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      SiRNA targeting EGFR effectively prevents posterior capsular opacification after cataract surgery

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      Molecular Vision
      Molecular Vision

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          Abstract

          Purpose

          We investigated the effect of epidermal growth factor receptor ( EGFR) siRNA on human lens epithelium (HLE) cells and the development of posterior capsular opacity (PCO).

          Methods

          We designed EGFR siRNA and used it to knockdown the expression of EGFR in HLE cells. Cell proliferation was examined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), cell growth curve assay and cell cycle analysis. Next, we selected an adaptable concentration of recombinant epidermal growth factor (EGF) for stimulating the growth of HLE cells to further test the suppressive effect of siRNA. At last, we established the model of PCO in rats to further investigate whether knocking down EGFR would prevent the progression of PCO in vivo.

          Results

          The cell proliferation of EGFR siRNA group was apparently inhibited no matter in short or long term and cell cycle was arrested in G 1 phase. Over expression EGF cannot rescue the inhibition of EGFR siRNA on HLE cells and the proliferation activity in HLE cells greatly decreased when EGF-EGFR signal pathway blockaded. In vivo experiments, the extent of PCO of EGFR siRNA group is much lower than the control group.

          Conclusions

          Our results demonstrate that EGFR siRNA can effectively inhibit the progression of PCO. Thus, siRNA targeting EGFR may provide a totally new way for preventing PCO or even cataract.

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          Most cited references23

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          Posterior capsular opacification: a problem reduced but not yet eradicated.

          Posterior capsular opacification (PCO) is the most frequent complication of cataract surgery. Advances in surgical techniques, intraocular lens materials, and designs have reduced the PCO rate, but it is still a significant problem. The only effective treatment for PCO, Nd:YAG laser capsulotomy carries vision-related complications and risks and puts a significant financial burden on the health care system. This review contains current knowledge about the mechanisms of PCO development. Posterior capsular opacification is caused mainly by remnant lens epithelial cell proliferation and migration, epithelial-mesenchymal transition, collagen deposition, and lens fiber generation. All of these processes are influenced by cytokines, growth factors, and extracellular matrix proteins. We also describe advances and improvements in surgical techniques, intraocular lens materials, and the designs and use of therapeutic agents leading to safe, effective, and less expensive strategies to eradicate PCO.
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            Transforming growth factor-beta-induced epithelial-mesenchymal transition in the lens: a model for cataract formation.

            The vertebrate lens has a distinct polarity and structure that are regulated by growth factors resident in the ocular media. Fibroblast growth factors, in concert with other growth factors, are key regulators of lens fiber cell differentiation. While members of the transforming growth factor (TGFbeta) superfamily have also been implicated to play a role in lens fiber differentiation, inappropriate TGFbeta signaling in the anterior lens epithelial cells results in an epithelial-mesenchymal transition (EMT) that bears morphological and molecular resemblance to forms of human cataract, including anterior subcapsular (ASC) and posterior capsule opacification (PCO; also known as secondary cataract or after-cataract), which occurs after cataract surgery. Numerous in vitro and in vivo studies indicate that this TGFbeta-induced EMT is part of a wound healing response in lens epithelial cells and is characterized by induced expression of numerous extracellular matrix proteins (laminin, collagens I, III, tenascin, fibronectin, proteoglycans), intermediate filaments (desmin, alpha-smooth muscle actin) and various integrins (alpha2, alpha5, alpha7B), as well as the loss of epithelial genes [Pax6, Cx43, CP49, alpha-crystallin, E-cadherin, zonula occludens-1 protein (ZO-1)]. The signaling pathways involved in initiating the EMT seem to primarily involve the Smad-dependent pathway, whereby TGFbeta binding to specific high affinity cell surface receptors activates the receptor-Smad/Smad4 complex. Recent studies implicate other factors [such as fibroblast growth factor (FGFs), hepatocyte growth factor, integrins], present in the lens and ocular environment, in the pathogenesis of ASC and PCO. For example, FGF signaling can augment many of the effects of TGFbeta, and integrin signaling, possibly via ILK, appears to mediate some of the morphological features of EMT initiated by TGFbeta. Increasing attention is now being directed at the network of signaling pathways that effect the EMT in lens epithelial cells, with the aim of identifying potential therapeutic targets to inhibit cataract, particularly PCO, which remains a significant clinical problem in ophthalmology.
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              Targeting EGFR and VEGF(R) pathway cross-talk in tumor survival and angiogenesis.

              The last decade has witnessed the approval of monoclonal antibodies (mAbs) and small molecule tyrosine kinase inhibitors (TKIs) for targeting of oncogenic signaling pathways. Generally, the clinical activity of these agents has been less than expected, in part due to unsuspected feed-back loops and cross-talk between different signaling pathways, thereby suggesting the interest of inhibiting multiple pathways. The extensive degree of EGFR-VEGF(R) pathway cross-talk identifies these pathways as particularly promising for joint targeting. Activation of the EGFR pathway increases the production of tumor-derived VEGF that acts on endothelial cells in a paracrine manner to promote angiogenesis. Accordingly, exposure to EGFR inhibitors is accompanied by attenuation of VEGF expression while resistance to EGFR inhibitors is frequently associated with enhanced VEGF levels. Recent data have expanded the biological activities of the two pathways by documenting a role for VEGF signaling in tumor cell survival and demonstrating the expression of EGFR by some tumor-associated endothelial cells. At least part of these signaling events are intracrine (intracellular and autocrine) and thus not readily accessible for the mAbs which target extracellular ligands and membrane receptors. This may explain why two major clinical trials combining EGFR and VEGF-targeted mAbs gave disappointing results and suggest a need for compounds that are able to inhibit intracrine signaling. Clinical application of new combinations should be preceded by preclinical development guided by functional biomarker analysis to identify active drug combinations and to facilitate the identification of patient subgroups likely, or not, to respond to dual pathway inhibition. Copyright © 2011 Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                Mol Vis
                MV
                Molecular Vision
                Molecular Vision
                1090-0535
                2011
                31 August 2011
                : 17
                : 2349-2355
                Affiliations
                [1]Tianjin Eye Hospital, Tianjin Medical University, Tianjin, China
                Author notes

                The first two authors contributed equally to this work

                Correspondence to: Xin Tang, Tianjin Eye Hospital, Tianjin Medical University, No. 4 Gan-Su Road, Tianjin, China; Phone: +86-022-27313336; FAX: +86-022-273133; email: Tangprofessor@ 123456163.com
                Article
                256 2011MOLVIS0271
                3171494
                21921987
                6f6c27db-ef13-437c-a093-1e4080c16eb1
                Copyright © 2011 Molecular Vision.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 18 June 2011
                : 25 August 2011
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                Vision sciences
                Vision sciences

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