Relationship of DDX1 and NAG gene amplification/overexpression to the prognosis of patients with MYCN-amplified neuroblastoma.
OBJECTIVE
Amplification of the MYCN gene strongly correlates with advanced stage, rapid tumor progression and poor prognosis in neuroblastoma (NB). Several genes in the MYCN amplicon, including the DEAD box polypeptide 1 (DDX1) gene, and neuroblastoma-amplified gene (NAG gene), have been found to be frequently co-amplified with MYCN in NB. The aim of this study was to clarify the prognostic significance of the co-amplification or overexpression of DDX1 and NAG with MYCN.


METHODS
The gene copy numbers and mRNA expression levels of MYCN, DDX1, and NAG in 113 primary NBs were determined by the real-time quantitative polymerase chain reaction or quantitative reverse transcriptase/polymerase chain reaction assay. The relationships between gene co-amplification/overexpression status and stage, age at diagnosis, and overall survival were analyzed.


RESULTS
For evaluating the frequency of DDX1 and NAG co-amplification, it proved appropriate to discriminate NBs with <40 copies of MYCN amplification from those with > or =40 copies of MYCN (DDX1, p = 0.00058; NAG, p = 0.0242, chi(2) for independence test). In patients with MYCN-amplified NB aged > or =18 months, those with tumor with enhanced DDX1 expression and low-NAG expression showed a significantly better outcome than those with low-DDX1 expression or enhanced NAG expression (p = 0.0245, log-rank test). None of the gene expression statuses had a significant relation to disease stage or survival for patients <18 months old. No relationship between any gene co-amplification status and disease stage, age at diagnosis, or overall survival was found.


CONCLUSIONS
Our findings suggest that there may be a subset of NB in which enhanced DDX1 and low-NAG expression consequent to DDX1 co-amplification without NAG amplification contributes to susceptibility to intensive therapy. A larger study using an age cut-off of 18 months will be required.
Kaneko
Setsuko
S
Department of Pediatric Surgery, Institute of Clinical Medicine, University of Tsukuba, Ibaraki 305-8575, Japan. mkaneko@md.tsukuba.ac.jp
Ohira
Miki
M
Nakamura
Yohko
Y
Isogai
Eriko
E
Nakagawara
Akira
A
Kaneko
Michio
M
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D053487:DEAD-box RNA Helicases / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D018572:Disease-Free Survival; D005784:Gene Amplification / Q000235:genetics*; D018628:Gene Dosage / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009363:Neoplasm Proteins / Q000235:genetics*; D009447:Neuroblastoma / Q000235:genetics* / Q000401:mortality / Q000628:therapy; D011379:Prognosis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D016019:Survival Analysis; D015996:Survival Rate; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; C117339:NBAS protein, human; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C086252:DDX1 protein, human; D053487:DEAD-box RNA Helicases