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Baker AM, Van Noorden S, Rodriguez-Justo M, Cohen P, Wright NA, Lampert IA. Distribution of the c-MYC gene product in colorectal neoplasia. Histopathology 2016; 69:222-9. [PMID: 26826706 PMCID: PMC4949543 DOI: 10.1111/his.12939] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 01/27/2016] [Indexed: 12/14/2022]
Abstract
AIMS Recent attempts to study MYC distribution in human samples have been confounded by a lack of agreement in immunohistochemical staining between antibodies targeting the N-terminus and those targeting the C-terminus of the MYC protein. The aim of this study was to use a novel in-situ hybridization (ISH) approach to detect MYC mRNA in clinically relevant samples, and thereby determine the reliability of MYC-targeting antibodies. METHODS AND RESULTS We performed immunohistochemistry on human formalin-fixed paraffin embedded normal colon (n = 15), hyperplastic polyp (n = 4) and neoplastic colon samples (n = 55), using the N-terminally directed antibody Y69, and the C-terminally directed antibody 9E10. The MYC protein distributions were then compared with the location of MYC mRNA, determined by ISH. We found that the localization of MYC mRNA correlated well with the protein distribution determined with the N-terminally directed antibody Y69, and was also associated with expression of the proliferation marker Ki67. The protein distribution determined with the C-terminally directed antibody 9E10 was not always associated with MYC mRNA, Y69, or Ki67, and indeed often showed a reciprocal pattern of expression, with staining being strongest in non-proliferating cells. CONCLUSIONS The observed discrepancy between the staining patterns suggests that the significance of 9E10 in immunohistochemical staining is currently uncertain, and therefore should be interpreted with caution.
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Affiliation(s)
- Ann-Marie Baker
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Susan Van Noorden
- Department of Histopathology, Imperial College London, Hammersmith Hospital, London, UK
| | | | - Patrizia Cohen
- Department of Cellular Pathology, Clarence Memorial Wing, St Mary's Hospital, London, UK
| | - Nicholas A Wright
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Irvin A Lampert
- Department of Histopathology, West Middlesex University Hospital, Isleworth, UK
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2
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Chebel A, Ffrench M. Transcriptional regulation of the human telomerase reverse transcriptase: new insights. Transcription 2012; 1:27-31. [PMID: 21327156 DOI: 10.4161/trns.1.1.12062] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 04/14/2010] [Accepted: 04/15/2010] [Indexed: 12/26/2022] Open
Abstract
hTERT and NFAT were thought until recently to belong to separate metabolic compartments. The involvement of NFAT in the induction of hTERT transcription suggested by hTERT expression variations during lymphocyte stimulation and immunosuppressive treatments explains the link between hTERT expression and cell stimulation and offers new insights for therapeutic developments.
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Affiliation(s)
- Amel Chebel
- Université Claude Bernard - UMR, Oullins, France
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3
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Morpurgo G, Fioretti B, Catacuzzeno L. The main product of specialized tissues regulates cell life and may cause neoplastic transformation. Med Hypotheses 2009; 74:847-54. [PMID: 20036074 DOI: 10.1016/j.mehy.2009.11.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Accepted: 11/24/2009] [Indexed: 11/15/2022]
Abstract
Many tissues and cells in vertebrates are highly specialized and devoted to a single function through the action of a single molecule, that we call the "main product" (MP) of the cell. The hypothesis here proposed is that these MPs control all aspects of the cell life, namely activity, division, differentiation and apoptosis. Evidences supporting this hypothesis are reported for the immune system, pancreatic beta-cells, melanocytes, connective tissues, thyroid cells, skin and erythroid cells. In all cases cell division and differentiation is promoted by a normal activity of the MP, while hyperactivity leads to cell apoptosis. Evidences are also provided that alterations of the activity of the MP may elicit pathological disorders; in particular mutations altering the structure of the MP may elicit tumoural transformation.
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Affiliation(s)
- Giorgio Morpurgo
- Dipartimento di Biologia Cellulare e Ambientale, Universita' di Perugia, Perugia, Italy
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4
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Funke S, Maisner A, Mühlebach MD, Koehl U, Grez M, Cattaneo R, Cichutek K, Buchholz CJ. Targeted cell entry of lentiviral vectors. Mol Ther 2008; 16:1427-36. [PMID: 18578012 DOI: 10.1038/mt.2008.128] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Retargeting of lentiviral vector entry to cell types of interest is a key factor in improving the safety and efficacy of gene transfer. In this study we show that the retargetable envelope glycoproteins of measles virus (MV), namely, the hemagglutinin (H) responsible for receptor recognition and the fusion protein (F), can pseudotype human immunodeficiency virus 1 (HIV-1) vectors when their cytoplasmic tails are truncated. We then pseudotyped HIV-1 vectors with MV glycoproteins displaying on H either the epidermal growth factor or a single-chain antibody directed against CD20, but without the ability to recognize their native receptors. Gene transfer into cells that expressed the targeted receptor was several orders of magnitude more efficient than into cells that did not. High-target versus nontarget cell discrimination was demonstrated in mixed cell populations, where the targeting vector selectively eliminated CD20-positive cells after suicide gene transfer. Remarkably, primary human CD20-positive B lymphocytes were transduced more efficiently by the CD20-targeted vector than by a vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein. In addition, the CD20-targeted vector was able to transduce even unstimulated primary B cells, whereas VSV-G pseudotyped vectors were unable to do so. Because MV enters cells through direct fusion at the cell membrane, this novel targeting system should be widely applicable.
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Affiliation(s)
- Sabrina Funke
- 1Division of Medical Biotechnology, Paul-Ehrlich-Institut, Langen, Germany
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5
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Zander L, Bemark M. Identification of genes deregulated during serum-free medium adaptation of a Burkitt's lymphoma cell line. Cell Prolif 2008; 41:136-55. [PMID: 18211290 DOI: 10.1111/j.1365-2184.2007.00500.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVE Serum is usually added to growth media when mammalian cells are cultured in vitro to supply the cells with growth factors, hormones, nutrients and trace elements. Defined proteins and metal ions, such as insulin, growth factors, transferrin and sodium selenite, are sometimes also included and can in some cases substitute serum components. How adaptation to serum free media influences cells has not been studied in detail. MATERIALS AND METHODS We have adapted the Burkitt's lymphoma line Ramos to a serum-free medium that supports long-term survival and studied gene expression changes that occurred during the adaptation process. RESULTS AND CONCLUSIONS The adaptation process was characterized by initial cell population growth arrest, and after that extensive cell death, followed by proliferation and long-term survival of clonal cultures. Proliferation and cell cycle progression of the serum-free cultures closely mimicked that of serum-dependent cells. Affymetrix micro-array technology was used to identify gene expression alterations that had occurred during the adaptation. Most changes were subtle, but frequently the genes with altered expression were involved in basal cellular functions such as cell division, cell cycle regulation, apoptosis and cell signalling. Some alterations were restored when the cells were transferred back to serum-containing medium, indicating that expression of these genes was controlled by components in serum. Others were not, and may represent changes that were selected during the adaptation process. Among these were, for example, several genes within the Wnt signalling pathway.
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Affiliation(s)
- L Zander
- Department of Microbiology and Immunology, Gothenburg University, Göteborg, Sweden
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6
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Deans JP, Li H, Polyak MJ. CD20-mediated apoptosis: signalling through lipid rafts. Immunology 2002; 107:176-82. [PMID: 12383196 PMCID: PMC1782791 DOI: 10.1046/j.1365-2567.2002.01495.x] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2002] [Accepted: 06/27/2002] [Indexed: 11/20/2022] Open
Abstract
CD20 is an effective target for therapeutic B-cell depletion with monoclonal antibodies. One proposed mechanism of action is direct cytotoxicity mediated via tyrosine kinase-dependent signalling pathways activated upon CD20 cross-linking. The association of CD20 with membrane microdomains known as lipid rafts, enriched in src-family tyrosine kinases and other signalling effectors, suggests an indirect mechanism of anti-CD20-induced apoptosis in which activation of src-family kinases occurs as a consequence of lipid raft clustering.
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Affiliation(s)
- Julie P Deans
- Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1.
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7
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Polyak MJ, Deans JP. Alanine-170 and proline-172 are critical determinants for extracellular CD20 epitopes; heterogeneity in the fine specificity of CD20 monoclonal antibodies is defined by additional requirements imposed by both amino acid sequence and quaternary structure. Blood 2002; 99:3256-62. [PMID: 11964291 DOI: 10.1182/blood.v99.9.3256] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In vivo ablation of malignant B cells can be achieved using antibodies directed against the CD20 antigen. Fine specificity differences among CD20 monoclonal antibodies (mAbs) are assumed not to be a factor in determining their efficacy because evidence from antibody-blocking studies indicates limited epitope diversity with only 2 overlapping extracellular CD20 epitopes. However, in this report a high degree of heterogeneity among antihuman CD20 mAbs is demonstrated. Mutation of alanine and proline at positions 170 and 172 (AxP) (single-letter amino acid codes; x indicates the identical amino acid at the same position in the murine and human CD20 sequences) in human CD20 abrogated the binding of all CD20 mAbs tested. Introduction of AxP into the equivalent positions in the murine sequence, which is not otherwise recognized by antihuman CD20 mAbs, fully reconstituted the epitope recognized by B1, the prototypic anti-CD20 mAb. 2H7, a mAb previously thought to recognize the same epitope as B1, did not recognize the murine AxP mutant. Reconstitution of the 2H7 epitope was achieved with additional mutations replacing VDxxD in the murine sequence for INxxN (positions 162-166 in the human sequence). The integrity of the 2H7 epitope, unlike that of B1, further depends on the maintenance of CD20 in an oligomeric complex. The majority of 16 antihuman CD20 mAbs tested, including rituximab, bound to murine CD20 containing the AxP mutations. Heterogeneity in the fine specificity of these antibodies was indicated by marked differences in their ability to induce homotypic cellular aggregation and translocation of CD20 to a detergent-insoluble membrane compartment previously identified as lipid rafts.
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Affiliation(s)
- Maria J Polyak
- Department of Biochemistry, Immunology Research Group, University of Calgary, Calgary, Alberta, Canada
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8
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Affiliation(s)
- P W Johnson
- CRC Medical Oncology Unit, Southampton University School of Medicine
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9
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Polyak MJ, Tailor SH, Deans JP. Identification of a Cytoplasmic Region of CD20 Required for Its Redistribution to a Detergent-Insoluble Membrane Compartment. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.7.3242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
CD20 is a B lymphocyte integral membrane protein with signal-transducing properties. Abs directed toward extracellular CD20 epitopes activate nonreceptor tyrosine kinases and modulate cell cycle progression of B lymphocytes. Recently, we demonstrated that binding of CD20 Abs to B cells induces the rapid redistribution of up to 95% of CD20 molecules to low density, detergent-insoluble membrane microdomains and induces the appearance of an approximately 50-kDa tyrosine-phosphorylated protein in the same compartment. Active relocalization of CD20 may thus be critical to the initiation of signaling events by CD20. The CD20 cDNA sequence predicts a nonglycosylated protein with four transmembrane-spanning regions and intracellular amino and carboxyl termini. Here we provide verification of the location of both the intracellular and extracellular regions of the CD20 molecule and identify a membrane-proximal sequence in the cytoplasmic carboxyl tail that is required for CD20 to redistribute to detergent-insoluble membrane microdomains.
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Affiliation(s)
- Maria J. Polyak
- Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Sweta H. Tailor
- Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Julie P. Deans
- Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
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10
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Popoff IJ, Savage JA, Blake J, Johnson P, Deans JP. The association between CD20 and Src-family Tyrosine kinases requires an additional factor. Mol Immunol 1998; 35:207-14. [PMID: 9736336 DOI: 10.1016/s0161-5890(98)00042-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
CD20 is a B cell surface protein which can initiate intracellular signals involving tyrosine kinase activation, and modify B cell growth and differentiation. CD20 is tightly associated with the Src-family kinases Lyn, Fyn and Lck; however, the mechanism of interaction remains to be determined. Association between CD20 and Src-family kinases has been detected in peripheral blood B cells and in 5 out of 8 unrelated B cell lines. The lack of CD20-associated kinase activity in some cell lines offered an opportunity to investigate the mechanism of CD20 associations. All 8 B cell lines were found to express Lyn, and, with one exception, all cell lines also expressed Fyn. Lck, however, was not detected in any of the cell lines in which CD20 failed to coprecipitate kinase activity. To test the possibility that Lck was required for assembly of the CD20 complex, Lck was transfected into one of the 3 CD20/kinase association-deficient lines, namely T51. CD20 did not coprecipitate kinase activity from the transfected T51 cells, despite their expression of high levels of exogenous Lck, as well as endogenous Lyn and Fyn. CD20 cDNA from T51 was sequenced and found to be normal. These data establish that association between CD20 and Src-family kinases requires an additional factor.
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Affiliation(s)
- I J Popoff
- Department of Medical Biochemistry, The University of Calgary, Alberta, Canada
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11
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Deans JP, Robbins SM, Polyak MJ, Savage JA. Rapid redistribution of CD20 to a low density detergent-insoluble membrane compartment. J Biol Chem 1998; 273:344-8. [PMID: 9417086 DOI: 10.1074/jbc.273.1.344] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
CD20 is a B cell integral membrane protein capable of initiating growth-modulating signals in human B lymphocytes upon its engagement with monoclonal anti-CD20 antibodies. In this report, we demonstrate that treatment of B cells with CD20 antibodies induces rapid redistribution of CD20 into a detergent-insoluble membrane compartment. Redistribution is detected as early as 15 s, following antibody addition, and involves up to 95% of CD20 molecules, depending on the antibody used. All of the detergent-insoluble CD20 was found in the low density fractions of sucrose density gradients, indicating that CD20 redistributes to glycolipid-rich membrane domains, analogous to caveolae in some cell types. As CD20 has previously been shown to associate with Src family tyrosine kinases, their co-existence in these compartments suggests a link to the role of CD20 in signal transduction. This study provides insight into the mechanism by which CD20 communicates signals to the cell interior and indicates that the search for membrane-proximal intracellular signaling partners should be directed to the Triton-insoluble fraction.
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Affiliation(s)
- J P Deans
- Immunology Research Group, Department of Medical Biochemistry, The University of Calgary, Calgary, Alberta T2N 4N1, Canada.
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12
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Snow EC. The role of c-myc during normal B cell proliferation, and as B cells undergo malignant transformation. Curr Top Microbiol Immunol 1997; 224:211-20. [PMID: 9308244 DOI: 10.1007/978-3-642-60801-8_21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- E C Snow
- Department of Microbiology and Immunology, University of Kentucky Medical Center, Lexington 40536-0084, USA
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13
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Andersson KB, Deggerdal A, Skjønsberg C, Smeland EB, Blomhoff HK. Constitutive expression of c-myc does not relieve cAMP-mediated growth arrest in human lymphoid Reh cells. J Cell Physiol 1993; 157:61-9. [PMID: 8408242 DOI: 10.1002/jcp.1041570108] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The Reh cell system is suitable for evaluating events important for control of proliferation independently of mechanisms involved in differentiation, as Reh cells are unable to differentiate. In the human pre-B cell line Reh, activation of adenylate cyclase by forskolin induces a five to tenfold rapid, transient down-regulation of steady-state c-myc RNA within 4 hours. Concurrently, the cells are strongly growth arrested in the G1 phase of the cell cycle. To clarify if the observed growth arrest could be relieved by constitutive expression of c-myc, an exogenous c-myc gene under constitutive promoter control was introduced into Reh cells by electroporation. The c-myc-expressing construct pDMmycHyg contained human c-myc exons 2 and 3 driven by the Mo-MLV LTR and conferred hygromycin resistance. Exogenous c-myc RNA transcripts and protein were constitutively expressed in the transfected clones at levels roughly twice as high as the level in nontransfected cells. Total c-myc protein levels were unchanged upon treatment of transfected clones with forskolin. Yet, the transfected cells were not released from growth arrest. Furthermore, the transfected Reh cells did not differentiate upon forskolin treatment. Constitutive overexpression of c-myc is therefore not sufficient for relieving forskolin-mediated effects on growth arrest in Reh cells.
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Affiliation(s)
- K B Andersson
- Norwegian Radium Hospital, Department of Immunology, Montebello, Oslo
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14
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Bubien JK, Zhou LJ, Bell PD, Frizzell RA, Tedder TF. Transfection of the CD20 cell surface molecule into ectopic cell types generates a Ca2+ conductance found constitutively in B lymphocytes. J Biophys Biochem Cytol 1993; 121:1121-32. [PMID: 7684739 PMCID: PMC2119683 DOI: 10.1083/jcb.121.5.1121] [Citation(s) in RCA: 258] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
CD20 is a plasma membrane phosphoprotein expressed exclusively by B lymphocytes. mAb binding to CD20 alters cell cycle progression and differentiation, indicating that CD20 plays an essential role in B lymphocyte function. Whole-cell patch clamp and fluorescence microscopy measurements of plasma membrane ionic conductance and cytosolic-free Ca2+ activity, respectively, were used to directly examine CD20 function. Transfection of human T and mouse pre-B lymphoblastoid cell lines with CD20 cDNA and subsequent stable expression of CD20 specifically increased transmembrane Ca2+ conductance. Transfection of CD20 cDNA and subsequent expression of CD20 in nonlymphoid cells (human K562 erythroleukemia cells and mouse NIH-3T3 fibroblasts) also induced the expression of an identical transmembrane Ca2+ conductance. The binding of a CD20-specific mAb to CD20+ lymphoblastoid cells also enhanced the transmembrane Ca2+ conductance. The mAb-enhanced Ca2+ currents had the same conductance characteristics as the CD20-associated Ca2+ currents in CD20 cDNA-transfected cells. C20 is structurally similar to several ion channels; each CD20 monomer possesses four membrane spanning domains, and both the amino and carboxy termini reside within the cytoplasm. Biochemical cross-linking of cell-surface molecules with subsequent immunoprecipitation analysis of CD20 suggests that CD20 may be present as a multimeric oligomer within the membrane, as occurs with several known membrane channels. Taken together, these findings indicate that CD20 directly regulates transmembrane Ca2+ conductance in B lymphocytes, and suggest that multimeric complexes of CD20 may form Ca2+ conductive ion channels in the plasma membrane of B lymphoid cells.
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Affiliation(s)
- J K Bubien
- Department of Medicine, University of Alabama, Birmingham 35294
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15
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Bourget I, Breittmayer JP, Grenier-Brossette N, Cousin JL. CD20 monoclonal antibodies down-regulate IgM at the surface of B cells. Eur J Immunol 1993; 23:768-71. [PMID: 7680616 DOI: 10.1002/eji.1830230330] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The CD20 molecule is a phosphoprotein expressed on the surface of B lymphocytes that plays a role in the regulation of B cell proliferation and differentiation. In this study it was found that monoclonal antibodies (mAb) directed to CD20 decrease the expression of IgM at the surface of normal human B lymphocytes and B cell lines. This effect was time-dependent with a half-time of about 5 h. Incubation of B cells with CD20 mAb B1 did not affect the steady-state level of IgM mRNA, suggesting that it acts at a nontranscriptional stage. Phorbol esters also produced inhibitory effect on surface IgM expression. Staurosporine reversed both the phorbol ester- and the CD20-induced down-regulation. Genistein did not reverse the down-regulation induced by the CD20 mAb B1. CD20 most likely triggers a protein kinase C-dependent pathway to down-regulate sIgM. CD20 mAb also counteracted the interleukin-4 (IL-4)-induced up-regulation of sIgM. The ability of anti-IgM to mobilize intracellular calcium was reduced in sIgM down-regulated cells, suggesting that B cells activation through the antigen receptor may be negatively regulated by CD20 and positively by IL-4.
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Affiliation(s)
- I Bourget
- Laboratoire d'Immunologie, Cellulaire et Moléculaire INSERM U210, Faculté de Médecine (Pasteur), Nice, France
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16
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Steube KG, Drexler HG. Differentiation and growth modulation of myeloid leukemia cells by the protein kinase C activating agent bryostatin-1. Leuk Lymphoma 1993; 9:141-8. [PMID: 8477194 DOI: 10.3109/10428199309148517] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Bryostatin-1 (Bryo), a macrocyclic lactone of the sea water bryozoan Bugula neritina, is a potent activator of protein kinase C and was found to exhibit antineoplastic activity in several systems. We studied the effect of Bryo on differentiation and growth modulation of human myeloid leukemia cell lines and freshly explanted blood cells from patients with myeloid leukemia. Alterations at the molecular level and phenotypic changes triggered by Bryo were similar, but not identical, to those induced by phorbol esters. Bryo was able to inhibit cellular proliferation as evidenced by [3H]-thymidine uptake and induced morphological changes associated with monocytic differentiation. In studies using continuous cell lines, the glucocorticoid dexamethasone was unable to prevent the Bryo-induced growth inhibition or the induced phenotypic changes. However, in fresh myeloid blood cells dexamethasone attenuated these Bryo-triggered effects. Our own data taken together with reports from the literature reviewed here suggest the following conclusions: (i) Bryo, while lacking tumor promoting activity, is able to induce differentiation in maturation arrested leukemia cells; (ii) it exhibits selective antiproliferative properties in normal or malignant hematopoietic cells and supports growth of multipotent stem cells. These features might qualify Bryostatin-1 as a potential candidate for promising research and possibly for future clinical applications.
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Affiliation(s)
- K G Steube
- German Collection of Microorganisms and Cell Cultures (DSM), Department of Human and Animal Cell Cultures, Braunschweig
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17
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Vitamin A is a key regulator for cell growth, cytokine production, and differentiation in normal B cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35934-9] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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18
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Farquharson C, Hesketh JE, Loveridge N. The proto-oncogene c-myc is involved in cell differentiation as well as cell proliferation: studies on growth plate chondrocytes in situ. J Cell Physiol 1992; 152:135-44. [PMID: 1618915 DOI: 10.1002/jcp.1041520118] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A combination of immunocytochemistry and microdensitometry has been used to localize and quantify the expression of the proto-oncogene c-myc within chondrocytes of the proximal growth plates of rat and chick long bones. Although the c-myc protein was localized in all chondrocytes of the growth plate of both species the most intense staining was restricted to the proliferating and differentiating chondrocytes. These were identified by their ability to synthesize DNA (bromodeoxyuridine positive) and the presence of alkaline phosphatase activity, respectively. Species differences did exist with the c-myc concentration of the chick proliferating and differentiating chondrocytes being higher (128% and 240%, respectively) than the respective chondrocytes of the rat. The higher c-myc concentration in the chick proliferating chondrocytes paralleled the differences in the bromodeoxyuridine labelling index between the two species. In the rat, the concentration of c-myc protein present in the differentiating chondrocytes was 74% higher than in the respective proliferating chondrocytes, while in the chick it was 146% higher. The data not only provides further evidence for a role of the c-myc protein in cell proliferation but also suggests involvement of this protein in chondrocyte differentiation and/or hypertrophy.
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Affiliation(s)
- C Farquharson
- Division of Biochemical Sciences, Rowett Research Institute, Bucksburn, Aberdeen, Scotland
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19
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Bruno S, Giaretti W, Darzynkiewicz Z. Effect of camptothecin on mitogenic stimulation of human lymphocytes: involvement of DNA topoisomerase I in cell transition from G0 to G1 phase of the cell cycle and in DNA replication. J Cell Physiol 1992; 151:478-86. [PMID: 1338332 DOI: 10.1002/jcp.1041510306] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The possible involvement of DNA topoisomerase I in cell transition from G0 to G1 and in progression through the cell cycle was studied by estimating the ability of human peripheral blood lymphocytes to undergo mitogenic stimulation in the presence of the topoisomerase I inhibitor camptothecin (CAM). Exposure of quiescent G0 lymphocytes to up to 3 microM CAM for 24 h had no significant effect on their ability to subsequently undergo mitogenic stimulation in the presence of phytohemagglutinin (PHA); higher doses of CAM, although not immediately cytotoxic, impaired the mitogenic response. Stimulation of lymphocytes with PHA in the presence of < or = 1.5 microM CAM resulted in unperturbed transition of these cells from G0 to G1 characterized as an increase in cellular rRNA content, appearance of interleukin-2 receptor, and, after removal of CAM, response to interleukin-2 by entering S phase of the cell cycle. However, lymphocytes were prevented from entering S phase in the presence of CAM at a concentration of > or = 30 nM, and their rate of progression through S was minimal even at CAM concentration as low as 3 nM. When cycling lymphocytes (48 h after stimulation by PHA) were treated with CAM, the cell progression through S and G2 was also very sensitive to the inhibitor: the cells were "frozen" in S and G2 at > or = 6 nM CAM. These cells died within 24 h; their selective loss from the cultures (with only G0/G1 cells remaining) coincided with the appearance of cells with fractional DNA content, typical of apoptotic cells. Human lymphocytic leukemic MOLT-4 cells were arrested in S and G2 at > or = 7.5 nM CAM. Thus, progressions through S and G2 of both normal and leukemic lymphocytes were perturbed at approximately two orders of magnitude lower CAM concentration than the G0 to G1 transition. These data suggest that DNA replication and chromosomal events during G2 are more sensitive to inhibition of DNA topoisomerase I, compared with the early events of lymphocyte stimulation, which involve activation and transcription of numerous genes associated with the G0 to G1 transition. The antitumor properties of CAM may be related to its high cytostatic/cytotoxic activity toward cycling cells and relative resistance of cells in G0 or undergoing transition from G0 to G1.
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Affiliation(s)
- S Bruno
- Cancer Research Institute, New York Medical College, Valhalla 10595
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20
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Karmali R, Hewison M, Rayment N, Farrow SM, Brennan A, Katz DR, O'Riordan JL. 1,25(OH)2D3 regulates c-myc mRNA levels in tonsillar T lymphocytes. Immunology 1991; 74:589-93. [PMID: 1783418 PMCID: PMC1384765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The effects of 1,25(OH)2D3 on proliferation, c-myc mRNA levels and 1,25(OH)2D3 receptor expression in activated tonsillar T lymphocytes were studied. Activation of resting T cells with phytohaemagglutinin (PHA) for 72 hr led to an increase in proliferation, c-myc mRNA levels and to induction of 1,25(OH)2D3 receptor expression. However, when activation was carried out in the presence of 1,25(OH)2D3, there was inhibition of PHA-stimulated proliferation and c-myc mRNA levels. Increased cell proliferation, c-myc mRNA expression and 1,25(OH)2D3 receptor number were also observed, albeit to a lesser extent, when T cells were stimulated by phorbol myristate acetate (PMA), anti-CD3 antibody or A23187. However, in these cases 1,25(OH)2D3 was unable to prevent increased proliferation or c-myc mRNA expression. PMA and anti-CD3 used in combination produced similar or greater changes in proliferation, c-myc mRNA levels, 1,25(OH)2D3 receptor expression and responsiveness to the hormone when compared to PHA alone. Thus the inhibition of c-myc expression in activated T lymphocytes by 1,25(OH)2D3 can be related to its anti-proliferative effects. Moreover this inhibition seems to be dependent on the level of 1,25(OH)2D3 receptor expression, which in turn appears to be related to the degree of cell activation.
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Affiliation(s)
- R Karmali
- Department of Medicine, Middlesex Hospital, London, U.K
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21
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Lømo J, Smeland EB, Stokke T, Holte H, Funderud S, Blomhoff HK. Differential effects of interferon-gamma and low molecular weight BCGF on growth of human B lymphocytes; interferon-gamma prolongs the increased c-MYC mRNA levels after activation. Scand J Immunol 1991; 33:365-73. [PMID: 1902001 DOI: 10.1111/j.1365-3083.1991.tb01783.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have characterized the growth-stimulating effect of Interferon-gamma (IFN-gamma) on various parameters of B cell growth, and compared the effects with those of low molecular weight B cell growth factor (lmw BCGF). We have found that IFN-gamma did not affect early changes induced by anti-mu, like initial calcium-flux and rise in mRNA-and protein levels of the proto-oncogene c-myc measured at 3 h. On the other hand, IFN-gamma enhanced the effect of anti-mu on parameters measured later in the G1 phase of the cell cycle, such as expression of the transferrin receptor and general transcriptional activity, measured as an increase in 7-aminoactinomycin D binding. In particular, whereas the c-myc levels in anti-mu-treated cells peaked at 3 h and then gradually declined, IFN-gamma together with anti-mu maintained the c-myc levels at 24 h at approximately the same levels as seen at 3 h. Overall, lmw BCGF had a more potent effect on the parameters affected by IFN-gamma, correlating with stronger enhancement of DNA synthesis. However, in contrast to IFN-gamma lmw BCGF did not affect anti-mu-induced c-myc mRNA levels. Thus this study has revealed differences between two B cell growth factors in effects on B cell cycle parameters.
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Affiliation(s)
- J Lømo
- Institute for Cancer Research, Norwegian Radium Hospital, Olso, Norway
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22
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Erikstein BK, Schwarze P, Blomhoff HK, Funderud S, Stokke T, Smeland EB. Use of size fractionation of in vitro-activated human B lymphocytes for studies of cell cycle-dependent growth regulation. Scand J Immunol 1991; 33:51-60. [PMID: 1899949 DOI: 10.1111/j.1365-3083.1991.tb02491.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cell cycle progression of in vitro-stimulated human B lymphocytes occurs asynchronously. In order to allow detailed studies of growth control in G1, B cells were stimulated with anti-mu and low molecular weight B-cell growth factor (LMW BCGF) for 50 h and subsequently separated into nine fractions of cells by means of centrifugal elutriation. As judged by volume profiles, activation antigen expression and DNA content, the cells in fractions 1-4 were in early to mid-G1, while fractions 5-7 mainly contained cells in late G1, and fractions 8-9 contained cells mainly in S and G2. Cells in fractions 5-7 had passed the commitment point, as demonstrated by a high spontaneous incorporation of [3H]thymidine when recultured in medium alone. Moreover, S-phase entry of these cells was largely unaffected by exogenous growth-promoting or growth-inhibitory signals. Cells in early (fractions 1-2) and intermediate fractions (fractions 3-4) showed a negligible spontaneous [3H]thymidine incorporation, but a significant proportion of these cells progressed to S phase upon restimulation. Moreover, while IL-4 or the anti-CD40 MoAb G28-5 potently stimulated cells in early and intermediate fractions, the responsiveness of LMW BCGF alone was obtained just prior to the commitment point.
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Affiliation(s)
- B K Erikstein
- Department of Tissue Culture, Norwegian Radium Hospital, Oslo
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23
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Smeland EB, Holte H, Kiil Blomhoff H, Asheim HC, Stokke T, Torjesen P, Funderud S. Inhibition of polyphosphoinositide breakdown and c-myc induction accompanying inhibition of human B-cell activation by two monoclonal antibodies against the leucocyte common antigen (CD45). Scand J Immunol 1990; 31:583-91. [PMID: 1693226 DOI: 10.1111/j.1365-3083.1990.tb02809.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this report we show that the two monoclonal anti-CD45 antibodies, EO-1 and FN-126, potently inhibit G0 to G1 transition and S phase entry in human B cells stimulated with anti-mu and low molecular weight B-cell growth factor. Both antibodies were found to inhibit anti-mu-induced inositol phospholipid breakdown and c-myc mRNA induction. In contrast, EO-1 and FN-126 only partially inhibited the early anti-mu-induced increase in cytoplasmic Ca2+ levels, both in normal and in Ca2(+)-depleted medium. B-cell activation provoked by 12-O-tetradecanoylphorbol 13-acetate (TPA) was not inhibited by these antibodies, except when using high concentrations of EO-1. In addition, both antibodies were found to inhibit G1 entry induced by the anti-CD20 antibody 1F5, which confers an activation of B cells without any detectable increase in [Ca2+]i or in phospholipid metabolism. This indicates that alternative mechanisms in addition to the inhibition of polyphosphoinositide (PI) breakdown are involved in the inhibitory action of these antibodies.
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Affiliation(s)
- E B Smeland
- Department of Pathology, Norwegian Radium Hospital, Oslo
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24
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Barrett TB, Shu GL, Draves KE, Pezzutto A, Clark EA. Signaling through CD19, Fc receptors or transforming growth factor-beta: each inhibits the activation of resting human B cells differently. Eur J Immunol 1990; 20:1053-9. [PMID: 1694130 DOI: 10.1002/eji.1830200516] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
To understand further the roles that negative regulatory signals may play in B cell immune responses, we compared three inhibitors of B cell proliferation: cross-linking CD19 with monoclonal antibody (mAb), signaling through Fc receptors by intact anti-mu mAb, and transforming growth factor-beta (TGF-beta). Each agent was tested for its ability to block proliferation and specific activation events induced in human tonsilar B cells activated by either cross-linking surface immunoglobulin, signaling through CD20, or direct activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate. We found that each inhibitor was functionally distinct. Both anti-CD19 mAb and anti-mu mAb inhibited anti-immunoglobulin activated cells and anti-CD20-activated cells, but neither inhibited cells activated by phorbol 12-myristate 13-acetate. TGF-beta, on the other hand, inhibited equally profoundly cells activated by each of the three regimens. These results suggest that TGF-beta blocks B cell activation at a step following the activation of PKC, whereas both signaling through CD19 and Fc receptor block early steps in the PKC activation pathway. Signaling through anti-CD19 mAb was unique in that proliferation of anti-immunoglobulin-activated cells was reduced on day 3 and then augmented subsequently. With all other inhibitory combinations the block was permanent. We conclude that each of these three inhibitors has unique important functions and therefore suggest that the effectiveness of negative signaling in B cell immune regulation will depend on the combinations of specific inhibitors modulating a specific activation program.
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Affiliation(s)
- T B Barrett
- Department of Microbiology, University of Washington, Seattle 98195
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25
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Pallavicini MG, Rosette C, Reitsma M, Deteresa PS, Gray JW. Relationship of c-myc gene copy number and gene expression: cellular effects of elevated c-myc protein. J Cell Physiol 1990; 143:372-80. [PMID: 2185254 DOI: 10.1002/jcp.1041430223] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The relationship between gene copy number and expression and cellular consequences of elevated levels of c-myc protein has been investigated using recombinant Chinese hamster ovary cell lines transfected with DNA coding for the murine c-myc gene. HC-8 and LC-5 recombinant cells carry approximately 800 and 50 copies of c-myc sequences, respectively, under control of an inducible heat shock promoter. Multivariate flow cytometric analysis and clonogenic assays were used to measure the relationship among c-myc expression, rate of DNA synthesis, and cell survival. Following heat exposure, maximally induced HC-8 cells produced approximately tenfold more c-myc protein than heated LC-5 cells, suggesting a close relationship between gene copy number and level of expression. However, considerable heterogeneity in the level and time of c-myc expression was observed following heat induction, even though the amounts of genomic c-myc were relatively constant. Heterogeneity in gene expression was not attributable to variation in heat induction methodologies and/or cell cycle phase distributions. The presence of high levels of recombinant c-myc protein was associated with a decreased rate of bromodeoxyuridine incorporation into DNA. High levels of c-myc protein in HC-8 cells were inversely correlated with cell survival postheating, suggesting that high levels of c-myc protein are incompatible with cell survival.
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Affiliation(s)
- M G Pallavicini
- Biomedical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California 94550
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26
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Drexler HG, Gignac SM, Pettit GR, Hoffbrand AV. Synergistic action of calcium ionophore A23187 and protein kinase C activator bryostatin 1 on human B cell activation and proliferation. Eur J Immunol 1990; 20:119-27. [PMID: 1689659 DOI: 10.1002/eji.1830200118] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this study we have examined the immunostimulatory effects of the macrocyclic lactone bryostatin 1 on various aspects of B cell activation and proliferation using human tonsillar B cells. Bryostatin 1 is an activator of protein kinase C (PKC) and its properties were compared to those of the classical PKC activator phorbol 12-myristate 13-acetate (PMA), a phorbol ester. Time-course kinetics and dose-response curves of RNA and DNA synthesis induced by bryostatin 1 or PMA were comparable, albeit the phorbol ester was significantly more potent. The responses triggered by both bryostatin 1 and PMA could be blocked by the PKC inhibitor H7. Bryostatin 1 and PMA mediated similar effects with regard to the activation parameters, increase in cell size, expression of activation-associated antigens and hyperexpression of major histocompatibility complex class II antigens. Addition of the calcium ionophore A23187 to bryostatin 1-treated cultures resulted in synergistically enhanced activation and proliferation responses, and this potentiation by A23187 could be inhibited by cyclosporin A. Bryostatin 1 antagonized the effects of PMA-triggered stimulation in a time- and dose-dependent manner. The basis for this modulation of PMA-induced effects and the reason for the difference in the abilities of the two agents to stimulate B cells is unclear; possibly, bryostatin 1 and PMA activate different isoforms of PKC and elicit different signals on intracellular biochemical pathways. Bryostatin 1 lacks the tumor-promoting activity of PMA and is a potent anti-neoplastic substance. These features together with its immunomodulatory properties qualify bryostatin 1 as a candidate for in vivo use as a biological response modifier.
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Affiliation(s)
- H G Drexler
- Department of Hematology, Royal Free Hospital School of Medicine, London
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27
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MESH Headings
- Animals
- B-Lymphocytes/pathology
- Burkitt Lymphoma/epidemiology
- Burkitt Lymphoma/etiology
- Burkitt Lymphoma/genetics
- Burkitt Lymphoma/immunology
- Burkitt Lymphoma/pathology
- Chickens
- Chromosomes, Human, Pair 14/ultrastructure
- Chromosomes, Human, Pair 2/ultrastructure
- Chromosomes, Human, Pair 22/ultrastructure
- Cocarcinogenesis
- Disease Models, Animal
- Female
- Gene Expression Regulation, Neoplastic
- Global Health
- Herpesvirus 4, Human/genetics
- Herpesvirus 4, Human/physiology
- Humans
- Immunoglobulins/genetics
- Immunologic Deficiency Syndromes/complications
- Male
- Mice
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Neoplasm Proteins/physiology
- Oncogenes
- Primates
- Proto-Oncogene Proteins/biosynthesis
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/physiology
- Proto-Oncogene Proteins c-myc
- Rats
- Translocation, Genetic
- Tumor Virus Infections/complications
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Affiliation(s)
- I Magrath
- Lymphoma Biology Section, National Cancer Institute, Bethesda, Maryland 20892
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28
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Smeland EB, Blomhoff HK, Funderud S, Shalaby MR, Espevik T. Interleukin 4 induces selective production of interleukin 6 from normal human B lymphocytes. J Exp Med 1989; 170:1463-8. [PMID: 2677211 PMCID: PMC2189485 DOI: 10.1084/jem.170.4.1463] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In this paper we have shown that extensively purified human B lymphocytes respond to IL-4 treatment with a marked production of IL-6. Addition of anti-mu potentiated the effect of IL-4 on IL-6 production. Other cytokines tested like TNF-alpha and-beta, IFN-gamma, IL-1, IL-2, and IL-5 did not induce IL-6 secretion when given to resting B cells. Although B cells generally also produced TNF-alpha and TNF-beta upon stimulation, IL-4 did not induce TNF secretion and seemingly had a specific effect on IL-6 production.
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Affiliation(s)
- E B Smeland
- Department of Pathology, Institute for Cancer Research, Montebello, Oslo, Norway
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29
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Ohlsson R. Growth factors, protooncogenes and human placental development. CELL DIFFERENTIATION AND DEVELOPMENT : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF DEVELOPMENTAL BIOLOGISTS 1989; 28:1-15. [PMID: 2679983 DOI: 10.1016/0922-3371(89)90018-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- R Ohlsson
- Center for Biotechnology, Karolinska Institute, Huddinge University Hospital, Sweden
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30
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Mongini PK, Rudich SM. Membrane Ig-mediated triggering of B cell tolerance and B cell clonal expansion: implications for rheumatoid factor production in rheumatoid synovitis. SPRINGER SEMINARS IN IMMUNOPATHOLOGY 1989; 11:93-122. [PMID: 2683163 DOI: 10.1007/bf00197185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- P K Mongini
- Department of Pathology, New York University School of Medicine, NY 10003
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31
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Kahan A, Gerfaux J, Kahan A, Joret AM, Menkès CJ, Amor B. Increased proto-oncogene expression in peripheral blood T lymphocytes from patients with systemic sclerosis. ARTHRITIS AND RHEUMATISM 1989; 32:430-6. [PMID: 2784967 DOI: 10.1002/anr.1780320412] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The expression of c-myc, c-myb, and c-ras proto-oncogenes, determined using RNA hybridization techniques (slot-blot), was significantly increased in peripheral blood T lymphocytes, but not in B cells, from 17 patients with systemic sclerosis with diffuse scleroderma, compared with the expression in normal control subjects. The magnitude of expression of c-myc and c-myb tended to be higher in patients with early, active disease. These results demonstrate an in vivo activation of T cells from systemic sclerosis patients, which may play an important role in the pathogenesis of the disease.
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Affiliation(s)
- A Kahan
- INSERM U-283, Hôpital Cochin, Paris, France
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32
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Holte H, Stokke T, Smeland E, Watt R, Blomhoff HK, Kaalhus O, Ohlsson R. Levels of myc protein, as analyzed by flow cytometry, correlate with cell growth potential in malignant B-cell lymphomas. Int J Cancer 1989; 43:164-70. [PMID: 2642893 DOI: 10.1002/ijc.2910430130] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have analyzed c-myc protein expression during the cell cycle in malignant B-cell lymphomas by dual flow cytometric detection of a fluoresceinated polyclonal anti-myc antibody and propidium iodide which binds stochiometrically to DNA. The data obtained were correlated to other parameters of cell activation such as histopathological grading, expression of the activation antigen 4F2, light scatter (proportional to cellular volume), DNA synthesis and percentage of S-phase cells. The c-myc protein level was strongly correlated to parameters of DNA synthesis/content. In addition, the oncoprotein level was largely unvarying from the late G1 phase through the rest of the cell cycle in both malignant cells and normal purified B cells stimulated to proliferate in vitro.
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Affiliation(s)
- H Holte
- Department of Pathology, Norwegian Cancer Hospital, Oslo
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33
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Clark EA, Ledbetter JA. Structure, function, and genetics of human B cell-associated surface molecules. Adv Cancer Res 1989; 52:81-149. [PMID: 2662716 DOI: 10.1016/s0065-230x(08)60211-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- E A Clark
- Department of Microbiology, University of Washington, Seattle 98195
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34
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Tedder TF, McIntyre G, Schlossman SF. Heterogeneity in the B1 (CD20) cell surface molecule expressed by human B-lymphocytes. Mol Immunol 1988; 25:1321-30. [PMID: 2467190 DOI: 10.1016/0161-5890(88)90047-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The B1 molecule (CD20) is a phosphoprotein expressed only by B-lymphocytes. In this study, analysis of B1 immunoprecipitated from surface iodinated B-cell lines and B-lymphocytes has shown that there are several expressed forms of B1. A predominant species of Mr 33,000 represents 75-80% of the iodinated cell surface B1 and a Mr 35,000 species represents 20-25%. Limited proteinase digestion of these two species generated similar peptide maps demonstrating that the different forms of B1 shared common peptides. Biosynthetic labeling with [35S]methionine revealed that the Mr 35,000 B1 species may actually represent two bands of Mr 34,500 and 36,000. Endoglycosidase digestion studies and metabolic labeling in the presence of tunicamycin indicated that neither the Mr 33,000 or 34,500-36,000 forms of B1 were glycosylated. The Mr 33,000 and 34,500-36,000 forms of B1 were constitutively phosphorylated in B-cell lines. However, exposure of B-cells to PMA resulted in a significant increase in the phosphorylation of the Mr 34,500-36,000 form. Exposure to PMA also resulted in an increase in the amount of Mr 34,500-36,000 protein immunoprecipitated from 35S labeled cells. These results suggest that there are multiple forms of the B1 molecule expressed by B-lymphocytes and that this heterogeneity may result from phosphorylation of the B1 protein.
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Affiliation(s)
- T F Tedder
- Division of Tumor Immunology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115
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35
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Smeland EB, Blomhoff HK, Ohlsson R, De Lange Davies C, Funderud S, Boye E. Transcription of protooncogenes during stimulation of normal human B lymphocytes. Eur J Immunol 1988; 18:1847-50. [PMID: 3060364 DOI: 10.1002/eji.1830181131] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Protooncogenes play important roles in the regulation of growth and differentiation of normal cells. In this study we have examined the cell cycle-dependent regulation of transcription of various protooncogenes after stimulation of human peripheral blood B lymphocytes. The transcriptional rate of various genes was determined by means of a nuclear run-on assay. We found that several protooncogenes were transcriptionally activated after stimulation (myc, p53, K-ras, H-ras, sis and ets), but with different kinetics of induction. In contrast, some oncogenes, especially those encoding membrane-associated or cytoplasmatic proteins like abl, rel or mil/raf, were transcribed at a relatively constant rate during the cell cycle.
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Affiliation(s)
- E B Smeland
- Department of Pathology, Norwegian Radium Hospital, Oslo, Norway
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36
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Beiske K, Clark EA, Holte H, Ledbetter JA, Smeland EB, Godal T. Triggering of neoplastic B cells via surface IgM and the cell surface antigens CD20 and CDw40. Responses differ from normal blood B cells and are restricted to certain morphologic subsets. Int J Cancer 1988; 42:521-8. [PMID: 2459071 DOI: 10.1002/ijc.2910420409] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
By raising monoclonal antibodies (MAbs) against B cells, a number of cell surface molecules have recently been identified which after binding by their specific antibody can trigger B cells, either alone or in co-operation with antibodies to surface immunoglobulin (sIg). The anti-CD20 (Bp35) MAb IF5 can deliver a strong activation signal to resting normal B cells, and the anti-CDw40 (Bp50) MAb G28-5 can promote activated G1 B cells to enter S phase. These antibodies were tested for their functional effects in vitro on suspended cells from 17 follicle-center-cell (FCC) lymphomas, 5 cases of chronic lymphatic B-cell leukemia (B-CLL) and 8 cases of various histological types. Changes in cellular volume, RNA and DNA synthesis were compared with the results obtained with a polyclonal anti-mu [F(ab')2] antiserum, a MAb to surface IgM (AF6), 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and B-cell growth factor (low-molecular-weight BCGF). Our data reveal differences in the requirements for triggering of various B-cell subsets: cells from CLL responded strongly to TPA but not to anti-mu, which is a potent stimulator not only of normal B cells but also of cells from individual cases of FCC lymphomas. Our observations suggest that the differentiation stage of B-CLL cells is distinct from that of small resting B cells from peripheral blood. Centrocytic lymphomas could not be activated by any of the reagents. CD20-mediated triggering was seen in neoplastic B cells from only 4 of 30 cases, indicating that most B-cell neoplasias were not responsive to this activation pathway. In contrast, the anti-CDw40 MAb consistently stimulated DNA synthesis together with anti-mu or TPA in cells from FCC lymphomas, but not from CLL. Together, these results suggest that activation in different neoplastic B-cell subsets depends on distinct signal transduction mechanisms.
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MESH Headings
- Antigens, CD20
- Antigens, Differentiation, B-Lymphocyte/immunology
- Antigens, Surface/immunology
- B-Lymphocytes/immunology
- CD40 Antigens
- DNA/biosynthesis
- Humans
- Immunoglobulin M/immunology
- Leukemia, Lymphocytic, Chronic, B-Cell/immunology
- Lymphocyte Activation
- Lymphoma, Non-Hodgkin/immunology
- Phenotype
- Receptors, Interleukin-4
- Receptors, Mitogen/physiology
- Tetradecanoylphorbol Acetate/pharmacology
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Affiliation(s)
- K Beiske
- Department of Pathology, Norwegian Radium Hospital, Oslo
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37
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Holte H, Torjesen P, Blomhoff HK, Ruud E, Funderud S, Smeland EB. Cyclic AMP has the ability to influence multiple events during B cell stimulation. Eur J Immunol 1988; 18:1359-66. [PMID: 2458941 DOI: 10.1002/eji.1830180909] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Negative regulators of cellular proliferation are important in maintaining a balanced growth control. In this study we have examined the effects of the diterpene forskolin on various parameters of B cell activation. Forskolin is known to elevate intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and thereby to influence B cell stimulation. We found that forskolin exerted an inhibitory effect on early as well as late events during stimulation of resting normal human B cells. Cells were activated either by antibodies to surface immunoglobulins (anti-mu), by the monoclonal antibody 1F5 reactive with the CD20 antigen or by 12-O-tetradecanoylphorbol 13-acetate. While anti-mu stimulation induces increased phosphatidylinositol (PI) turnover and [Ca2+]i fluxes, the latter two reagents confer an activation of B cells independent of the PI/Ca2+ pathway. We found a clear inhibitory effect of forskolin on the anti-mu-induced PI turnover and [Ca2+]i fluxes as well as on later parameters of cell activation. There was also a clear inhibition of G1 entry and DNA synthesis when PI/Ca2+-independent activation was employed, indicating that cAMP interferes with B lymphocyte stimulation in several ways. Importantly, forskolin maintained its inhibitory effect when added late after anti-mu stimulation, implying an effect also at multiple stages of activation. When examining the inhibitory effect of forskolin on neoplastic B cells, we found essentially no differences from the responses in normal cells.
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Affiliation(s)
- H Holte
- Department of Pathology, Institute for Cancer Research, Oslo, Norway
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38
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Rudich SM, Roux KH, Winchester RJ, Mongini PK. Anti-IgM-mediated B cell signaling. Molecular analysis of ligand binding requisites for human B cell clonal expansion and tolerance. J Exp Med 1988; 168:247-66. [PMID: 2456368 PMCID: PMC2188966 DOI: 10.1084/jem.168.1.247] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The ligand binding requisites for membrane IgM-mediated signaling of human B lymphocyte clonal expansion and B cell tolerance were investigated with a well-characterized set of soluble murine anti-human IgM mAbs. Evaluation of the impact of mu chain domain specificity, affinity, and binding stoichiometry for membrane IgM on antibody-induced regulation of normal and leukemic B cell DNA synthesis revealed that the ligand binding requisites for inducing or, alternatively, suppressing B cell DNA synthesis are significantly different. First, while the induction of S phase entry required micrograms/ml concentrations of ligand, orders of magnitude lower concentrations of ligand sufficed for inhibitory signaling. Second, while an upper affinity threshold for achieving maximal stimulation of B cell DNA synthesis was never detected, inhibitory signaling by bivalent ligands appeared to become relatively affinity independent at Fab binding affinities greater than 7.0 x 10(6) M-1. Third, while a C mu 1-specific mAb with an enhanced incidence of monogamous binding to mIgM was ineffective at inducing B cell DNA synthesis, the antibody was not significantly compromised in ability to initiate inhibitory signals. These differences could be observed in a clonal B cell population which positively or negatively responded to mIgM ligation depending upon its state of activation. The accumulated observations indicate that the ligand binding requisites for inhibitory signal transduction in human B lymphocytes are much less rigorous than those for stimulatory signal transduction and suggest that many physiologically relevant anti-Ig antibodies are more likely to function in the negative feedback regulation of B cell responses than in the direct triggering of human B cell clonal expansion.
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Affiliation(s)
- S M Rudich
- Department of Rheumatic Diseases, Hospital for Joint Diseases, New York University Medical School, New York 10003
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39
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Tedder TF, Schlossman SF. Phosphorylation of the B1 (CD20) molecule by normal and malignant human B lymphocytes. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)81618-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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40
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Two-step stimulation of B lymphocytes to enter DNA synthesis: synergy between anti-immunoglobulin antibody and cytochalasin on expression of c-myc and a G1-specific gene. Mol Cell Biol 1988. [PMID: 3285181 DOI: 10.1128/mcb.8.3.1371] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously we demonstrated that stimulation of resting murine splenic B lymphocytes with goat anti-mouse immunoglobulin antibody (GaMIg) plus cytochalasin D (CD) led to DNA synthesis; GaMIg and CD added simultaneously, or GaMIg added before CD, induced this response (T. L. Rothstein, J. Immunol. 136:813-816, 1986). Cells similarly treated with GaMIg or CD alone did not enter S phase. Here we have measured the effects of this two-signal stimulation on the c-myc, 2F1, and gamma-actin genes. The expression of these growth-related genes is known to change either during the G0-to-G1 transition or in the G1 phase of the cell cycle. For the 2F1 and c-myc genes, neither the GaMIg nor CD stimulus alone led to a prolonged increase in mRNA levels, whereas GaMIg plus CD allowed for continuous elevated expression of these genes. Furthermore, GaMIg pretreatment rendered expression of the c-myc and 2F1 genes susceptible to subsequent action by CD. In contrast, CD alone was sufficient to produce changes in gamma-actin gene expression. Thus there are synergistic effects of competence- and progressionlike factors on the expression of the c-myc and 2F1 genes, and these effects correlate with the progression of B lymphocytes to DNA synthesis.
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41
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Koizumi T, Nakao Y, Matsui T, Katakami Y, Mihara K, Takahashi R, Maeda S, Sugiyama T, Fujita T. C-myc expression in lymphocytes of MRL/MP-lpr mice activated by A23187 and TPA. Immunol Suppl 1988; 64:93-6. [PMID: 3133310 PMCID: PMC1385191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In order to analyse the molecular mechanism of lymphocyte activation defect in MRL/MP-lpr (MRL/1) mice, c-myc proto-oncogene expression was examined in MRL/1 lymph node cells stimulated by various agents. Since a transient increase of c-myc RNA in early hours is required for lymphocyte activation, detection of c-myc messenger RNA is useful to determine whether or not an appropriate signal is transduced to the nucleus. Stimulation by concanavalin A (Con A) plus 12-O-tetradecanoyl phorbol 13-acetate (TPA) or A23187 plus TPA markedly increased c-myc mRNA expression and cell proliferation, whereas stimulation by Con A alone failed to do so. These results suggest that an abnormality exists in the early signal transduction process, and that it could be bypassed by calcium influx and direct activation of protein kinase C.
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Affiliation(s)
- T Koizumi
- Department of Medicine and Pathology, Kobe University School of Medicine, Japan
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42
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Buckler AJ, Rothstein TL, Sonenshein GE. Two-step stimulation of B lymphocytes to enter DNA synthesis: synergy between anti-immunoglobulin antibody and cytochalasin on expression of c-myc and a G1-specific gene. Mol Cell Biol 1988; 8:1371-5. [PMID: 3285181 PMCID: PMC363285 DOI: 10.1128/mcb.8.3.1371-1375.1988] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Previously we demonstrated that stimulation of resting murine splenic B lymphocytes with goat anti-mouse immunoglobulin antibody (GaMIg) plus cytochalasin D (CD) led to DNA synthesis; GaMIg and CD added simultaneously, or GaMIg added before CD, induced this response (T. L. Rothstein, J. Immunol. 136:813-816, 1986). Cells similarly treated with GaMIg or CD alone did not enter S phase. Here we have measured the effects of this two-signal stimulation on the c-myc, 2F1, and gamma-actin genes. The expression of these growth-related genes is known to change either during the G0-to-G1 transition or in the G1 phase of the cell cycle. For the 2F1 and c-myc genes, neither the GaMIg nor CD stimulus alone led to a prolonged increase in mRNA levels, whereas GaMIg plus CD allowed for continuous elevated expression of these genes. Furthermore, GaMIg pretreatment rendered expression of the c-myc and 2F1 genes susceptible to subsequent action by CD. In contrast, CD alone was sufficient to produce changes in gamma-actin gene expression. Thus there are synergistic effects of competence- and progressionlike factors on the expression of the c-myc and 2F1 genes, and these effects correlate with the progression of B lymphocytes to DNA synthesis.
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Affiliation(s)
- A J Buckler
- Department of Microbiology, Boston University School of Medicine, Massachusetts 02118
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43
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Rollins BJ, Stiles CD. Regulation of c-myc and c-fos proto-oncogene expression by animal cell growth factors. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY : JOURNAL OF THE TISSUE CULTURE ASSOCIATION 1988; 24:81-4. [PMID: 3125143 DOI: 10.1007/bf02623883] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Animal cell growth factors stimulate expression of the proto-oncogenes c-myc and c-fos. The products of these genes seem to act as intracellular mediators of the mitogenic response to growth factors. Phosphatidyl inositol breakdown products function as cytoplasmic second messengers to induce transcription of c-myc and c-fos although they may not play an exclusive role in this regard. Post-transcriptional events may contribute to the modulation of c-myc gene expression. Following induction, the c-myc and c-fos mRNAs are selectively degraded within the cell.
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Affiliation(s)
- B J Rollins
- Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115
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44
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Tedder TF, Streuli M, Schlossman SF, Saito H. Isolation and structure of a cDNA encoding the B1 (CD20) cell-surface antigen of human B lymphocytes. Proc Natl Acad Sci U S A 1988; 85:208-12. [PMID: 2448768 PMCID: PMC279513 DOI: 10.1073/pnas.85.1.208] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The B1 (CD20) molecule is a Mr 33,000 phosphoprotein on the surface of human B lymphocytes that may serve a central role in the humoral immune response by regulating B-cell proliferation and differentiation. In this report, a cDNA clone that encodes the B1 molecule was isolated and the amino acid sequence of B1 was determined. B-cell-specific cDNA clones were selected from a human tonsillar cDNA library by differential hybridization with labeled cDNA derived from either size-fractionated B-cell mRNA or size-fractionated T-cell mRNA. Of the 261 cDNA clones isolated, 3 cross-hybridizing cDNA clones were chosen as potential candidates for encoding B1 based on their selective hybridization to RNA from B1-positive cell lines. The longest clone, pB1-21, contained a 2.8-kilobase insert with an 891-base-pair open reading frame that encodes a protein of 33 kDa. mRNA synthesized from the pB1-21 cDNA clone in vitro was translated into a protein of the same apparent molecular weight as B1. Limited proteinase digestion of the pB1-21 translation product and B1 generated peptides of the same sizes, indicating that the pB1-21 cDNA encodes the B1 molecule. Gel blot analysis indicated that pB1-21 hybridized with two mRNA species of 2.8 and 3.4 kilobases only in B1-positive cell lines. The amino acid sequence deduced from the pB1-21 nucleotide sequence apparently lacks a signal sequence and contains three extensive hydrophobic regions. The deduced B1 amino acid sequence shows no significant homology with other known proteins.
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Affiliation(s)
- T F Tedder
- Division of Tumor Immunology, Dana-Faber Cancer Institute, Boston, MA
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45
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Lindsten T, June CH, Thompson CB. Stimulation of the antigen receptor complex leads to transcriptional activation of the c-myc gene in normal human T cells. Curr Top Microbiol Immunol 1988; 141:223-30. [PMID: 3265089 DOI: 10.1007/978-3-642-74006-0_30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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46
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Roifman CM, Mills GB, Stewart D, Cheung RK, Grinstein S, Gelfand EW. Response of human B cells to different anti-immunoglobulin isotypes: absence of a correlation between early activation events and cell proliferation. Eur J Immunol 1987; 17:1737-42. [PMID: 3500860 DOI: 10.1002/eji.1830171209] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cross-linking of surface immunoglobulin (sIg) by antibodies against IgM, IgG and IgD activates B cells and in some circumstances can induce cell proliferation. We studied the potential link between anti-Ig-induced changes in the cytosolic free Ca2+ concentration ([Ca2+]i), inositol phosphate production and the ability to induce cell proliferation in the presence or absence of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA). Anti-IgM, but not anti-IgD or anti-IgG, induced cell proliferation in the presence but not the absence of TPA. Each of the antibodies induced a rapid increase in [Ca2+]i which appeared to be due to release of Ca2+ from internal stores. This was followed by a sustained increase in [Ca2+]i, apparently due to Ca2+ uptake from the extracellular medium. Anti-IgD induced the greatest increase in [Ca2+]i, anti-IgM induced intermediate changes and anti-IgG the lowest change. Since inositol 1,3,5-trisphosphate (IP3) can release Ca2+ from internal stores, we tested the ability of each anti-Ig isotype to increase concentrations of IP3. In contrast to the change in [Ca2+]i and proliferation, anti-IgG induced the most significant increase in IP3 concentrations. Taken together these data indicate that changes in [Ca2+]i, inositol phosphate production and anti-Ig-induced human B cell proliferation are not directly linked. They also demonstrate that changes in [Ca2+]i, inositol phosphate production and activation of protein kinase C are not sufficient to induce proliferation of human B cells. It appears that anti-IgM induces an additional Ca2+-independent, inositol phosphate-independent and protein kinase C-independent activation signal which can collaborate with TPA to induce B cell proliferation. The molecular events involved in this signal remain to be identified.
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Affiliation(s)
- C M Roifman
- Division of Immunology/Rheumatology, Hospital for Sick Children, Toronto, Ontario, Canada
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Hardt C. Activation of murine CD8+ lymphocytes: two distinct signals regulate c-myc and interleukin 2 receptor RNA expression. Eur J Immunol 1987; 17:1711-7. [PMID: 3121357 DOI: 10.1002/eji.1830171206] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Resting cytotoxic T lymphocyte precursors (CTL-P; CD8+) constitutively express T cell receptors (TcR) on their cell surfaces. CTL-P are preactivated if binding of the corresponding antigen (mitogens, allogeneic major histocompatibility complex (MHC) determinants, viral proteins or haptens in conjunction with self MHC structures) to the TcR takes place. Using a myc-specific probe I show that within 12 h first antigen binding leads to optimal c-myc RNA expression which seems to be the first sign that resting CTL-P are preactivated. Thereafter, c-myc RNA expression was remarkably reduced only at day 5. Antigen alone, however, is not sufficient for interleukin 2 receptor (IL2R) RNA expression. A monocyte-derived, soluble mediator termed IL2R-inducing factor (RIF) acts in conjunction with antigen to induced the expression of IL2R RNA and functional IL2R on the cell surface. RIF is a 44-kDa heat-labile protein produced by accessory cells and its function is restricted to CD8+ lymphocytes. IL2R RNA is first expressed 12 h after onset of culture, maximally expressed on day 3 and it decreases thereafter. Cells kept in long-term culture without mitogen but in the presence of IL2 do not express high amounts of IL2R RNA. Expression of IL2R RNA can be very efficiently reinduced, however, by mitogenic stimulation. In contrast to primary cultures, IL2R RNA expression peaks earlier and is independent of RIF. The results obtained here show that (a) for CD8+ lymphocytes of primary cultures two distinct activation signals (mitogen and RIF) are necessary for c-myc and IL2R RNA expression and (b) for CD8+ lymphocytes of secondary cultures the mitogenic signal alone is sufficient for re-expression of IL2R RNA.
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Affiliation(s)
- C Hardt
- Junior Research Unit, Max-Planck-Institut für Immunobiologie, Freiburg, FRG
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48
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Platelet-derived growth factor-inducible genes respond differentially to at least two distinct intracellular second messengers. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)48175-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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49
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Valentine MA, Cotner T, Gaur L, Torres R, Clark EA. Expression of the human B-cell surface protein CD20: alteration by phorbol 12-myristate 13-acetate. Proc Natl Acad Sci U S A 1987; 84:8085-9. [PMID: 3500472 PMCID: PMC299482 DOI: 10.1073/pnas.84.22.8085] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The monoclonal antibody 1F5 recognizes human B-cell surface protein CD20 and can activate resting B cells; with this antibody we found CD20 to be a 35/37-kDa non-disulfide-linked protein. The protein has a pI of 7.5-8.0 and is phosphorylated in B-cell lines, tonsillar B cells, and peripheral blood B cells. Both CD20 surface expression and phosphorylation are increased on buoyant tonsillar B cells activated in vivo. Because phorbol 12-myristate 13-acetate (PMA) supports the activation signal initiated by monoclonal antibody 1F5, we studied the effect of PMA on CD20 expression. After brief incubation with mitogenic levels of PMA, the number of dense tonsillar B cells positive for CD20 protein transiently decreased. Paradoxically, the cells remaining positive had more surface CD20 than did control cells, and these remaining surface CD20 molecules were hyperphosphorylated. Furthermore, PMA not only induced phosphorylation of CD20 protein on Raji cells but also increased the internalization of CD20 molecules; both phosphorylation and internalization of CD20 molecules were decreased with the protein kinase C inhibitor palmitoyl carnitine. Conditions that increase CD20 phosphorylation are shown also to increase surface mobility of the molecule, suggesting that CD20 protein internalization may be a critical early event for B-cell entry into the G1 phase of the cell cycle.
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Affiliation(s)
- M A Valentine
- Department of Microbiology, University of Washington, Seattle 98195
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50
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Affiliation(s)
- E C Snow
- Department of Microbiology and Immunology, University of Kentucky Medical Center, Lexington 40536-0084
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