ROS1 amplification mediates resistance to gefitinib in glioblastoma cells
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Hashim Aljohani1,*, Robert F. Koncar1,*, Ahmad Zarzour2, Byung Sun Park3, So Ha Lee3 and El Mustapha Bahassi1
1 Department of Internal Medicine; Division of Hematology and Oncology, Cincinnati, OH, USA
2 Department of Internal Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA
3 Chemical Kinomics Research Center, Korea Institute of Science and Technology, Hwarangno, Seongbuk-gu, Seoul, Republic of Korea
* These authors have contributed equally to this work
El Mustapha Bahassi, email:
Keywords: tyrosine kinase inhibitors, EGFR, gefitinib, ROS1, DDR1
Received: October 23, 2014 Accepted: April 15, 2015 Published: May 04, 2015
Glioblastoma (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. The majority of GBM tumors show a mutated or overexpressed EGFR, however, tumors treated with tyrosine kinase inhibitors (TKIs) will inevitably recur highlighting the need to identify signalling pathways involved in GBM resistance to these drugs. To this end, we treated GBM cells that overexpress EGFR with increasing concentrations of gefitinib and isolated resistant clones. These resistant clones were subject to RNAseq and the expression of several genes was found to be upregulated. These genes are mainly tyrosine kinase receptors and include ROS1, DDR1 and PDGFRA and are known to control several downstream targets of EGFR. The upregulation of ROS1 and DDR1 was confirmed at the protein level by western blot. Treatment with a potent and highly specific pyrazole ROS1 inhibitor in ROS1 overexpressing clones led to a sensitization of these cells to low concentrations of gefitinib. Combined treatment with gefitinib and ROS1 inhibitor induces massive cell death by apoptosis following a prolonged S phase cell cycle arrest. Our current study led to the discovery of alternative pathways used by GBM cells to evade cell death following treatment with gefitinib and identifies new therapeutic targets to prevent GBM cell resistance to the drug.
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