Article

Expression of the nerve growth factor receptor c-TRK in human myeloid leukemia cells

British Journal of Haematology

November 1996
95(1):102-9

DOI:10.1046/j.1365-2141.1996.d01-1874.x

Source
PubMed

Authors:

Jürgen Lohmeyer

Justus-Liebig-Universität Gießen

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Nerve growth factor (NGF) is of major importance for the survival, development and maintenance of peripheral sympathetic and central neuronal tissue. Most of the cellular effects are mediated by binding to their high-affinity receptor c-TRK, a transmembrane receptor tyrosine kinase. C-TRK protein has been detected in neuronal tissue and also in mast cells, monocytes and some haemopoletic progenitor cells. Here we report c-TRK gene expression in myeloid leukaemic cell lines (HEL, K562 and KG-1) and for the first time in the primary leukaemic cells of 44% (n = 59) of patients with acute myelogenous leukaemia (AML). Moreover, in the human promyelocytic cell line HL-60, c-TRK expression was inducible by differentiation induction with tetradecanoyl-phorbol 13-acetate (TPA). In c-TRK gene-expressing cells the transmembrane receptor tyrosine kinase was detectable by Western blotting and by in vitro kinase assay. In the AML group, c-TRK expression was not correlated to the FAB-classified morphology or any other clinical parameter. In all cases tested we could not detect NGF mRNA by means of reverse transcriptase PCR, excluding an autocrine loop involving the TRK/NGF receptor-ligand system in leukaemogenesis. Our results show another example of possible communication between neuronal and haemopoietic tissue. However, we still lack positive evidence of a c-TRK function in haemopoiesis.

Revisiting NTRKs as an emerging oncogene in hematological malignancies

Article

Full-text available

Sep 2019

NTRK fusions are dominant oncogenic drivers found in rare solid tumors. These fusions have also been identified in more common cancers, such as lung and colorectal carcinomas, albeit at low frequencies. Patients harboring these fusions demonstrate significant clinical response to inhibitors such as entrectinib and larotrectinib. Although current trials have focused entirely on solid tumors, there is evidence supporting the use of these drugs for patients with leukemia. To assess the broader applicability for Trk inhibitors in hematological malignancies, this review describes the current state of knowledge about alterations in the NTRK family in these disorders. We present these findings in relation to the discovery and therapeutic targeting of BCR–ABL1 in chronic myeloid leukemia. The advent of deep sequencing technologies has shown that NTRK fusions and somatic mutations are present in a variety of hematologic malignancies. Efficacy of Trk inhibitors has been demonstrated in NTRK-fusion positive human leukemia cell lines and patient-derived xenograft studies, highlighting the potential clinical utility of these inhibitors for a subset of leukemia patients.

Hemmung oder Überexpression der Tyrosinkinase Trk in hämatologischen Zelllinien und ihre Effekte

Article

Christiane Heineck

Seit Jahren ist das Gebiet der Signaltransduktion von Rezeptorproteinen über eine verzweigte Kaskade von intrazellulären Proteinen bis zur Regulation der Gen-expression im Zellkern als Antwort auf extrazelluläre Wachstumsfaktoren oder Hormone von grossem Interesse. Das durch diese Mechanismen kontrollierte Zellwachstum und die Differenzierung der Zellen können durch geringe Fehler in den Signaltransduktionsketten zu unkontrolliertem Wachstum und damit zur Neoplasieentwicklung führen. Die meisten der entdeckten Onkogene sind Varianten der physiologischen Signaltransduktionsproteine, oder veränderte Wachstumsfaktoren, die Einfluss auf die maligne Entwicklung der Zellen nehmen. Die Wirkung des Wachstumsfaktors NGF über Trk als Rezeptor wurde in Nervenzellen bisher ausführlich untersucht. Die Familie der Trk-Tyrosin-kinasen hat aber nicht nur im Nervensystem, sondern auch in vielen anderen Organsystemen bei der Entwicklung und Differenzierung der Zellen als Rezeptoren der Neurotrophine Bedeutung. Innerhalb des hämatologischen Sytems, insbesondere bei den Leukämien, deutet ihr Vorkommen auf eine mögliche außergewöhnliche wachstumsregulierende Rolle hin. Um die Funktion von Trk im hämatologischen System zu charakterisieren, wurde in dieser Arbeit zunächst versucht, Trk durch Antisense-Oligonukleotide zu supprimieren, um von einer möglicherweise hierdurch bedingten Veränderung der Zellen auf die Funktion von Trk schliessen zu können. Es wurde die Wirkung von Antisense-Oligonukleotiden auf die Expression von Trk als Rezeptorprotein, auf die trk-mRNA, auf das Zellwachstum und die Differenzierung der Zellen untersucht. Da in den durchgeführten Experimenten unter verschiedenen Versuchsbedingungen keine messbaren Veränderungen von Trk auf Protein- oder RNA-Ebene und keine biologischen Effekte in den Zelllinien HEL und K562 beobachtet werden konnten, wurde im Weiteren die Wirkung von NGF auf mit trk transfizierte 32D-trk und K562-trk Zellen im Vergleich zu ihren Wildtypen 32D-wt und K562-wt untersucht. Hierbei konnte eine deutliche Abnahme des Zellwachstums unter NGF-Inkubation bei den 32D-trk Zellen beobachtete werden, welche durch spezifische Hemmung von Trk durch K252a vollständig reversibel war. Zusätzlich konnte die durch NGF über Trk induzierte Signal-kaskade mit Phosphorylierung von Erk und Akt und ihrer jeweils spezifischen Hemmung, weiterhin die Expression und Phosphorylierung von Fos und zuletzt die Anlagerung des genregulatorischen Proteins AP-1 an DNA gezeigt werden. Hiermit wurde erstmalig in diesem hämatologischen Zellsystem der Weg der Signaltransduktionskaskade vom Wachstumsfaktor NGF bis zur Genregulation dargestellt. Die wachstumsinhibierende Wirkung von NGF in den beschriebenen Experimenten wird am ehesten durch die Aktivierung von Fos über die nach-gewiesene Signaltransduktionskaskade und die zusätzliche Aktivierung des zellzyklusinhibierenden Proteins p21Cip/Waf erklärt. Durch weitere Entschlüsselung des verzweigten Systems der Signalübermittlung in den Zellen, mit Übersetzung der Information der Wachstumsfaktoren und Hormone in spezielle Muster der Genexpression und damit spezifischen Zell-reaktion, können eventuell neue Ansatzpunkte für eine gezielte Regulierung maligner Zellwachstumsformen gefunden werden.

Characterization of TRKA signaling in acute myeloid leukemia

Article

Full-text available

Jul 2018

Tropomyosin-related kinase A (TRKA) translocations have oncogenic potential and have been found in rare cases of solid tumors. Accumulating evidence indicates that TRKA and its ligand, nerve growth factor (NGF), may play a role in normal hematopoiesis and may be deregulated in leukemogenesis. Here, we report a comprehensive evaluation of TRKA signaling in normal and leukemic cells. TRKA expression is highest in common myeloid progenitors and is overexpressed in core binding factor and megakaryocytic leukemias, especially Down syndrome-related AML. Importantly, NGF can rescue GM-CSF dependent TF-1 AML cells, but does not drive proliferation in other TRKA-expressing lines. Although TRKA expression is heterogeneous between and within AML samples, NGF stimulation broadly induces ERK signaling, demonstrating the functional ability of AML cells to respond to NGF/ TRKA signaling. However, neither shRNA knockdown nor pharmacologic inhibition have significant anti-proliferative effects on human AML cells in vitro and in vivo. Thus, despite functional NGF/TRKA signaling, the importance of TRKA in AML remains unclear.

Remarkable leukemogenic potency and quality of a constitutively active neurotrophin receptor, ΔTrkA

Article

Full-text available

Oct 2007

Neurotrophins and their receptors play a key role in neurogenesis and survival. However, we and others have recently obtained evidence for a potential involvement of this receptor system in leukemia. To investigate mechanisms underlying the leukemogenic potential of activated neurotrophin receptor signaling, we analyzed in vivo leukemogenesis mediated by deltaTrkA, a mutant of TRKA (tropomyosin-related kinase A) isolated from a patient with acute myeloid leukemia (AML). Retroviral expression of deltaTrkA in myeloid 32D cells induced AML in syngeneic C3H/Hej mice (n=11/11, latency approximately 4 weeks). C57Bl/6J mice transplanted with deltaTrkA-transduced primary lineage negative (Lin-) bone marrow cells died of a transient polyclonal AML (n=7/15, latency of <12 days). Serial transplantation of AML cells did not re-induce this disease but rather acute lymphoblastic leukemia (ALL, latency >78 days). All primary recipients surviving the early AML developed clonal ALL or myeloid leukemia (latency >72 days) that required additional genetic lesions. PI3K and mTOR-raptor were identified as the crucial mediators of leukemic transformation, whereas STAT and MAP kinase signaling pathways were not activated. Thus, our findings reveal potent and unique transforming properties of altered neurotrophin receptor signaling in leukemogenesis, and encourage further analyses of neurotrophin receptors and downstream signaling events in hematological malignancies.

High nerve growth factor receptor (p75NTR) expression is a favourable prognostic factor in paediatric B cell precursor-acute lymphoblastic leukaemia

Article

Dec 2007

Nerve growth factor (NGF) plays a pivotal role in cellular survival/death decisions with the low affinity receptor p75NTR predominately transmitting anti-proliferative signals. In spite of its established role in B-cell function and identification as a prognostically favourable marker in a number of malignancies, little is known about the expression pattern and prognostic significance of p75NTR in B cell precursor-acute lymphoblastic leukaemia (BCP-ALL). p75NTR expression was prospectively studied on primary ALL-blasts in a cohort of paediatric patients with common ALL (n = 86) and preB-ALL (n = 34) treated within the Co-operative study group for childhood acute lymphoblastic leukaemia (CoALL) protocol, CoALL06-97. Flow cytometric analysis showed that almost half of the patients expressed no or negligible amounts of p75NTR (<10%). The median expression in patients expressing p75NTR beyond that threshold was 49% (range 11-100%). In patients classified as low-risk at diagnosis, p75NTR expression was significantly higher than in high-risk patients (P = 0.001). Of note, p75NTR expression was lower in the 21 patients who subsequently developed relapse compared with those remaining in remission (P = 0.038). Accordingly, relapse-free survival was significantly better in patients expressing high surface p75NTR (P = 0.041). Thus, in this prospective analysis, high p75NTR expression was a strong prognostic marker that identified a group of paediatric ALL patients with favourable outcome.

Transcriptomic Context of RUNX3 Expression in Monocytes: A Cross-Sectional Analysis

Article

Full-text available

Jun 2023

The runt-related transcription factor 3 (RUNX3) regulates the differentiation of monocytes and their response to inflammation. However, the transcriptomic context of RUNX3 expression in blood monocytes remains poorly understood. We aim to learn about RUNX3 from its relationships within transcriptomes of bulk CD14+ cells in adults. This study used immunomagnetically sorted CD14+ cell gene expression microarray data from the Multi-Ethnic Study of Atherosclerosis (MESA, n = 1202, GSE56047) and the Correlated Expression and Disease Association Research (CEDAR, n = 281, E-MTAB-6667) cohorts. The data were preprocessed, subjected to RUNX3-focused correlation analyses and random forest modeling, followed by the gene ontology analysis. Immunity-focused differential ratio analysis with intermediary inference (DRAIMI) was used to integrate the data with protein–protein interaction network. Correlation analysis of RUNX3 expression revealed the strongest positive association for EVL (rmean = 0.75, pFDR-MESA = 5.37 × 10−140, pFDR-CEDAR = 5.52 × 10−80), ARHGAP17 (rmean = 0.74, pFDR-MESA = 1.13 × 10−169, pFDR-CEDAR = 9.20 × 10−59), DNMT1 (rmean = 0.74, pFDR-MESA = 1.10 × 10−169, pFDR-CEDAR = 1.67 × 10−58), and CLEC16A (rmean = 0.72, pFDR-MESA = 3.51 × 10−154, pFDR-CEDAR = 2.27 × 10−55), while the top negative correlates were C2ORF76 (rmean = −0.57, pFDR-MESA = 8.70 × 10−94, pFDR-CEDAR = 1.31 × 10−25) and TBC1D7 (rmean = −0.55, pFDR-MESA = 1.36 × 10−69, pFDR-CEDAR = 7.81 × 10−30). The RUNX3-associated transcriptome signature was involved in mRNA metabolism, signal transduction, and the organization of cytoskeleton, chromosomes, and chromatin, which may all accompany mitosis. Transcriptomic context of RUNX3 expression in monocytes hints at its relationship with cell growth, shape maintenance, and aspects of the immune response, including tyrosine kinases.

Discovery and Characterization of Targetable NTRK Point Mutations in Hematologic Neoplasms

Article

Full-text available

Feb 2020

Much of what is known about the neurotrophic receptor tyrosine kinase (NTRK) genes in cancer is through the identification and characterization of activating Trk fusions across many tumor types. A resurgence of interest in these receptors has emerged owing to the realization that they are promising therapeutic targets. The remarkable efficacy of the pan-Trk inhibitors, larotrectinib and entrectinib, in clinical trials led to their accelerated, tissue agnostic FDA approval for adult and pediatric patients with Trk-driven solid tumors. Despite our enhanced understanding of Trk biology in solid tumors, the importance of Trk signaling in hematological malignancies is underexplored and warrants further investigation. Herein, we describe mutations in NTRK2 and NTRK3 that were identified via deep sequencing of 185 patients with hematological malignancies. Ten patients contained a point mutation in NTRK2 or NTRK3. Among these patients, we identified nine unique point mutations. Of these nine mutations, four were oncogenic-NTRK2A203T, NTRK2R458G, NTRK3E176D, and NTRK3L449F-as determined via cytokine-independent cellular assays. Our data demonstrate that these mutations have transformative potential to promote downstream survival signaling and leukemogenesis. Specifically, the three mutations located within the extracellular (i.e., NTRK2A203T and NTRK3E176D) and transmembrane (i.e., NTRK3L449F) domains increased receptor dimerization and cell-surface abundance. The fourth mutation, NTRK2R458G, residing in the juxtamembrane domain, activates TrkB via non-canonical mechanisms that may involve altered interactions between the mutant receptor and lipids in the surrounding environment. Importantly, these four activating mutations can be clinically targeted using entrectinib. Our findings contribute to ongoing efforts focused on defining the mutational landscape that drives hematological malignancies and underscore the utility of FDA-approved Trk inhibitors for patients with aggressive Trk-driven leukemias.

The TP53 Apoptotic Network is a Primary Mediator of Resistance to BCL2 inhibition in AML Cells

Article

Full-text available

May 2019

To study mechanisms underlying resistance to the BCL2 inhibitor venetoclax in acute myeloid leukemia (AML), we used a genome-wide CRISPR/Cas9 screen to identify gene knockouts resulting in drug resistance. We validated TP53, BAX, and PMAIP1 as genes whose inactivation results in venetoclax resistance in AML cell lines. Resistance to venetoclax resulted from an inability to execute apoptosis driven by BAX loss, decreased expression of BCL2, and/or reliance on alternative BCL2 family members such as BCL2L1. The resistance was accompanied by changes in mitochondrial homeostasis and cellular metabolism. Evaluation of TP53 knockout cells for sensitivities to a panel of small-molecule inhibitors revealed a gain of sensitivity to TRK inhibitors. We relate these observations to patient drug responses and gene expression in the Beat AML dataset. Our results implicate TP53, the apoptotic network, and mitochondrial functionality as drivers of venetoclax response in AML and suggest strategies to overcome resistance. Significance AML is challenging to treat due to its heterogeneity, and single-agent therapies have universally failed, prompting a need for innovative drug combinations. We used a genetic approach to identify genes whose inactivation contributes to drug resistance as a means of forming preferred drug combinations to improve AML treatment. See related commentary by Savona and Rathmell, p. 831. This article is highlighted in the In This Issue feature, p. 813

NERVE GROWTH FACTOR: A SURVEY OF ACTIVITY ON IMMUNE AND HEMATOPOIETIC CELLS

Research

Full-text available

Dec 2015

Stefano De Santis

Nerve growth factor (NGF) is a well characterized molecule required for the survival and differentiation of a variety of cell types both in the peripheral and central nervous system. Numerous studies published in recent years have demonstrated that NGF affects different functional activities of mature immune and hematopoietic cells. Other studies have revealed that hematopoietic progenitor cells from bone marrow, umbilical cord blood and peripheral blood are receptive to the action of NGF and that bone marrow stromal cells produce/respond to NGF during different steps of normal hematopoiesis. Elevated levels of NGF have been found in a number of inflammatory diseases, including those of autoimmune nature and in myeloproliferative pathologies. This review presents these data and discusses the hypothesis of a possible functional role of NGF in immune and hematopoietic disorders. ? 1999 John Wiley & Sons, Ltd.

Fine-Tuning Roles of Endogenous Brain-Derived Neurotrophic Factor, TrkB and Sortilin in Colorectal Cancer Cell Survival

Article

Full-text available

Sep 2011
PLOS ONE

Neurotrophin receptors were initially identified in neural cells. They were recently detected in some cancers in association with invasiveness, but the function of these tyrosine kinase receptors was not previously investigated in colorectal cancer (CRC) cells. We report herein that human CRC cell lines synthesize the neural growth factor Brain-derived neurotrophic factor (BDNF) under stress conditions (serum starvation). In parallel, CRC cells expressed high- (TrkB) and low-affinity (p75(NTR)) receptors at the plasma membrane, whereas TrkA and TrkC, two other high affinity receptors for NGF and NT-3, respectively, were undetectable. We demonstrate that BDNF induced cell proliferation and had an anti-apoptotic effect mediated through TrkB, as assessed by K252a, a Trk pharmacologic inhibitor. It suppressed both cell proliferation and survival of CRC cells that do not express TrkA nor TrkC. In parallel to the increase of BDNF secretion, sortilin, a protein acting as a neurotrophin transporter as well as a co-receptor for p75(NTR), was increased in the cytoplasm of primary and metastatic CRC cells, which suggests that sortilin could regulate neurotrophin transport in these cells. However, pro-BDNF, also detected in CRC cells, was co-expressed with p75(NTR) at the cell membrane and co-localized with sortilin. In contrast to BDNF, exogenous pro-BDNF induced CRC apoptosis, which suggests that a counterbalance mechanism is involved in the control of CRC cell survival, through sortilin as the co-receptor for p75(NTR), the high affinity receptor for pro-neurotrophins. Likewise, we show that BDNF and TrkB transcripts (and not p75(NTR)) are overexpressed in the patients' tumors by comparison with their adjacent normal tissues, notably in advanced stages of CRC. Taken together, these results highlight that BDNF and TrkB are essential for CRC cell growth and survival in vitro and in tumors. This autocrine loop could be of major importance to define new targeted therapies.

NGF Inhibits Human Leukemia Proliferation by Downregulating Cyclin A1 Expression through Promoting Acinus/CtBP2 Association

Article

Sep 2009

Cyclin A1 is essential for leukemia progression, and its expression is tightly regulated by acinus, a nuclear speckle protein. However, the molecular mechanism of how acinus mediates cyclin A1 expression remains elusive. Here we show that transcription corepressor CtBP2 directly binds acinus, which is regulated by nerve growth factor (NGF), inhibiting its stimulatory effect on cyclin A1, but not cyclin A2, expression in leukemia. NGF, a cognate ligand for the neurotrophic receptor TrkA, promotes the interaction between CtBP2 and acinus through triggering acinus phosphorylation by Akt. Overexpression of CtBP2 diminishes cyclin A1 transcription, whereas depletion of CtBP2 abolishes NGF's suppressive effect on cyclin A1 expression. Strikingly, gambogic amide, a newly identified TrkA agonist, potently represses cyclin A1 expression, thus blocking K562 cell proliferation. Moreover, gambogic amide ameliorates the leukemia progression in K562 cells inoculated nude mice. Hence, NGF downregulates cyclin A1 expression through escalating CtBP2/acinus complex formation, and gambogic amide might be useful for human leukemia treatment.

Identification and Characterization of an Activating TrkA Deletion Mutation in Acute Myeloid Leukemia

Article

Full-text available

Jan 2001

In this study, we utilized retroviral transfer of cDNA libraries in order to identify oncogenes that are expressed in acute myeloid leukemia (AML). From screens using two different cell types as targets for cellular transformation, a single cDNA encoding a variant of the TrkA protooncogene was isolated. The protein product of this protooncogene, TrkA, is a receptor tyrosine kinase for nerve growth factor. The isolated transforming cDNA encoded a TrkA protein that contains a 75-amino-acid deletion in the extracellular domain of the receptor and was named DeltaTrkA. DeltaTrkA readily transformed fibroblast and epithelial cell lines. The deletion resulted in activation of the tyrosine kinase domain leading to constitutive tyrosine phosphorylation of the protein. Expression of DeltaTrkA in cells led to the constitutive activation of intracellular signaling pathways that include Ras, extracellular signal-regulated kinase/mitogen-activated protein kinase, and Akt. Importantly, DeltaTrkA altered the apoptotic and growth properties of 32D myeloid progenitor cells, suggesting DeltaTrkA may have contributed to the development and/or maintenance of the myeloid leukemia from which it was isolated. Unlike Bcr-Abl, expression of DeltaTrkA did not activate Stat5 in these cells. We have detected expression of DeltaTrkA in the original AML sample by reverse transcriptase PCR and by Western blot analysis. While previous TrkA mutations identified from human tumors involved fusion to other proteins, this report is the initial demonstration that deletions within TrkA may play a role in human cancers. Finally, this report is the first to indicate mutations in TrkA may contribute to leukemogenesis.

Receptor tyrosine kinase mutations in myeloid neoplasms

Article

Jul 2002

Expression of the p75 neurotrophin receptor in acute leukaemia

Article

Nov 2005

The dLNGFR is a cytoplasmically deleted form of the low-affinity nerve growth factor receptor (LNGFR, also known as p75NTR). Recently, we observed a myeloid leukaemia in mice transplanted with dLNGFR-modified bone marrow cells. Retroviral-mediated expression of dLNGFR was suspected to contribute to the murine leukaemia. This led us to investigate the expression of p75NTR in human leukaemia. Expression of p75NTR was observed in nine of 119 (8%) adult patients with acute leukaemia by flow cytometry analysis, particularly in acute lymphoblastic leukaemia (26%). These results support further detailed analyses of neurotrophin receptors and downstream signalling pathways in haematological malignancies.

Inhibition of Abl tyrosine kinase enhances nerve growth factor-mediated signaling in Bcr–Abl transformed cells via the alteration of signaling complex and the receptor turnover

Article

May 2008

Receptor tyrosine kinase-mediated signaling is tightly regulated by a number of cytoplasmic signaling molecules. In this report, we show that Bcr-Abl transformed chronic myelogenous leukemia (CML) cell lines, K562 and Meg-01, express the receptor for nerve growth factor (NGF), TrkA, on the cell surface; however, the NGF-mediated signal is not particularly strong. Treatment with imatinib, a potent inhibitor of Bcr-Abl tyrosine kinase, downmodulates phosphorylation of downstream molecules. Upon stimulation with NGF, Erk and Akt are phosphorylated to a much greater degree in imatinib-treated cells than in untreated cells. Knockdown of expression of Bcr-Abl using small interfering RNA technique also enhanced NGF-mediated Akt phosphorylation, indicating that Bcr-Abl kinase modifies NGF signaling directly. Imatinib treatment also enhanced NGF signaling in rat adrenal pheochromocytoma cell line PC12 that expresses TrkA and c-Abl, suggesting that it is not only restoration of responsiveness to NGF after blocking oncoprotein activity, but also c-Abl tyrosine kinase per se may be a negative regulator of growth factor signaling. Furthermore, inhibition of Abl tyrosine kinase enhanced clearance of surface TrkA after NGF treatment and simultaneously enhanced NGF-mediated signaling, suggesting that as in neuronal cells 'signaling endosomes' are formed in hematopoietic cells. To examine the role of TrkA in CML cells, we studied cell growth or colony formation in the presence or absence of imatinib with or without NGF. We found that NGF treatment induces cell survival in imatinib-treated CML cell lines, as well as colony formation of primary CD34+ CML cells, strongly suggesting that NGF/TrkA signaling contributes to aberrant signaling in CML.

L'expression du nerve growth factor (NGF) et de ses récepteurs dans le lymphome folliculaire: étude anatomo-clinique de 25 observations

Thesis

Oct 2000

Piet Ounnoughene Maud

Le Nerve Growth Factor (NGF), chef de file de la famille des neurotrophines, protéine essentielle à la survie, au développement et à la différenciation des neurones se lie à deux récepteurs p75[exposant NTR](Neurotrophin Receptor) et TrkA (Tropomyosin-related kinase). Ces molécules ont récemment été identifiées dans le tissu lymphoïde humain normal ou pathologique. Dans une étude anatomoclinique rétrospective de 25 lymphomes folliculaires (LF), nous avons recherché l'existence et l'intensité d'expression de ces molécules. Les techniques immunohistochimiques (HIC) ont été réalisées sur des tissus congelés ou fixés dans du formol. Elles ont fait appel à des montages en troiscouches utilisant la streptavidine-biotine, à des méthodes d'amplification par la tyramine biotinylée ainsi qu'à des systèmes de révélation de l'anticorps primaire par la peroxydase ou la phosphatase alcaline. Les transcrits ont été recherchés par RT-PCR. Avec ces techniques, nous n'avons pu mettre en évidence que les transcrits de GF. En IHC, le NGF et ses récepteurs étaient exprimésdans les cellules du micro-environnement. L'expression du NGF était otiservée dans les cellules réticulaires interdigitées ; celle de p75[exposant NTR] dans les filets nerveux périvasculaires et sous-capsulaires, les cellules endothéliales et les cellules folliculaires dendritiques ; et celle de TrkA dans les cellulesréticulaires interdigitées, les cellules endothéliales et les cellules folliculaires dendritiques. En revanche, l'expression de NGF, p75[exposant NTR] et TrkA a été observée pour la première fois, in vivo, dans les cellules tumorales. Aucune corrélation n'a été observée entre le niveau d'expression du NGFavec les critères péjoratifs habituels des LF (le stade d'Ann Arbor au moment du diagnostic, l'élévation sérique du taux de [bêta]2-microglobuline ou des LDH, l'existence de symptômes B, d'une altération de l'état général ou d'une «forte» masse tumorale) ou avec l'immunoréactivité P53, Bcl2, Bcl6 et Ki67. En revanche, l'hyperexpression de p75[exposant NTR] était corrélée avec le stade d'AnnArbor élevé au moment du diagnostic (r=0,45). Au vu de nos résultats acquis sur une petite série aux caractéristiques superposables à celles des grandes séries de la littérature, p75[exposant NTR] pourraitconstituer un facteur pronostic prédictif dans les LF de stade élevé. Toutefois, ces résultats devraient être vérifiés sur de grandes séries multicentriques.

Expression of placenta growth factor in mouse hair follicle cycle

Article

Jan 2005

Aim. The hair follicle cycle comprises an anagen growth phase followed by a catagen regression phase and a telogen resting phase. During anagen neoangiogenesis events occur leading to a marked increase in the extension of the perifollicular vascular network. The aim of the present study was to evaluate the expression of the angiogenic cytokine placenta growth factor (PlGF) in hair follicle and its relationship with changes in perifollicular vascularization during hair cycle. Methods. A murine model of synchronized hair follicle cycling induced by depilation was employed to obtain skin samples at different time points of the hair cycle. The evaluation of PlGF expression and perifollicular vessels was performed by immunohistochemical analysis. A computer assisted morphometric analysis was used to quantify perifollicular vessel size and density. Results. Immunoreactivity for PlGF was detected during anagen in follicular keratinocytes of the outer root sheath, with maximum signal 8 days after depilation (middle anagen), while no PlGF staining was observed in catagen and telogen phases. Computer assisted morphometric analysis in perifollicular dermis showed a significant increase in average vessel size and in percentage of dermal area occupied by blood vessels during late anagen. Conclusion. The present study shows that PlGF protein is upregulated in anagen mouse hair follicles, immediately before the maximum peak of perifollicular angiogenesis. These results suggest a role for PlGF in modulation of hair follicle-associated angiogenesis events. PlGF might act in synergism with the closely related vascular endothelial growth factor (VEGF) which has recently been shown to promote anagen angiogenesis and hair growth.

32 Side effects in gene therapy with hematopoietic cells

Article

Sep 2003
TOXICOL LETT

Nerve growth factor: A survey of activity on immune and hematopoietic cells

Article

Mar 1999
HEMATOL ONCOL

High-affinity neurotrophin receptors and ligands promote leukemogenesis

Article

Full-text available

Feb 2009
BLOOD

Neurotrophins (NTs) and their receptors play a key role in neurogenesis and survival. The TRK (tropomyosin-related kinase) receptor protein tyrosine kinases (TRKA, TRKB, TRKC) are high-affinity NT receptors that are expressed in a variety of human tissues. Their role in normal and malignant hematopoiesis is poorly understood. In a prospective study involving 94 adult patients we demonstrate for the first time cell-surface expression of the 3 TRKs and constitutive activation in blasts from patients with de novo or secondary acute leukemia. At least one TRK was expressed in 55% of the analyzed cases. We establish a clear correlation between the TRK expression pattern and FAB classification. Although only few point mutations were found in TRK sequences by reverse-transcriptase-polymerase chain reaction (RT-PCR), we observed coexpression of BDNF (ligand for TRKB) in more than 50% of TRKB(+) cases (16/30). Activation of TRKA or TRKB by NGF and BDNF, respectively, efficiently rescued murine myeloid cells from irradiation-induced apoptosis. Coexpression of TRKB/BDNF or TRKA/NGF in murine hematopoietic cells induced leukemia. Moreover, activation of TRKs was important for survival of both human and murine leukemic cells. Our findings suggest that TRKs play an important role in leukemogenesis and may serve as a new drug target.

Expression of Neurotrophins and their Receptors in Human Bone Marrow

Article

Mar 1999

The expression of neurotrophins and their receptors, the low-affinity nerve growth factor receptor (p75LNGFR) and the Trk receptors (TrkA, TrkB, and TrkC), was investigated in human bone marrow from 16 weeks fetal age to adulthood. Using reverse transcription-polymerase chain reaction, all transcripts encoding for catalytic and truncated human TrkB or TrkC receptors were detected together with trkAI transcripts, whereas trkAII transcripts were found only in control nerve tissues. Transcripts for the homologue of the rat truncated TrkC(ic113) receptor were identified for the first time in human tissue. Stromal adventitial reticular cells were found immunoreactive for all neutrophin receptors. In contrast, hematopoietic cell types were not immunoreactive for p75LNGFR but showed immunoreactivity for one or several Trk receptors. TrkA immunoreactivity was found in immature erythroblasts. Catalytic TrkB immunoreactivity was observed in eosinophilic metamyelocytes and polymorphonuclear cells. Truncated TrkB immunoreactivity was found in erythroblasts and megacaryocytes. Immunoreactivity for both catalytic and truncated TrkC receptor was observed in promyelocytes, myelocytes, some polymorphonuclear cells and megacaryocytes. Neutrophin transcript levels appeared higher at fetal than at adult stages, no variation in Trk family transcript levels was observed. The local expression of neurotrophin genes suggests a wide range of paracrine and/or autocrine mode of action through their corresponding receptors within the bone marrow.

Nerve Growth Factor: A Neurotrophin with activity on cells of the immune system

Article

May 1999

Numerous studies published in the last two decades provide evidence that nerve growth factor (NGF), a polypeptide originally discovered because of its neurotrophic activity, acts on a variety of cells of the immune system, including mast cells, eosinophils, and B and T lymphocytes. NGF has been shown to increase during inflammatory responses, autoimmune disorders, parasitic infections, and allergic diseases. Moreover, stress, which is characterized also by activation of a variety of immune cells, causes a significant increase in basal plasma NGF levels. Recently published studies reveal that hematopoietic progenitor cells seem to be able to produce and/or respond to NGF. We report these data and discuss the hypothesis of the possible implication of NGF on the functional activities of immune cells.

Detection of NGF-receptors TrkA and p75NTR in human tumor cell lines and effect of NGF on the growth characteristic of the UT-7/EPO cell line

Article

Full-text available

Jul 2002
J Exp Clin Canc Res

The receptors for nerve growth factor (NGF)--TrkA and p75NTR--were detected at the mRNA and the protein level in various human tumor cell lines. The NGF receptor TrkA was found on all examined tumor cell lines and is not restricted to cells belonging to the nervous system. NGF did not influence the proliferation rate of TrkA-positive cells NMB, K562, UT-7/EPO and PC-12. After NGF induction, the production level of the differentiation marker c-fos was increased in UT-7/EPO and PC- 12 cells. NGF-treatment of the UT-7/EPO cells and deprivation of erythropoietin (EPO) led to the new adherent cell line UT-7/NGF. Although UT-7/NGF showed a similar growth curve as UT-7/EPO, there were differences in the pattern of adhesion molecules and of the cytoskeleton. The effect of NGF on the cytoskeleton could not be induced in other human cell lines like NMB or KTCTL-30. TrkA inhibition with K252a--a blocker of Trk-induced receptor kinase--suggests, that the NGF signal may be transduced by the TrkA receptor in UT-7/NGF cells. This indicates that NGF is a decisive mediator of cellular adhesion.

Signaling mechanisms coupled to tyrosines in the granulocyte colony-stimulating factor receptor orchestrate G-CSF-induced expansion of myeloid progenitor cells

Article

Full-text available

May 2003

Granulocyte colony-stimulating factor (G-CSF) is the major regulator of neutrophil production. Studies in cell lines have established that conserved tyrosines Tyr704, Tyr729, Tyr744, Tyr764 within the cytoplasmic domain of G-CSF receptor (G-CSF-R) contribute significantly to G-CSF-induced proliferation, differentiation, and cell survival. However, it is unclear whether these tyrosines are equally important under more physiologic conditions. Here, we investigated how individual G-CSF-R tyrosines affect G-CSF responses of primary myeloid progenitors. We generated G-CSF-R-deficient mice and transduced their bone marrow cells with tyrosine "null" mutant (m0), single tyrosine "add-back" mutants, or wild-type (WT) receptors. G-CSF-induced responses were determined in primary colony assays, serial replatings, and suspension cultures. We show that removal of all tyrosines had no major influence on primary colony growth. However, adding back Tyr764 strongly enhanced proliferative responses, which was reverted by inhibition of ERK activity. Tyr729, which we found to be associated with the suppressor of cytokine signaling, SOCS3, had a negative effect on colony formation. After repetitive replatings, the clonogenic capacities of cells expressing m0 gradually dropped compared with WT. The presence of Tyr729, but also Tyr704 and Tyr744, both involved in activation of signal transducer and activator of transcription 3 (STAT3), further reduced replating efficiencies. Conversely, Tyr764 greatly elevated the clonogenic abilities of myeloid progenitors, resulting in a more than 10(4)-fold increase of colony-forming cells over m0 after the fifth replating. These findings suggest that tyrosines in the cytoplasmic domain of G-CSF-R, although dispensable for G-CSF-induced colony growth, recruit signaling mechanisms that regulate the maintenance and outgrowth of myeloid progenitor cells.

Side effects of retroviral gene transfer into hematopoietic stem cells

Article

Apr 2003

Recent conceptual and technical improvements have resulted in clinically meaningful levels of gene transfer into repopulating hematopoietic stem cells. At the same time, evidence is accumulating that gene therapy may induce several kinds of unexpected side effects, based on preclinical and clinical data. To assess the therapeutic potential of genetic interventions in hematopoietic cells, it will be important to derive a classification of side effects, to obtain insights into their underlying mechanisms, and to use rigorous statistical approaches in comparing data. We here review side effects related to target cell manipulation; vector production; transgene insertion and expression; selection procedures for transgenic cells; and immune surveillance. We also address some inherent differences between hematopoiesis in the most commonly used animal model, the laboratory mouse, and in humans. It is our intention to emphasize the need for a critical and hypothesis-driven analysis of "transgene toxicology," in order to improve safety, efficiency, and prognosis for the yet small but expanding group of patients that could benefit from gene therapy.

c-kit Receptor and ligand expression in postnatal development of the mouse cerebellum suggests a function for c-kit in inhibitory interneurons

Article

Full-text available

Jan 1993

The c-kit receptor and its cognate ligand, KL, are encoded at the white spotting locus (W) and the steel locus (Sl) of the mouse, respectively. Sl and W mutations affect the same cellular targets in melanogenesis, gametogenesis and hematopoiesis during embryonic development and in adult life. c-kit is expressed in cellular targets of W and Sl mutations, whereas KL is expressed in the microenvironment of these targets. c-kit and KL, however, are also expressed in tissues and cell types that are not targets of W and Sl mutations, including the brain. The cerebellum contains a small number of neural cell types whose developmental origins, pathways of migration, and synaptic contacts are known. We have investigated the patterns of expression of the c-kit and KL RNA and protein products in postnatal cerebellar development of the mouse. In the adult cerebellum, c-kit RNA and protein expression was evident in basket, stellate, and Golgi neurons. Most strikingly, the c-kit protein is expressed in the basket cell axons that form "basket" and "pinceau" structures entwining the Purkinje cell soma and the initial segment of the Purkinje cell axon. KL RNA expression was found in Purkinje cells, and the KL protein was detected in Purkinje cell bodies and dendrites. Soluble KL protein was also present in c-kit-expressing basket, stellate, and Golgi cells, presumably as a result of internalization of ligand-receptor complexes. During postnatal development, c-kit and KL RNA and protein expression in Golgi and Purkinje neurons, respectively, was evident by day 0 and persisted subsequently. c-kit expression in basket and stellate cells was detected from their time of birth, starting at day 4. These results suggest a role for the c-kit receptor system in postnatal development of the cerebellum.

Localization of mRNA for c-kit receptor and its ligand in the brain of adult rats: an analysis using in situ hybridization histochemistry

Article

Full-text available

Oct 1992
Mol Brain Res

Localization of mRNA for the c-kit receptor and its ligand (Sl factor) in the brain of adult rats was studied using in situ hybridization histochemistry. The mRNA for the c-kit receptor was detected in the forebrain, the lower brain stem and the cerebellum. In the forebrain, the c-kit mRNA signals were detected in the olfactory bulb, the caudate-putamen, throughout the superficial cortex, the accumbens nucleus, the nucleus of vertical limb diagonal band, the bed nucleus of anterior commissure, Ammon's horn, the entopeduncular nucleus, the subthalamic nucleus, the dorsal raphe nucleus, the parasubiculum, the presubiculum, the ventricular nucleus of lateral lemniscus, and the entorhinal cortex. In the lower brain stem, the signals were detected in the inferior colliculus, the spinal vestibular nucleus, the spinal tract nucleus of trigeminal nerve, and the pyramidal tract. In the cerebellum, the signals were detected in the molecular layer of the cortex and cerebellar nuclei. By contrast, the signals of mRNA for Sl factor were detected in the forebrain and the cerebellum. In the forebrain, the signals were detected in the olfactory bulb, the endopiriform nucleus, the septohippocampal nucleus, the habenular nuclei, and most of the thalamic nuclei. In the cerebellum, the signals were detected in Purkinje cells. Several pairs of structures were found in which mRNA of either the c-kit receptor or the Sl factor was expressed and between which the synaptic connection had been reported, suggesting that the interaction between the c-kit receptor and the Sl factor may play some roles in the development of such synaptic connections.

Molecular and biochemical characterization of the human trk proto-oncogene

Article

Full-text available

Feb 1989

Molecular analysis of the human trk oncogene, a transforming gene isolated from a colon carcinoma biopsy, revealed the existence of a novel member of the tyrosine kinase gene family. This locus, which we now designate the trk proto-oncogene, codes for a protein of 790 amino acid residues that has several features characteristic of cell surface receptors. They include (i) a 32-amino-acid-long putative signal peptide, (ii) an amino-terminal moiety (residues 33 to 407) rich in consensus sites for N-glycosylation, (iii) a transmembrane domain, (iv) a kinase catalytic region highly related to that of other tyrosine kinases, and (v) a very short (15 residue) carboxy-terminal tail. Residues 1 to 392 were absent in the trk oncogene, as they were replaced by tropomyosin sequences. However, no other differences were found between the transforming and nontransforming trk alleles (residues 392 to 790), suggesting that no additional mutations are required to activate the transforming potential of this gene. The human trk proto-oncogene codes for a 140,000-dalton glycoprotein, designated gp140proto-trk. However, its primary translational product is a 110,000-dalton glycoprotein which becomes immediately glycosylated, presumably during its translocation into the endoplasmic reticulum. This molecule, designated gp110proto-trk, is further glycosylated to yield the mature form, gp140proto-trk. Both gp110proto-trk and gp140proto-trk proteins possess in vitro kinase activity specific for tyrosine residues. Finally, iodination of intact NIH 3T3 cells expressing trk proto-oncogene products indicated that only the mature form, gp140proto-trk, cross the plasma membrane, becoming exposed to the outside of the cell. These results indicate that the product of the human trk locus is a novel tyrosine kinase cell surface receptor for an as yet unknown ligand.

Matsuda H, Coughlin MD, Bienenstock J, Denburg JA.. Nerve growth factor promotes human hemopoietic colony growth and differentiation. Proc Natl Acad Sci USA 85: 6508-6512

Article

Full-text available

Oct 1988

Nerve growth factor (NGF) is a neurotropic polypeptide necessary for the survival and growth of some central neurons, as well as sensory afferent and sympathetic neurons. Much is now known of the structural and functional characteristics of NGF, whose gene has recently been cloned. Since it is synthesized in largest amounts by the male mouse submandibular gland, its role exclusively in nerve growth is questionable. NGF also causes histamine release from rat peritoneal mast cells in vitro, and we have shown elsewhere that it causes significant, dose-dependent, generalized mast cell proliferation in the rat in vivo when administered neonatally. Our experiments now indicate that NGF causes a significant stimulation of granulocyte colonies grown from human peripheral blood in standard hemopoietic methylcellulose assays. Further, NGF appears to act in a relatively selective fashion to induce the differentiation of eosinophils and basophils/mast cells. Depletion experiments show that the NGF effect may be T-cell dependent and that NGF augments the colony-stimulating effect of supernatants from the leukemic T-cell (Mo) line. The hemopoietic activity of NGF is blocked by polyclonal and monoclonal antibodies to NGF. We conclude that NGF may indirectly act as a local growth factor in tissues other than those of the nervous system by causing T cells to synthesize or secrete molecules with colony-stimulating activity. In view of the synthesis of NGF in tissue injury, the involvement of basophils/mast cells and eosinophils in allergic and other inflammatory processes, and the association of mast cells with fibrosis and tissue repair, we postulate that NGF plays an important biological role in a variety of repair processes.

Tyrphostin-induced inhibition of p210bcr-abl tyrosine kinase activity induces K562 to differentiate

Article

Full-text available

Jan 1994

We report on the potency of two Tyrphostin tyrosine kinase blockers, AG 1112 and AG 568, to inhibit p210bcr-abl tyrosine kinase activity in K562 cells, concomitant with the induction of erythroid differentiation. AG 568 and especially AG 1112 represent a specific group of nontoxic protein tyrosine kinase blockers among more than 1,400 tested. These compounds possess therapeutic potential for purging Philadelphia chromosome-positive cells in preparation for autologous bone marrow transplantation in chronic myelogenous leukemia.

Nerve Growth Factor Stimulates Clonal Growth of Human Lung Cancer Cell Lines and a Human Glioblastoma Cell Line Expressing High-Affinity Nerve Growth Factor Binding Sites Involving Tyrosine Kinase Signaling

Article

Full-text available

Jun 1995

The growth of a panel of 22 different human tumor, leukemia, and lymphoma cell lines was examined in a human tumor cloning assay in agar or methylcellulose and a tritiated thymidine uptake assay. The cultures were performed in the absence or presence of increasing concentrations (0.5-500 ng/ml) of nerve growth factor (NGF). The growth of 17 of the 22 cell lines was not significantly and reproducibly affected by NGF. There was minor (1.2-fold) but reproducible stimulation of clonal growth in one glioblastoma cell line (86-HG-39) by NGF, but in this cell line NGF induced no growth modulation in a tritiated thymidine uptake assay. However, clonal growth of another glioblastoma cell line (87-HG-31) and all three lung cancer cell lines tested (HTB 119, HTB 120, CCL 185) could be stimulated up to 3-fold by NGF with a dose-response relationship for the growth factor. Growth stimulation by NGF could be completely reversed by neutralizing anti-NGF antibody and by the tyrosine kinase inhibitor genistein. Evaluation of secondary plating efficiency revealed the stimulation of colony formation as representing self-renewal and not terminal differentiation. Reverse transcriptase-PCR experiments in the five responding cell lines showed expression of both low-affinity NGF receptor (glycoprotein 75) and c-trk transcripts on the mRNA level. Of the five responding cell lines, only 86-HG-39, the cell line with the lowest responsiveness, revealed low-affinity NGF receptor on the protein level; the other four cell lines with high responsiveness, including the three lung cancer cell lines, expressed no low-affinity NGF receptor as shown by fluorescence-activated cell sorter analysis and immunoprecipitation using the ME 20.4 antibody. Immunoprecipitation using anti-trk antibodies was negative in all five responding cell lines. However, binding studies with iodinated NGF showed only low-affinity binding on the 86-HG-39 cell line and only high-affinity binding on the high-responder cell lines CCL 185 and 87-HG-31. In summary, our data suggest that NGF can be operative in stimulation of clonal growth of malignant tumor cells. High-affinity but not low-affinity binding sites mediate signal transduction for clonal growth and signaling involves tyrosine kinase activity.

Association between High Levels of Expression of the TRK Gene and Favorable Outcome in Human Neuroblastoma

Article

Full-text available

Mar 1993

The nerve growth factor receptor is expressed in some neuroblastomas, in which its primary component is encoded by the TRK protooncogene. To determine the relation of the expression of TRK messenger RNA in neuroblastomas to other clinical and laboratory variables, we studied frozen tumor samples from 77 patients. In addition, we tested two primary neuroblastomas that expressed TRK for responsiveness to nerve growth factor. TRK expression strongly correlated with favorable tumor stage (I, II, and IVS vs. III and IV), younger age (< 1 year vs. > or = 1 year), normal N-myc copy number, and low level of N-myc expression. N-myc amplification (indicated by a high copy number) correlated with advanced tumor stage, older age, an adrenal site of the primary tumor, low level of expression of TRK, and high level of expression of N-myc. Analysis of five-year cumulative-survival rates demonstrated an association of a very favorable outcome with a high level of TRK expression (86 percent vs. 14 percent) and with normal N-myc copy number (84 percent vs. 0 percent). Univariate analysis showed that these two variables were the most powerful predictors of outcome (chi-square = 51.30, P < 0.001; and chi-square = 93.61, P < 0.001, respectively). TRK expression still had significant prognostic value when the analysis was restricted to tumors without N-myc amplification. In primary cultures of neuroblastoma cells expressing TRK, exposure to nerve growth factor induced early gene expression and neurite outgrowth, but deprivation of nerve growth factor led to neuronal cell death. A high level of expression of the TRK proto-oncogene in a neuroblastoma is strongly predictive of a favorable outcome. A tumor with a functional nerve growth factor receptor may be dependent on the neurotrophin nerve growth factor for survival and may regress in its absence, allowing a new approach to the treatment of certain patients with neuroblastoma.

Expression of c-myc and c-fms oncogenes in trophoblastic cells in hydatidiform mole and normal human placenta

Article

Full-text available

Apr 1993

To compare the expression of c-myc and c-fms proto-oncogenes in the placenta and hydatidiform mole. Twelve hydatidiform moles and six induced abortion cases were collected. c-myc and c-fms proto-oncogene expression was analysed by northern blot hybridisation and immunohistochemical staining. The results of northern blot hybridisation analysis showed that c-fms was expressed more strongly in hydatidiform moles compared with normal placenta of similar gestational age. Moreover, c-fms mRNA concentrations increased with more advanced gestational age in moles but not in normal placentas. c-myc expression was very low in hydatidiform moles and normal placentas. Both oncogenes, however, had no direct correlation with the clinical course of the molar pregnancies. The difference in c-fms expression between hydatidiform moles and normal placentas suggests that c-fms may have a role in the development of molar pregnancies.

Santoro M, Melillo RM, Grieco M, Berlingieri MT, Vecchio G, Fusco A.. The TRK and RET tyrosine kinase oncogenes cooperate with ras in the neoplastic transformation of a rat thyroid epithelial cell line. Cell Growth Differ 4: 77-84

Article

Full-text available

Mar 1993
Cell Growth Differ

We have recently reported that about 50% of papillary thyroid carcinomas harbor an activated TRK or RET oncogene. Two retroviral vectors containing the activated TRK or RET/PTC oncogene have been used to infect a differentiated rat thyroid epithelial cell line, namely the PC Clone 3 cell line. Upon infection with the TRK virus, the PC Clone 3 cells lost only the ability to trap iodide and to express the thyroperoxidase gene. Conversely, when infected with the PTC virus, the PC Clone 3 cells completely lost all of their differentiated functions. However, both the PC-TRK and PC-PTC cell lines were unable to grow in soft agar, and they were not tumorigenic when injected into nude mice. A completely undifferentiated and malignant phenotype was obtained by the cooperation between the TRK or RET and the viral Ha-ras or Ki-ras oncogenes.

Demonstration of a TGF-α-EGF-Receptor autocrine loop and c-Myc protein over-Expression in papillary thyroid carcinomas

Article

Aug 1993
INT J CANCER

Autocrine growth stimulation has been identified in several types of human cancer. In the present study we wanted to establish whether autocrine stimulation of the epidermal-growth-factor receptor (EGF-r) by its ligand, transforming growth factor alpha (TGF-α) occurs in thyroid neoplasia. We examined 190 fresh, frozen thyroid tissue samples from 70 patients by immunohistochemistry with antibodies to EGF-r, TGF-α, c-erbB-2 and c-myc. EGF-r expression was detected in 17 out of 19 papillary carcinomas, TGF-a expression in 10, and c-erbB-2 expression in IS. No papillary carcinoma expressed TGF-a without also expressing EGF-r. Concomitant expression of EGF-r, TGF-α and c-erbB-2 was seen in 7 papillary carcinomas. No EGF-r, TGF-α or c-erbB-2 immunopositivity was found in normal-appearing thyroid tissue (25 cases), whereas a few of the non-neoplastic lesions (colloid goitres and diffuse hyperplasias) expressed either EGF-r or TGF-α. c-myc expression was detectable in all tissue samples, and expression was invariably nuclear. Increased expression was observed in 10 out of 19 papillary carcinomas, and 8 of these also co-expressed EGF-r and TGF-α. In situ hybridization confirmed the presence of TGF-α mRNA in tumour epithelium of TGF-α-immunopositive samples. The concomitant expression of EGF-r, TGF-α and TGF-α mRNA gives evidence for a TGF-α-EGF-r autocrine loop in thyroid papillary carcinomas. The increased c-myc expression may reflect the proliferative advantage of these tumours. © 1993 Wiley-Liss, Inc.

Mast cells increase in tissues of neonatal rats injected with the nerve growth factor

Article

Oct 1977
BRAIN RES

Effect of nerve growth factor on the release of inflammatory mediators by mature human basophils

Article

Jun 1992

Nerve growth factor (NGF) is a neurotrophic cytokine known to regulate the survival and function of peripheral and central neuronal cells. Recently, the spectrum of action could be extended to non-neuronal cell types such as rat mast cells and human B lymphocytes. The present study shows that NGF affects the function of mature human basophils isolated from the peripheral blood of healthy donors. Both murine NGF 7S and recombinant human NGF beta enhance histamine release and strongly modulate the formation of lipid mediators by basophils in response to various stimuli. This priming effect of NGF on basophils occurs rapidly within 10 to 15 minutes of preincubation, is dose-dependent, and requires similarly low concentrations (1 to 40 pmol/L) of human NGF beta as the induction of neurite outgrowth in ganglion cells. Cell fractionation studies indicate that NGF acts directly on human basophils without an involvement of other cell types, suggesting the presence of high-affinity NGF receptors on basophils. NGF by itself (up to 4 nmol/L of human NGF beta) does not induce the release of inflammatory mediators directly. The effect of human NGF on basophil mediator release is similar to that of the hematopoietic growth factors interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor. The present study further demonstrates that NGF acts as a pleiotropic cytokine at the interface between the nervous and the immune system, and that NGF may be involved in inflammatory processes and hypersensitivity reactions.

Nerve growth factor specifically induces IgG4 production

Article

Jan 1991

The effect of nerve growth factor (NGF) on human IgG4 production was studied. NGF specifically enhanced IgG4 production in cultures of human tonsillar mononuclear cells without affecting production of other isotypes or other IgG subclasses. Optimal enhancement of IgG4 production by NGF required the presence of T cells. However, NGF induced significant IgG4 production by small resting B cells in the absence of T cells, and this production was enhanced by stimulation with Staphylococcus aureus Cowan strain I (SAC). In contrast to small B cells, large activated B cells produced IgG4 spontaneously; this production was enhanced by NGF. NGF also enhanced IgM and IgA production by large B cells, while production of IgG1, IgG2, IgG3 and IgE was not affected. The enhancement of IgG4 production was blocked by anti-NGF serum but not by control serum. NGF, T cells and SAC, separately or together, failed to induce IgG4 production by surface (sIgG4+)-depleted B cells. In contrast to NGF, other recombinant human cytokines including interleukin (IL) 1 beta, IL 2, IL 4, IL 5, IL 6, granulocyte-macrophage colony-stimulating factor, interferon alpha and gamma failed to induce IgG4 production. These results suggest that NGF directly and preferentially stimulates activated sIgG4+ B cells to produce IgG4.

Nerve growth factor inhibits immunoglobulin production by but not proliferation of human plasma cell lines

Article

Aug 1991

The effects of nerve growth factor (NGF) on human plasma cells were studied. NGF inhibited immunoglobulin (Ig) production but not thymidine uptake by human plasma cell lines IM-9 and AF-10 in a dose-dependent fashion. This NGF-induced inhibition of Ig production was specific, since inhibition was blocked by anti-NGF serum but not by control serum. Interleukin (IL)-6 did not affect Ig production by IM-9 and AF-10; however, IL-6 restored NGF-induced inhibition of Ig production. NGF also inhibited Ig production (IgG, IgM, and IgA) without affecting thymidine uptake by PCA-1+ plasma cells generated in vitro. This inhibition was also blocked by anti-NGF serum but not by control serum and was restored by IL-6. These results suggest that NGF may interact with IL-6 in control of Ig production by plasma cells.

Evidence for the presence of nerve growth factor (NGF) and NGF receptors in human testis

Article

Oct 1990

Nerve growth factor (NGF) affects morphology and function of isolated and cultured seminiferous tubules from human testis. Quantitative determination of this neurotrophic protein revealed an amount of 5.4 ng per g human testis, suggesting a crucial function of NGF in spermatogenic tissue. With the use of immunohistochemical methods target cells for NGF were identified within the lamina propria. NGF receptors were also visualized on sympathetic nerve fibers crossing the interstitial compartment among adjacent tubules and spatially correlated blood vessels. NGF receptors could be demonstrated on isolated lamina-propria cells even after 2 weeks of culture. Most of the NGF receptor-bearing cells differed from myoid cells of the lamina propria expressing desmin, a marker for smooth muscle. However, some NGF receptor-expressing cells were found sharing morphological and structural similarities with myoid cells. The present data indicate the existence of a NGF-responsive lamina-propria cell that influences the tubular wall and also the seminiferous epithelium.

The molecular control of cell division, differentiation commitment and maturation in haemopoietic cells

Article

Jun 1989

D Metcalf

Several glycoproteins that control blood-cell production and function have been purified and sequenced. The four colony-stimulating factors interact in a complex way to regulate the differentiation and maturation of the granulocyte and macrophage lineages and have potential applications for the clinical manipulation of blood-cell production.

Nerve Growth Factor Induces Growth and Differentiation of Human B Lymphocytes

Article

Jan 1990

Nerve growth factor (NGF) is known to affect peripheral sympathetic and sensory neurons as well as defined populations of neurons in the central nervous system. This paper presents evidence that NGF is also active in modulation of B-cell-mediated immune responses. NGF receptors were immunoprecipitated from highly purified human B-cell populations, and to a lesser extent, from T-cell populations, by using a monoclonal antibody recognizing NGF receptors present on neural cells. NGF receptors were also detected in significant amounts in human spleen and lymph node tissue. In addition, NGF induced a dose-dependent increase in B-cell DNA synthesis as determined by incorporation of [3H]thymidine. This B-cell growth-promoting activity was inhibited by a neutralizing anti-NGF monoclonal antibody. Immunoglobulin secretion, principally affecting IgM synthesis, was also modulated by NGF. The concentrations that affected B-cell proliferation are consistent with the presence of functional high-affinity NGF receptors. The results suggest that NGF, in addition to its neurotrophic function, also acts as an immunoregulatory cytokine.

The trk oncogene abrogates growth factor requirements and transforms hematopoietic cells

Article

Oct 1989
ONCOGENE

Oncogenes may cause transformation by altering the requirements of cells for growth factors which normally regulate growth. This type of transformation is particularly evident in the ability of oncogenes of the tyrosine protein kinase gene family to abrogate the requirement of hematopoietic cells for growth factors such as interleukin-3 (IL-3). We have used this property to study the effect of the human trk oncogene on hematopoietic cells. This oncogene was generated by a genetic rearrangement that fused a non-muscle tropomyosin gene to a tyrosine protein kinase with structural features characteristic of growth factor receptors. The results presented here demonstrate that a replication-defective murine retrovirus expressing the human trk oncogene can abrogate the growth factor requirements of hematopoietic cells through a non-autocrine mechanism. In these trk-transformed cells, many of the cellular proteins which are phosphorylated on tyrosine residues following IL-3 stimulation are constitutively phosphorylated, with the notable exception of a 140 kDa membrane, IL-3-binding protein. The 140 kDa protein becomes phosphorylated only following stimulation with IL-3 in these trk oncogene-transformed hematopoietic cells.

A human oncogene formed by the fusion of truncates tropomyosin and protein kinase sequences

Article

Feb 1986

A biologically active complementary DNA clone of a transforming gene present in a human colon carcinoma contains gene sequences of both tropomyosin and a previously unknown protein tyrosine kinase. The predicted protein (641 amino acids) encoded by this oncogene seems to have been formed by a somatic rearrangement that replaced the extracellular domain of a putative transmembrane receptor by the first 221 amino acids of a non-muscle tropomyosin molecule.

Establishment and characterization of a permanent human IgA 2 /kappa myeloma cell line

Article

Aug 1988

A human myeloma cell line designated LOPRA-1 has been established from ascites fluid containing malignant plasma cells of a patient with IgA2/kappa multiple myeloma. The cultured cells which are Epstein-Barr virus (EBV) negative have retained the morphological, cytochemical, ultrastructural and immunophenotypical features of well-differentiated plasma cells. They express the plasma cell antigen PCA-1, the antigens CD28 (Kolt-2) and CD38 (OKT10), the transferrin-receptor (OKT9), and some epitopes of the CD24 antigen (HB8, VIB E3), but are negative for surface immunoglobulins. HLA class II antigens (HLA-DP, -DQ, -DR) and other B-cell markers such as CD10 (CALLA), CD19 (B4), CD20 (B1), CD21 (B2), CD22 (HD39), CD23 (MHM6), CD37 (BL14) and CD39 (G28-8) as analysed by both flow cytometry and immunocytochemistry (PAP/APAAP). With respect to immunoglobulin synthesis, two stable clones were selected by single cell cloning: clone LOPRA-1/5 synthesizes large amounts of alpha 2 heavy and kappa light chains, but secretes only small amounts of these molecules, whereas clone LOPRA-1/4 is clearly devoid of intracellular immunoglobulin heavy and light chains and thus appears to be a chain loss variant. Cytogenetic analysis revealed a pseudotriploid phenotype with several structurally abnormal marker chromosomes: 3n + -, 70, XX, -X, -1, -4, -6, -8, -8, -13, -16, +7, +18, +21, +i(1q), +i(1q), +6q-, +3mar.

Shape changes induced by biologically active peptides and NGF in blood platelets of rabbits

Article

Dec 1981

Nerve growth factor (NGF), substance P (SP) and thymopoietin all caused shape change reactions of rapid onset in rabbit platelets. NGF had the highest maximal effect, and SP the lowest EC 50 (concentration causing half maximal shape change). The action of SP was reversible within 5 min, whereas that of NGF lasted for at least 1 h. A series of other peptides were inactive. After preincubation of platelets with SP, a second application of SP no longer caused a shape change reaction, whereas the effect of NGF was not influenced. An oxidized NGF‐derivative without biological activity did not cause a shape change reaction, neither did epidermal growth factor. Prostaglandin E 1 (PGE 1 ) and pretreatment of the platelets with 3% butanol, which counteract the shape changes caused by 5‐hydroxytryptamine (5‐HT) and adenosine 3′, 5′‐diphosphate, also antagonized those induced by NGF and SP. Neither heparin nor methysergide, an antagonist of 5‐HT‐receptors, influenced the shape change induced by NGF or SP. The action of NGF was also antagonized by a specific antibody to NGF. Thymopoietin, like the basic polypeptide polyornithine (mol. wt. 40,000), was not antagonized by PGE 1 and butanol. Heparin, which counteracted the effect of polyornithine, did not influence that of thymopoietin. In conclusion, different modes of action are involved in the shape change of blood platelets induced by polypeptides and proteins. SP and NGF may act by stimulating specific membrane receptors.

Human ??-nerve growth factor gene sequence highly homologous to that of mouse

Article

Jul 1983

Nerve growth factor (NGF) is thought to have a profound effect on the development and maintenance of sympathetic and embryonic sensory neurones (see refs 1-3 for review). NGF activity isolated from the male mouse submaxillary gland (MSG) consists of three types of subunits, alpha, beta and gamma, which specifically interact to form a 7S, approximately 130,000-molecular weight (Mr) complex. The 7S complex contains two identical 118-amino acid beta-chains, which are solely responsible for the nerve growth-stimulating activity of NGF. While NGF is found in almost all vertebrates, most research has focused on murine NGF, as the mouse male submaxillary gland contains higher levels of this polypeptide than other tissues. Even so, beta-NGF comprises only approximately 0.1% of the protein in this small gland, which has made the study of this polypeptide difficult. The amino acid sequence of the mouse NGF beta-chain has been determined and some information has been obtained regarding the size of a mouse precursor molecule, pro-beta-NGF, but little was known about the structure and relatedness of beta-NGF from other vertebrates. Here we describe the isolation of mouse beta-NGF complementary DNA (cDNA) and present its nucleotide sequence, which predicts a prepro-beta-NGF molecule of Mr 27,000 (27K) and a pro-beta-NGF molecule of Mr 25K. We have used the mouse beta-NGF cDNA clone to isolate the human beta-NGF gene, the coding regions of which are highly homologous to the mouse prepro-beta-NGF nucleotide and amino acid sequences.

Expression of the receptor kinase c-Kit in oligodendrocyte progenitor cells

Article

Dec 1993

The growth and differentiation of neural precursor cells in the central nervous system (CNS) are regulated by their response to polypeptide growth factors which interact with specific transmembrane receptor tyrosine kinases (RTKs). We demonstrate that rat oligodendrocyte-type 2 astrocyte (O-2A) glial progenitor cells, precursors of the myelin-forming cells in the CNS, express the transmembrane RTK c-kit, the gene product of the murine dominant white spotting (W) locus and receptor for stem cell factor. Expression of c-kit transcripts and immunoreactive protein is lost when O-2A progenitors differentiate into post-mitotic oligodendrocytes. Analysis of developing rat brain revealed an increase in the expression of c-kit transcripts between postnatal days 10 and 12, a window of time preceding the emergence of oligodendrocytes and the onset of myelination in vivo. Expression of c-kit in vitro and in vivo suggests a role for this receptor and its ligand during oligodendrocyte development.

Rearrangements of TRK proto-oncogene in papillary thyroid carcinomas

Article

Mar 1995

Expression of the c-kit Protein in Human Solid Tumors and in Corresponding Fetal and Adult Normal Tissues

Article

Feb 1993

The proto-oncogene c-kit encodes a transmembrane tyrosine kinase receptor that is thought to play an important role in hematopoiesis, spermatogenesis, and melanogenesis. We previously showed that the c-kit messenger RNA is preferentially expressed in small cell lung cancer and that its ligand, stem cell factor, is expressed in a broad spectrum of human cancers. Using anti-c-kit antisera raised against synthetic peptides, in situ localization of the c-kit protein in various human solid tumors as well as in corresponding fetal and adult normal tissues was studied by the ABC method. The results suggest that the c-kit gene products may be involved in the pathogenesis of a very restricted subset of human solid tumors such as small cell lung cancer. Interestingly, nuclear protein immunologically related to c-kit was found in both normal and neoplastic medullary cells of the adrenal gland.

The role of tyrosine kinases and their substrates in signal transmission of hematopoietic growth factors: A short review

Article

Jun 1995

Both structure-function analysis of hematopoietic growth factor receptors and identification of novel signal transduction molecules have provided new insights into the processes involved in signal transmission pathways engaged by hematopoietic growth factors. These investigations have pointed to the importance of post-translational modifications of pre-existing proteins, in particular tyrosine phosphorylation, in transmitting signals and thereby linking extracellular signals to the activation of nuclear effector molecules which govern gene expression. These observations not only contribute to our understanding of the pleiotropism and redundancy ascribed to hematopoietic growth factors, but also help to trace some of the molecules conferring signal specificity. It is to be expected that this rapidly evolving research field will provide us with a significant collection of new findings in the near future and that the precise understanding of the processes involved in ligand-binding and signal transmission will also stimulate the development of novel therapeutic drugs affecting these processes. This article gives a short overview on the role of tyrosine kinases and their substrates in signal transmission processes initiated by hematopoietic growth factors.

Expression of PDGF and PDGF receptors in human astrocytoma operation specimens supports the existence of an autocrine loop

Article

Jan 1995

Established cell lines derived from human malignant astrocytomas typically express a combination of platelet-derived growth factor (PDGF) and PDGF receptor which could form an autocrine loop. In this study, we screened for the essential components of a PDGF autocrine loop in fresh surgical isolates of human astrocytomas, using in situ hybridization and immunohistochemical techniques. Eight malignant astrocytomas (6 glioblastomas and 2 anaplastic astrocytomas), 5 low-grade astrocytomas and 4 non-neoplastic glial specimens (mesial temporal sclerosis) were evaluated. Malignant astrocytomas, and to a lesser extent low-grade astrocytomas, expressed more PDGF-A and PDGF-B than non-neoplastic glia. PDGF-alpha-receptor expression was elevated both in malignant and in low-grade astrocytomas. These data support the argument that PDGF autocrine loops contribute to the unregulated growth of human astrocytomas. Expression of PDGF and PDGF receptor in low-grade astrocytomas suggests that activation of PDGF autocrine loops may be an early event in the pathogenesis of malignant astrocytomas.

Expression of a Trk high affinity nerve growth factor receptor in the human prostate

Article

Feb 1995

Nerve growth factor-beta (NGF beta) and a NGF beta-immunoreactive protein derived from human prostatic stromal cell secretory protein (hPS) have been shown to stimulate the growth of prostate epithelial cells. An NGF beta-immunoreactive protein has been localized to the stroma of human prostate tissues, and a low affinity NGF receptor (gp75NGFR) has been localized to the adjacent epithelia, consistent with the paracrine regulation of prostate growth. Interestingly, gp75NGFR is progressively lost during neoplastic progression of the human prostate. In this report we have characterized the expression of the signal-transducing component of the NGF receptor, the Trk tyrosine receptor kinase, in prostate epithelial cells that bind exogenous NGF beta and an endogenous NGF beta-immunoreactive protein in hPS. In this context, a pan-Trk antibody that recognizes all of the members of the Trk receptor family (TrkA, TrkB, and TrkC) specifically localized expression of the Trk receptor to the epithelial component of normal prostate tissue, benign prostatic hyperplasia, and adenocarcinoma tissue. The binding of [125I]NGF beta to the surface of primary cultures of human prostate epithelia and the TSU-pr1 human metastatic prostate tumor cell line was displaced with either excess cold NGF beta or hPS, whereas binding was not displaced by epidermal growth factor or platelet-derived growth factor. Scatchard plot analysis of [125I]NGF beta binding to these cells identified a low affinity binding site (Kd = 1.9 x 10(-9) M) and a high affinity binding site (Kd = 1.8 x 10(-11) M) on the primary prostate epithelia, whereas only a high affinity binding site (Kd = 1.3 x 10(-11) M) was observed on the TSU-pr1 tumor cells. Stimulation of TSU-pr1 cells with either NGF beta or hPS induced tyrosine phosphorylation of Trk proteins, whereas no phosphorylation was evident in untreated cells, cells treated with hPS immunoprecipitated with anti-NGF beta antibody, or brain-derived neurotrophic factor- and neurotrophin-3-treated cells. The Trk protein was also observed in these cells by immunoblot analysis with pan-Trk antibody. These results demonstrate a functional Trk receptor in the epithelia of the human prostate that is responsive to exogenous NGF beta and an endogenous NGF beta-immunoreactive protein in hPS, thereby supporting the concept of the paracrine regulation of growth in the human prostate via a stromal neurotrophin-epithelial Trk receptor interaction.

Neurotrophin Signal Transduction by the Trk Receptor

Article

Nov 1994

The initial event in the neuronal differentiation of PC12 cells is the binding of the neurotrophin nerve growth factor (NGF) to the Trk receptor. This interaction stimulates the intrinsic tyrosine kinase activity of Trk, initiating a signalling cascade involving the phosphorylation of intracellular proteins on tyrosine, serine, and threonine residues. These signals are then in turn propagated to other messengers, ultimately leading to differentiation, neurotrophin-dependent survival, and the loss of proliferative capacity. To transmit NGF signals, NGF-activated Trk rapidly associates with the cytoplasmic proteins, SHC, PI-3 kinase, and PLC-gamma 1. These proteins are involved in stimulating the formation of various second messenger molecules and activating the Ras signal transduction pathway. Studies with Trk mutants indicate that the activation of the Ras pathway is necessary for complete differentiation of PC12-derived cells and for the maintenance of the differentiated phenotype. Trk also induces the tyrosine phosphorylation of SNT, a specific target of neurotrophic factor activity in neuronal cells. This review will discuss the potential roles of Trk and the proteins of the Trk signalling pathways in NGF function, and summarize our attempts to understand the mechanisms used by Trk to generate the many phenotypic responses of PC12 cells to NGF.

Barbacid MThe Trk family of neurotrophin receptors. J Neurobiol 25: 1386-1403

Article

Nov 1994

Mariano Barbacid

Accumulating evidence indicates that the Trk family of tyrosine protein kinase receptors, Trk (also known as TrkA), TrkB, and TrkC, are responsible for mediating the trophic effects of the NGF family of neurotrophins. Nerve growth factor (NGF) specifically recognizes Trk, a receptor identified in all major NGF targets, including sympathetic, trigeminal, and dorsal root ganglia as well as in cholinergic neurons of the basal forebrain and the striatum. Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) specifically activate the TrkB tyrosine kinase receptor. trkB transcripts encoding this receptor are found throughout multiple structures of the central and peripheral nervous system. Neurotrophin-3 (NT-3) primarily activates the TrkC tyrosine protein kinases, four related isoforms encoded by alternative splicing of trkC, a gene also widely expressed throughout the mammalian nervous system. Unlike the other neurotrophins, NT-3 appears to be somewhat promiscuous since it can activate Trk and TrkB kinase receptors, at least in certain cell systems. The trkB and trkC genes also encode noncatalytic neurotrophin receptor isoforms of an as yet, unknown function. Recently, strains of mice lacking each of these tyrosine kinase receptors have been generated. Preliminary characterization of these mutant mice has provided significant information regarding the role of these receptors in the ontogeny of the mammalian nervous system. For instance, mice deficient for Trk receptors lack most sympathetic neurons and do not display nociceptive and temperature sensations, two defects likely to result from severe neuronal cell loss in their trigeminal and dorsal root ganglia. Mice lacking TrkB tyrosine kinase receptors die postnatally due to their inability to intake food. Neuron cell loss in their trigeminal, nodose and petrosal sensory ganglia as well as in the facial motor nucleus are likely to contribute to this phenotype. Finally, TrkC-deficient mice display strikingly abnormal movements consistent with loss of proprioception, a defect likely to be a consequence of the complete loss of Ia muscle afferents observed in this mutant mice.

Demonstration of a TGF-alpha-EGF-receptor autocrine loop and c-myc protein over-expression in papillary thyroid carcinomas

Article

Sep 1993

Autocrine growth stimulation has been identified in several types of human cancer. In the present study we wanted to establish whether autocrine stimulation of the epidermal-growth-factor receptor (EGF-r) by its ligand, transforming growth factor alpha (TGF-alpha) occurs in thyroid neoplasia. We examined 190 fresh, frozen thyroid tissue samples from 70 patients by immunohistochemistry with antibodies to EGF-r, TGF-alpha, c-erbB-2 and c-myc. EGF-r expression was detected in 17 out of 19 papillary carcinomas, TGF-alpha expression in 10, and c-erbB-2 expression in 15. No papillary carcinoma expressed TGF-alpha without also expressing EGF-r. Concomitant expression of EGF-r, TGF-alpha and c-erbB-2 was seen in 7 papillary carcinomas. No EGF-r, TGF-alpha or c-erbB-2 immunopositivity was found in normal-appearing thyroid tissue (25 cases), whereas a few of the non-neoplastic lesions (colloid goitres and diffuse hyperplasias) expressed either EGF-r or TGF-alpha. c-myc expression was detectable in all tissue samples, and expression was invariably nuclear. Increased expression was observed in 10 out of 19 papillary carcinomas, and 8 of these also co-expressed EGF-r and TGF-alpha. In situ hybridization confirmed the presence of TGF-alpha mRNA in tumour epithelium of TGF-alpha-immunopositive samples. The concomitant expression of EGF-r, TGF-alpha and TGF-alpha mRNA gives evidence for a TGF-alpha-EGF-r autocrine loop in thyroid papillary carcinomas. The increased c-myc expression may reflect the proliferative advantage of these tumours.

Hematopoietic Regulators: Redundancy or Subtlety?

Article

Jan 1994

D Metcalf

EMATOPOIESIS requires a highly complex series of H cellular events in which a small population of stem cells needs to generate continuously large populations of maturing cells in eight major lineages. Normally, the diverse proliferative, differentiative, and maturation events re- quired to achieve this occur with precision, which leads to the expectation that the regulatory mechanisms involved would need to be complex. It can also be anticipated that the entry of mature cells into the circulation, their selective localization in appropriate tissues, and their functional acti- vation are also events requiring sophisticated regulatory control. Given the likely complexity of these events and the knowl- edge that much of this regulation is achieved by the use of regulatory molecules that can be humoral or cell-associated, it is not surprising that many such regulatory molecules have been Characterized, purified, and produced in recombi- nant form. The known regulators with proliferative effects on one or other hematopoietic population already exceed 20 in number and to these need to be added a variety of inhibitory factors and a number of factors allowing selective cell-cell adhesion. Many additional candidate factors are in the early phase of characterization. This degree of complexity in biologic processes is familiar enough to those who have addressed the details of coagula- tion or complement activation. However, for some of those working with the proliferative hematopoietic regulatory fac- tors, there are aspects of the regulators so far characterized that have a raised a growing conviction that these regulators may exhibit a high degree of redundancy. In short, there appear to be more regulators with similar or overlapping actions than would seem to be really necessary to achieve the required cell proliferation.

Expression of functional trK protooncogene in human monocytes

Article

Jul 1993

There is increasing evidence that neurotrophins, including nerve growth factor (NGF), exert specific effects on cells of the immune system in addition to their neurotrophic actions. This report shows that human monocytes express the trk protooncogene, encoding the signal-transducing receptor unit for NGF. This receptor is functional, since interaction of NGF with monocytes triggered a respiratory burst, the major component of monocyte cytotoxic activity. During in vitro differentiation of human blood monocytes to macrophages trk expression decreased, suggesting a maturation-dependent trk expression decreased, suggesting a maturation-dependent trk regulation. Treatment of monocytes with Staphylococcus aureus Cowan I, a potent activator of monocytes, stimulated trk mRNA synthesis in a time-dependent way, implying a modulatory role for NGF in immune functions. The finding that dibutyryl cAMP elicited a time-dependent trk induction in monocytes as well as in phorbol ester-differentiated promonocytic U937 cells indicates that adenylate cyclase is involved in monocytic trk regulation. These results suggest that NGF, in addition to its neurotrophic function, is an immunoregulatory cytokine acting on monocytes.

Expression of the nerve growth factor receptor c-TRK in human myeloid leukemia cells

Abstract

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