title: Survival advantage combining a BRAF inhibitor and radiation in BRAF V600E-mutant glioma.
abstract: 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.
authors.affiliation: Valley Radiotherapy Associates, 1500 Rosecrans Avenue, Manhattan Beach, CA, 90266, USA. tinadasgupta2006@gmail.com.
authors.forename: Tina
authors.initials: T
authors.lastname: Dasgupta
authors.affiliation: Department of Laboratory Medicine, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.|Department of Radiation Oncology, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Aleksandra K
authors.initials: AK
authors.lastname: Olow
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA.
authors.forename: Rintaro
authors.initials: R
authors.lastname: Hashizume
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.|Department of Pediatrics, University of California, San Francisco, San Francisco, CA, 94143, USA.
authors.forename: Theodore P
authors.initials: TP
authors.lastname: Nicolaides
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Maxwell
authors.initials: M
authors.lastname: Tom
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Mitchel S
authors.initials: MS
authors.lastname: Berger
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.|Department of Pediatrics, University of California, San Francisco, San Francisco, CA, 94143, USA.|Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Weiss
authors.affiliation: Department of Radiotherapy, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lukas J A
authors.initials: LJ
authors.lastname: Stalpers
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Prados
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA.
authors.forename: C David
authors.initials: CD
authors.lastname: James
authors.affiliation: Department of Pediatrics, University of California, San Francisco, San Francisco, CA, 94143, USA.|Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Sabine
authors.initials: S
authors.lastname: Mueller
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.|Department of Neurological Surgery, University of California, San Francisco (UCSF), San Francisco, CA, 94143, USA.
authors.forename: Daphne A
authors.initials: DA
authors.lastname: Haas-Kogan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001932:Brain Neoplasms / Q000235:genetics / Q000401:mortality* / Q000473:pathology / Q000628:therapy*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D059248:Chemoradiotherapy; D005720:Gamma Rays; D005910:Glioma; D006801:Humans; D007124:Immunoenzyme Techniques; D007211:Indoles / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D009154:Mutation / Q000235:genetics*; D060787:Neoplasm Grading; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics*; D013449:Sulfonamides / Q000494:pharmacology*; D015996:Survival Rate; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D007211:Indoles; C528407:PLX 4720; D013449:Sulfonamides; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF V600E; High-grade gliomas; Radiotherapy; Targeted inhibitors