Derived Growth Factor Receptor Beta Research Articles

Vascular endothelialgrowth factor (vEGF) inhibition causes an increase in pericytes and platelet derived growth factor receptor beta(PDGFR-beta) in the vasculogenesis of pulmonary metastasis

Vascular endothelialgrowth factor (vEGF) inhibition causes an increase in pericytes and platelet derived growth factor receptor beta(PDGFR-beta) in the vasculogenesis of pulmonary metastasis

Glivec/STI571 Treatment Stimulates Megakaryopoiesis and Normalizes PDGF Receptor beta Kinase Expression in Thrombocytopenic Patients with Myeloid Metaplasia with Myelofibrosis.

Myeloid Metaplasia with Myelofibrosis (MMM) is a Philadelphia negative chronic myeloproliferative disorder associated with myeloid metaplasia in the spleen and liver, bone marrow fibrosis and neoangiogenesis. The myeloproliferation is characterized by an increased number of circulating CD34+ hematopoietic progenitors (up to 200 folds) with a prominent amplification of dystrophic megakaryocytes (Mk). Alteration of tyrosine kinase signals is suspected to play a key role in the myeloproliferation and in the increased sensitivity of hematopoietic progenitors to growth factors. Glivec is a small-molecule tyrosine kinase inhibitor of the ABL fusion gene, platelet derived growth factor receptor beta (PDGFRB) and SCF receptor (c-kit). In this study, we investigated the effect of Glivec/STI571 on the megakaryopoiesis and the kinase expression of 11 MMM patients enrolled in a European EUMNET clinical trial. We showed that 50 percents of the treated patients exhibited a tendency to a decrease in the CD34+ cell number from 261/μL to 56/μL with a normalization of the CD34+ cell count (1–10/μL) in 20 percents of these patients (2/10). We also observed a reduction of a CD34+CD41+ Mk subpopulation co-expressing the CD9 tetraspanin that is suggested to be a marker of MMM. Normalization of the CD9 gene expression level was further confirmed by quantitative RT-PCR in MMM mononuclear cells. In contrast, 55 percents of MMM patients (5/9 patients) showed an increase in their platelet count from 191 x 109/L to 282 x 109/L during treatment with Glivec. Interestingly, an increase in the platelet count was also observed in three of the five thrombopenic patients who exhibited an increase greater than 50 x 109/L (p= 0.02) being associated with an augmentation in the number of clonogenic megakaryocytic progenitors (CFU-Mk). The effect of Glivec treatment on megakaryopoiesis was further illustrated by a morphometric analysis on bone marrow histological sections showing a normalization of the size and shape of the dystrophic MMM Mk. We also analyzed by quantitative RT-PCR the effect of Glivec treatment on receptor kinase gene expression in circulating mononuclear cells from MMM patients and demonstrated a normalization of the receptor beta of the PDGF, a cytokine involved in Mk differentiation. Actually, the PDGFB expression that was down-regulated in MMM PBMC before Glivec as compared to normal PBMC (−1.14 +/− 0.76 and − 0.14 +/− 0.42, respectively; p= 0.02) was significantly increased during therapy, reaching a normal level in 60% of tested patients. In conclusion, our results show that Glivec treatment reduced the CD34+ cell number and stimulated the megakaryopoiesis of MMM thrombopenic patients, probably by restoring Mk progenitor differentiation.

Protein Gene Product 9.5 is Expressed by Fibroblasts in Human Cutaneous Wounds

In a study initially designed to evaluate reinnervation of human cutaneous wounds using an antibody to the neuroneal marker protein gene product (PGP) 9.5, we observed marked immunostaining of cells with morphologic features of fibroblasts in the wounds. PGP 9.5 has recently been shown to be an important enzyme in the highly conserved ubiquitin system of proteolysis. Because the ubiquitin system is known to play an important role in regulating the cell cycle, the presence of PGP 9.5 in cells at a wound site was of considerable interest. Our objectives were to clarify the time frame for the appearance of PGP 9.5 and ubiquitin in wounds, to verify that PGP 9.5 is produced by wound fibroblasts, and to evaluate a potential role for these proteins in the tissue repair process. Standard incisional human wounds were stained with antibodies specific for PGP 9.5 and ubiquitin. At 7 d, stellate cells with morphologic features of fibroblasts stained for PGP 9.5, whereas earlier wounds were generally negative. In 14 and 21 d incised wounds and in chronic granulation tissue from nonhealing ulcers there was strong cellular staining for PGP 9.5 and for ubiquitin. These stellate cells also showed expression of mRNA for PGP 9.5 by reverse transcriptase-polymerase chain reaction in situ hybridization. PGP 9.5 was detected in cultured fibroblasts both by reverse transcriptase-polymerase chain reaction and by northern blot analysis. Confocal microscopy showed colocalization of antibodies to PGP 9.5 and prolyl-4-hydroxylase (a fibroblast marker) as well as colocalization of PGP 9.5 and the platelet derived growth factor beta receptor. We conclude that ubiquitin and PGP 9.5 were expressed by fibroblasts during the granulation tissue and remodeling phases wound healing. The mRNA for PGP 9.5 was demonstrated in stellate cells in chronic wounds and in fibroblasts in culture. The appearance of these degradative proteins in later wounds suggests a downregulation function in the wound healing response.

The synergistic activity of alphavbeta3 integrin and PDGF receptor increases cell migration.

Integrins and growth factor receptors act synergistically to modulate cellular functions. The alphavbeta3 integrin and the platelet-derived growth factor receptor have both been shown to play a positive role in cell migration. We show here that a platelet derived growth factor-BB gradient stimulated migration of rat microvascular endothelial cells on vitronectin (9.2-fold increase compared to resting cells) in a alphavbeta3 and RGD-dependent manner. In contrast, this response was not observed on a beta1 integrin ligand, laminin; background levels of migration, in response to a platelet derived growth factor-BB gradient, were observed on this substrate or on bovine serum albumin (2.4- or 2.0-fold, respectively). Comparable results were obtained using NIH-3T3 cells. Platelet derived growth factor-BB did not change the cells' ability to adhere to vitronectin, nor did it stimulate a further increase in proliferation on vitronectin versus laminin. In addition, platelet derived growth factor-BB stimulation of NIH-3T3 cells did not alter the ability of alphavbeta3 to bind RGD immobilized on Sepharose. The alphavbeta3 integrin and the platelet derived growth factor receptor-beta associate in both microvascular endothelial cells and NIH-3T3 cells, since they coprecipitated using two different antibodies to either alphavbeta3 or to the platelet derived growth factor receptor-beta. In contrast, beta1 integrins did not coprecipitate with the platelet derived growth factor receptor-beta. These results point to a novel pathway, mediated by the synergistic activity of alphavbeta3 and the platelet derived growth factor receptor-beta, that regulates cell migration and, therefore, might play a role during neovessel formation and tissue infiltration.

A domain of TEL conserved in a subset of ETS proteins defines a specific oligomerization interface essential to the mitogenic properties of the TEL-PDGFR beta oncoprotein.

TEL is a novel member of the ETS family of transcriptional regulators which is frequently involved in human leukemias as the result of specific chromosomal translocations. We show here by co-immunoprecipitation and GST chromatography analyses that TEL and TEL-derived fusion proteins form homotypic oligomers in vitro and in vivo. Deletion mutagenesis identifies the TEL oligomerization domain as a 65 amino acid region which is conserved in a subset of the ETS proteins including ETS-1, ETS-2, FLI-1, ERG-2 and GABP alpha in vertebrates and PNTP2, YAN and ELG in Drosophila. TEL-induced oligomerization is shown to be essential for the constitutive activation of the protein kinase activity and mitogenic properties of TEL-platelet derived growth factor receptor beta (PDGFR beta), a fusion oncoprotein characteristic of the leukemic cells of chronic myelomonocytic leukemia harboring a t(5;12) chromosomal translocation. Swapping experiments in which the TEL oligomerization domain was exchanged by the homologous domains of representative vertebrate ETS proteins including ETS-1, ERG-2 and GABP alpha show that oligomerization is a specific property of the TEL amino-terminal conserved domain. These results indicate that the amino-terminal domain conserved in a subset of the ETS proteins has evolved to generate a specialized protein-protein interaction interface which is likely to be an important determinant of their specificity as transcriptional regulators.

Pathology of the human mesangium in situ.

Mesangial cells play an important role in the development and progression of human glomerular disease. This article summarizes some important aspects of mesangial properties and behaviour in situ. Intrinsic mesangial cells express alpha-smooth muscle actin and are best characterized as myofibroblasts or glomerular pericytes. The main integrin receptor in the mesangium is the alpha 1 beta 1 integrin. The beta 2 and beta 3 integrins have not been detected. Mesangial cells in situ fail to react with many monoclonal antibodies which stain human mesangial cells in culture, including leukocyte activation antigens. Prominent reactions in glomerular disease are mesangial expansion and progressive glomerular sclerosis, which are preceded by or associated with mesangial cell hypertrophy and/or proliferation. Mesangial enlargement is accompanied by an altered integrin expression and an abnormal composition of extracellular mesangial matrix. From the numerous autocrine and paracrine mediators identified in vitro which stimulate or inhibit mesangial cell growth and extracellular matrix synthesis, up to now only a few factors have been shown to be present in selected human glomerulopathies. These include platelet derived growth factors and platelet derived growth factor receptor beta, transforming growth factors beta, interleukin 1 beta, tumor necrosis factor alpha, and interleukin 6. Further identification of such mediators in situ will improve our understanding of pathological glomerular processes, particularly with respect to the multifunctional properties of the mesangial cell.