Oncotarget

Research Papers:

Targeting oncogenic Ras by the Clostridium perfringens toxin TpeL

Björn Schorch _, Hannah Heni, Nour-Imene Zahaf, Tilman Brummer, Marina Mione, Gudula Schmidt, Panagiotis Papatheodorou and Klaus Aktories

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Oncotarget. 2018; 9:16489-16500. https://doi.org/10.18632/oncotarget.24740

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Abstract

Björn Schorch1, Hannah Heni1, Nour-Imene Zahaf1, Tilman Brummer2,3,4, Marina Mione5,6, Gudula Schmidt1, Panagiotis Papatheodorou1,7,8 and Klaus Aktories1,4

1Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

2Institut für Molekulare Medizin und Zellforschung, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

3German Cancer Consortium (DKTK), Partner Site Freiburg, Germany, and German Cancer Research Center (DKFZ), Heidelberg, Germany

4Centre for Biological Signalling Studies (BIOSS), Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

5Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggestein-Leopoldshafen, Germany

6Present Address: Center for Integrative Biology, University of Trento, Trento, Italy

7Present Address: Institute of Pharmaceutical Biotechnology, University of Ulm, Ulm, Germany

8Present Address: Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany

Correspondence to:

Klaus Aktories, email: klaus.aktories@pharmakol.uni-freiburg.de

Keywords: Clostridium perfringens toxin; glycosylation; immunotoxins; paradoxical activation; Ras

Received: April 04, 2017     Accepted: March 02, 2018     Published: March 27, 2018

ABSTRACT

Clostridium perfringens toxin TpeL belongs to the family of large clostridial glycosylating toxins. The toxin causes N-acetylglucosaminylation of Ras proteins at threonine35 thereby inactivating the small GTPases. Here, we show that all main types of oncogenic Ras proteins (H-Ras, K-Ras and N-Ras) are modified by the toxin in vitro and in vivo. Toxin-catalyzed modification of Ras was accompanied by inhibition of the MAP kinase pathway. Importantly, TpeL inhibited the paradoxical activation of the MAP kinase pathway induced by the BRAF inhibitor Vemurafenib in the human melanoma cell line SBCL2. The toxin also blocked Ras signaling in a zebrafish embryo model expressing oncogenic H-RasG12V, resulting in a reduction of melanocyte number. By using the binding and translocation component of anthrax toxin (protective antigen), the glucosyltransferase domain of TpeL was effectively introduced into target cells that were not sensitive to native TpeL toxin. To reach a higher specificity towards cancer cells, a chimeric TpeL toxin was engineered that possessed the knob region of adenovirus serotype 35 fiber, which interacts with CD46 of target cells frequently overexpressed in cancer cells. The chimeric TpeL fusion toxin efficiently inhibited Ras and MAP kinases in human pancreatic cancer Capan-2 cells, which were insensitive to the wild-type toxin. The data reveal that TpeL and TpeL-related immunotoxins provide a new toolset as Ras-inactivating agents.


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