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Oncogene. 2016 Mar 17;35(11):1353-62. doi: 10.1038/onc.2015.212. Epub 2015 Jun 15.

Targeting of β1 integrins impairs DNA repair for radiosensitization of head and neck cancer cells.

Dickreuter E1,2, Eke I1,2,3, Krause M1,2,3,4,5, Borgmann K6, van Vugt MA7, Cordes N1,2,3,4,5.

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OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany.
Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany.
German Cancer Consortium (DKTK), 01307 Dresden, Germany, and German Cancer Research Center (DKFZ), Heidelberg, Germany.
Laboratory of Radiobiology and Experimental Radiooncology, Clinic of Radiotherapy and Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Department of Medical Oncology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.


β1 Integrin-mediated cell-extracellular matrix interactions allow cancer cell survival and confer therapy resistance. It was shown that inhibition of β1 integrins sensitizes cells to radiotherapy. Here, we examined the impact of β1 integrin targeting on the repair of radiation-induced DNA double-strand breaks (DSBs). β1 Integrin inhibition was accomplished using the monoclonal antibody AIIB2 and experiments were performed in three-dimensional cell cultures and tumor xenografts of human head and neck squamous cell carcinoma (HNSCC) cell lines. AIIB2, X-ray irradiation, small interfering RNA-mediated knockdown and Olaparib treatment were performed and residual DSB number, protein and gene expression, non-homologous end joining (NHEJ) activity as well as clonogenic survival were determined. β1 Integrin targeting impaired repair of radiogenic DSB (γH2AX/53BP1, pDNA-PKcs T2609 foci) in vitro and in vivo and reduced the protein expression of Ku70, Rad50 and Nbs1. Further, we identified Ku70, Ku80 and DNA-PKcs but not poly(ADP-ribose) polymerase (PARP)-1 to reside in the β1 integrin pathway. Intriguingly, combined inhibition of β1 integrin and PARP using Olaparib was significantly more effective than either treatment alone in non-irradiated and irradiated HNSCC cells. Here, we support β1 integrins as potential cancer targets and highlight a regulatory role for β1 integrins in the repair of radiogenic DNA damage via classical NHEJ. Further, the data suggest combined targeting of β1 integrin and PARP as promising approach for radiosensitization of HNSCC.

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