Gene Summary

Gene:DDX1; DEAD-box helicase 1
Aliases: DBP-RB, UKVH5d
Summary:DEAD box proteins, characterized by the conserved motif Asp-Glu-Ala-Asp (DEAD), are putative RNA helicases. They are implicated in a number of cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. Based on their distribution patterns, some members of this family are believed to be involved in embryogenesis, spermatogenesis, and cellular growth and division. This gene encodes a DEAD box protein of unknown function. It shows high transcription levels in 2 retinoblastoma cell lines and in tissues of neuroectodermal origin. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:ATP-dependent RNA helicase DDX1
Source:NCBIAccessed: 01 September, 2019


What does this gene/protein do?
Show (29)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Nuclear Proteins
  • Neuroblastoma
  • myc Genes
  • Chromosome 2
  • Gene Expression Profiling
  • Turkey
  • Tumor Suppressor Proteins
  • DEAD-box RNA Helicases
  • Genetic Predisposition
  • RNA Helicases
  • Chromosome Mapping
  • Up-Regulation
  • Alveolar Rhabdomyosarcoma
  • Staging
  • Oligonucleotide Array Sequence Analysis
  • Neoplasm Proteins
  • Infant
  • Cancer RNA
  • DDX1
  • Wilms Tumour
  • Base Sequence
  • Newborns
  • Cancer Gene Expression Regulation
  • Polymerase Chain Reaction
  • Survival Rate
  • N-Myc Proto-Oncogene Protein
  • Childhood Cancer
  • Molecular Sequence Data
  • Biomarkers, Tumor
  • Messenger RNA
  • Gene Amplification
  • RNA Nucleotidyltransferases
  • Cancer DNA
  • Transcriptional Activation
  • Retinoblastoma
  • Gene Dosage
  • Oncogene Proteins
  • FISH
  • DNA, Complementary
Tag cloud generated 01 September, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: DDX1 (cancer-related)

Tanaka K, Ikeda N, Miyashita K, et al.
DEAD box protein DDX1 promotes colorectal tumorigenesis through transcriptional activation of the LGR5 gene.
Cancer Sci. 2018; 109(8):2479-2489 [PubMed] Free Access to Full Article Related Publications
DDX1, a member of the DEAD box RNA helicase family, plays a critical role in testicular tumors. However, it remains to be clarified whether DDX1 is involved in other types of malignant tumors such as colorectal cancer. We disrupted the DDX1 gene in a human colorectal cancer cell line LoVo using the CRISPR/Cas9-mediated gene-targeting system. DDX1-KO LoVo cells exhibited a much slower growth rate, produced fewer colonies in soft agar medium, and generated smaller solid tumors in nude mice than parental LoVo cells. Such phenotypes of the DDX1-KO cells were mostly reversed by exogenous expression of DDX1. These results indicate that DDX1 is required for tumorigenicity of colorectal cancer cells. In the DDX1-KO cells, the cancer stem cell marker genes LGR5, CD133, ALDH1 and SOX2 were markedly suppressed. Among them, expression of LGR5, which is essential for tumorigenicity of colorectal cancer cells, was restored in the DDX1-transfected DDX1-KO cells. Consistently, the DDX1-KO cells lost sphere-forming capacity in a DDX1-dependent fashion. Reporter and chromatin immunoprecipitation assays revealed that DDX1 directly bound to the -1837 to -1662 region of the enhancer/promoter region of the human LGR5 gene and enhanced its transcription in LoVo cells. Repression of LGR5 by DDX1 knockdown was observed in 2 other human colorectal cancer cell lines, Colo320 and SW837. These results suggest that LGR5 is a critical effector of DDX1 in colorectal cancer cells. The DDX1-LGR5 axis could be a new drug target for this type of malignant cancer.

Koenig AB, Barajas JM, Guerrero MJ, Ghoshal K
A Comprehensive Analysis of Argonaute-CLIP Data Identifies Novel, Conserved and Species-Specific Targets of miR-21 in Human Liver and Hepatocellular Carcinoma.
Int J Mol Sci. 2018; 19(3) [PubMed] Free Access to Full Article Related Publications
MicroRNAs are ~22 nucleotide RNAs that regulate gene expression at the post-transcriptional level by binding messenger RNA transcripts. miR-21 is described as an oncomiR whose steady-state levels are commonly increased in many malignancies, including hepatocellular carcinoma (HCC). Methods known as cross-linking and immunoprecipitation of RNA followed by sequencing (CLIP-seq) have enabled transcriptome-wide identification of miRNA interactomes. In our study, we use a publicly available Argonaute-CLIP dataset (GSE97061), which contains nine HCC cases with matched benign livers, to characterize the miR-21 interactome in HCC. Argonaute-CLIP identified 580 miR-21 bound target sites on coding transcripts, of which 332 were located in the coding sequences, 214 in the 3'-untranslated region, and 34 in the 5'-untranslated region, introns, or downstream sequences. We compared the expression of miR-21 targets in 377 patients with liver cancer from the data generated by The Cancer Genome Atlas (TCGA) and found that mRNA levels of 402 miR-21 targets are altered in HCC. Expression of three novel predicted miR-21 targets (CAMSAP1, DDX1 and MARCKSL1) correlated with HCC patient survival. Analysis of RNA-seq data from SK-Hep1 cells treated with a miR-21 antisense oligonucleotide (GSE65892) identified RMND5A, an E3 ubiquitin ligase, as a strong miR-21 candidate target. Collectively, our analysis identified novel miR-21 targets that are likely to play a causal role in hepatocarcinogenesis.

He L, Chen Y, Wu Y, et al.
Nucleic acid sensing pattern recognition receptors in the development of colorectal cancer and colitis.
Cell Mol Life Sci. 2017; 74(13):2395-2411 [PubMed] Related Publications
Colorectal cancer (CRC) is a leading cause of cancer-related deaths that is often associated with inflammation initiated by activation of pattern recognition receptors (PRRs). Nucleic acid sensing PRRs are one of the major subsets of PRRs that sense nucleic acid (DNA and RNA), mainly including some members of Toll-like receptors (TLR3, 7, 8, 9), AIM2-like receptors (AIM2, IFI16), STING, cGAS, RNA polymerase III, and DExD/H box nucleic acid helicases (such as RIG-I like receptors (RIG-I, MDA5, LPG2), DDX1, 3, 5, 7, 17, 21, 41, 60, and DHX9, 36). Activation of these receptors eventually leads to the release of cytokines and activation of immune cells, which are well known to play crucial roles in host defense against intracellular bacterial and virus infection. However, the functions of these nucleic acid sensing PRRs in the other diseases such as CRC and colitis remain largely unknown. Recent studies indicated that nucleic acid sensing PRRs contribute to CRC and/or colitis development, and therapeutic modulation of nucleic acid sensing PRRs may reduce the risk of CRC development. However, until now, a comprehensive review on the role of nucleic acid sensing PRRs in CRC and colitis is still lacking. This review provided an overview of the roles as well as the mechanisms of these nucleic acid sensing PRRs (AIM2, STING, cGAS, RIG-I and its downstream molecules, DDX3, 5, 6,17, and DHX9, 36) in CRC and colitis, which may aid the diagnosis, therapy, and prognostic prediction of CRC and colitis.

Akter KA, Mansour MA, Hyodo T, Senga T
FAM98A associates with DDX1-C14orf166-FAM98B in a novel complex involved in colorectal cancer progression.
Int J Biochem Cell Biol. 2017; 84:1-13 [PubMed] Related Publications
Protein Arginine Methyl Transferase 1 (PRMT1) is deemed to be a potential oncogenic protein considering its overexpression in several malignancies including colorectal cancer. However, the molecular pathogenesis regarding PRMT1 overexpression and overall poor patient survival involved in this devastating and life threatening cancer remains obscured. In our previous study, we have identified FAM98A as a novel substrate of PRMT1 and also identified its role in ovarian cancer progression. Here, we showed that the two structural homologs FAM98A and FAM98B included in a novel complex with DDX1 and C14orf166 are required for PRMT1 expression. Analysis of the data from The Cancer Genome Atlas (TCGA) database and clinical colorectal cancer specimens also demonstrated a strong positive correlation and co-occurrence of PRMT1, FAM98A and FAM98B. These findings provide a mechanistic insight into how knockdown of FAM98A or FAM98B can suppress the malignant characteristics of cancer cells. Besides, we showed that FAM98A and FAM98B are working in the same axis as knockdown of both proteins together does not cause additional reduction in the cellular proliferation and colony formation of colorectal cancer cells.

Micale MA, Embrey B, Macknis JK, et al.
Constitutional 560.49 kb chromosome 2p24.3 duplication including the MYCN gene identified by SNP chromosome microarray analysis in a child with multiple congenital anomalies and bilateral Wilms tumor.
Eur J Med Genet. 2016; 59(12):618-623 [PubMed] Related Publications
Fewer than 100 patients with partial chromosome 2p trisomy have been reported. Clinical features are variable and depend on the size of the duplicated segment, but generally include psychomotor delay, facial anomalies, congenital heart defect, and other abnormalities. We report a 560.49 kb duplication of chromosome 2p in a 13 month-old male with hydrocephaly, ventricular septal defect, partial agenesis of the corpus callosum, and bilateral Wilms tumor. After discovery of bilateral renal masses at four months of age, the child underwent neoadjuvant chemotherapy followed by right radical nephrectomy that revealed triphasic Wilms' tumor. A needle core biopsy on one of two lesions on the left kidney also revealed Wilms tumor. A partial left nephrectomy revealed focally positive margins that necessitated left flank radiotherapy. The tumor karyotype was 46,XY,t(7;8)(q36;p11)[8]/46,XY [12] while his constitutional karyotype was 46,XY, suggesting that the t(7;8)(q36;p11) was associated with the malignancy. Single nucleotide polymorphism (SNP) chromosome microarray analysis of peripheral blood identified a maternally-inherited 560.49 kb chromosome 2p24.3 duplication that involved four OMIM genes: NBAS, DDX1, MYCNOS, and MYCN. SNP array analysis of the tumor revealed the same 2p24.3 duplication. At present, the now 5-year-old boy continues to do well without clinical or radiographic evidence of recurrent disease. This case is instructive because the child's health insurer initially denied authorization for chromosome microarray analysis (CMA), and it took more than one year before such authorization was finally granted. That initial decision to deny coverage could have had untoward health implications for this child, as the identification of constitutional MYCN duplication necessitated surveillance imaging for a number of pediatric malignancies associated with MYCN overexpression/dysregulation.

Pastuszak-Lewandoska D, Kordiak J, Migdalska-Sęk M, et al.
Quantitative analysis of mRNA expression levels and DNA methylation profiles of three neighboring genes: FUS1, NPRL2/G21 and RASSF1A in non-small cell lung cancer patients.
Respir Res. 2015; 16:76 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Tumor suppressor gene (TSG) inactivation plays a crucial role in carcinogenesis. FUS1, NPRL2/G21 and RASSF1A are TSGs from LUCA region at 3p21.3, a critical chromosomal region in lung cancer development. The aim of the study was to analyze and compare the expression levels of these 3 TSGs in NSCLC, as well as in macroscopically unchanged lung tissue surrounding the primary lesion, and to look for the possible epigenetic mechanism of TSG inactivation via gene promoter methylation.
METHODS: Expression levels of 3 TSGs and 2 DNA methyltransferases, DNMT1 and DNMT3B, were assessed using real-time PCR method (qPCR) in 59 primary non-small cell lung tumors and the matched macroscopically unchanged lung tissue samples. Promoter methylation status of TSGs was analyzed using methylation-specific PCRs (MSP method) and Methylation Index (MI) value was calculated for each gene.
RESULTS: The expression of all three TSGs were significantly different between NSCLC subtypes: RASSF1A and FUS1 expression levels were significantly lower in squamous cell carcinoma (SCC), and NPRL2/G21 in adenocarcinoma (AC). RASSF1A showed significantly lower expression in tumors vs macroscopically unchanged lung tissues. Methylation frequency was 38-76%, depending on the gene. The highest MI value was found for RASSF1A (52%) and the lowest for NPRL2/G21 (5%). The simultaneous decreased expression and methylation of at least one RASSF1A allele was observed in 71% tumor samples. Inverse correlation between gene expression and promoter methylation was found for FUS1 (rs = -0.41) in SCC subtype. Expression levels of DNMTs were significantly increased in 75-92% NSCLCs and were significantly higher in tumors than in normal lung tissue. However, no correlation between mRNA expression levels of DNMTs and DNA methylation status of the studied TSGs was found.
CONCLUSIONS: The results indicate the potential role of the studied TSGs in the differentiation of NSCLC histopathological subtypes. The significant differences in RASSF1A expression levels between NSCLC and macroscopically unchanged lung tissue highlight its possible diagnostic role in lung cancer in situ recognition. High percentage of lung tumor samples with simultaneous RASSF1A decreased expression and gene promoter methylation indicates its epigenetic silencing. However, DNMT overexpression doesn't seem to be a critical determinate of its promoter hypermethylation.

Han C, Liu Y, Wan G, et al.
The RNA-binding protein DDX1 promotes primary microRNA maturation and inhibits ovarian tumor progression.
Cell Rep. 2014; 8(5):1447-60 [PubMed] Free Access to Full Article Related Publications
Posttranscriptional maturation is a critical step in microRNA (miRNA) biogenesis that determines mature miRNA levels. In addition to core components (Drosha and DGCR8 [DiGeorge syndrome critical region gene 8]) in the microprocessor, regulatory RNA-binding proteins may confer the specificity for recruiting and processing of individual primary miRNAs (pri-miRNAs). Here, we identify DDX1 as a regulatory protein that promotes the expression of a subset of miRNAs, including five members in the microRNA-200 (miR-200) family and four miRNAs in an eight-miRNA signature of a mesenchymal ovarian cancer subtype. A majority of DDX1-dependent miRNAs are induced after DNA damage. This induction is facilitated by the ataxia telangiectasia mutated (ATM)-mediated phosphorylation of DDX1. Inhibiting DDX1 promotes ovarian tumor growth and metastasis in a syngeneic mouse model. Analysis of The Cancer Genome Atlas (TCGA) reveals that low DDX1 levels are associated with poor clinical outcome in patients with serous ovarian cancer. These findings suggest that DDX1 is a key modulator in miRNA maturation and ovarian tumor suppression.

Johanneson B, Chen D, Enroth S, et al.
Systematic validation of hypothesis-driven candidate genes for cervical cancer in a genome-wide association study.
Carcinogenesis. 2014; 35(9):2084-8 [PubMed] Related Publications
A large number of genetic associations with cervical cancer have been reported in hypothesis-driven candidate gene studies, but most studies have not included an independent replication or the results have been inconsistent between studies. In order to independently validate these associations, we reexamined 58 candidate gene/regions previously reported to be associated with cervical cancer using the gene-based Adaptive Rank Truncated Product test in a genome-wide association study (GWAS) of 1034 cervical cancer patients and 3948 controls from the Swedish population. Of the 58 gene/regions, 8 had a nominal P value < 0.05 [tumor necrosis factor (TNF), P = 5.0 × 10(-4); DEAD (Asp-Glu-Ala-Asp) box helicase 1 [DDX1], P = 2.2 × 10(-3); exonuclease 1 [EXO1], P = 4.7 × 10(-3); excision repair cross-complementing rodent repair deficiency, complementation group 1 [ERCC1], P = 0.020; transmembrane channel-like 6 and 8 genes [TMC6-TMC8], P = 0.023; secreted phosphoprotein 1 [SPP1], P = 0.028; v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 [ERBB2], P = 0.033 and chloride channel, voltage-sensitive 7 [CLCN7], P = 0.047). After correction for multiple testing, only TNF remained statistically significant (P = 0.028). Two single-nucleotide polymorphisms that are in nearly perfect linkage disequilibrium (rs2857602 and rs2844484) contributed most to the association with TNF. However, they are not independent from the previously reported associations within the MHC region. The very low number of previously reported associations with cervical cancer that replicate in the Swedish population underscore the need to apply more stringent criteria when reporting associations, including the prerequisite of replicating the association as part of the original study.

Fievet A, Belaud-Rotureau MA, Dugay F, et al.
Involvement of germline DDX1-MYCN duplication in inherited nephroblastoma.
Eur J Med Genet. 2013; 56(12):643-7 [PubMed] Related Publications
This report concerns a 3-year-old girl with prenatal bilateral nephroblastomatosis and a family history of nephroblastoma. This girl had a chromosome 8 pericentric inversion inherited from her father. This inversion was observed in healthy individuals of the family and was absent in other individuals suffering from embryonic kidney tumor. We then supposed that another genetic anomaly predisposed her to tumorogenesis. Additional cryptic imbalances are reported in cases of apparently balanced chromosomal rearrangements with an abnormal phenotype. Array-CGH analysis showed a 569 kb duplication at 2p24.3 including the DDX1 and MYCN genes. This duplication was inherited from the patient's father who also had a nephroblastoma. A link between germline MYCN duplication and the occurrence of other embryonic cancers such as neuroblastoma has already been described. We supposed that germline DDX1-MYCN duplication could also be involved in the apparition of nephroblastomas.

Bagci O, Tumer S, Olgun N, Altungoz O
Copy number status and mutation analyses of anaplastic lymphoma kinase (ALK) gene in 90 sporadic neuroblastoma tumors.
Cancer Lett. 2012; 317(1):72-7 [PubMed] Related Publications
Somatic and germline mutations of the anaplastic lymphoma kinase (ALK) gene were recently described in neuroblastoma (NB). In this study, we investigated the association of ALK copy number alterations with copy number status 2p24.1 amplicon harboring DEAD box polypeptide 1 (DDX1), MYCN and neuroblastoma-amplified (NAG) genes in 90 primary tumors of sporadic NB cases by multiplex ligation-dependent probe amplification (MLPA). We also performed mutation analysis of ALK gene by directly sequencing the exons 20-28 which cover the region that encodes juxtamembrane and kinase domains. A total of 39 (43.3%) NB cases revealed copy numbers alterations of ALK gene. There was highly significant association of ALK copy number gains with gains of one or more of the genes at 2p24.1 (DDX1, MYCN or NAG) in MYCN unamplified tumors (P<0.000). In addition, 15 of 17 MYCN amplified cases (88.2%) had aberrant ALK status. Solitary gain of ALK with normal copy number status of all other genes was observed only in one case. DNA sequencing of exons 20-28 of ALK revealed two different nucleotide changes in three cases leading to amino acid substitutions of F1245V and R1275Q in tyrosine kinase domain. In conclusion, the frequency of ALK mutations in NB is low and solitary copy number change of it is rarely observed.

Taunk NK, Goyal S, Wu H, et al.
DEAD box 1 (DDX1) expression predicts for local control and overall survival in early stage, node-negative breast cancer.
Cancer. 2012; 118(4):888-98 [PubMed] Related Publications
BACKGROUND: DEAD box 1 (DDX1) is an RNA helicase with a number of roles, including translation initiation, RNA splicing and modification, and possibly DNA double-strand break repair. Amplification of DDX1 expression has been implicated in tumors including neuroblastoma, Wilms tumor, retinoblastoma, and testicular carcinoma. The purpose of this study was to evaluate the prognostic significance of DDX1 expression in patients with breast cancer treated with breast-conserving therapy.
METHODS: Paraffin-embedded specimens from 282 women with node-negative stage 1 and 2 breast cancer treated with breast-conserving surgery and radiation therapy were constructed into tissue microarrays and stained for DDX1. The molecular profiles were correlated with clinicopathologic factors and overall, local, and distant metastatic-free survival.
RESULTS: DDX1 positivity was identified in 142 (50%) patients. The median age at diagnosis was 53 years. Eighty percent of the patients had T1 disease; 11% were HER2neu-positive, and 18% had triple-negative disease. DDX1 negativity was strongly associated with triple-negative phenotype (P = .01). DDX1 positivity was found to be associated with improved local relapse-free survival (96% vs 85%, P = .0233), distant metastatic-free survival (95% vs 85%, P = .0320), and overall survival (92% vs 84%, P = .0474) at 10 years.
CONCLUSIONS: Node-negative, early stage breast cancer patients with high levels of DDX1 were found to have a significant improvement in local control, distant metastatic-free survival, and overall survival compared with patients with low levels of DDX1.

de Souza DR, Sanabani SS, de Souza AC, et al.
Prognostic impact of MYCN, DDX1, TrkA, and TrkC gene transcripts expression in neuroblastoma.
Pediatr Blood Cancer. 2011; 56(5):749-56 [PubMed] Related Publications
BACKGROUND: The aims of this study were to define the mRNA expression profiles of MYCN, DDX1, TrkA, and TrkC in biopsy tumor samples from 64 Brazilian patients with neuroblastomas of different risk stages and to correlate altered expression with prognostic values.
PROCEDURE: Patients were retrospectively classified into low- (n = 11), intermediate- (n = 18), and high-risk (n = 35) groups using standard criteria. The mRNA levels of the above genes were measured by quantitative real-time polymerase chain reaction. Univariate analyses were performed and survival curves were plotted by the Kaplan-Meier method.
RESULTS: Of the 64 patients, 53% were female and 62.5% were older than 18 months. The 5-year overall survival (OS) for the entire cohort was 40.3%, with inferior median OS in patients identified in the intermediate- and high-risk groups. A significant difference in OS with respect to TrkA mRNA expression was found for the high-risk group vs. either the low- or intermediate-risk groups (P < 0.01, log rank test). Within the intermediate-risk group, neuroblastoma patients with positive TrkA mRNA expression had better clinical outcomes than patients with no TrkA transcript expression (P = 0.004). Another difference in OS was only found between the intermediate- and high-risk groups (P < 0.027, log rank test). No significant correlation of mRNA expression and survival outcome could be detected for the MYCN, DDX1.
CONCLUSIONS: Positive expression of TrkA mRNA may be a clinically useful addition to the current risk classification system, allowing the identification of NB tumors with favorable prognosis.

Germain DR, Graham K, Glubrecht DD, et al.
DEAD box 1: a novel and independent prognostic marker for early recurrence in breast cancer.
Breast Cancer Res Treat. 2011; 127(1):53-63 [PubMed] Related Publications
Breast cancer is a heterogeneous disease characterized by diverse molecular signatures and a variable response to therapy. Clinical management of breast cancer is guided by the expression of estrogen and progesterone receptors and HER2 amplification. New prognostic and predictive markers, as well as additional targets for therapy, are needed for more effective management of this disease. Gene expression microarrays were probed with RNAs from 176 primary breast cancer samples and tissue microarrays immunostained with anti-DDX1 antibody, an antibody to DEAD box protein DDX1, a putative RNA-RNA and RNA-DNA unwinding protein normally found in the nucleus. Half of the patient cohort had experienced early relapse despite standard adjuvant therapy, but were otherwise matched for estrogen receptor and HER2 status, stage and duration of follow-up. Here, we identify DDX1 RNA overexpression as an independent prognostic marker for early recurrence in primary breast cancer, with a hazard ratio of 4.31 based on logrank analysis of Kaplan-Meier curves. Elevated levels of DDX1 protein in the cytoplasm also independently correlate with early recurrence with a hazard ratio of 1.90. In conclusion, our data indicate a strong and independent association between poor prognosis and deregulation of the DEAD box protein DDX1. We propose that elevated levels of DDX1 RNA or the presence of DDX1 in the cytoplasm could serve as an effective prognostic biomarker for early recurrence in primary breast cancer.

Noguera R, Villamón E, Berbegall A, et al.
Gain of MYCN region in a Wilms tumor-derived xenotransplanted cell line.
Diagn Mol Pathol. 2010; 19(1):33-9 [PubMed] Related Publications
Wilms tumor is one of the most common pediatric malignant tumors of the kidney. Although the WT1 gene, located at 11p13, has been proven to be implicated in the development of Wilms tumor, other genes such as MYCN are also involved. The purpose of this study is to genetically characterize a Wilms tumor metastasis xenotransplanted in nude mice. Immunogenotype evolution of the xenografts material was monitored for 29 months using molecular techniques, fluorescent in situ hybridization and multiplex ligation-dependent probe amplification, in addition to immunohistochemistry in tissue microarrays. Genetic alterations present in the original tumor and retained in the xenotransplanted tumor were located in +1q, +3, +6, -7p, +7q, +8, -9p, +9q, +12. The multiplex ligation-dependent probe amplification detected a nondeleted status of genes located close to WT genes, except for a deletion of the EGFR gene (located at 7p11.2) and the GHRHR gene (located at 7p15), both flanking the WT5 gene. The MYCN gene (2p24 exon 3) and DDX1 gene (2p24 exons 2, 7, 15, and 24) were gained in passage 4 and the following passages. MYCN expression was positive from the beginning, without evidence of MYCN gain by fluorescent in situ hybridization. Histopathologic and growth rate changes were observed at those passages where low extra copy number of MYCN was present. In addition to other genetic abnormalities, the WT5 gene located at 7p13-14 is deleted and the MYCN gene gain began after 16 months in vivo evolution in athymic nude mice. MYCN is already used as a stratifying marker in neuroblastomas, and it may be also useful in implementing MYCN testing in prospective studies of Wilms tumors.

Barr FG, Duan F, Smith LM, et al.
Genomic and clinical analyses of 2p24 and 12q13-q14 amplification in alveolar rhabdomyosarcoma: a report from the Children's Oncology Group.
Genes Chromosomes Cancer. 2009; 48(8):661-72 [PubMed] Free Access to Full Article Related Publications
Alveolar rhabdomyosarcoma (ARMS) is an aggressive pediatric cancer that is related to the skeletal muscle lineage and characterized by recurrent chromosomal translocations. Within the ARMS category, there is clinical and genetic heterogeneity, consistent with the premise that "primary" genetic events collaborate with "secondary" events to give rise to subsets with varying clinical features. Previous studies demonstrated that genomic amplification occurs frequently in ARMS. In the current study, we used oligonucleotide arrays to localize two common amplicons to the 2p24 and 12q13-q14 chromosomal regions. Based on the copy number array data, we sublocalized the minimum common regions of 2p24 and 12q13-q14 amplification to a 0.83 Mb region containing the DDX1 and MYCN genes, and a 0.55 Mb region containing 27 genes, respectively. Using fluorescent in situ hybridization assays to measure copy number of the 2p24 and 12q13-q14 regions in over 100 cases, we detected these amplicons in 13% and 12% of cases, respectively. Comparison with fusion status revealed that 2p24 amplification occurred preferentially in cases positive for PAX3-FOXO1 or PAX7-FOXO1 while 12q13-q14 amplification occurred preferentially in PAX3-FOXO1-positive cases. Expression studies demonstrated that MYCN was usually overexpressed in cases with 2p24 amplification while multiple genes were overexpressed in cases with 12q13-q14 amplification. Finally, although 2p24 amplification did not have a significant association with clinical outcome, 12q13-q14 amplification was associated with significantly worse failure-free and overall survival that was independent of gene fusion status.

Tanaka K, Okamoto S, Ishikawa Y, et al.
DDX1 is required for testicular tumorigenesis, partially through the transcriptional activation of 12p stem cell genes.
Oncogene. 2009; 28(21):2142-51 [PubMed] Related Publications
Cytogenetic analysis has identified 12p gain as the most frequent abnormality in human testicular germ cell tumors (TGCTs). It has been suggested that amplification and overexpression of stem cell-associated genes, including cyclin-D2, on the human chromosome 12p region are involved in germ cell tumorigenesis. By subtractive cDNA analysis, we identified Ddx1, a member of the DEAD-box protein family, as a gene predominantly expressed in the primordial germ cells of mouse embryos. Knockdown of Ddx1 in a mouse spermatogonia-derived cell line, GC-1spg, by short interference RNA repressed the expression of cyclin-D2, CD9 and GDF3 genes. In the mouse cyclin-D2 gene, a genomic DNA region between -348 and -329 was responsible for transcriptional activation by DDX1 based on reporter and gel shift assays. Similarly, DDX1 knockdown in the human TGCT cell line NEC8 repressed the expression of stem cell-associated genes localized on chromosome 12p13.3, including cyclin-D2, CD9 and NANOG. DDX1-knocked-down TGCT cells could not form solid tumors in nude mice. Furthermore, in situ hybridization revealed that DDX1 mRNA was produced in both seminoma and nonseminoma types of human TGCT samples. We conclude that DDX1 is a critical factor for testicular tumorigenesis.

Hodgson JG, Yeh RF, Ray A, et al.
Comparative analyses of gene copy number and mRNA expression in glioblastoma multiforme tumors and xenografts.
Neuro Oncol. 2009; 11(5):477-87 [PubMed] Free Access to Full Article Related Publications
Development of model systems that recapitulate the molecular heterogeneity observed among glioblastoma multiforme (GBM) tumors will expedite the testing of targeted molecular therapeutic strategies for GBM treatment. In this study, we profiled DNA copy number and mRNA expression in 21 independent GBM tumor lines maintained as subcutaneous xenografts (GBMX), and compared GBMX molecular signatures to those observed in GBM clinical specimens derived from the Cancer Genome Atlas (TCGA). The predominant copy number signature in both tumor groups was defined by chromosome-7 gain/chromosome-10 loss, a poor-prognosis genetic signature. We also observed, at frequencies similar to that detected in TCGA GBM tumors, genomic amplification and overexpression of known GBM oncogenes, such as EGFR, MDM2, CDK6, and MYCN, and novel genes, including NUP107, SLC35E3, MMP1, MMP13, and DDX1. The transcriptional signature of GBMX tumors, which was stable over multiple subcutaneous passages, was defined by overexpression of genes involved in M phase, DNA replication, and chromosome organization (MRC) and was highly similar to the poor-prognosis mitosis and cell-cycle module (MCM) in GBM. Assessment of gene expression in TCGA-derived GBMs revealed overexpression of MRC cancer genes AURKB, BIRC5, CCNB1, CCNB2, CDC2, CDK2, and FOXM1, which form a transcriptional network important for G2/M progression and/or checkpoint activation. Our study supports propagation of GBM tumors as subcutaneous xenografts as a useful approach for sustaining key molecular characteristics of patient tumors, and highlights therapeutic opportunities conferred by this GBMX tumor panel for testing targeted therapeutic strategies for GBM treatment.

Godbout R, Li L, Liu RZ, Roy K
Role of DEAD box 1 in retinoblastoma and neuroblastoma.
Future Oncol. 2007; 3(5):575-87 [PubMed] Related Publications
Analysis of hereditary and nonhereditary retinoblastoma led to the formulation of the two-hit hypothesis of cancer in the early 1970s. The two-hit hypothesis was validated in the 1980s when both copies of the RB1 gene were shown to be mutated in hereditary and nonhereditary retinoblastoma. However, consistent genetic abnormalities other than RB1 mutations suggest that additional events may be required for the formation of these malignant tumors. For example, MYCN amplification has long been known to occur in both retinoblastoma and neuroblastoma tumors and is strongly associated with poor prognosis in neuroblastoma. The DEAD box gene, DEAD box 1 (DDX1), is often coamplified with MYCN in both these childhood tumors. Here, we examine possible roles for DDX1 overexpression in retinoblastoma and neuroblastoma.

Defferrari R, Tonini GP, Conte M, et al.
Concomitant DDX1 and MYCN gain in neuroblastoma.
Cancer Lett. 2007; 256(1):56-63 [PubMed] Related Publications
DDX1, a gene mapping to the 2p24 region, has been observed to be co-amplified with MYCN in neuroblastoma. Co-amplification of the DDX1 gene is a consequence of the short physical distance between the two genes. Recently, it has been found that neuroblastoma cells can show a low increase in MYCN gene copy number, defined as MYCN gain. We studied 13 neuroblastomas with MYCN gain to evaluate the status of the DDX1 gene. We investigated DDX1/MYCN gain by double-colour FISH on interphase nuclei. All cases showed concomitant low extra copy number of DDX1 and MYCN. Heterogeneous distribution of nuclei displaying DDX1/MYCN gain was observed in almost all tumours, suggesting a clonal evolution of cells with DDX1/MYCN gain. This is the first report that shows DDX1 co-gained with MYCN in neuroblastoma and indicates that DDX1 over-representation is closely associated with an increase in MYCN copy number in neuroblastoma cells. Since DDX1 has already been found co-amplified with MYCN, DDX1 gain seems to be a further rearrangement due to the physical proximity of the two genes. Moreover, all patients with DDX1/MYCN gain show a good overall survival but a high frequency of adverse events.

Sunden Y, Semba S, Suzuki T, et al.
Identification of DDX1 as a JC virus transcriptional control region-binding protein.
Microbiol Immunol. 2007; 51(3):327-37 [PubMed] Related Publications
To investigate the mechanism behind JC virus (JCV) cell specificity we performed electrophoretic mobility shift assays (EMSA) using probes derived from the JCV transcriptional control region (JCV-TCR). Using nuclear extracts from the JCV-susceptible neuroblastoma cell line IMR-32, EMSA revealed a 670 kDa JCV-TCR-binding protein complex designated as #3-bp. This complex could not be detected in nuclear extracts from non-susceptible cell lines. Using column chromatographic purifi-cation and microsequencing, we identified cleavage stimulation factor (CstF) as a component of #3-bp. However, as CstF is present in many cell types, we speculated that the IMR-32-specific component(s) of #3-bp bind CstF. We performed a yeast two-hybrid assay using CstF-77 as the bait against a HeLa cDNA-subtracted IMR-32 cDNA library. This analysis detected binding between CstF-77 and the RNA helicase DDX1. Subsequently, biotinylated DNA affinity precipitation and chromatin immunoprecipitation assays also confirmed that DDX1 binds specifically to JCV-TCR. Our findings indicate that an association between DDX1 and the JCV-TCR may play a significant role in JCV infection in IMR-32 cells.

Lo KC, Rossi MR, Burkhardt T, et al.
Overlay analysis of the oligonucleotide array gene expression profiles and copy number abnormalities as determined by array comparative genomic hybridization in medulloblastomas.
Genes Chromosomes Cancer. 2007; 46(1):53-66 [PubMed] Related Publications
Combined analysis of gene expression array data and array-based comparative genomic hybridization data have been used in a series of 26 pediatric brain tumors to define up- and downregulated genes that coincide with losses, gains, and amplifications involving specific chromosome regions. Frequent losses were defined in chromosome arms 3q, 6q, 8p, 10q, 16q, 17p, and gains were identified in chromosome 7, and chromosome arms 9p and 17q. Amplification of a 2p region was seen in only one tumor, which corresponded to increased expression of the MYCN and DDX1 genes. To facilitate the analysis of the two data sets, we have developed a custom overlay tool that defines genes that are underexpressed in regions of deletions and overexpressed in regions of gain, across the genome and specifically within regions showing recurrent involvement in medulloblastomas.

Kaneko S, Ohira M, Nakamura Y, et al.
Relationship of DDX1 and NAG gene amplification/overexpression to the prognosis of patients with MYCN-amplified neuroblastoma.
J Cancer Res Clin Oncol. 2007; 133(3):185-92 [PubMed] Related Publications
PURPOSE: 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.
PROCEDURE: 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.

Abdelhaleem M
Do human RNA helicases have a role in cancer?
Biochim Biophys Acta. 2004; 1704(1):37-46 [PubMed] Related Publications
Human RNA helicases (HRH) represent a large family of enzymes that play important roles in RNA processing. The biochemical characteristics and biological functions of the majority of HRH are still to be determined. However, there are examples of dysregulation of HRH expression in various types of cancer. In addition, some HRH have been shown to be involved in the regulation of, or the molecular interaction with, molecules implicated in cancer. Other helicases take part in fusion transcripts resulting from cancer-associated chromosomal translocation. These findings raise the question of whether HRH can contribute to cancer development/progression. In this review, I summarize the cancer-related features of HRH.

Weber A, Imisch P, Bergmann E, Christiansen H
Coamplification of DDX1 correlates with an improved survival probability in children with MYCN-amplified human neuroblastoma.
J Clin Oncol. 2004; 22(13):2681-90 [PubMed] Related Publications
PURPOSE: Amplification of the MYCN oncogene at chromosome 2p24-25 identifies an aggressive subtype of human neuroblastoma with a poor clinical outcome. Differences in amplicon structure and coamplification of genes telomeric and centromeric to the MYCN oncogene have previously been described. A relevant role of gene coamplification for neuroblastoma pathogenesis remains elusive.
PATIENTS AND METHODS: We analyzed 98 primary neuroblastoma tumors with MYCN amplification for coamplification of seven additional genes at chromosome 2p24-25 (DDX1, NAG, NSE1, LPIN1, EST-AA581763, SMC6, and SDC1). Two semiquantitative multiplex polymerase chain reactions were used to obtain the amplification status of the target genes in relation to a reference gene on chromosome 2q (Inhibin-beta-b). Furthermore, mRNA expression pattern of coamplified genes in a subset of tumors was analyzed.
RESULTS: Our results show that the frequency of gene coamplification on 2p24-25 in neuroblastoma is correlated directly to the physical distance to MYCN. Coamplification is correlated to an upregulated gene expression for DDX1 and NAG. Coamplification of the DDX1 gene within 400kb telomeric to MYCN identifies a subgroup of advanced stage neuroblastoma tumors with a more favorable outcome (P =.027, log-rank test). A high expression level of DDX1 is associated with a trend towards a better survival probability (P =.058, log-rank test).
CONCLUSION: Our results indicate that DDX1 coamplification correlates with a better prognosis and improved patient survival in MYCN-amplified neurobastoma.

Scott D, Elsden J, Pearson A, Lunec J
Genes co-amplified with MYCN in neuroblastoma: silent passengers or co-determinants of phenotype?
Cancer Lett. 2003; 197(1-2):81-6 [PubMed] Related Publications
Amplification of the MYCN oncogene in neuroblastoma is associated with poor prognosis. The amplified unit of DNA can be up to 1 Mb in size and so could contain additional genes that affect tumour phenotype. Identification of such genes may assist in optimising the determination of prognosis, and could provide new targets for treatment. Three genes have so far been identified, which are frequently co-amplified with MYCN in neuroblastoma, DDX1, NAG and N-cym. In this review, the known or putative properties of the protein products of the genes are discussed, and their possible roles in determining tumour behaviour are assessed.

Scott DK, Board JR, Lu X, et al.
The neuroblastoma amplified gene, NAG: genomic structure and characterisation of the 7.3 kb transcript predominantly expressed in neuroblastoma.
Gene. 2003; 307:1-11 [PubMed] Related Publications
Amplification of the MYCN oncogene in neuroblastoma is associated with poor prognosis. The amplified unit of DNA can be up to 1 Mb in size and so could contain additional genes which affect tumour phenotype. The neuroblastoma amplified gene (NAG) gene was initially located 400 kb telomeric to MYCN at 2p24 and reported to be co-amplified in 5/8 (63%) cell lines and 9/13 (70%) tumours. The sequence of a 4.5 kb transcript was proposed from the analysis of overlapping cDNA clones. However, our Northern blot hybridisation experiments indicate that the main RNA species expressed in neuroblastoma is 7-8 kb in size. We describe for the first time the cloning and sequencing of the 7.3 kb transcript of the NAG gene together with its precise genomic location and full exon structure. The 5' end of the gene is located 30 kb telomeric to DDX1, with the two genes lying in opposite orientations. The 52 exons of the 7.3 kb transcript cover 420 kb of genomic DNA. In vitro translation studies confirmed the protein coding potential of the transcript. Co-amplification of the entire NAG gene with MYCN was found in 1/6 (17%) neuroblastoma cell lines and 10/50 (20%) primary tumours. Previous studies had measured co-amplification of only the 5' end of the gene, nearest to MYCN. In this study, co-amplification of the NAG gene was found to be significantly associated with low disease stage in MYCN-amplified tumours (P=0.0063).

Fischer M, Berthold F
Characterization of the gene expression profile of neuroblastoma cell line IMR-5 using serial analysis of gene expression.
Cancer Lett. 2003; 190(1):79-87 [PubMed] Related Publications
The serial analysis of gene expression (SAGE) technique was used to generate a database of the most abundant transcripts of the MYCN-amplified neuroblastoma cell line IMR-5. A total of 8568 tags were sequenced and shown to represent 4034 unique tags, each of which corresponds to an individual transcript. Expression levels of genes are reflected by the frequency of occurrence of the respective tags. To validate fidelity of SAGE data, relative abundances of seven transcripts were evaluated by semiquantitative reverse transcriptase-polymerase chain reaction. Transcripts that were detected nine times or more (>0.1% of the total tag population) accounted for 36% of the total messenger RNA mass but only 3% of the total number of individual transcripts. A strong preponderance of genes involved in protein synthesis, in particular those encoding for ribosomal proteins, were observed among these high-abundance transcripts. Tags corresponding to the amplified gene DDX1 were conspicuously overrepresented in comparison to the other amplified genes MYCN, neuroblastoma amplified gene and MEIS1, which suggests an additional mechanism apart from genomic amplification contributing to the strong upregulation of this gene. This study provides a comprehensive gene expression profile of neuroblastoma cell line IMR-5 and may be used as a reference database for identification of candidate genes that are involved in etiology and pathogenesis of neuroblastoma.

De Preter K, Speleman F, Combaret V, et al.
Quantification of MYCN, DDX1, and NAG gene copy number in neuroblastoma using a real-time quantitative PCR assay.
Mod Pathol. 2002; 15(2):159-66 [PubMed] Related Publications
Amplification of the proto-oncogene MYCN is a strong adverse prognostic factor in neuroblastoma patients in all tumor stages. The status of the MYCN gene has become an important factor in clinical decision making and therapy stratification. Consequently, fast and accurate assessment of MYCN gene copy number is of the utmost importance and the use of two independent methods to determine MYCN status is recommended. For these reasons we have developed and evaluated a real-time quantitative PCR (Q-PCR) assay as an alternative for time-consuming Southern blot analysis (SB), and as a second independent technique in parallel with fluorescence in situ hybridization (FISH) analysis. Advantages of Q-PCR are a large dynamic range of quantification, no requirement for post-PCR sample handling and the need for very small amounts of starting material. The accuracy of the assay was illustrated by measurement of MYCN single gene copy changes in DNA samples of two patients with 2p deletion and duplication, respectively. Two different detection chemistries i.e., a sequence specific TaqMan probe and a generic DNA binding dye SYBR Green I were evaluated and shown to yield similar results. Also, two different calculation methods for copy number determination were used i.e., the kinetic method and the comparative C(T) method, and shown to be equivalent. In total, 175 neuroblastoma samples with known MYCN status, as determined by FISH and/or SB, were examined. Q-PCR data were highly concordant with FISH and SB data. In addition to MYCN copy number evaluation, DDX1 and NAG gene copy numbers were determined using a similar Q-PCR strategy. Survival analysis pointed out that DDX1 and/or NAG amplification has no additional adverse effect on prognosis.

Wimmer K, Zhu XX, Lamb BJ, et al.
Two-dimensional DNA electrophoresis identifies novel CpG islands frequently coamplified with MYCN in neuroblastoma.
Med Pediatr Oncol. 2001; 36(1):75-9 [PubMed] Related Publications
BACKGROUND: Amplification of the oncogene MYCN in neuroblastoma has been found to correlate with aggressive tumour growth and is used as a predictor of clinical outcome. The MYCN amplicon is known to involve coamplification of extensive DNA regions. Therefore it is possible that other genes are coamplified in this amplicon and that they may play a role in the poor outcome of MYCN amplified tumours.
PROCEDURE: We have implemented an approach for the two-dimensional separation of human genomic restriction fragments to detect and isolate as yet unknown amplified sequences in the MYCN amplicon in neuroblastoma. Using this approach we have recently cloned a novel gene referred to as NAG that is frequently coamplified with MYCN in neuroblastoma.
RESULTS AND CONCLUSIONS: We report here the identification and cloning of two additional CpG islands that are amplified in neuroblastoma. One contains a sequence that is identical to the first intron of DDX1. The other represents a novel CpG island that is associated with an as yet unidentified gene. We show that the novel CpG island is located in close proximity to the MYCN locus on chromosome 2 and is as frequently coamplified with MYCN in neuroblastoma as NAG and DDX1.

Pandita A, Zielenska M, Thorner P, et al.
Application of comparative genomic hybridization, spectral karyotyping, and microarray analysis in the identification of subtype-specific patterns of genomic changes in rhabdomyosarcoma.
Neoplasia. 1999; 1(3):262-75 [PubMed] Free Access to Full Article Related Publications
Rhabdomyosarcoma (RMS) in children occurs predominantly as two major histologically defined subtypes called embryonal RMS (RMS-E) and the prognostically less favorable alveolar RMS (RMS-A). Comparative genomic hybridization (CGH) was performed on 21 RMS and identified consistent gains affecting chromosomes 2 (8/10), 5 (5/10), 6 (3/10), 7 (7/10), 8 (9/10), 11 (6/ 10), and 12 (5/10) in RMS-E. Losses/deletions involved chromosomes 19 (2/10) and chromosomes 4, 9, 10, 17, 21 (1/10 each). High copy number amplification, involving the 2p24 region (5/11) and less frequently, the 12q13-21 (2/11), 9p22 (1/11), and 17q22-25 (1/11) regions, was detected in RMS-A. Gene amplification at band 2p24 was present in 6/12 alveolar tumors, and in each case, MYCN was amplified, together with the distally placed DDX1 gene. For these patients there was a shorter disease free interval and a higher mortality than patients with tumors without amplification. Detailed spectral karyotype analysis (SKY) was performed on two RMS cell lines (one of each subtype) and identified a surprisingly high level of structural change. Gene expression studies with the Atlas Human Cancer Array (588 genes) showed that 153 genes generated a signal of similar intensity in both cell lines, and 45 genes appeared to have subtype-specific expression. The chromosomal location of differentially expressed genes was compared to the pattern of genomic alteration in RMS as determined by CGH in this study and the literature.

Squire JA, Thorner PS, Weitzman S, et al.
Co-amplification of MYCN and a DEAD box gene (DDX1) in primary neuroblastoma.
Oncogene. 1995; 10(7):1417-22 [PubMed] Related Publications
DEAD box proteins are putative RNA helicases that have been implicated in cellular processes involving alteration of RNA secondary structure, such as translation initiation and splicing. These proteins share eight conserved amino acid motifs, including Asp(D)-Glu-(E)-Ala(A)-Asp(D) which is part of a more extended motif. Recently, we have shown that the novel DDX1 gene containing a DEAD box motif maps to the same chromosome band as MYCN at 2p24 and is co-amplified with MYCN in retinoblastoma cell lines. Here, we show that the DDX1 gene is co-amplified with the MYCN gene in 2 of three neuroblastoma cell lines and that DDX1 RNA levels correlate with DDX1 gene copy number. Since amplification of MYCN is an indicator of poor prognosis in neuroblastoma, it was of interest to determine whether co-amplification with DDX1 occurred in clinical samples of neuroblastoma and whether such a finding carried any additional prognostic significance. We determined the gene copy number of DDX1 in 32 neuroblastoma patient samples (representative of all stages): 13 were MYCN amplified and 19 had normal copy numbers of the MYCN gene. Of the 13 neuroblastomas that were MYCN amplified, seven were also DDX1 amplified. Of the 19 that were not MYCN amplified, none were DDX1 amplified. This is the first example of a gene that is co-amplified with MYCN at a high frequency in neuroblastoma. While there was a trend towards a worse clinical outcome with co-amplification, the numbers were too small to reach significance.

George RE, Kenyon RM, McGuckin AG, et al.
Investigation of co-amplification of the candidate genes ornithine decarboxylase, ribonucleotide reductase, syndecan-1 and a DEAD box gene, DDX1, with N-myc in neuroblastoma. United Kingdom Children's Cancer Study Group.
Oncogene. 1996; 12(7):1583-7 [PubMed] Related Publications
Although N-myc amplification is strongly associated with a poor prognosis, not all patients with neuroblastomas having N-myc amplification fare badly. To investigate whether genes other than N-myc are responsible for contributing to the prognosis, we examined seven cell lines and 87 primary tumours for co-amplification of candidate genes known to be present near the normal N-myc locus: ornithine decarboxylase (ODC), ribonucleotide reductase (RRM2), syndecan-1 and a DEAD box protein gene, DDX1. Sequence analysis of the pG21 cDNA clone previously reported to represent an expressed gene frequently co-amplified with N-myc, showed this to be from the DDX1 gene. No co-amplification with the first three genes was found in any of the cell lines or tumour samples. DDX1, however was found to be amplified along with N-myc in 4/6 (67%) cell lines and 6/16 (38%) of the N-myc amplified tumours. Co-amplification of DDX1 and N-myc was found more frequently in stage 4 or 4S tumours than lower stage (1-3) tumours. With the exclusion of a single 4S case, there was a highly significant reduction in the mean disease-free interval from 24.4 +/- 4.7 (SE, n = 10) months for cases with co-amplification of N-myc and DDX1 compared with 9.2 +/- 1.8 (SE, n = 5) months for those cases showing amplification of N-myc alone (P = 0.0056, Welch's unpaired t-test). No amplification of DDX1, ODC, RRM2, or syndecan-1 was found in the absence of N-myc amplification. These observation indicate that the N-myc amplicon is of varied size and/or position relative to the N-myc gene, with DDX1 representing at least one other gene frequently co-amplified with N-myc. Further studies are required to confirm the biological and prognostic significance of DDX1 co-amplification and to elucidate the role that DDX1 plays in tumour genesis and progression.

Godbout R, Hale M, Bisgrove D
A human DEAD box protein with partial homology to heterogeneous nuclear ribonucleoprotein U.
Gene. 1994; 138(1-2):243-5 [PubMed] Related Publications
In a previous report, we showed that a novel DEAD box protein-encoding gene, DDX1, was amplified in two retinoblastoma (RB) cell lines. In addition to the eight conserved motifs that characterize all DEAD box proteins, the deduced amino acid sequence of DDX1 contains a subregion with considerable homology to heterogeneous nuclear ribonucleoprotein U.

Godbout R, Squire J
Amplification of a DEAD box protein gene in retinoblastoma cell lines.
Proc Natl Acad Sci U S A. 1993; 90(16):7578-82 [PubMed] Free Access to Full Article Related Publications
DEAD box proteins, characterized by the conserved motif Asp-Glu-Ala-Asp, are putative RNA helicases implicated in a number of cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. Based on their distribution patterns, some members of this family are believed to be involved in embryogenesis, spermatogenesis, and cellular growth and division. Here, we report that the mRNA encoding a DEAD box protein, designated HuDBP-RB, is present at elevated levels in two of six retinoblastoma (RB) cell lines tested and is preferentially expressed in fetal tissues of neuroectodermal origin. It is not possible to classify HuDBP-RB as a member of any of the DEAD box protein subgroups identified to date since the regions of amino acid similarity between HuDBP-RB and other DEAD box proteins are restricted to the conserved motifs found in all members of this family. The HuDBP-RB gene, which has been mapped to chromosome band 2p24, is amplified in the RB cell lines that overexpress HuDBP-RB RNA. Furthermore, the MYCN gene is also present in multiple copies in these two cell lines, suggesting coamplification of the two genes.

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