FGFR3 overexpression is a useful detection tool for FGFR3 fusions and sequence variations in glioma.

November 20, 2020

Schittenhelm J1 2, Ziegler L2, Sperveslage J3 4, Mittelbronn M5 6 7 8 9, Capper D10 11, Burghardt I1 12, Poso A13, Biskup S14, Skardelly M1 15, Tabatabai G1 12 16 17

Abstract

Background: Fibroblast growth factor receptor (FGFR) inhibitors are currently used in clinical development. A subset of glioblastomas carries gene fusion of FGFR3 and transforming acidic coiled-coil protein 3. The prevalence of other FGFR3 alterations in glioma is currently unclear.

Methods: We performed RT-PCR in 101 glioblastoma samples to detect FGFR3-TACC3 fusions (“RT-PCR cohort”) and correlated results with FGFR3 immunohistochemistry (IHC). Further, we applied FGFR3 IHC in 552 tissue microarray glioma samples (“TMA cohort”) and validated these results in two external cohorts with 319 patients. Gene panel sequencing was carried out in 88 samples (“NGS cohort”) to identify other possible FGFR3 alterations. Molecular modeling was performed on newly detected mutations.

Results: In the “RT-PCR cohort,” we identified FGFR3-TACC3 fusions in 2/101 glioblastomas. Positive IHC staining was observed in 73/1024 tumor samples of which 10 were strongly positive. In the “NGS cohort,” we identified FGFR3 fusions in 9/88 cases, FGFR3 amplification in 2/88 cases, and FGFR3 gene mutations in 7/88 cases in targeted sequencing. All FGFR3 fusions and amplifications and a novel FGFR3 K649R missense mutation were associated with FGFR3 overexpression (sensitivity and specificity of 93% and 95%, respectively, at cutoff IHC score > 7). Modeling of these data indicated that Tyr647, a residue phosphorylated as a part of FGFR3 activation, is affected by the K649R mutation.

Conclusions: FGFR3 IHC is a useful screening tool for the detection of FGFR3 alterations and could be included in the workflow for isocitrate dehydrogenase (IDH) wild-type glioma diagnostics. Samples with positive FGFR3 staining could then be selected for NGS-based diagnostic tools.

  1. Center for Neuro-Oncology, Comprehensive Cancer Center Tuebingen-Stuttgart, University Hospital of Tuebingen, Eberhard Karls University of Tuebingen, Tuebingen, Germany.
  2. Department of Neuropathology, Institute of Pathology and Neuropathology, University Hospital of Tuebingen, Eberhard Karls University of Tuebingen, Tuebingen, Germany.
  3. Department of Pathology, Institute of Pathology and Neuropathology, University Hospital of Tuebingen, Eberhard Karls University of Tuebingen, Tuebingen, Germany.
  4. Gerhard-Domagk-Institute of Pathology, University Hospital Münster, Münster, Germany.
  5. Luxembourg Center of Neuropathology (LCNP), Dudelange, Luxembourg.
  6. Centre for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg.
  7. National Center of Pathology (NCP), Laboratoire National de Santé (LNS), Dudelange, Luxembourg.
  8. Department of Oncology (DONC), Luxembourg Institute of Health (LIH), Luxembourg, Luxembourg.
  9. Edinger Institute (Neurological Institute), University of Frankfurt, Frankfurt, Germany.
  10. Institute of Neuropathology, Berlin Institute of Health, Berlin, Germany.
  11. Charité-Universitätsmedizin Berlin, Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.
  12. Department of Neurology & Interdisciplinary Neurooncology, University Hospital Tübingen, Hertie-Institute for Clinical Brain Research, Eberhard Karls University Tübingen, Tuebingen, Germany.
  13. Department of Internal Medicine VIII, University Hospital Tuebingen, Tuebingen, Germany.
  14. CeGaT GmbH and Praxis für Humangenetik Tuebingen, Tuebingen, Germany.
  15. Department of Neurosurgery, University Hospital of Tuebingen, Eberhard Karls University Tuebingen, Tuebingen, Germany.
  16. Center for Personalized Medicine, Eberhard Karls University of Tuebingen, Tuebingen, Germany.
  17. German Consortium for Translational Cancer Research (DKTK), DKFZ partner site Tuebingen, Tuebingen, Germany.