Maria Artesi1, Jerome Kroonen1, Markus Bredel1, Minh Nguyen-Khac1, Manuel Deprez1, Laurent Schoysman1, Christophe Poulet1, Arnab Chakravarti1, Hyunsoo Kim1, Denise Scholtens1, Tatjana Seute1, Bernard Rogister1, Vincent Bours1, Pierre A Robe1. 1. Department of Human Genetics, CBIG/GIGA Research Center, University of Liège, Liège, Belgium (M.A., J.K., M.N.-K., L.S., C.P., V.B., P.A.R.); Department of Neurology and Neurosurgery and T. and P. Bonhenn Neuro-Oncology Laboratory, University Hospital of Utrecht, Utrecht, Netherlands (J.K., L.S., T.S., P.A.R.); Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Chicago, Illinois (D.S.); Center for Population Health Sciences, Institute for Public Health and Medicine, Northwestern University, Chicago (D.S.); Division of Neuropathology, University Hospital of Liège, Liège, Belgium (M.D.); Division of Neurobiology, CBIG/GIGA Research Center, University Hospital of Liège, Liège, Belgium (B.R.); Department of Radiation Oncology, Arthur G James Comprehensive Cancer Center and Richard L. Solove Research Institute, The Ohio State University Medical Center, Columbus, Ohio (A.C., P.A.R.); Department of Radiation Oncology, Hazelrig-Salter Radiation Oncology Center and UAB Comprehensive Cancer Center, Birmingham, Alabama (M.B., H.K.).
Abstract
BACKGROUND: Glioblastomas remain ominous tumors that almost invariably escape treatment. Connexins are a family of transmembrane, gap junction-forming proteins, some members of which were reported to act as tumor suppressors and to modulate cellular metabolism in response to cytotoxic stress. METHODS: We analyzed the copy number and expression of the connexin (Cx)30 gene gap junction beta-6 (GJB6), as well as of its protein immunoreactivity in several public and proprietary repositories of glioblastomas, and their influence on patient survival. We evaluated the effect of the expression of this gap junction protein on the growth, DNA repair and energy metabolism, and treatment resistance of these tumors. RESULTS: The GJB6 gene was deleted in 25.8% of 751 analyzed tumors and mutated in 15.8% of 158 tumors. Cx30 immunoreactivity was absent in 28.9% of 145 tumors. Restoration of Cx30 expression in human glioblastoma cells reduced their growth in vitro and as xenografts in the striatum of immunodeficient mice. Cx30 immunoreactivity was, however, found to adversely affect survival in 2 independent retrospective cohorts of glioblastoma patients. Cx30 was found in clonogenic assays to protect glioblastoma cells against radiation-induced mortality and to decrease radiation-induced DNA damage. This radioprotection correlated with a heat shock protein 90-dependent mitochondrial translocation of Cx30 following radiation and an improved ATP production following this genotoxic stress. CONCLUSION: These results underline the complex relationship between potential tumor suppressors and treatment resistance in glioblastomas and single out GJB6/Cx30 as a potential biomarker and target for therapeutic intervention in these tumors.
BACKGROUND:Glioblastomas remain ominous tumors that almost invariably escape treatment. Connexins are a family of transmembrane, gap junction-forming proteins, some members of which were reported to act as tumor suppressors and to modulate cellular metabolism in response to cytotoxic stress. METHODS: We analyzed the copy number and expression of the connexin (Cx)30 gene gap junction beta-6 (GJB6), as well as of its protein immunoreactivity in several public and proprietary repositories of glioblastomas, and their influence on patient survival. We evaluated the effect of the expression of this gap junction protein on the growth, DNA repair and energy metabolism, and treatment resistance of these tumors. RESULTS: The GJB6 gene was deleted in 25.8% of 751 analyzed tumors and mutated in 15.8% of 158 tumors. Cx30 immunoreactivity was absent in 28.9% of 145 tumors. Restoration of Cx30 expression in humanglioblastoma cells reduced their growth in vitro and as xenografts in the striatum of immunodeficientmice. Cx30 immunoreactivity was, however, found to adversely affect survival in 2 independent retrospective cohorts of glioblastomapatients. Cx30 was found in clonogenic assays to protect glioblastoma cells against radiation-induced mortality and to decrease radiation-induced DNA damage. This radioprotection correlated with a heat shock protein 90-dependent mitochondrial translocation of Cx30 following radiation and an improved ATP production following this genotoxic stress. CONCLUSION: These results underline the complex relationship between potential tumor suppressors and treatment resistance in glioblastomas and single out GJB6/Cx30 as a potential biomarker and target for therapeutic intervention in these tumors.
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