Growth Factor Receptor Beta Expression Research Articles

High tumor cell platelet-derived growth factor receptor beta expression is associated with shorter survival in malignant pleural epithelioid mesothelioma.

Malignant pleural mesothelioma (MPM) has a rich stromal component containing mesenchymal fibroblasts. However, the properties and interplay of MPM tumor cells and their surrounding stromal fibroblasts are poorly characterized. Our objective was to spatially profile known mesenchymal markers in both tumor cells and associated fibroblasts and correlate their expression with patient survival. The primary study cohort consisted of 74 MPM patients, including 16 patients who survived at least 60 months. We analyzed location‐specific tissue expression of seven fibroblast markers in clinical samples using multiplexed fluorescence immunohistochemistry (mfIHC) and digital image analysis. Effect on survival was assessed using Cox regression analyses. The outcome measurement was all‐cause mortality. Univariate analysis revealed that high expression of secreted protein acidic and cysteine rich (SPARC) and fibroblast activation protein in stromal cells was associated with shorter survival. Importantly, high expression of platelet‐derived growth factor receptor beta (PDGFRB) in tumor cells, but not in stromal cells, was associated with shorter survival (hazard ratio [HR] = 1.02, p < 0.001). A multivariable survival analysis adjusted for clinical parameters and stromal mfIHC markers revealed that tumor cell PDGFRB and stromal SPARC remained independently associated with survival (HR = 1.01, 95% confidence interval [CI] = 1.00–1.03 and HR = 1.05, 95% CI = 1.00–1.11, respectively). The prognostic effect of PDGFRB was validated with an artificial intelligence‐based analysis method and further externally validated in another cohort of 117 MPM patients. In external validation, high tumor cell PDGFRB expression associated with shorter survival, especially in the epithelioid subtype. Our findings suggest PDGFRB and SPARC as potential markers for risk stratification and as targets for therapy.

Non-Invasively Distinguishing Progress of Liver Fibrosis by Visualizing Hepatic Platelet Derived Growth Factor Receptor-Beta Expression with an MRI Modality in Mice

Background: Activated hepatic stellate cells (HSCs) are the most critical cell responsible for liver fibrosis. In liver fibrogenesis, platelet-derived growth factor (PDGF) is the most prominent mitogen for HSCs. This study aims to explore the potential of gadolinium (Gd)-labeled cyclic peptides (pPB) targeted to PDGF receptor-β (PDGFR-β) as an MRI radiotracer to identify the progress of liver fibrosis by imaging hepatic PDGFR-β expression. Methods: Mouse models of liver fibrosis caused by bile duct ligation (BDL) and CCl 4 treatment were both used to determine the association of hepatic PDGFR-β expression and the progress of hepatic fibrosis. The binding activity of FITC-labeled pPB to PDGFR-β was assessed in culture-activated human HSCs (HSC-LX2). MR imaging was performed to visualize hepatic PDGFR-β expression in mice with different degrees of liver fibrosis after Gd-labeled pPB were injected. Findings: Hepatic PDGFR-β expression level was found to be paralleled with the severity of liver fibrosis, which was increased with the progression of fibrosis and reduced with the regression. Majority of cells expressing PDGFR-β was determined to be activated HSCs in fibrotic livers. Culture-activated HSC-LX2 expressed abundant PDGFR-β, and FITC-labeled pPB could bind to HSC-LX2 in a concentration and time dependent manner. Interpretation: With Gd-labeled pPB as a tracer, the relative hepatic T1-weighed MR signal value was increased progressively along with severity of hepatic fibrosis and reduced with the remission, suggesting that hepatic PDGFR-β expression reflects the progress of hepatic fibrosis. MR imaging using Gd-labeled pPB as a tracer may distinguish different stages of liver fibrosis in mice. Funding Statement: This work was supported by the National Natural Science Foundation of China (Grant NO. 81270007 & 81670513 to Li F), Shanghai Talent Development Funds (Grant NO. 201304 to Li F), Shanghai Rising-Star Program (Grant NO. 13QA1400700 to Li F), And Shanghai Outstanding Young Talent Training Plan in Health System (Grant NO. 13YO56 to Li F). Declaration of Interests: The authors declare no conflict of interests. Ethics Approval Statement: The study was approved by Institutional Ethical Committee of Animal Experimentation, all experiments and postoperative animal care procedures were performed according to the governmental and international guidelines on animal experimentation.

Surface proteome analysis identifies platelet derived growth factor receptor-alpha as a critical mediator of transforming growth factor-beta-induced collagen secretion

Fibroblasts are extracellular matrix-producing cells in the lung. Fibroblast activation by transforming growth factor-beta leads to myofibroblast-differentiation and increased extracellular matrix deposition, a hallmark of pulmonary fibrosis. While fibroblast function with respect to migration, invasion, and extracellular matrix deposition has been well-explored, little is known about the surface proteome of lung fibroblasts in general and its specific response to fibrogenic growth factors, in particular transforming growth factor-beta.We thus performed a cell-surface proteome analysis of primary human lung fibroblasts in presence/absence of transforming growth factor-beta, followed by characterization of our findings using FACS analysis, Western blot, and siRNA-mediated knockdown experiments.We identified 213 surface proteins significantly regulated by transforming growth factor-beta, platelet derived growth factor receptor-alpha being one of the top down-regulated proteins. Transforming growth factor beta-induced downregulation of platelet derived growth factor receptor-alpha induced upregulation of platelet derived growth factor receptor-beta expression and phosphorylation of Akt, a downstream target of platelet derived growth factor signaling. Importantly, collagen type V expression and secretion was strongly increased after forced knockdown of platelet derived growth factor receptor-alpha, an effect that was potentiated by transforming growth factor-beta. We therefore show previously underappreciated cross-talk of transforming growth factor-beta and platelet derived growth factor signaling in human lung fibroblasts, resulting in increased extracellular matrix deposition in a platelet derived growth factor receptor-alpha dependent manner. These findings are of particular importance for the treatment of lung fibrosis patients with high pulmonary transforming growth factor-beta activity.

Thrombin Stimulated Platelet-Derived Exosomes Inhibit Platelet-Derived Growth Factor Receptor-Beta Expression in Vascular Smooth Muscle Cells

Background/Aims: It is difficult to predict acute thrombotic cardiovascular events in the clinic. Few studies have reported the presence of plasma exosomes containing microRNAs (miRNAs) in cardiovascular events. Therefore, we aimed to investigate the levels of miR-223, miR-339 and miR-21 in plasma exosomes before thrombosis in mouse models of carotid tandem stenosis, as well as the mechanisms underlying the origin and function of these exosomal miRNAs. Methods: Plasma samples were collected from the carotid tandem stenosis and sham control groups of our successfully developed atherothrombosis mouse models before thrombosis. Platelets from healthy volunteers and mice were purified to obtain thrombin stimulated platelet-derived exosomes. Exosomes were isolated via differential ultracentrifugation, and western blotting and transmission electron microscopy were used for their identification. The total RNA was extracted, and quantitative real-time PCR was performed to determine the expression levels of miR-223, miR-339 and miR-21. DAVID Tools were used to analyze the pathways that were enriched among the miRNA target genes. Immuno-fluorescence staining was performed to identify the protein expression levels of platelet-derived exosome target genes in vascular smooth muscle cells (SMCs) in vitro and in vivo. Results: The levels of miR-223, miR-339 and miR-21, which are associated with platelet activation, were elevated in pooled mouse plasma exosomes before thrombosis and enriched in thrombin-stimulated platelet-derived exosomes in vitro. Platelet-derived growth factor receptor-beta (PDGFRβ) was a target of these miRNAs, and PDGFRβ expression in vascular smooth muscle cells (SMCs) was inhibited following incubation with platelet-derived exosomes. Platelet-derived exosomes could also inhibit PDGF-stimulated SMC proliferation. Furthermore, a decrease in PDGFRβ expression was observed in vascular SMCs around thrombotic areas in vivo. Conclusions: Our data indicate that activated platelet-derived exosomes containing miR-223, miR-339 and miR-21 could be transferred into SMCs and inhibit PDGFRβ expression; these exosomal miRNAs may be a biomarker for predicting atherothrombosis.

Inhibition Effect of Mannose-6-Phosphate on Expression of Transforming Growth Factor Beta Receptor in Flexor Tendon Cells

Transforming growth factor beta (TGF-β) has an important role in tendon healing and adhesion formation. Inhibiting TGF-β and its receptor expression may prevent adhesions after tendon open. The goal of this study was to examine the effects of mannose-6-phosphate, a natural inhibitor of TGF-β, on TGF-β and its receptor production in tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes of rabbit flexor tendons. Tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes were isolated from rabbit flexor tendons and cultured separately. The cells were divided into 2 groups at random: an experiment group supplemented with mannose-6-phosphate and a control group without mannose-6-phosphate. The expression of TGF-β and TGF-β receptor was quantified with enzyme-linked immunosorbent assay. The luciferase assay measured TGF-β bioactivity. Transforming growth factor beta expression in the experimental group was not decreased compared with the control group, with no significant difference (P>.05) Transforming growth factor beta receptor expression in the experiment group was significantly lower than that in control group (P<.05). Mannose-6-phosphate significantly decreased the expression of TGF-β receptor and TGF-β bioactivity. Modulation of mannose-6-phosphate levels may provide a means of modulating the effects of TGF-β on adhesion formation in flexor tendon wound healing.

Regulation of transforming growth factor-beta receptor expression by hypoxia in vitro and in vivo

Regulation of transforming growth factor-beta receptor expression by hypoxia in vitro and in vivo

The RNA binding protein HuR/ELAV1 regulates the estrogen receptor and epidermal growth factor receptor beta expression in BT 474 cells.

Abstract Abstract #3076 The RNA binding protein HuR has been shown to increase the mRNA stability of the majority of transcripts to which in binds. Recent data has linked the cytoplasmic distribution of HuR to the tumorigenesis process in many cancer types. HuR levels were found to be higher in more metastatic, higher grade breast tumors, suggesting that it may play a role for stabilization of growth-promoting transcripts in breast cancer cells. Previously, our lab has shown that the DNA methyltransferase inhibitor 5-aza- 2'deoxycytidine (AZA) and histone deacetylase inhibitor Trichostatin A (TSA) decreased the cytoplasmic accumulation of HuR in MDA-MB-231 and MCF-7 cells. Therefore, to examine the role of HuR in the more tumorigenic, estrogen receptor (ER) positive, Tamoxifen resistant BT 474 cells were treated with AZA/TSA or siRNA probes specifically targeting HuR expression. The BT 474 cells had a baseline increase in the cytoplasmic distribution of HuR as compared to MCF-7 and MDA-MB-231 cells. The half-life of ER mRNA was also increased. Following AZA/TSA treatment for 24-96 hours, cytoplasmic HuR was noticeably lower after 48 hours of treatment. Subsequent mRNA levels of both ER and epidermal growth factor beta (erbB2/HER2) were also found to drop with treatment. siRNA inhibition of HuR had a similar effect on the mRNA levels. Biotin pulldown assays using probes specific for the ER 3' UTR showed HuR binding was decreased with AZA/TSA treatment. These were similar findings as previously reported in MCF7 cells. Since ER and erbB2 are central to hormonal therapy, Tamoxifen sensitivity was assessed using BT 474 cells transfected with siRNA probes specifically targeting HuR expression. Cellular viability following Tamoxifen treatment was significantly decreased when HuR expression was inhibited and Tamoxifen sensitivity was restored. Similar studies investigating the role of HuR in herceptin resistance are currently ongoing. Taken together, our data suggests that HuR plays a key role in both de novo and acquired Tamoxifen resistance. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3076.

The effect of imatinib mesylate (Glivec) on human tumor-derived cells

Imatinib mesylate is a specific inhibitor of the Bcr-Abl protein tyrosine kinase that competes with ATP for its specific binding site in the kinase domain. It has activity against platelet-derived growth factor receptor alpha and beta (PDGFR-alpha and -beta), and c-kit, the receptor for stem cell factor. We have used a standardized ATP-tumor chemosensitivity assay and immunohistochemistry to determine the cytotoxicity of imatinib mesylate in tumor-derived cells from cutaneous and uveal melanoma, and ovarian carcinoma. Imatinib mesylate was tested at concentrations ranging from 2.0 to 0.0625 micromol/l alone and in combination with a cytotoxic drug (cisplatin, doxorubicin, paclitaxel or treosulfan). Imatinib mesylate showed low inhibition (IndexSUM>300) across the range of concentrations tested in this study, with few tumors exhibiting increasing inhibition with increased drug concentration. The median IC90 values for cutaneous and uveal melanoma and ovarian carcinoma were 13.2 micromol/l (4.0-294.3 micromol/l), 12.0 micromol/l (2.0-285.4 micromol/l) and 7.71 micromol/l (6.51-11.02 micromol/l), respectively. Imatinib mesylate potentiated the effect of different cytotoxics in 9% (5/54) of cases and had a negative effect in 13% (7/54) of cases, with no effect in the remainder. No correlation of effect was noted with c-kit, platelet-derived growth factor receptor-alpha or platelet-derived growth factor receptor-beta expression, assessed by immunohistochemistry. The signaling pathways mediated by activation of c-kit or platelet-derived growth factor receptor may act as antiapoptotic survival signals in some cancers and inhibition of these pathways may potentiate the activity of some cytotoxic drugs by inhibiting the survival signal. Growth inhibition, however, may reduce the efficacy of cytotoxic drugs, which tend to target proliferating cells preferentially, and clinical effects are therefore difficult to predict.

Myc is an essential negative regulator of platelet-derived growth factor beta receptor expression.

Platelet-derived growth factor BB (PDGF BB) is a potent mitogen for fibroblasts as well as many other cell types. Interaction of PDGF BB with the PDGF beta receptor (PDGF-betaR) activates numerous signaling pathways and leads to a decrease in receptor expression on the cell surface. PDGF-betaR downregulation is effected at two levels, the immediate internalization of ligand-receptor complexes and the reduction in pdgf-betar mRNA expression. Our studies show that pdgf-betar mRNA suppression is regulated by the c-myc proto-oncogene. Both constitutive and inducible ectopic Myc protein can suppress pdgf-betar mRNA and protein. Suppression of pdgf-betar mRNA in response to Myc is specific, since expression of the related receptor pdgf-alphar is not affected. We further show that Myc suppresses pdgf-betar mRNA expression by a mechanism which is distinguishable from Myc autosuppression. Analysis of c-Myc-null fibroblasts demonstrates that Myc is required for the repression of pdgf-betar mRNA expression in quiescent fibroblasts following mitogen stimulation. In addition, it is evident that the Myc-mediated repression of pdgf-betar mRNA levels plays an important role in the regulation of basal pdgf-betar expression in proliferating cells. Thus, our studies suggest an essential role for Myc in a negative-feedback loop regulating the expression of the PDGF-betaR.

Vascular types I and II transforming growth factor-beta receptor expression: differential dependency on tyrosine kinases during induction by TGF- β

Recent evidence indicates that the type II transforming growth factor- β (TGF- β) receptor (T βRII) is a serine-threonine-tyrosine kinase. However, the significance of its tyrosine kinase is unclear. We investigated in vascular smooth muscle cells the effects of tyrosine kinase inhibition on the expression of TGF- β receptor types I (ALK-5) and II (T βRII) mRNA, induced by TGF- β 1. TGF- β 1 elevated ALK-5 mRNA levels 5-fold; essentially similar TGF- β 1-dependent elevations were observed with growth factors, PDGF-BB and FGF-2. The tyrosine kinase inhibitor genistein abolished these TGF- β 1 and growth factor responses. TGF- β 1 also elevated T βRII mRNA levels which were not inhibited by genistein. We conclude that tyrosine kinases participate in defining how cells respond to TGF- β.

Differential expression of platelet‐derived growth factor receptor‐β in an aging model of wound repair

Impaired wound healing as a result of age is a well-documented phenomenon. However, the overall deficit in healing is substantially increased when the healing wound of an aged animal is ischemic. We hypothesized that both of these deficits are cytokine mediated. We have studied the messenger RNA expression of platelet-derived growth factor receptor-beta, using the rabbit dermal ulcer model of wound repair, in young (3 to 6 months) and aged (48 months and 60 months) rabbits under normal and ischemic conditions. Platelet-derived growth factor receptor-beta mRNA expression was measured with the use of quantitative reverse transcriptase-polymerase chain reaction with incorporation of a synthetic, nonhomologous DNA fragment complementary to platelet-derived growth factor receptor-beta primers as a competitive internal standard. Results in young rabbits showed a large upregulation of platelet-derived growth factor receptor-beta mRNA expression after wounding. In both aged animal groups, platelet-derived growth factor receptor-beta expression was found to be significantly decreased in nonischemic wounds relative to young nonischemic controls. Ischemia was found to have little effect on platelet-derived growth factor receptor-beta mRNA expression in young animals relative to matched controls. However, ischemia induced a large decrease in the platelet-derived growth factor receptor-beta mRNA levels of wounds of aged animals relative to paired aged nonischemic wounds. Results suggest an age-related delay in platelet-derived growth factor receptor-beta mRNA expression in healing wounds, as well as an age-related decline in responsiveness to confounding ischemia.

Interferon-gamma induces high-affinity transforming growth factor-beta receptor expression on human corneal fibroblasts.

The effect of interferon-gamma (IFN-gamma) on the expression of transforming growth factor-beta (TGF-beta) receptors on cultured human corneal stromal fibroblasts was examined. Scatchard analysis of specific saturable TGF-beta 1 binding data indicated that corneal fibroblasts expressed TGF-beta receptors with an average association constant of 6 x 10 M-1, before and after IFN-gamma treatment. An additional population of higher affinity TGF-beta receptors, with an average association constant of 4 x 10(12) M-1, was demonstrated only on IFN-gamma-treated corneal fibroblasts Interferon-gamma may alter the response of corneal fibroblasts to transforming growth factor-betas by upregulating their higher affinity TGF-beta receptors. The induction of higher affinity TGF-beta receptors by an immune cytokine and an associated autocrine elevation of TGF-beta output by the corneal fibroblasts may be a transient compensatory mechanism that maintains the homeostasis of corneal optical competency through enhancement of corneal immunoseclusion.