299:C805-17. [PMID: 20631246 DOI: 10.1152/ajpcell.00086.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intestinal smooth muscle cells are normally quiescent, but in the widely studied model of trinitrobenzene sulfonic acid (TNBS)-induced colitis in the rat, the onset of inflammation causes proliferation that leads to increased cell number and an altered phenotype. The factors that drive this are unclear and were studied in primary cultures of circular smooth muscle cells (CSMC) from the rat colon. While platelet-derived growth factor (PDGF)-AA, fibroblast growth factor (FGF), and epidermal growth factor (EGF) were ineffective, PDGF-BB and insulin-like growth factor-1 (IGF-1) caused significant increase in [(3)H]thymidine incorporation, bromodeoxyuridine uptake, and increased CSMC number, with PDGF-BB (≥0.2 nM) substantially more effective than IGF-1. Surprisingly, CSMC lacked expression of PDGF receptor-β (PDGF-Rβ) upon isolation but by 4 days in vitro, CSMC gained expression of PDGF-Rβ as shown by quantitative PCR, Western blot analysis, and immunocytochemistry; these CSMC responded to PDGF-BB but not IGF-1. PDGF-BB caused PDGF-Rβ phosphorylation and mobilization from the surface membrane, leading to activation of both Akt and ERK signaling pathways, which were essential for subsequent proliferation. In contrast, PDGF-AA, FGF, EGF, and IGF-1 were ineffective. In vivo, control CSMC lacked expression of PDGF-Rβ. However, this changed rapidly with TNBS-colitis, and by day 2 when CSMC proliferation in vivo is maximal, freshly isolated CSMC showed on-going PDGF-Rβ phosphorylation that was further increased by exogenous PDGF-BB. This suggests that the onset of PDGF-Rβ expression is a key factor in CSMC growth in vitro and in vivo, where inflammation may damage intrinsic inhibitory mechanisms and thus lead to hyperplasia.
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Affiliation(s)
- Roger D P Stanzel
- Gastrointestinal Diseases Research Unit, Queen's Univ., Kingston General Hospital, 76 Stuart St., Kingston, Ontario, Canada
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Longobardi L, Granero-Moltó F, O'Rear L, Myers TJ, Li T, Kregor PJ, Spagnoli A. Subcellular localization of IRS-1 in IGF-I-mediated chondrogenic proliferation, differentiation and hypertrophy of bone marrow mesenchymal stem cells. Growth Factors 2009; 27:309-20. [PMID: 19639489 DOI: 10.1080/08977190903138874] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Bone marrow derived mesenchymal stem cells (BM-MSC) can differentiate into chondrocytes. Understanding the mechanisms and growth factors that control the MSC stemness is critical to fully implement their therapeutic use in cartilage diseases. The activated type 1 insulin-like growth factor receptor (IGF-IR), interacting with the insulin receptor substrate-1 (IRS-1), can induce cancer cell proliferation and transformation. In cancer or transformed cells, IRS-1 has been shown to localize in the cytoplasm where it activates the canonical Akt pathway, as well as in the nucleus where it binds to nuclear proteins. We have previously demonstrated that IGF-I has distinct time-dependent effect on primary BM-MSC chondrogenic pellets: initially (2-day culture), IGF-I induces proliferation; subsequently, IGF-I promotes chondrocytic differentiation (7-day culture). In the present study, by using MSC from the BM of IRS-1(- / - ) mice we show that IRS-1 mediates almost 50% of the IGF-I mitogenic response and the MAPK-MEK/ERK signalling accounts for the other 50%. After stimulation with IGF-I, we found that in 2-day old human and mouse derived BM-MSC pellets, IRS-1 (total and phosphorylated) is nuclearly localized and that proliferation prevails over differentiation. The IGF-I mitogenic effect is Akt-independent. In 7-day MSC pellets, IGF-I stimulates the chondrogenic differentiation of MSC into chondrocytes, pre-hypertrophic and hypertrophic chondrocytes and IRS-1 accumulates in the cytoplasm. IGF-I-dependent differentiation is exclusively Akt-dependent. Our data indicate that in the physiologically relevant model of primary cultured MSC, IGF-I induces a temporally regulated nuclear or cytoplasmic localization of IRS-1 that correlate with the transition from proliferation to chondrogenic differentiation.
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Affiliation(s)
- Lara Longobardi
- Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7039, USA
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Kim B, Feldman EL. Insulin receptor substrate (IRS)-2, not IRS-1, protects human neuroblastoma cells against apoptosis. Apoptosis 2009; 14:665-73. [PMID: 19259821 DOI: 10.1007/s10495-009-0331-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin receptor substrates (IRS)-1 and -2 are major substrates of insulin and type I insulin-like growth factor (IGF-I) receptor (IGF-IR) signaling. In this study, SH-EP human neuroblastoma cells are used as a model system to examine the differential roles of IRS-1 and IRS-2 on glucose-mediated apoptosis. In the presence of high glucose, IRS-1 underwent caspase-mediated degradation, followed by focal adhesion kinase (FAK) and Akt degradation and apoptosis. IRS-2 expression blocked all these changes whereas IRS-1 overexpression had no effect. In parallel, IRS-2, but not IRS-1, overexpression enhanced IGF-I-mediated Akt activation without affecting extracellular regulated kinase signaling. While IRS-1 was readily degraded by caspases, hyperglycemia-mediated IRS-2 degradation was unaffected by caspase inhibitors but blocked by proteasome and calpain inhibitors. Our data suggest that the differential degradation of IRS-1 and IRS-2 contributes to their distinct modes of action and the increased neuroprotective effects of IRS-2 in this report are due, in part, to its resistance to caspase-mediated degradation.
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Affiliation(s)
- Bhumsoo Kim
- Department of Neurology, University of Michigan, 5371 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
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