Targeted therapy for BRAFV600E malignant astrocytoma.
OBJECTIVE
Malignant astrocytomas (MA) are aggressive central nervous system tumors with poor prognosis. Activating mutation of BRAF (BRAF(V600E)) has been reported in a subset of these tumors, especially in children. We have investigated the incidence of BRAF(V600E) in additional pediatric patient cohorts and examined the effects of BRAF blockade in preclinical models of BRAF(V600E) and wild-type BRAF MA.


METHODS
BRAF(V600E) mutation status was examined in two pediatric MA patient cohorts. For functional studies, BRAF(V600E) MA cell lines were used to investigate the effects of BRAF shRNA knockdown in vitro, and to investigate BRAF pharmacologic inhibition in vitro and in vivo.


RESULTS
BRAF(V600E) mutations were identified in 11 and 10% of MAs from two distinct series of tumors (six of 58 cases total). BRAF was expressed in all MA cell lines examined, among which BRAF(V600E) was identified in four instances. Using the BRAF(V600E)-specific inhibitor PLX4720, pharmacologic blockade of BRAF revealed preferential antiproliferative activity against BRAF(V600E) mutant cells in vitro, in contrast to the use of shRNA-mediated knockdown of BRAF, which inhibited cell growth of glioma cell lines regardless of BRAF mutation status. Using orthotopic MA xenografts, we show that PLX4720 treatment decreases tumor growth and increases overall survival in mice-bearing BRAF(V600E) mutant xenografts, while being ineffective, and possibly tumor promoting, against xenografts with wild-type BRAF.


CONCLUSIONS
Our results indicate a 10% incidence of activating BRAF(V600E) among pediatric MAs. With regard to implications for therapy, our results support evaluation of BRAF(V600E)-specific inhibitors for treating BRAF(V600E) MA patients.
University of California, San Francisco, San Francisco, CA 94158, USA.
Theodore P
TP
Nicolaides
Huifang
H
Li
David A
DA
Solomon
Sujatmi
S
Hariono
Rintaro
R
Hashizume
Krister
K
Barkovich
Suzanne J
SJ
Baker
Barbara S
BS
Paugh
Chris
C
Jones
Tim
T
Forshew
Guy F
GF
Hindley
J Graeme
JG
Hodgson
Jung-Sik
JS
Kim
David H
DH
Rowitch
William A
WA
Weiss
Todd A
TA
Waldman
C David
CD
James
D000293:Adolescent; D019943:Amino Acid Substitution; D000818:Animals; D001254:Astrocytoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D001483:Base Sequence; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007223:Infant; D053208:Kaplan-Meier Estimate; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D013449:Sulfonamides / Q000494:pharmacology; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D055815:Young Adult
D007211:Indoles; C528407:PLX 4720; D013449:Sulfonamides; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf