Article

Nontoxic chemical interdiction of the epithelial-to-mesenchymal transition by targeting cap-dependent translation.

Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
ACS Chemical Biology (Impact Factor: 5.36). 05/2009; 4(5):367-77. DOI: 10.1021/cb9000475
Source: PubMed

ABSTRACT Normal growth and development depends upon high fidelity regulation of cap-dependent translation initiation, a process that is usurped and redirected in cancer to mediate acquisition of malignant properties. The epithelial-to-mesenchymal transition (EMT) is a key translationally regulated step in the development of epithelial cancers and pathological tissue fibrosis. To date, no compounds targeting EMT have been developed. Here we report the synthesis of a novel class of histidine triad nucleotide binding protein (HINT)-dependent pronucleotides that interdict EMT by negatively regulating the association of eIF4E with the mRNA cap. Compound eIF4E inhibitor-1 potently inhibited cap-dependent translation in a dose-dependent manner in zebrafish embryos without causing developmental abnormalities and prevented eIF4E from triggering EMT in zebrafish ectoderm explants without toxicity. Metabolism studies with whole cell lysates demonstrated that the prodrug was rapidly converted into 7-BnGMP. Thus we have successfully developed the first nontoxic small molecule able to inhibit EMT, a key process in the development of epithelial cancer and tissue fibrosis, by targeting the interaction of eIF4E with the mRNA cap and demonstrated the tractability of zebrafish as a model organism for studying agents that modulate EMT. Our work provides strong motivation for the continued development of compounds designed to normalize cap-dependent translation as novel chemo-preventive agents and therapeutics for cancer and fibrosis.

0 Followers
 · 
127 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: eIF4E1b, closely related to the canonical translation initiation factor 4E (eIF4E1a), cap-binding protein, is highly expressed in mouse, Xenopus and zebrafish oocytes. We have previously characterised eIF4E1b as a component of the CPEB mRNP translation repressor complex along with the eIF4E-binding protein 4E-Transporter, the Xp54/DDX6 RNA helicase and additional RNA-binding proteins. eIF4E1b exhibited only very weak interactions with m7GTP-Sepharose and rather than binding eIF4G, interacted with 4E-T.Here we undertook a detailed examination of both Xenopus and human eIF4E1b interactions with cap analogues using fluorescence titration and homology modeling. The predicted structure of eIF4E1b maintains the α + β fold characteristic of eIF4E proteins and its cap-binding pocket is similarly arranged by critical amino acids: Trp56, Trp102, Glu103, Trp166, Arg112, Arg157, Lys162 and residues of the C-terminal loop. However, we demonstrate that eIF4E1b is three-fold less well able to bind the cap than eIF4E1a, both proteins being highly stimulated by methylation at N7 of guanine. Moreover, eIF4E1b proteins are distinguishable from eIF4E1a by a set of conserved amino acid substitutions, several of which are located near to cap-binding residues. Indeed, eIF4E1b possesses several distinct features, namely enhancement of cap-binding by a benzyl group at N7 position of guanine, a reduced response to increasing length of the phosphate chain and increased binding to a cap separated by a linker from Sepharose, suggesting differences in the arrangement of the protein’s core. In agreement, mutagenesis of the amino acids differentiating eIF4E1b from eIF4E1a reduces cap-binding by eIF4E1a two-fold, demonstrating their role in modulating cap-binding.
    Journal of Molecular Biology 11/2014; 427(2). DOI:10.1016/j.jmb.2014.11.009 · 3.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Elevated protein synthesis is an important feature of many cancer cells and often arises as a consequence of increased signaling flux channeled to eukaryotic initiation factor 4F (eIF4F), the key regulator of the mRNA-ribosome recruitment phase of translation initiation. In many cellular and preclinical models of cancer, eIF4F deregulation results in changes in translational efficiency of specific mRNA classes. Importantly, many of these mRNAs code for proteins that potently regulate critical cellular processes, such as cell growth and proliferation, enhanced cell survival and cell migration that ultimately impinge on several hallmarks of cancer, including increased angiogenesis, deregulated growth control, enhanced cellular survival, epithelial-to-mesenchymal transition, invasion, and metastasis. By being positioned as the molecular nexus downstream of key oncogenic signaling pathways (e.g., Ras, PI3K/AKT/TOR, and MYC), eIF4F serves as a direct link between important steps in cancer development and translation initiation. Identification of mRNAs particularly responsive to elevated eIF4F activity that typifies tumorigenesis underscores the critical role of eIF4F in cancer and raises the exciting possibility of developing new-in-class small molecules targeting translation initiation as antineoplastic agents. Cancer Res; 75(2); 250-63. ©2014 AACR. ©2014 American Association for Cancer Research.
    Cancer Research 01/2015; 75(2):250-263. DOI:10.1158/0008-5472.CAN-14-2789 · 9.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on a facile and reliable preparation of polypyrrole vessel structures modified with gold nanoparticles that are able to encapsulate organic molecules of biological importance. The polymer is coated onto the surface of aqueous droplets through photopolymerization of the monomer. When gold nanoparticles and/or biomolecules are contained in the droplets, these species become incorporated within the formed polymer microvessels. Herein, we provide thorough physicochemical characterization of the polymer structures including electron and optical microscopy, spectroscopy (steady state and time-resolved fluorescence, XPS, XRF) and other experimental techniques. Polymer microvessels are promising as smart drug carriers for new experimental therapies. As model drugs we use mRNA cap analogues which are nucleotide-derived compounds that have been shown to be potential anti-cancer agents. We demonstrate that embedding the metallic nanoparticles within the microvessels provides usefully high contrast in micro-computed tomography (microCT) which is promising from the standpoint of monitoring the fate of administered drug carriers inside the body. Moreover, our in vivo studies on rats demonstrate that intravenous administration of the microvessels does not evoke acute toxicity or death of the animals.
    Polymer 12/2014; 57. DOI:10.1016/j.polymer.2014.12.019 · 3.77 Impact Factor

Full-text (2 Sources)

Download
75 Downloads
Available from
Jun 3, 2014