Survival advantage combining a BRAF inhibitor and radiation in BRAF V600E-mutant glioma

J Neurooncol. 2016 Feb;126(3):385-93. doi: 10.1007/s11060-015-1939-2. Epub 2015 Sep 18.


Radiation (RT) is critical to the treatment of high-grade gliomas (HGGs) but cures remain elusive. The BRAF mutation V600E is critical to the pathogenesis of 10-20% of pediatric gliomas, and a small proportion of adult HGGs. Here we aim to determine whether PLX4720, a specific BRAF V600E inhibitor, enhances the activity of RT in human HGGs in vitro and in vivo. Patient-derived HGG lines harboring wild-type BRAF or BRAF V600E were assessed in vitro to determine IC50 values, cell cycle arrest, apoptosis and senescence and elucidate mechanisms of combinatorial activity. A BRAF V600E HGG intracranial xenograft mouse model was used to evaluate in vivo combinatorial efficacy of PLX4720+RT. Tumors were harvested for immunohistochemistry to quantify cell cycle arrest and apoptosis. RT+PLX4720 exhibited greater anti-tumor effects than either monotherapy in BRAF V600E but not in BRAF WT lines. In vitro studies showed increased Annexin V and decreased S phase cells in BRAF V600E gliomas treated with PLX4720+RT, but no significant changes in β-galactosidase levels. In vivo, concurrent and sequential PLX4720+RT each significantly prolonged survival compared to monotherapies, in the BRAF V600E HGG model. Immunohistochemistry of in vivo tumors demonstrated that PLX4720+RT decreased Ki-67 and phospho-MAPK, and increased γH2AX and p21 compared to control mice. BRAF V600E inhibition enhances radiation-induced cytotoxicity in BRAF V600E-mutated HGGs, in vitro and in vivo, effects likely mediated by apoptosis and cell cycle, but not senescence. These studies provide the pre-clinical rationale for clinical trials of concurrent radiotherapy and BRAF V600E inhibitors.

Keywords: BRAF V600E; High-grade gliomas; Radiotherapy; Targeted inhibitors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Brain Neoplasms / genetics
  • Brain Neoplasms / mortality*
  • Brain Neoplasms / pathology
  • Brain Neoplasms / therapy*
  • Cell Cycle / drug effects
  • Cell Proliferation / drug effects
  • Chemoradiotherapy*
  • Gamma Rays*
  • Glioma
  • Humans
  • Immunoenzyme Techniques
  • Indoles / pharmacology*
  • Mice
  • Mice, Nude
  • Mutation / genetics*
  • Neoplasm Grading
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors
  • Proto-Oncogene Proteins B-raf / genetics*
  • Sulfonamides / pharmacology*
  • Survival Rate
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays


  • Indoles
  • PLX 4720
  • Sulfonamides
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf