MEK inhibitors as a novel therapy for neuroblastoma: Their in vitro effects and predicting their efficacy.
BACKGROUND
A recent study reported that relapsed neuroblastomas had frequent RAS-ERK pathway mutations. We herein investigated the effects and pathways of MEK inhibitors, which inhibit the RAS-ERK pathway, as a new molecular-targeted therapy for refractory neuroblastomas.


METHODS
Five neuroblastoma cell lines were treated with trametinib (MEK inhibitor) or CH5126766 (RAF/MEK inhibitor). Growth inhibition was analyzed using a cell viability assay. ERK phosphorylation and the MYCN expression were analyzed by immunoblotting or immunohistochemistry. RAS/RAF mutations were identified by direct sequencing or through the COSMIC database.


RESULTS
Both MEK inhibitors showed growth inhibition effects on cells with ERK phosphorylation, but almost no effect on cells without. In immunoblotting analyses, ERK phosphorylation and MYCN expression were suppressed in ERK active cells by these drugs. Furthermore, phosphorylated-ERK immunohistochemistry corresponded to the drug responses. Regarding the relationship between RAS/Raf mutations and ERK phosphorylation, ERK was phosphorylated in one cell line (NLF) without RAS/Raf mutations.


CONCLUSIONS
MEK inhibitors are a promising molecular-targeted therapeutic option for ERK active neuroblastomas. The efficacy of MEK inhibitors corresponds to ERK phosphorylation, while RAS/RAF mutations are not always detected in drug-sensitive cells. Phosphorylated-ERK immunohistochemistry is thus a useful method to analyze ERK activity and predict the therapeutic effects of MEK inhibitors.
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Tomoko
T
Tanaka
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Mayumi
M
Higashi
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Koseki
K
Kimura
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Junko
J
Wakao
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Shigehisa
S
Fumino
Department of Pediatrics, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Tomoko
T
Iehara
Department of Pediatrics, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Hajime
H
Hosoi
Department of Molecular-Targeting Cancer Prevention, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Toshiyuki
T
Sakai
Department of Pediatric Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan. Electronic address: taji@koto.kpu-m.ac.jp.
Tatsuro
T
Tajiri
D045744:Cell Line, Tumor; D003374:Coumarins / Q000627:therapeutic use*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D058990:Molecular Targeted Therapy / Q000379:methods*; D009364:Neoplasm Recurrence, Local; D009447:Neuroblastoma / Q000175:diagnosis / Q000188:drug therapy*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011728:Pyridones / Q000627:therapeutic use*; D011744:Pyrimidinones / Q000627:therapeutic use*; D015398:Signal Transduction / Q000187:drug effects
D003374:Coumarins; D047428:Protein Kinase Inhibitors; D011728:Pyridones; D011744:Pyrimidinones; C577924:RO5126766; C560077:trametinib
CH5126766; MEK inhibitor; Neuroblastoma; RAF/MEK inhibitor; RAS–ERK pathway; Trametinib