451
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Takahashi N, Okumura T, Motomura W, Fujimoto Y, Kawabata I, Kohgo Y. Activation of PPARgamma inhibits cell growth and induces apoptosis in human gastric cancer cells. FEBS Lett 1999; 455:135-9. [PMID: 10428487 DOI: 10.1016/s0014-5793(99)00871-6] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We investigated the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and the role of PPARgamma in cell growth in human gastric cancer cells. Reverse transcription-polymerase chain reaction, Northern blot and Western blot analyses showed that a human gastric cancer cell line, MKN45, expressed PPARgamma mRNA and protein. Luciferase assay in MKN45 cells showed that troglitazone, a selective ligand for PPARgamma, transactivated the transcription of a peroxisome proliferator response element-driven promoter. Troglitazone or pioglitazone, selective ligands for PPARgamma, inhibited the growth of MKN45 cells in a dose-dependent manner. Co-incubation of MKN45 cells with troglitazone induced DNA ladder formation. These results suggest that human gastric cancer cells express PPARgamma and that activation of PPARgamma inhibits cell growth and induces apoptosis in gastric cancer cells.
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Affiliation(s)
- N Takahashi
- Third Department of Internal Medicine, Asahikawa Medical College, Japan
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452
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Abstract
Peroxisome proliferator-activated receptors (PPAR) were discovered in 1990, ending 25 years of uncertainty about the molecular mechanisms of peroxisome proliferation. Subsequently, PPARs have improved our understanding of adipocyte differentiation. But there is more to PPARs than solving a puzzle about an organelle (the peroxisome) long considered an oddity, and their medical significance goes beyond obesity too. Enhanced PPAR type alpha expression protects against cardiovascular disorders though the role of enhanced PPARgamma expression seems less favourable. PPAR mechanisms, mainly via induction of more differentiated cell phenotypes, protect against some cancers. The differentiation of many cell types (hepatocyte, fibroblast, adipocyte, keratinocyte, myocyte, and monocyte/macrophage) involves PPARs, and these nuclear receptors are now attracting the attention of many medical specialties and the pharmaceutical industry.
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Affiliation(s)
- J Vamecq
- INSERM/Neuropaediatrics Department of Professor Jean-Pierre Nuyts, CHU Lille, France.
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453
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Gelman L, Auwerx J. Peroxisome proliferator-activated receptors: mediators of a fast food impact on gene regulation. Curr Opin Clin Nutr Metab Care 1999; 2:307-12. [PMID: 10453311 DOI: 10.1097/00075197-199907000-00010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Peroxisome proliferator-activated receptors are nuclear receptors with pleiotropic effects on intra- and extracellular lipid metabolism, glucose homeostasis, inflammation control, and cell proliferation. This review addresses the respective roles of the different peroxisome proliferator-activated receptor isoforms in these different processes.
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Affiliation(s)
- L Gelman
- Département d'Athérosclérose, Institut Pasteur de Lille, France
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454
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Sarraf P, Mueller E, Smith WM, Wright HM, Kum JB, Aaltonen LA, de la Chapelle A, Spiegelman BM, Eng C. Loss-of-function mutations in PPAR gamma associated with human colon cancer. Mol Cell 1999; 3:799-804. [PMID: 10394368 DOI: 10.1016/s1097-2765(01)80012-5] [Citation(s) in RCA: 377] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The gamma isoform of the peroxisome proliferator-activated receptor, PPAR gamma, regulates adipocyte differentiation and has recently been shown to be expressed in neoplasia of the colon and other tissues. We have found four somatic PPAR gamma mutations among 55 sporadic colon cancers: one nonsense, one frameshift, and two missense mutations. Each greatly impaired the function of the protein. c.472delA results in deletion of the entire ligand binding domain. Q286P and K319X retain a total or partial ligand binding domain but lose the ability to activate transcription through a failure to bind to ligands. R288H showed a normal response to synthetic ligands but greatly decreased transcription and binding when exposed to natural ligands. These data indicate that colon cancer in humans is associated with loss-of-function mutations in PPAR gamma.
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Affiliation(s)
- P Sarraf
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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455
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Su JL, Winegar DA, Wisely GB, Sigel CS, Hull-Ryde EA. Use of a PPAR gamma-specific monoclonal antibody to demonstrate thiazolidinediones induce PPAR gamma receptor expression in vitro. Hybridoma (Larchmt) 1999; 18:273-80. [PMID: 10475242 DOI: 10.1089/027245799315934] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Troglitazone and rosiglitazone (BRL49653), members of the thiazolidinedione (TZD) class of antidiabetic drugs, are peroxisome proliferator-activated receptor gamma (PPARgamma) ligands that induce adipocyte differentiation and increase the expression of PPARgamma protein. Here, we report the characterization of a PPARgamma specific monoclonal antibody (MAb), PgammaA53.25, and its use to monitor PPARgamma expression in the noncommitted pluripotent murine mesenchymal stem cell line, C3H10T1/2, treated with TZDs. MAb PgammaA53.25 was raised against a region in the N-terminal domain of human PPARgamma shared by splice variants PPARgamma1 and PPARgamma2. It recognizes immunizing antigen in enzyme-linked immunoadsorbent assay (ELISA), and does not cross-react with the N-terminal domains of PPARalpha or PPARdelta. In Western blotting, PgammaA53.25 reacts with the immunizing antigen as well as distinct protein bands corresponding to the molecular weight of full length PPARgamma from C3H10T1/2 cells and rat tissue lysates. In fluorescent microscopy, PgammaA53.25 immunostains nuclei of C3H10T1/2 cells treated with PPARgamma ligands. The fluorescence intensity of the treated cells is TZD dose-dependent, and correlates with lipid accumulation consistent with adipogenesis. Based on these results, we propose that MAb PgammaA53.25 will be a useful tool for elucidating the role of PPARgamma in fatty acid metabolism and adipocyte differentiation.
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Affiliation(s)
- J L Su
- Department of Molecular Sciences, Glaxo Wellcome Research and Development, Research Triangle Park, NC 27709, USA
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456
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Abstract
Steroid and thyroid hormones and vitamin A metabolites (retinoids) regulate the expression of complex gene programs by binding to members of the nuclear receptor family of ligand-activated transcription factors. The nuclear receptor family also includes many "orphan" members that currently lack known ligands but that represent candidate receptors for new hormones. Recently, natural and synthetic ligands have been identified for several orphan receptors and used to dissect their biological roles. This "reverse endocrinology" strategy has resulted in the discovery of unanticipated nuclear signaling pathways for retinoids, fatty acids, eicosanoids, and steroids with important physiological and pharmacological ramifications.
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Affiliation(s)
- S A Kliewer
- Department of Molecular Endocrinology, Glaxo Wellcome Research and Development, Five Moore Drive, Research Triangle Park, NC 27709, USA.
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457
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Meade EA, McIntyre TM, Zimmerman GA, Prescott SM. Peroxisome proliferators enhance cyclooxygenase-2 expression in epithelial cells. J Biol Chem 1999; 274:8328-34. [PMID: 10075740 DOI: 10.1074/jbc.274.12.8328] [Citation(s) in RCA: 222] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The formation of prostaglandins requires the catalytic activity of cyclooxygenase (COX) which converts arachidonic acid to the prostaglandin endoperoxide PGH2, from which all other prostaglandins are formed. COX-2 is the highly inducible isozyme of COX which is responsible for much of the prostaglandin production in inflammation and is a key factor in colon carcinogenesis. Because COX-2 activity can be rate-limiting in prostaglandin formation, COX-2 expression must be regulated tightly. Numerous factors, including mitogens, tumor promoters, and cytokines have been found to stimulate the transcription of COX-2. We show that fatty acids, prostaglandins, and non-steroidal anti-inflammatory drugs, compounds that are substrates, products, and inhibitors, respectively, of COX enzymatic activity, also increase its expression. These compounds are members of a heterogeneous group of compounds known as peroxisome proliferators, and the prototypical peroxisome proliferator, WY-14, 643, also enhanced COX-2 expression. We demonstrate that these compounds increase COX-2 transcription, and we identify a region of the COX-2 promoter containing a peroxisome proliferator response element that is responsible for the enhancement of COX-2 expression seen with these compounds.
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Affiliation(s)
- E A Meade
- Eccles Program in Human Molecular Biology and Genetics, the Huntsman Cancer Institute, the University of Utah, Salt Lake City, Utah 84112, USA
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458
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Unger RH, Zhou YT, Orci L. Regulation of fatty acid homeostasis in cells: novel role of leptin. Proc Natl Acad Sci U S A 1999; 96:2327-32. [PMID: 10051641 PMCID: PMC26783 DOI: 10.1073/pnas.96.5.2327] [Citation(s) in RCA: 315] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is proposed that an important function of leptin is to confine the storage of triglycerides (TG) to the adipocytes, while limiting TG storage in nonadipocytes, thus protecting them from lipotoxicity. The fact that TG content in nonadipocytes normally remains within a narrow range, while that of adipocytes varies enormously with food intake, is consistent with a system of TG homeostasis in normal nonadipocytes. The facts that when leptin receptors are dysfunctional, TG content in nonadipocytes such as islets can increase 100-fold, and that constitutively expressed ectopic hyperleptinemia depletes TG, suggest that leptin controls the homeostatic system for intracellular TG. The fact that the function and viability of nonadipocytes is compromised when their TG content rises above or falls below the normal range suggests that normal homeostasis of their intracellular TG is critical for optimal function and to prevent lipoapoptosis. Thus far, lipotoxic diabetes of fa/fa Zucker diabetic fatty rats is the only proven lipodegenerative disease, but the possibility of lipotoxic disease of skeletal and/or cardiac muscle may require investigation, as does the possible influence of the intracellular TG content on autoimmune and neoplastic processes.
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Affiliation(s)
- R H Unger
- Gifford Laboratories, Center for Diabetes Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA.
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459
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Abstract
Thiazolidinediones (TZDs) are a new class of oral antidiabetic agents. They selectively enhance or partially mimic certain actions of insulin, causing a slowly generated antihyperglycaemic effect in Type 2 (noninsulin dependent) diabetic patients. This is often accompanied by a reduction in circulating concentrations of insulin, triglycerides and nonesterified fatty acids. TZDs act additively with other types of oral antidiabetic agents (suphonylureas, metformin and acarbose) and reduce the insulin dosage required in insulin-treated patients. The glucose-lowering effect of TZDs is attributed to increased peripheral glucose disposal and decreased hepatic glucose output. This is achieved substantively by the activation of a specific nuclear receptor - the peroxisome proliferator-activated receptor-gamma (PPARgamma), which increases transcription of certain insulin-sensitive genes. To date one TZD, troglitazone, has been introduced into clinical use (in Japan, USA and UK in 1997). This was suspended after 2 months in the UK pending further investigation of adverse effects on liver function. TZDs have been shown to improve insulin sensitivity in a range of insulin-resistant states including obesity, impaired glucose tolerance (IGT) and polycystic ovary syndrome (PCOS). In Type 2 diabetes, the TZDs offer a new type of oral therapy to reduce insulin resistance and assist glycaemic control.
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Affiliation(s)
- C Day
- Diabetes Research Group, Life and Health Sciences, Aston University, Birmingham, UK
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460
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Versteeg HH, van Bergen en Henegouwen PM, van Deventer SJ, Peppelenbosch MP. Cyclooxygenase-dependent signalling: molecular events and consequences. FEBS Lett 1999; 445:1-5. [PMID: 10069362 DOI: 10.1016/s0014-5793(99)00105-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Non-steroidal anti-inflammatory drugs (NSAIDs) currently attract large interest. Next to pain relief, NSAIDs have important anti-thrombotic and anti-oncogenic effects. NSAIDs exert their action by inhibition of cyclooxygenase, the enzyme responsible for the production of prostanoids. Prostanoid signal transduction is still poorly understood, but it has become clear that these inflammatory lipids influence cellular physiology at three different levels: (1) activation of a 7 x transmembrane receptor coupled to heterotrimeric G proteins, (2) the inhibition of inflammation by activating corticosteroid-like receptors, (3) participation in receptor protein tyrosine kinase signal transduction. In this review prostanoid signalling at these three different levels will be reviewed and the relevance in (patho)physiological processes will be evaluated.
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Affiliation(s)
- H H Versteeg
- Laboratory for Experimental Internal Medicine, Academic Medical Centre, Amsterdam, The Netherlands
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461
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Qi C, Zhu Y, Pan J, Yeldandi AV, Rao MS, Maeda N, Subbarao V, Pulikuri S, Hashimoto T, Reddy JK. Mouse steroid receptor coactivator-1 is not essential for peroxisome proliferator-activated receptor alpha-regulated gene expression. Proc Natl Acad Sci U S A 1999; 96:1585-90. [PMID: 9990068 PMCID: PMC15526 DOI: 10.1073/pnas.96.4.1585] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/1998] [Accepted: 12/15/1998] [Indexed: 01/22/2023] Open
Abstract
Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors, and it is assumed that the biological effects of these receptors depend on interactions with recently identified coactivators, including steroid receptor coactivator-1 (SRC-1). We assessed the in vivo function of SRC-1 on the PPARalpha-regulated gene expression in liver by generating mice in which the SRC-1 gene was inactivated by gene targeting. The homozygous (SRC-1(-/-)) mice were viable and fertile and exhibited no detectable gross phenotypic defects. When challenged with a PPARalpha ligand, such as ciprofibrate or Wy-14,643, the SRC-1(-/-) mice displayed typical pleiotropic responses, including hepatomegaly, peroxisome proliferation in hepatocytes, and increased mRNA and protein levels of genes that are regulated by PPARalpha. These alterations were indistinguishable from those exhibited by SRC-1(+/+) wild-type mice fed either ciprofibrate- or Wy-14, 643-containing diets. These results indicate that SRC-1 is not essential for PPARalpha-mediated transcriptional activation in vivo and suggest redundancy in nuclear receptor coactivators.
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Affiliation(s)
- C Qi
- Department of Pathology, Northwestern University Medical School, Chicago, IL 60611, USA
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462
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463
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