TRPM8 is required for survival and radioresistance of glioblastoma cells
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Dominik Klumpp1, Stephanie C. Frank2,3, Lukas Klumpp1,4,5, Efe C. Sezgin1, Marita Eckert1, Lena Edalat1,6, Martin Bastmeyer2,3, Daniel Zips1, Peter Ruth6 and Stephan M. Huber1
1Department of Radiation Oncology, University of Tübingen, Tübingen, Germany
2Zoological Institute, Department of Cell- and Neurobiology, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
3Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
4Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart, Germany
5University of Tübingen, Tübingen, Germany
6Department of Pharmacology, Toxicology and Clinical Pharmacy, University of Tübingen, Tübingen, Germany
Stephan M. Huber, email: firstname.lastname@example.org
Keywords: glioblastoma; radioresistance; TRPM8 channels; Ca2+ signaling; cell migration
Received: July 26, 2017 Accepted: August 25, 2017 Published: September 30, 2017
TRPM8 is a Ca2+-permeable nonselective cation channel belonging to the melastatin sub-group of the transient receptor potential (TRP) family. TRPM8 is aberrantly overexpressed in a variety of tumor entities including glioblastoma multiforme where it reportedly contributes to tumor invasion. The present study aimed to disclose further functions of TRPM8 in glioma biology in particular upon cell injury by ionizing radiation. To this end, TCGA data base was queried to expose the TRPM8 mRNA abundance in human glioblastoma specimens and immunoblotting was performed to analyze the TRPM8 protein abundance in primary cultures of human glioblastoma. Moreover, human glioblastoma cell lines were irradiated with 6 MV photons and TRPM8 channels were targeted pharmacologically or by RNA interference. TRPM8 abundance, Ca2+ signaling and resulting K+ channel activity, chemotaxis, cell migration, clonogenic survival, DNA repair, apoptotic cell death, and cell cycle control were determined by qRT-PCR, fura-2 Ca2+ imaging, patch-clamp recording, transfilter migration assay, wound healing assay, colony formation assay, immunohistology, flow cytometry, and immunoblotting. As a result, human glioblastoma upregulates TRPM8 channels to variable extent. TRPM8 inhibition or knockdown slowed down cell migration and chemotaxis, attenuated DNA repair and clonogenic survival, triggered apoptotic cell death, impaired cell cycle and radiosensitized glioblastoma cells. Mechanistically, ionizing radiation activated and upregulated TRPM8-mediated Ca2+ signaling that interfered with cell cycle control probably via CaMKII, cdc25C and cdc2. Combined, our data suggest that TRPM8 channels contribute to spreading, survival and radioresistance of human glioblastoma and, therefore, might represent a promising target in future anti-glioblastoma therapy.
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