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Abouzayed A, Tano H, Nagy Á, Rinne SS, Wadeea F, Kumar S, Westerlund K, Tolmachev V, Eriksson Karlström A, Orlova A. Preclinical Evaluation of the GRPR-Targeting Antagonist RM26 Conjugated to the Albumin-Binding Domain for GRPR-Targeting Therapy of Cancer. Pharmaceutics 2020; 12:E977. [PMID: 33081166 PMCID: PMC7594083 DOI: 10.3390/pharmaceutics12100977] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/12/2020] [Accepted: 10/14/2020] [Indexed: 01/02/2023] Open
Abstract
The targeting of gastrin-releasing peptide receptors (GRPR) was recently proposed for targeted therapy, e.g., radiotherapy. Multiple and frequent injections of peptide-based therapeutic agents would be required due to rapid blood clearance. By conjugation of the GRPR antagonist RM26 (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) to an ABD (albumin-binding domain), we aimed to extend the blood circulation of peptides. The synthesized conjugate DOTA-ABD-RM26 was labelled with indium-111 and evaluated in vitro and in vivo. The labelled conjugate was stable in PBS and retained specificity and its antagonistic function against GRPR. The half-maximal inhibitory concentration (IC50) of natIn-DOTA-ABD-RM26 in the presence of human serum albumin was 49 ± 5 nM. [111In]In-DOTA-ABD-RM26 had a significantly longer residence time in blood and in tumors (without a significant decrease of up to 144 h pi) than the parental RM26 peptide. We conclude that the ABD-RM26 conjugate can be used for GRPR-targeted therapy and delivery of cytotoxic drugs. However, the undesirable elevated activity uptake in kidneys abolishes its use for radionuclide therapy. This proof-of-principle study justified further optimization of the molecular design of the ABD-RM26 conjugate.
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Affiliation(s)
- Ayman Abouzayed
- Department of Medicinal Chemistry, Uppsala University, 751 83 Uppsala, Sweden; (A.A.); (S.S.R.); (F.W.)
| | - Hanna Tano
- Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden; (H.T.); (Á.N.); (S.K.); (K.W.); (A.E.K.)
| | - Ábel Nagy
- Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden; (H.T.); (Á.N.); (S.K.); (K.W.); (A.E.K.)
| | - Sara S. Rinne
- Department of Medicinal Chemistry, Uppsala University, 751 83 Uppsala, Sweden; (A.A.); (S.S.R.); (F.W.)
| | - Fadya Wadeea
- Department of Medicinal Chemistry, Uppsala University, 751 83 Uppsala, Sweden; (A.A.); (S.S.R.); (F.W.)
| | - Sharmishtaa Kumar
- Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden; (H.T.); (Á.N.); (S.K.); (K.W.); (A.E.K.)
| | - Kristina Westerlund
- Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden; (H.T.); (Á.N.); (S.K.); (K.W.); (A.E.K.)
| | - Vladimir Tolmachev
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85 Uppsala, Sweden;
- Research Centrum for Oncotheranostics, Research School of Chemistry and Applied Biomedical Sciences, Tomsk Polytechnic University, Tomsk 634050, Russia
| | - Amelie Eriksson Karlström
- Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden; (H.T.); (Á.N.); (S.K.); (K.W.); (A.E.K.)
| | - Anna Orlova
- Department of Medicinal Chemistry, Uppsala University, 751 83 Uppsala, Sweden; (A.A.); (S.S.R.); (F.W.)
- Research Centrum for Oncotheranostics, Research School of Chemistry and Applied Biomedical Sciences, Tomsk Polytechnic University, Tomsk 634050, Russia
- Science for Life Laboratory, Uppsala University, 751 05 Uppsala, Sweden
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Tikhonova IG, Gigoux V, Fourmy D. Understanding Peptide Binding in Class A G Protein-Coupled Receptors. Mol Pharmacol 2019; 96:550-561. [PMID: 31436539 DOI: 10.1124/mol.119.115915] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 06/13/2019] [Indexed: 12/13/2022] Open
Abstract
Many physiologic processes are controlled through the activation of G protein-coupled receptors (GPCRs) by regulatory peptides, making peptide GPCRs particularly useful targets for major human diseases such as diabetes and cancer. Peptide GPCRs are also being evaluated as next-generation targets for the development of novel antiparasite agents and insecticides in veterinary medicine and agriculture. Resolution of crystal structures for several peptide GPCRs has advanced our understanding of peptide-receptor interactions and fueled interest in correlating peptide heterogeneity with receptor-binding properties. In this review, the knowledge of recently crystalized peptide-GPCR complexes, previously accumulated peptide structure-activity relationship studies, receptor mutagenesis, and sequence alignment are integrated to better understand peptide binding to the transmembrane cavity of class A GPCRs. Using SAR data, we show that peptide class A GPCRs can be divided into groups with distinct hydrophilic residues. These characteristic residues help explain the preference of a receptor to bind the C-terminal free carboxyl group, the C-terminal amidated group, or the N-terminal ammonium group of peptides.
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Affiliation(s)
- Irina G Tikhonova
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
| | - Veronique Gigoux
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
| | - Daniel Fourmy
- School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom, (I.G.T.) and INSERM ERL1226-Receptology and Therapeutic Targeting of Cancers, Laboratoire de Physique et Chimie des Nano-Objets, CNRS UMR5215-INSA, Université de Toulouse III, Toulouse, France (V.G., D.F.)
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3
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Moody TW, Moreno P, Jensen RT. Neuropeptides as lung cancer growth factors. Peptides 2015; 72:106-11. [PMID: 25836991 DOI: 10.1016/j.peptides.2015.03.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 03/20/2015] [Accepted: 03/20/2015] [Indexed: 12/28/2022]
Abstract
This manuscript is written in honor of the Festschrift for Abba Kastin. I met Abba at a Society for Neuroscience meeting and learned that he was Editor-in-Chief of the Journal Peptides. I submitted manuscripts to the journal on "Neuropeptides as Growth Factors in Cancer" and subsequently was named to the Editorial Advisory Board. Over the past 30 years I have published dozens of manuscripts in Peptides and reviewed hundreds of submitted manuscripts. It was always rewarding to interact with Abba, a consummate professional. When I attended meetings in New Orleans I would sometimes go out to dinner with him at the restaurant "Commanders Palace". When I chaired the Summer Neuropeptide Conference we were honored to have him receive the Fleur Strand Award one year in Israel. I think that his biggest editorial contribution has been the "Handbook of Biologically Active Peptides." I served as a Section Editor on "Cancer/Anticancer Peptides" and again found that it was a pleasure working with him. This review focuses on the mechanisms by which bombesin-like peptides, neurotensin and vasoactive intestinal peptide regulate the growth of lung cancer.
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Affiliation(s)
- Terry W Moody
- Department of Health and Human Services, National Cancer Institute, Center for Cancer Research, Office of the Director, Bethesda, MD 20892, USA.
| | - Paola Moreno
- National Institute of Diabetes, Digestive, and Kidney Disease, Digestive Diseases Branch, Bethesda, MD 20892, USA
| | - Robert T Jensen
- National Institute of Diabetes, Digestive, and Kidney Disease, Digestive Diseases Branch, Bethesda, MD 20892, USA
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4
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Abstract
All forms of the neuropeptide gastrin-releasing peptide (GRP) are derived from the precursor proGRP1-125. Amidated GRP18-27, which together with amidated GRP1-27 was long thought to be the only biologically relevant product of the GRP gene, is involved in a multitude of physiological functions and acts as a mitogen, morphogen, and proangiogenic factor in certain cancers. Recently, GRP has been implicated in several psychiatric conditions, in the maintenance of circadian rhythm, in spinal transmission of the itch sensation, and in inflammation and wound repair. The actions of GRP are mediated by the GRP receptor. Over the last decade, nonamidated peptides derived from proGRP, such as the glycine-extended form GRP18-28 and recombinant and synthetic fragments from proGRP31-125, have been shown to be biologically active in a range of tissues and in cancer cell lines. While GRP18-28 acts via the GRP receptor, the identity of the receptor for proGRP31-125 and its fragments has not yet been established. Nonamidated fragments are also present in normal tissues and in various cancers. In fact, proGRP31-98 is the most sensitive serum biomarker in patients with small cell lung cancer and is a significant predictor of poor survival in patients with advanced prostate cancer.
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Affiliation(s)
- Joseph Ischia
- Department of Surgery, University of Melbourne, Austin Health, Melbourne, Victoria, Australia
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Baldwin GS, Patel O, Shulkes A. Phylogenetic analysis of the sequences of gastrin-releasing peptide and its receptors: Biological implications. ACTA ACUST UNITED AC 2007; 143:1-14. [PMID: 17395282 DOI: 10.1016/j.regpep.2007.02.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Revised: 02/04/2007] [Accepted: 02/06/2007] [Indexed: 11/17/2022]
Abstract
The many biological activities of the hormone gastrin-releasing peptide (GRP), including stimulation of acid secretion and of tumour growth, are mediated by the gastrin-releasing peptide receptor (GRP-R). Here sequence comparisons are utilised to investigate the likely bioactive regions of the 125 amino acid GRP precursor and of GRP-R. Comparison of the sequences of the GRP precursor from 21 species revealed homology not only in the GRP region between amino acids 1 and 30, but also in C-terminal regions from amino acids 43 to 97. This observation is consistent with recent reports that peptides derived from the C-terminal region are biologically active. Comparison of the GRP-R sequence with the related receptors NMB-R and BRS-3 revealed that the family could be distinguished from other G-protein coupled receptors by the presence of the motif GVSVFTLTALS at the cytoplasmic end of transmembrane helix 3. Comparison of the sequences of the GRP-R from 21 species revealed that the most highly conserved regions occurred in transmembrane helices 2, 3, 5, 6 and 7, and in the third intracellular loop. These results will be important in guiding future structure-function studies of the GRP precursor and of GRP receptors.
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Affiliation(s)
- Graham S Baldwin
- University of Melbourne, Department of Surgery, Austin Health, Studley Rd., Heidelberg, Victoria 3084, Australia.
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Patel O, Shulkes A, Baldwin GS. Gastrin-releasing peptide and cancer. Biochim Biophys Acta Rev Cancer 2006; 1766:23-41. [PMID: 16490321 DOI: 10.1016/j.bbcan.2006.01.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 01/09/2006] [Accepted: 01/10/2006] [Indexed: 02/07/2023]
Abstract
Over the past 20 years, abundant evidence has been collected to suggest that gastrin-releasing peptide (GRP) and its receptors play an important role in the development of a variety of cancers. In fact, the detection of GRP and the GRP receptor in small cell lung carcinoma (SCLC), and the demonstration that anti-GRP antibodies inhibited proliferation in SCLC cell lines, established GRP as the prototypical autocrine growth factor. All forms of GRP are generated by processing of a 125-amino acid prohormone; recent studies indicate that C-terminal amidation of GRP18-27 is not essential for bioactivity, and that peptides derived from residues 31 to 125 of the prohormone are present in normal tissue and in tumors. GRP receptors can be divided into four classes, all of which belong to the 7 transmembrane domain family and bind GRP and/or GRP analogues with affinities in the nM range. Over-expression of GRP and its receptors has been demonstrated at both the mRNA and protein level in many types of tumors including lung, prostate, breast, stomach, pancreas and colon. GRP has also been shown to act as a potent mitogen for cancer cells of diverse origin both in vitro and in animal models of carcinogenesis. Other actions of GRP relevant to carcinogenesis include effects on morphogenesis, angiogenesis, cell migration and cell adhesion. Future prospects for the use of radiolabelled and cytotoxic GRP analogues and antagonists for cancer diagnosis and therapy appear promising.
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Affiliation(s)
- Oneel Patel
- University of Melbourne, Department of Surgery, Austin Health, Studley Rd., Heidelberg, Victoria 3084, Australia
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Montuenga LM, Guembe L, Burrell MA, Bodegas ME, Calvo A, Sola JJ, Sesma P, Villaro AC. The diffuse endocrine system: from embryogenesis to carcinogenesis. PROGRESS IN HISTOCHEMISTRY AND CYTOCHEMISTRY 2003; 38:155-272. [PMID: 12756892 DOI: 10.1016/s0079-6336(03)80004-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In the present review we will summarise the current knowledge about the cells comprising the Diffuse Endocrine System (DES) in mammalian organs. We will describe the morphological, histochemical and functional traits of these cells in three major systems gastrointestinal, respiratory and prostatic. We will also focus on some aspects of their ontogeny and differentiation, as well as to their relevance in carcinogenesis, especially in neuroendocrine tumors. The first chapter describes the characteristics of DES cells and some of their specific biological and biochemical traits. The second chapter deals with DES in the gastrointestinal organs, with special reference to the new data on the differentiation mechanisms that leads to the appearance of endocrine cells from an undifferentiated stem cell. The third chapter is devoted to DES of the respiratory system and some aspects of its biological role, both, during development and adulthood. Neuroendocrine hyperplasia and neuroendocrine lung tumors are also addressed. Finally, the last chapter deals with the prostatic DES, discussing its probable functional role and its relevance in hormone-resistant prostatic carcinomas.
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Affiliation(s)
- Luis M Montuenga
- Department of Histology and Pathology, Schools of Science and Medicine, University of Navarra, 31080 Pamplona, Spain.
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Oiry C, Pannequin J, Bernad N, Artis AM, Galleyrand JC, Devin C, Cristau M, Fehrentz JA, Martinez J. A synthetic glycine-extended bombesin analogue interacts with the GRP/bombesin receptor. Eur J Pharmacol 2000; 403:17-25. [PMID: 10969139 DOI: 10.1016/s0014-2999(00)00576-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
alpha-amidation of a peptide (which takes place from a glycine-extended precursor) is required to produce biologically active amidated hormones, such as gastrin-releasing peptide (GRP)/Pyr-Gln-Arg-Leu-Gly-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH(2) (bombesin). It was shown that glycine-extended gastrin mediates mitogenic effects on various cell lines by interacting with a specific receptor, different from the classical CCK(1) or CCK(2) receptors. On the basis of this observation, we have extended the concept of obtaining active glycine-extended forms of others amidated peptides to produce new active analogues. In this study, we have tested the biological behaviour of a synthetic analogue of the glycine-extended bombesin (para-hydroxy-phenyl-propionyl-Gln-Trp-Ala-Val-Gly-His-Leu-Met-Gly-OH or JMV-1458) on various in vitro models. We showed that compound JMV-1458 was able to inhibit specific (3-[125I]iodotyrosyl(15)) GRP ([125I]GRP) binding in rat pancreatic acini and in Swiss 3T3 cells with K(i) values of approximately 10(-8) M. In isolated rat pancreatic acini, we found that JMV-1458 induced inositol phosphates production and amylase secretion in a dose-dependent manner. In Swiss 3T3 cells, the glycine-extended bombesin analogue dose-dependently produced [3H]thymidine incorporation. By using potent GRP/bombesin receptor antagonists, we showed that this synthetic glycine-extended bombesin analogue induces its biological activities via the classical GRP/bombesin receptor.
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Affiliation(s)
- C Oiry
- Laboratoire des Amino Acides, Peptides et Protéines (L.A.P.P.), UMR CNRS 5810, Universités Montpellier I et II, Faculté de Pharmacie, 15 Av. C. Flahault, 34060 Cedex, Montpellier, France
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Moody TW, Leyton J, Zia F, Tuthill C, Badamchian M, Goldstein AL. Thymosinalpha1 is chemopreventive for lung adenoma formation in A/J mice. Cancer Lett 2000; 155:121-7. [PMID: 10822126 DOI: 10.1016/s0304-3835(00)00405-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The effects of thymosin (THN) alpha1 were investigated using the urethane injection carcinogenesis A/J mouse model. Lung adenomas were observed 2.5, 3, and 4 months after urethane injection (400 mg/kg i.p.) into female A/J mice. Daily administration of THNalpha1 (0.4 mg/kg, s.c.) reduced lung adenoma multiplicity significantly, by approximately 45, 40, and 17%, respectively, 2.5, 3, and 4 months after urethane injection. Animals treated with THNalpha1 had a significantly greater white cell density than control A/J mice. Endogenous THNalpha1-like peptides were detected in the mouse lung. By radioimmunoassay and by Western blot, prothymosin alpha was detected in the mouse lung. By immunocytochemistry, THNalpha1-like peptides were detected in all lung compartments including the bronchus, adenoma, bronchioles, and alveoli. These results indicate that exogenous THNalpha1 prevents lung carcinogenesis in A/J mice.
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Affiliation(s)
- T W Moody
- Medicine Branch, National Cancer Institute, MD 20850, Rockville, MD 20850, USA.
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Hong SS, Galaup A, Peytavi R, Chazal N, Boulanger P. Enhancement of adenovirus-mediated gene delivery by use of an oligopeptide with dual binding specificity. Hum Gene Ther 1999; 10:2577-86. [PMID: 10566886 DOI: 10.1089/10430349950016627] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The efficiency of human adenovirus serotype 5 (Ad5) transgene delivery was tested on several human and animal cell lines in vitro, by using a bimodular 35-mer oligopeptide carrying two peptide domains with different ligand specificities. One domain mimicked the fiber knob-binding region of the alpha2 domain of human MHC-1 molecules (MH20), and the other corresponded to the gastrin-releasing peptide (GRP). Two synthetic peptides with different configurations were analyzed in Ad-mediated gene transfer assays using Ad5Luc3 vector carrying the luciferase reporter gene. One peptide (GRP-MH20) had the GRP domain on the N-terminal side of MH20, while the other (MH20-GRP), the C-terminally amidified GRP, was on the C-terminal side of MH20. The GRP-MH20 peptide, but not MH20-GRP, was capable of enhancing luciferase gene delivery to Ad-susceptible cells in a GRP receptor-dependent manner. More importantly, GRP-MH20 could also confer susceptibility to Ad infection to normal or cancer cells that lack fiber receptors for the virus. Our data suggested that GRP receptors could function efficiently as alternative attachment receptors for Ad5, but that Ad5 bound to GRP receptors still depended, at least partially, on the penton base-mediated endocytotic pathway for subsequent cell entry. Gene delivery by a human adenovirus serotype 5 (Ad5) vector was assayed with a bimodular oligopeptide carrying two peptide domains of different binding specificities. One domain was a high-affinity peptide ligand of the Ad5 fiber knob (MH20), and the other corresponded to the gastrin-releasing peptide (GRP). The synthetic peptide GRP-MH20 was found to be capable of enhancing Ad-mediated gene transfer to Ad-susceptible cells in a GRP receptor-dependent manner. More importantly, GRP-MH20 could also confer susceptibility to Ad infection to normal or cancer cells that lack fiber receptors. Our data suggested that GRP receptors could function efficiently as alternative attachment receptors for Ad5, but virus bound to GRP receptors still depended partially on the penton base-mediated pathway for cell entry.
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Affiliation(s)
- S S Hong
- Laboratoire de Virologie et Pathogénèse Virale, CNRS UMR-5537, Faculté de Médecine R.T.H. Laennec, Lyon, France
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Guembe L, Villaro AC, Treston AM. Immunocytochemical mapping of the amidating enzyme PAM in the developing and adult mouse lung. J Histochem Cytochem 1999; 47:623-36. [PMID: 10219055 DOI: 10.1177/002215549904700505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The enzyme PAM is required for activation of many peptide hormones. In adult mouse lung, immunostaining for PAM was located in Clara cells, which constitute most of the epithelial cells of the mouse bronchial/bronchiolar tree. Immunoreactivity appeared for the first time in the epithelium on gestational Day 16, being slight and mostly restricted to the apical cytoplasm. As the lung developed, the labeling became gradually stronger and extended throughout the cell. Smooth muscle of airways and blood vessels, and some parenchymal cells, probably macrophages, also showed PAM immunoreactivity. Of the two enzymatically active domains of PAM, only PHM and not PAL immunoreactivity was found at all stages studied. The early appearance of PAM in developing mouse lung, as well as its presence in a variety of tissues, probably indicates a complex role of this enzyme in pulmonary development and function.
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Affiliation(s)
- L Guembe
- Department of Cytology and Histology, University of Navarra, Pamplona, Spain
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Abstract
In the past decade, over 1000 continuous human cell lines have been established from lung cancer biopsy specimens. Numerous growth factors and receptors have been identified in the small cell lung cancer (SCLC) cell lines. SCLC is a neuroendocrine tumor which contains numerous peptides, including bombesin/gastrin releasing peptide (BN/GRP), and receptors. High levels of GRP mRNA and immunoreactivity are present in SCLC cells. The secretion rate of GRP from SCLC cells is increased by vasoactive intestinal peptide (VIP), which elevates the intracellular cAMP. GRP binds to cell surface receptors, elevates cytosolic calcium and stimulates the growth of SCLC cells. Additional SCLC growth factors include insulin-like growth factor I (IGF-I) and transferrin. IGF-I mRNA and protein is present in SCLC. IGF-I binds with high affinity to SCLC cells and stimulates tyrosine kinase activity and growth. Transferrin is also present in SCLC cells. Transferrin binds with high affinity to SCLC cells and stimulates iron transport and growth. Synthetic peptide antagonists and monoclonal antibodies have been identified which disrupt autocrine growth pathways and inhibit SCLC growth.
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Affiliation(s)
- T W Moody
- Department of Biochemistry and Molecular Biology, George Washington University School of Medicine and Health Sciences, Washington, D.C. 20037
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