RASSF5

Gene Summary

Gene:RASSF5; Ras association (RalGDS/AF-6) domain family member 5
Aliases: RAPL, Maxp1, NORE1, NORE1A, NORE1B, RASSF3
Location:1q32.1
Summary:This gene is a member of the Ras association domain family. It functions as a tumor suppressor, and is inactivated in a variety of cancers. The encoded protein localizes to centrosomes and microtubules, and associates with the GTP-activated forms of Ras, Rap1, and several other Ras-like small GTPases. The protein regulates lymphocyte adhesion and suppresses cell growth in response to activated Rap1 or Ras. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:ras association domain-containing protein 5
HPRD
Source:NCBIAccessed: 27 February, 2015

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 27 February 2015 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.

Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

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: RASSF5 (cancer-related)

Schmidt ML, Donninger H, Clark GJ
Ras regulates SCF(β-TrCP) protein activity and specificity via its effector protein NORE1A.
J Biol Chem. 2014; 289(45):31102-10 [PubMed] Article available free on PMC after 07/11/2015 Related Publications
Ras is the most frequently activated oncogene found in human cancer, but its mechanisms of action remain only partially understood. Ras activates multiple signaling pathways to promote transformation. However, Ras can also exhibit a potent ability to induce growth arrest and death. NORE1A (RASSF5) is a direct Ras effector that acts as a tumor suppressor by promoting apoptosis and cell cycle arrest. Expression of NORE1A is frequently lost in human tumors, and its mechanism of action remains unclear. Here we show that NORE1A forms a direct, Ras-regulated complex with β-TrCP, the substrate recognition component of the SCF(β-TrCP) ubiquitin ligase complex. This interaction allows Ras to stimulate the ubiquitin ligase activity of SCF(β-TrCP) toward its target β-catenin, resulting in degradation of β-catenin by the 26 S proteasome. However, the action of Ras/NORE1A/β-TrCP is substrate-specific because IκB, another substrate of SCF(β-TrCP), is not sensitive to NORE1A-promoted degradation. We identify a completely new signaling mechanism for Ras that allows for the specific regulation of SCF(β-TrCP) targets. We show that the NORE1A levels in a cell may dictate the effects of Ras on the Wnt/β-catenin pathway. Moreover, because NORE1A expression is frequently impaired in tumors, we provide an explanation for the observation that β-TrCP can act as a tumor suppressor or an oncogene in different cell systems.

Burghel GJ, Lin WY, Whitehouse H, et al.
Identification of candidate driver genes in common focal chromosomal aberrations of microsatellite stable colorectal cancer.
PLoS One. 2013; 8(12):e83859 [PubMed] Article available free on PMC after 07/11/2015 Related Publications
Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. Chromosomal instability (CIN) is a major driving force of microsatellite stable (MSS) sporadic CRC. CIN tumours are characterised by a large number of somatic chromosomal copy number aberrations (SCNA) that frequently affect oncogenes and tumour suppressor genes. The main aim of this work was to identify novel candidate CRC driver genes affected by recurrent and focal SCNA. High resolution genome-wide comparative genome hybridisation (CGH) arrays were used to compare tumour and normal DNA for 53 sporadic CRC cases. Context corrected common aberration (COCA) analysis and custom algorithms identified 64 deletions and 32 gains of focal minimal common regions (FMCR) at high frequency (>10%). Comparison of these FMCR with published genomic profiles from CRC revealed common overlap (42.2% of deletions and 34.4% of copy gains). Pathway analysis showed that apoptosis and p53 signalling pathways were commonly affected by deleted FMCR, and MAPK and potassium channel pathways by gains of FMCR. Candidate tumour suppressor genes in deleted FMCR included RASSF3, IFNAR1, IFNAR2 and NFKBIA and candidate oncogenes in gained FMCR included PRDM16, TNS1, RPA3 and KCNMA1. In conclusion, this study confirms some previously identified aberrations in MSS CRC and provides in silico evidence for some novel candidate driver genes.

Guo H, Liu H, Wei J, et al.
Functional single nucleotide polymorphisms of the RASSF3 gene and susceptibility to squamous cell carcinoma of the head and neck.
Eur J Cancer. 2014; 50(3):582-92 [PubMed] Article available free on PMC after 07/11/2015 Related Publications
BACKGROUND: RASSF3 suppresses tumour formation through uncertain mechanisms, but it is an important gene of p53-dependent apoptosis. RASSF3 depletion impairs DNA repair after DNA damage, leading to polyploidy. The authors hypothesised that potential functional single-nucleotide polymorphisms (SNPs) of RASSF3 are associated with risk of squamous cell carcinoma of the head and neck (SCCHN).
METHODS: The authors used a functional SNP approach to evaluate the associations between common (minor allele frequency⩾0.05), putative functional variants in RASSF3 and risk of SCCHN. Four selected such functional SNPs (rs6581580 T>G, rs7313765 G>A, rs12311754 G>C and rs1147098 T>C) in RASSF3 were identified and genotyped in 1087 patients and 1090 cancer-free controls in a non-Hispanic white population.
RESULTS: The authors found that two SNPs were significantly associated with SCCHN risk. Carriers of the variant rs6581580G and rs7313765A alleles were at a reduced SCCHN risk, compared with the corresponding common homozygotes [adjusted odds ratio (OR)=0.75 and 0.73 and 95% confidence interval (CI)=0.62-0.91 and 0.60-0.88, respectively, for dominant models; and Ptrend=0.012 and 0.041, respectively, for additive models], particularly for non-oropharyngeal tumours (adjusted OR=0.68 and 0.60 and 95% CI=0.53-0.86 and 0.47-0.77, respectively, for dominant models). In the genotype-phenotype correlation analysis of peripheral blood mononuclear cells from 102 cancer-free controls, the rs6581580 GG genotype was associated with significantly increased expression levels of RASSF3 mRNA (P=0.038), compared with the TT genotype. Additional functional experiments further showed that variant G allele of rs6581580 had a significantly stronger binding affinity to the nuclear protein extracts than the T allele.
CONCLUSION: Taken together, these findings indicate that the RASSF3 promoter rs6581580 T>G SNP is potentially functional, modulating susceptibility to SCCHN among non-Hispanic whites. Larger replication studies are needed to confirm our findings.

Fukatsu A, Ishiguro F, Tanaka I, et al.
RASSF3 downregulation increases malignant phenotypes of non-small cell lung cancer.
Lung Cancer. 2014; 83(1):23-9 [PubMed] Related Publications
BACKGROUND: Ras-Association Family1A (RASSF1A) is a well-established tumor suppressor. Ten RASSF homologues comprise this family, and each member is considered a tumor suppressor. RASSF3 is one of the RASSF family members, but its function has not yet been clarified. Recently, we found that RASSF3 interacts with MDM2 and facilitates its ubiquitination, which induces apoptosis through p53 stabilization. However, the role of RASSF3 in human malignancies remains largely unknown.
PATIENTS AND METHODS: Ninety-five non-small cell lung cancer (NSCLC) patients from Nagoya University Hospital and 45 NSCLC patients from Aichi Cancer Center Hospital underwent pulmonary resection at each hospital, and lung cancer and corresponding non-cancerous lung tissues were collected. The expression levels of RASSF3 were analyzed using quantitative real-time reverse transcription PCR. We performed statistical analysis to investigate the correlation with RASSF3 expression and the clinicopathological characteristics. We also transfected RASSF3-siRNA into NSCLC cells, and performed motility assays to evaluate the influence on migration ability.
RESULTS: RASSF3 expression levels were downregulated in 125 of a total 140 NSCLCs. In a multivariate logistic regression analysis, the low RASSF3 expression group below the median value was independently correlated with progressive phenotypes (lymph node metastasis and pleural invasion), non-adenocarcinoma histology and wild-type epidermal growth factor receptor (EGFR) status. In motility assays, RASSF3-knockdown NSCLC cells increased the migration rate compared to the control cells.
CONCLUSIONS: We found that the expression levels of RASSF3 were frequently downregulated in NSCLCs. Downregulation of RASSF3 strongly correlated with the progressive phenotypes of NSCLCs and EGFR wild-type status. In vitro studies also suggested that RASSF3 downregulation increases migration ability of lung cancer cells. Together, our findings indicate RASSF3 is a candidate tumor suppressor gene of NSCLCs.

Zhou Y, Zhang X, Klibanski A
Genetic and epigenetic mutations of tumor suppressive genes in sporadic pituitary adenoma.
Mol Cell Endocrinol. 2014; 386(1-2):16-33 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
Human pituitary adenomas are the most common intracranial neoplasms. Approximately 5% of them are familial adenomas. Patients with familial tumors carry germline mutations in predisposition genes, including AIP, MEN1 and PRKAR1A. These mutations are extremely rare in sporadic pituitary adenomas, which therefore are caused by different mechanisms. Multiple tumor suppressive genes linked to sporadic tumors have been identified. Their inactivation is caused by epigenetic mechanisms, mainly promoter hypermethylation, and can be placed into two groups based on their functional interaction with tumor suppressors RB or p53. The RB group includes CDKN2A, CDKN2B, CDKN2C, RB1, BMP4, CDH1, CDH13, GADD45B and GADD45G; AIP and MEN1 genes also belong to this group. The p53 group includes MEG3, MGMT, PLAGL1, RASSF1, RASSF3 and SOCS1. We propose that the tumor suppression function of these genes is mainly mediated by the RB and p53 pathways. We also discuss possible tumor suppression mechanisms for individual genes.

Peng H, Liu H, Zhao S, et al.
Silencing of RASSF3 by DNA hypermethylation is associated with tumorigenesis in somatotroph adenomas.
PLoS One. 2013; 8(3):e59024 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
The pathogenic mechanisms underlying pituitary somatotroph adenoma formation, progression are poorly understood. To identify candidate tumor suppressor genes involved in pituitary somatotroph adenoma tumorigenesis, we used HG18 CpG plus Promoter Microarray in 27 human somatotroph adenomas and 4 normal human adenohypophyses. RASSF3 was found with frequent methylation of CpG island in its promoter region in somatotroph adenomas but rarely in adenohypophyses. This result was confirmed by pyrosequencing analysis. We also found that RASSF3 mRNA level correlated negatively to its gene promoter methylation level. RASSF3 hypermethylation and downregulation was also observed in rat GH3 and mouse GT1.1 somatotroph adenoma cell lines. 5-Aza-2' deoxycytidine and trichostatin-A treatment induced RASSF3 promoter demethylation, and restored its expression in GH3 and GT1.1 cell lines. RASSF3 overexpression in GH3 and GT1.1 cells inhibited proliferation, induced apoptosis accompanied by increased Bax, p53, and caspase-3 protein and decreased Bcl-2 protein expression. We also found that the antitumor effect of RASSF3 was p53 dependent, and p53 knockdown blocked RASSF3-induced apoptosis and growth inhibition. Taken together, our results suggest that hypermethylation-induced RASSF3 silencing plays an important role in the tumorigenesis of pituitary somatotroph adenomas.

Ng YK, Lau WS, Lui VW, et al.
Full-length Mst1 exhibits growth promoting function in human hepatocellular carcinoma cells.
FEBS Lett. 2013; 587(5):496-503 [PubMed] Related Publications
The putative tumor suppressor Mst1, when cleaved to its 36kDa cleaved form, amplifies apoptotic signals. We found that Mst1 was predominantly expressed in its full-length form in 76% (17/25 cases) of hepatocellular carcinoma (HCC) tumors. Mst1 cleavage was basically absent in HCC cells. Ectopic full-length Mst1 expression increased the growth of HCC cells by 55-80% within 3days after transfection. Expression of exogenous NORE1B, a tumor suppressor commonly lost in HCC tumors (~56% of our cohort), was sufficient to suppress the growth promotion of full-length Mst1. Hence, Mst1 exhibits a growth promoting activity in HCC cells upon NORE1B downregulation.

Bradly DP, Gattuso P, Pool M, et al.
CDKN2A (p16) promoter hypermethylation influences the outcome in young lung cancer patients.
Diagn Mol Pathol. 2012; 21(4):207-13 [PubMed] Related Publications
PURPOSE: Non-small cell lung cancer (NSCLC) occurs most frequently in individuals older than 60 years of age. Currently, no biological indicators associated with NSCLC in younger patients (30 to 60 y) have been identified. To explore epigenetic influences, promoter methylation of selected tumor suppressor genes was analyzed in early-stage NSCLC patients ranging in age from 30 to 87 years at diagnosis.
EXPERIMENTAL DESIGN: The analysis was performed on formalin-fixed tumor tissue from 193 surgically treated NSCLC patients (127, older than 60 y; 66, 60 y and younger). Methylation was quantified in p16, MGMT, DAPK, RASSF1, CDH1, LET7-3-a, NORE1(RASSF5), and PTEN promoters by pyrosequencing. p16 protein expression was assessed by immunohistochemistry (IHC). Outcome, defined by time to recurrence and overall survival, was evaluated by Kaplan-Meier analysis.
RESULTS: Promoter methylation levels were generally higher in patients older than 60 years of age than in patients 60 years or younger at diagnosis. Of the genes tested, methylation levels of the p16 promoter showed age-related differences. Although p16 promoter methylation was significantly lower using cut-points of 50 years or younger and 40 years or younger (P=0.001 to 0.012, respectively), p16 protein expression increased with age. Patients 60 years or younger with p16 promoter hypermethylation had a significantly shortened time to recurrence (P=0.002) and a shortened survival time (P=0.011). No effect of p16 hypermethylation was seen in patients older than 60 years.
CONCLUSIONS: p16 promoter hypermethylation was associated with a worse outcome in patients with age at diagnosis of 60 years or younger, but was not associated with the outcome in the older than 60-year age group. Overall, these data support methylation-dependent and methylation-independent age-related regulation of p16 expression with differential effects on the outcome after surgical resection for early-stage NSCLC.

Kiss NB, Kogner P, Johnsen JI, et al.
Quantitative global and gene-specific promoter methylation in relation to biological properties of neuroblastomas.
BMC Med Genet. 2012; 13:83 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: In this study we aimed to quantify tumor suppressor gene (TSG) promoter methylation densities levels in primary neuroblastoma tumors and cell lines. A subset of these TSGs is associated with a CpG island methylator phenotype (CIMP) in other tumor types.
METHODS: The study panel consisted of 38 primary tumors, 7 established cell lines and 4 healthy references. Promoter methylation was determined by bisulphate Pyrosequencing for 14 TSGs; and LINE-1 repeat element methylation was used as an indicator of global methylation levels.
RESULTS: Overall mean TSG Z-scores were significantly increased in cases with adverse outcome, but were unrelated to global LINE-1 methylation. CIMP with hypermethylation of three or more gene promoters was observed in 6/38 tumors and 7/7 cell lines. Hypermethylation of one or more TSG (comprising TSGs BLU, CASP8, DCR2, CDH1, RASSF1A and RASSF2) was evident in 30/38 tumors. By contrast only very low levels of promoter methylation were recorded for APC, DAPK1, NORE1A, P14, P16, TP73, PTEN and RARB. Similar involvements of methylation instability were revealed between cell line models and neuroblastoma tumors. Separate analysis of two proposed CASP8 regulatory regions revealed frequent and significant involvement of CpG sites between exon 4 and 5, but modest involvement of the exon 1 region.
CONCLUSIONS/SIGNIFICANCE: The results highlight the involvement of TSG methylation instability in neuroblastoma tumors and cell lines using quantitative methods, support the use of DNA methylation analyses as a prognostic tool for this tumor type, and underscore the relevance of developing demethylating therapies for its treatment.

Fernandes MS, Carneiro F, Oliveira C, Seruca R
Colorectal cancer and RASSF family--a special emphasis on RASSF1A.
Int J Cancer. 2013; 132(2):251-8 [PubMed] Related Publications
The RAS-association domain family, commonly referred to as RASSF, is a family of 10 members (RASSF1-10) implicated in a variety of key biological processes, including cell cycle regulation, apoptosis and microtubule stability. Furthermore, RASSFs have been implicated in tumorigenesis and several family members are now thought to be tumor suppressors. As opposed to the KRAS oncogene, for which mutational activation is frequent in colorectal cancer (CRC), RASSFs are found to be silenced mainly by aberrant promoter methylation. In particular, RASSF1A, RASSF2 and RASSF5 methylation has been associated with CRC development, though the mechanisms of action remain poorly understood. This review focus on the current knowledge of RASSF inactivation in CRC, particularly RASSF1A, and on the implications RASSFs may have as potential biomarkers and for the development of new targeted therapies for CRC.

Djos A, Martinsson T, Kogner P, Carén H
The RASSF gene family members RASSF5, RASSF6 and RASSF7 show frequent DNA methylation in neuroblastoma.
Mol Cancer. 2012; 11:40 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: Hypermethylation of promotor CpG islands is a common mechanism that inactivates tumor suppressor genes in cancer. Genes belonging to the RASSF gene family have frequently been reported as epigenetically silenced by promotor methylation in human cancers. Two members of this gene family, RASSF1A and RASSF5A have been reported as methylated in neuroblastoma. Data from our previously performed genome-wide DNA methylation array analysis indicated that other members of the RASSF gene family are targeted by DNA methylation in neuroblastoma.
RESULTS: In the current study, we found that several of the RASSF family genes (RASSF2, RASSF4, RASSF5, RASSF6, RASSF7, and RASSF10) to various degrees were methylated in neuroblastoma cell lines and primary tumors. In addition, several of the RASSF family genes showed low or absent mRNA expression in neuroblastoma cell lines. RASSF5 and RASSF6 were to various degrees methylated in a large portion of neuroblastoma tumors and RASSF7 was heavily methylated in most tumors. Further, CpG methylation sites in the CpG islands of some RASSF family members could be used to significantly discriminate between biological subgroups of neuroblastoma tumors. For example, RASSF5 methylation highly correlated to MYCN amplification and INRG stage M. Furthermore, high methylation of RASSF6 was correlated to unfavorable outcome, 1p deletion and MYCN amplification in our tumor material.
IN CONCLUSION: This study shows that several genes belonging to the RASSF gene family are methylated in neuroblastoma. The genes RASSF5, RASSF6 and RASSF7 stand out as the most promising candidate genes for further investigations in neuroblastoma.

Lee D, Park SJ, Sung KS, et al.
Mdm2 associates with Ras effector NORE1 to induce the degradation of oncoprotein HIPK1.
EMBO Rep. 2012; 13(2):163-9 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
The Ras effector NORE1 is frequently silenced in primary adenocarcinomas, although the significance of this silencing for tumorigenesis is unclear. Here we show that NORE1 induces polyubiquitination and proteasomal degradation of oncoprotein HIPK1 by facilitating its interaction with the Mdm2 E3 ubiquitin ligase. Endogenous HIPK1 is stabilized in Nore1-deficient mouse embryonic fibroblasts, and depletion of HIPK1 in NORE1-silenced lung adenocarcinoma cells inhibits anchorage-independent cell growth and tumour formation in nude mice. These findings indicate that the control of HIPK1 stability by Mdm2-NORE1 has a major effect on cell behaviour, and epigenetic inactivation of NORE1 enables adenocarcinoma formation in vivo through HIPK1 stabilization.

Zhang Y, Wang R, Song H, et al.
Methylation of multiple genes as a candidate biomarker in non-small cell lung cancer.
Cancer Lett. 2011; 303(1):21-8 [PubMed] Related Publications
Aberrant DNA methylation is a common phenomenon in human cancer. The aims of this study were to investigate the methylation profiles of non-small cell lung cancer (NSCLC) in the Chinese population. Twenty tumor suppressor genes (TSGs) were determined of the methylation status using methylation-specific PCR in 78 paired NSCLC specimens and adjacent normal tissues, as well as in 110 Stage I/II NSCLC and 50 cancer-free plasmas. The results showed that, nine genes (APC, CDH13, KLK10, DLEC1, RASSF1A, EFEMP1, SFRP1, RARβ and p16(INK4A)) demonstrated a significantly higher frequency of methylation in NSCLC compared with the normal tissues (P≤0.001), while the others (RUNX3, hMLH1, DAPK, BRCA1, p14(ARF), MGMT, NORE1A, FHIT, CMTM3, LSAMP and OPCML) showed relatively low sensitivity or specificity. Furthermore, methylation of multiple genes was more frequentin cancerous tissue, CpG island methylator phenotype positive (CIMP+) cases were detected in 65.38% of (51/78) NSCLC while only in 1.28% (1/78) of adjacent normal tissues (P<0.001), and CIMP+ was associated with advanced stage (P=0.017), lymphatic metastasis (P=0.001) and adverse 2-year progression-free survival (P=0.027). The nine genes validated in tissues also showed a significantly higher frequency of tumor-specific hypermethylation in NSCLC plasma, as compared with the cancer-free plasmas, and a 5-gene set (APC, RASSF1A, CDH13, KLK10 and DLEC1) achieved a sensitivity of 83.64% and a specificity of 74.0% for cancer diagnosis. Thus, the results indicated that methylated alteration of multiple genes plays an important role in NSCLC pathogenesis and a panel of candidate epigenetic biomarkers for NSCLC detection in the Chinese population was identified.

Overmeyer JH, Maltese WA
Death pathways triggered by activated Ras in cancer cells.
Front Biosci (Landmark Ed). 2011; 16:1693-713 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
Ras GTPases are best known for their ability to serve as molecular switches regulating cell growth, differentiation and survival. Gene mutations that result in expression of constitutively active forms of Ras have been linked to oncogenesis in animal models and humans. However, over the past two decades, evidence has gradually accumulated to support a paradoxical role for Ras proteins in the initiation of cell death pathways. In this review we survey the literature pointing to the ability of activated Ras to promote cell death under conditions where cancer cells encounter apoptotic stimuli or Ras is ectopically expressed. In some of these cases Ras acts through known effectors and well defined apoptotic death pathways. However, in other cases it appears that Ras operates by triggering novel non-apoptotic death mechanisms that are just beginning to be characterized. Understanding these mechanisms and the factors that go into changing the nature of Ras signaling from pro-survival to pro-death could set the stage for development of novel therapeutic approaches aimed at manipulating pro-death Ras signaling pathways in cancer.

Underhill-Day N, Hill V, Latif F
N-terminal RASSF family: RASSF7-RASSF10.
Epigenetics. 2011; 6(3):284-92 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
Epigenetic inactivation of tumor suppressor genes is a hallmark of cancer development. RASSF1A (Ras Association Domain Family 1 isoform A) tumor suppressor gene is one of the most frequently epigenetically inactivated genes in a wide range of adult and children's cancers and could be a useful molecular marker for cancer diagnosis and prognosis. RASSF1A has been shown to play a role in several biological pathways, including cell cycle control, apoptosis and microtubule dynamics. RASSF2, RASSF4, RASSF5 and RASSF6 are also epigenetically inactivated in cancer but have not been analysed in as wide a range of malignancies as RASSF1A. Recently four new members of the RASSF family were identified these are termed N-Terminal RASSF genes (RASSF7-RASSF10). Molecular and biological analysis of these newer members has just begun. This review highlights what we currently know in respects to structural, functional and molecular properties of the N-Terminal RASSFs.

Lee CK, Lee JH, Lee MG, et al.
Epigenetic inactivation of the NORE1 gene correlates with malignant progression of colorectal tumors.
BMC Cancer. 2010; 10:577 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: NORE1 (RASSF5) is a newly described member of the RASSF family with Ras effector function. NORE1 expression is frequently inactivated by aberrant promoter hypermethylation in many human cancers, suggesting that NORE1 might be a putative tumor suppressor. However, expression and mutation status of NORE1 and its implication in colorectal tumorigenesis has not been evaluated.
METHODS: Expression, mutation, and methylation status of NORE1A and NORE1B in 10 cancer cell lines and 80 primary tumors were characterized by quantitative PCR, SSCP, and bisulfite DNA sequencing analyses. Effect of NORE1A and NORE1B expression on tumor cell growth was evaluated using cell number counting, flow cytometry, and colony formation assays.
RESULTS: Expression of NORE1A and NORE1B transcript was easily detectable in all normal colonic epithelial tissues, but substantially decreased in 7 (70%) and 4 (40%) of 10 cancer cell lines and 31 (38.8%) and 25 (31.3%) of 80 primary carcinoma tissues, respectively. Moreover, 46 (57.6%) and 38 (47.5%) of 80 matched tissue sets exhibited tumor-specific reduction of NORE1A and NORE1B, respectively. Abnormal reduction of NORE1 was more commonly observed in advanced stage and high grade tumors compared to early and low grade tumors. While somatic mutations of the gene were not identified, its expression was re-activated in all low expressor cells after treatment with the demethylating agent 5-aza-dC. Bisulfite DNA sequencing analysis of 31 CpG sites within the promoter region demonstrated that abnormal reduction of NORE1A is tightly associated with promoter CpG sites hypermethylation. Moreover, transient expression and siRNA-mediated knockdown assays revealed that both NORE1A and NORE1B decrease cellular growth and colony forming ability of tumor cells and enhance tumor cell response to apoptotic stress.
CONCLUSION: Our data indicate that epigenetic inactivation of NORE1 due to aberrant promoter hypermethylation is a frequent event in colorectal tumorigenesis and might be implicated in the malignant progression of colorectal tumors.

Schagdarsurengin U, Richter AM, Hornung J, et al.
Frequent epigenetic inactivation of RASSF2 in thyroid cancer and functional consequences.
Mol Cancer. 2010; 9:264 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: The Ras association domain family (RASSF) encodes for distinct tumor suppressors and several members are frequently silenced in human cancer. In our study, we analyzed the role of RASSF2, RASSF3, RASSF4, RASSF5A, RASSF5C and RASSF6 and the effectors MST1, MST2 and WW45 in thyroid carcinogenesis.
RESULTS: Frequent methylation of the RASSF2 and RASSF5A CpG island promoters in thyroid tumors was observed. RASSF2 was methylated in 88% of thyroid cancer cell lines and in 63% of primary thyroid carcinomas. RASSF2 methylation was significantly increased in primary thyroid carcinoma compared to normal thyroid, goiter and follicular adenoma (0%, 17% and 0%, respectively; p < 0.05). Patients which were older than 60 years were significantly hypermethylated for RASSF2 in their primary thyroid tumors compared to those younger than 40 years (90% vs. 38%; p < 0.05). RASSF2 promoter hypermethylation correlated with its reduced expression and treatment with a DNA methylation inhibitor reactivated RASSF2 transcription. Over-expression of RASSF2 reduced colony formation of thyroid cancer cells. Functionally our data show that RASSF2 interacts with the proapoptotic kinases MST1 and MST2 and induces apoptosis in thyroid cancer cell lines. Deletion of the MST interaction domain of RASSF2 reduced apoptosis significantly (p < 0.05).
CONCLUSION: These results suggest that RASSF2 encodes a novel epigenetically inactivated candidate tumor suppressor gene in thyroid carcinogenesis.

Shinmura K, Tao H, Nagura K, et al.
Suppression of hydroxyurea-induced centrosome amplification by NORE1A and down-regulation of NORE1A mRNA expression in non-small cell lung carcinoma.
Lung Cancer. 2011; 71(1):19-27 [PubMed] Related Publications
The candidate tumor suppressor NORE1A is a nucleocytoplasmic shuttling protein, and although a fraction of the NORE1A in cells is localized to their centrosomes, the role of centrosomal NORE1A has not been elucidated. In this study we investigated the role of NORE1A in the numerical integrity of centrosomes and chromosome stability in lung cancer cells. Exposure of p53-deficient H1299 lung cancer cell line to hydroxyurea (HU) resulted in abnormal centrosome amplification (to 3 or more centrosomes per cell) as determined by immunofluorescence analysis with anti-γ-tubulin antibody, and forced expression of wild-type NORE1A partially suppressed the centrosome amplification. The nuclear export signal (NES) mutant (L377A/L384A) of NORE1A did not localize to centrosomes and did not suppress the centrosome amplification induced by HU. Fluorescence in situ hybridization analyses with probes specific for chromosomes 2 and 16 showed that wild-type NORE1A, but not NES-mutant NORE1A, suppressed chromosome instability in HU-exposed H1299 cells that was likely to have resulted from centrosome amplification. We next examined the status of NORE1A mRNA expression in non-small cell lung carcinoma (NSCLC) and detected down-regulation of NORE1A mRNA expression in 25 (49%) of 51 primary NSCLCs by quantitative real-time-polymerase chain reaction analysis. These results suggest that NORE1A has activity that suppresses the centrosome amplification induced by HU and that NORE1A mRNA down-regulation is one of the common gene abnormalities in NSCLCs, both of which imply a key preventive role of NORE1A against the carcinogenesis of NSCLC.

Bomben R, Dal-Bo M, Benedetti D, et al.
Expression of mutated IGHV3-23 genes in chronic lymphocytic leukemia identifies a disease subset with peculiar clinical and biological features.
Clin Cancer Res. 2010; 16(2):620-8 [PubMed] Related Publications
PURPOSE: B-cell chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease whose outcome can be foreseen by investigating the mutational status of immunoglobulin heavy chain variable (IGHV) genes. Moreover, a different prognosis was reported for CLL expressing specific IGHV genes in the context or not of stereotyped B-cell receptors. Here we investigated novel associations between usage of specific IGHV genes and clinical features in CLL.
EXPERIMENTAL DESIGN: Among 1,426 CLL-specific IG-rearrangements, stereotyped B-cell receptor clusters never utilized the IGHV3-23 gene. Given this notion, this study was aimed at characterizing the IGHV3-23 gene in CLL, and identifying the properties of IGHV3-23-expressing CLL.
RESULTS: IGHV3-23 was the second most frequently used (134 of 1,426) and usually mutated (M; 109 of 134) IGHV gene in our CLL series. In the vast majority of M IGHV3-23 sequences, the configuration of the 13 amino acids involved in superantigen recognition was consistent with superantigen binding. Clinically, M IGHV3-23 CLL had shorter time-to-treatment than other M non-IGHV3-23 CLL, and multivariate analyses selected IGHV3-23 gene usage, Rai staging, and chromosomal abnormalities as independent prognosticators for M CLL. Compared with M non-IGHV3-23 CLL, the gene expression profile of M IGHV3-23 CLL was deprived in genes, including the growth/tumor suppressor genes PDCD4, TIA1, and RASSF5, whose downregulation is under control of miR-15a and miR-16-1. Accordingly, relatively higher levels of miR-15a and miR-16-1 were found in M IGHV3-23 compared with M non-IGHV3-23 CLL.
CONCLUSIONS: Altogether, expression of the IGHV3-23 gene characterizes a CLL subset with distinct clinical and biological features.

Steinmann K, Sandner A, Schagdarsurengin U, Dammann RH
Frequent promoter hypermethylation of tumor-related genes in head and neck squamous cell carcinoma.
Oncol Rep. 2009; 22(6):1519-26 [PubMed] Related Publications
Squamous cell carcinomas of head and neck (HNSCC) are a result of multiple genetic and epigenetic alterations. Epigenetic inactivation of tumor suppressor genes is an important event in head and neck carcinogenesis. Here we analyzed the promoter methylation of 15 genes (RASSF1A, p16, MGMT, DAPK, RARbeta, MLH1, CDH1, GSTP1, RASSF2, RASSF4, RASSF5, MST1, MST2, LATS1, LATS2) in 54 HNSCC and in matching 23 normal tissues. Methylation of these tumor-related genes (TRG) was significantly more frequent in HNSCC (42%) compared to normal samples (23%; p<0.05). Particularly, methylation of p16 (60%), MGMT (53%), DAPK (67%), RARbeta (75%), MLH1 (69%), CDH1 (43%), RASSF5 and MST1 (96%) was often found in HNSCC. Methylation of RASSF1A (18%), GSTP1 (4%), RASSF4 (13%), MST2 (4%), LATS1 (24%) and LATS2 (8%) was less frequently detected. A trend of increased TRG methylation in more advanced tumor stages and less differentiated HNSCC was observed. Methylation of p16 was significantly higher in poorly differentiated HNSCC (p=0.037) and RASSF5 methylation occurred preferentially in advanced tumor stages (p<0.05). Methylation of RASSF4 was higher in patients with recurrent HNSCC (23%) than patients without relapse (0%; p=0.033). Methylation of TRG in head and neck cancer cell lines was observed at similar frequency as in primary HNSCC. In summary, frequent hyper-methylation of tumor-related genes in HNSCC was detected and this epigenetic silencing event may have an essential role in head and neck carcinogenesis.

Buckingham L, Penfield Faber L, Kim A, et al.
PTEN, RASSF1 and DAPK site-specific hypermethylation and outcome in surgically treated stage I and II nonsmall cell lung cancer patients.
Int J Cancer. 2010; 126(7):1630-9 [PubMed] Related Publications
The primary objective of this study is to identify prognostic site-specific epigenetic changes in surgically treated Stage I and II nonsmall cell lung cancer (NSCLC) patients by quantifying methylation levels at multiple CpG sites within each gene promoter. Paraffin-embedded tumors from stage Ib, IIa and IIb in training and validation groups of 75 and 57 surgically treated NSCLC patients, respectively, were analyzed for p16, MGMT, RASSF1, RASSF5, CDH1, LET7, DAPK and PTEN promoter hypermethylation. Hypermethylation status was quantified individually at multiple CpG sites within each promoter by pyrosequencing. Molecular and clinical characteristics with time to recurrence (TTR) and overall survival (OS) were evaluated. Overall average promoter methylation levels of MGMT and RASSF1 were significantly higher in smokers than in nonsmokers (p = 0.006 and p = 0.029, respectively). Methylation levels of the p16 promoter were significantly higher in squamous cell carcinoma than in adenocarcinoma (p = 0.020). In univariate analysis, hypermethylation of RASSF1 at CpG sites -53 and -48 and PTEN at CpG site -1310 were the significantly associated with shorter TTR (p = 0.002 and p < 0.000, respectively). Hypermethylation of PTEN at -1310 and DAPK at -1482 were most significantly associated with outcome in multivariate analysis. These results show that methylation of specific promoter CpG sites in PTEN, RASSF1 and DAPK is associated with outcome in early stage surgically treated NSCLC.

Hanlon K, Rudin CE, Harries LW
Investigating the targets of MIR-15a and MIR-16-1 in patients with chronic lymphocytic leukemia (CLL).
PLoS One. 2009; 4(9):e7169 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: MicroRNAs (miRNAs) are short, noncoding RNAs that regulate the expression of multiple target genes. Deregulation of miRNAs is common in human tumorigenesis. The miRNAs, MIR-15a/16-1, at chromosome band 13q14 are down-regulated in the majority of patients with chronic lymphocytic leukaemia (CLL).
METHODOLOGY/PRINCIPAL FINDINGS: We have measured the expression of MIR-15a/16-1, and 92 computationally-predicted MIR-15a/16-1 target genes in CLL patients and in normal controls. We identified 35 genes that are deregulated in CLL patients, 5 of which appear to be specific targets of the MIR-15a/16-1 cluster. These targets included 2 genes (BAZ2A and RNF41) that were significantly up-regulated (p<0.05) and 3 genes (RASSF5, MKK3 and LRIG1) that were significantly down-regulated (p<0.05) in CLL patients with down-regulated MIR-15a/16-1 expression.
SIGNIFICANCE: The genes identified here as being subject to MIR-15a/16-1 regulation could represent direct or indirect targets of these miRNAs. Many of these are good biological candidates for involvement in tumorigenesis and as such, may be important in the aetiology of CLL.

Newell P, Toffanin S, Villanueva A, et al.
Ras pathway activation in hepatocellular carcinoma and anti-tumoral effect of combined sorafenib and rapamycin in vivo.
J Hepatol. 2009; 51(4):725-33 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND/AIMS: The success of sorafenib in the treatment of advanced hepatocellular carcinoma (HCC) has focused interest on the role of Ras signaling in this malignancy. We investigated the molecular alterations of the Ras pathway in HCC and the antineoplastic effects of sorafenib in combination with rapamycin, an inhibitor of mTOR pathway, in experimental models.
METHODS: Gene expression (qRT-PCR, oligonucleotide microarray), DNA copy number changes (SNP-array), methylation of tumor suppressor genes (methylation-specific PCR) and protein activation (immunohistochemistry) were analysed in 351 samples. Anti-tumoral effects of combined therapy targeting the Ras and mTOR pathways were evaluated in cell lines and HCC xenografts.
RESULTS: Different mechanisms accounted for Ras pathway activation in HCC. H-ras was up-regulated during different steps of hepatocarcinogenesis. B-raf was overexpressed in advanced tumors and its expression was associated with genomic amplification. Partial methylation of RASSF1A and NORE1A was detected in 89% and 44% of tumors respectively, and complete methylation was found in 11 and 4% of HCCs. Activation of the pathway (pERK immunostaining) was identified in 10.3% of HCC. Blockade of Ras and mTOR pathways with sorafenib and rapamycin reduced cell proliferation and induced apoptosis in cell lines. In vivo, the combination of both compounds enhanced tumor necrosis and ulceration when compared with sorafenib alone.
CONCLUSIONS: Ras activation results from several molecular alterations, such as methylation of tumor suppressors and amplification of oncogenes (B-raf). Sorafenib blocks signaling and synergizes with rapamycin in vivo, preventing tumor progression. These data provide the rationale for testing this combination in clinical studies.

Calvisi DF, Donninger H, Vos MD, et al.
NORE1A tumor suppressor candidate modulates p21CIP1 via p53.
Cancer Res. 2009; 69(11):4629-37 [PubMed] Related Publications
NORE1A (RASSF5) is a proapoptotic Ras effector that is frequently inactivated by promoter methylation in human tumors. It is structurally related to the RASSF1A tumor suppressor and is itself implicated as a tumor suppressor. In the presence of activated Ras, NORE1A is a potent inducer of apoptosis. However, when expressed at lower levels in the absence of activated Ras, NORE1A seems to promote cell cycle arrest rather than apoptosis. The mechanisms underlying NORE1A action are poorly understood. We have used microarray analysis of an inducible NORE1A system to screen for physiologic signaling targets of NORE1A action. Using this approach, we have identified several potential signaling pathways modulated by NORE1A. In particular, we identify the cyclin-dependent kinase inhibitor p21(CIP1) as a target for NORE1A activation and show that it is a vital component of NORE1A-mediated growth inhibition. In primary human hepatocellular carcinomas (HCC), loss of NORE1A expression is frequent and correlates tightly with loss of p21(CIP1) expression. NORE1A down-regulation in HCC also correlates with poor prognosis, enhanced proliferation, survival, and angiogenic tumor characteristics. Experimental inactivation of NORE1A results in the loss of p21(CIP1) expression and promotes proliferation. The best characterized activator of p21(CIP1) is the p53 master tumor suppressor. Further experiments showed that NORE1A activates p21(CIP1) via promoting p53 nuclear localization. Thus, we define the molecular basis of NORE1A-mediated growth inhibition and implicate NORE1A as a potential component of the ill-defined connection between Ras and p53.

Whang YM, Park KH, Jung HY, et al.
Microtubule-damaging agents enhance RASSF1A-induced cell death in lung cancer cell lines.
Cancer. 2009; 115(6):1253-66 [PubMed] Related Publications
BACKGROUND: Tumor suppressor gene product RASSF1A has been reported to induce mitotic arrest and apoptosis through its interaction with microtubule and binding to the Ras effector NORE1. Despite this promising antitumor action of microtubule-targeted drugs, clinical studies demonstrated that paclitaxel (TXL) and vincristine (VCS) have differential antitumor effects, depending on the status of microtubule-related genes in lung cancer patients. In this study, to provide effective chemotherapeutic treatment for lung cancer patients with the microtubule-targeted drugs, the authors investigated whether RASSF1A could enhance sensitivity to TXL and VCS, as an intrinsic microtubule modulator, in nonsmall cell lung cancer (NSCLC) cells.
METHODS: The growth inhibitory effects of TXL and VCS on RASSF1A-transfected cells were assessed using clonogenic and flow cytometry-based propidium iodide-labeled assay. The levels of mitosis-related proteins in RASSF1A-transfected cells after treatment with TXL or VCS were examined by Western blot analysis and in vitro kinase assay.
RESULTS: RASSF1A enhanced the growth inhibitory effect of TXL and VCS on NSCLC cells and bronchial epithelial transformed cells (BEAS-2B) by inducing cell cycle arrest at the G2/M-phase. Accumulation of cyclin B1, G2/M-phase-related protein, was observed when RASSF1A-transfected H1299 cells were treated with TXL or VCS, accompanied with an increase of cyclin A. Inhibition of the activity of cyclin B1/Cdc2 complex by RASSF1A and TXL or VCS was confirmed by kinase assay and knockdown of RASSF1A expression by using small interfering RNA.
CONCLUSIONS: RSAAF1A protein has a cooperative growth inhibitory effect with microtubule-targeted drugs through cyclin B1 accumulation on NSCLC cells, suggesting novel insights for the selection of chemotherapeutic agents.

Jacquemart IC, Springs AE, Chen WY
Rassf3 is responsible in part for resistance to mammary tumor development in neu transgenic mice.
Int J Oncol. 2009; 34(2):517-28 [PubMed] Related Publications
MMTV/neu transgenic mouse line is a well-documented model for studying HER2/neu-related breast cancer. Approximately 80% of these mice develop mammary tumors by 11 months of age, whereas a small percentage appears to have naturally acquired resistance to HER2/neu tumorigenesis. To identify factors responsible for tumor resistance in these transgenic mice, comparative genetic profiling was used to screen alterations in gene expression in the mammary gland. A novel gene, the RAS association domain (RalGDS/AF-6) family 3 (Rassf3), which belongs to a family of RAS effectors and tumor suppressor genes, was identified. Data indicated 1) that Rassf3 is overexpressed in mammary gland of tumor-resistant MMTV/neu mice compared to tumor-susceptible MMTV/neu littermates or non-transgenic mice, and 2) Rassf3 is significantly up-regulated in neu-specific mouse mammary tumors compared to adjacent normal tissues. In vitro overexpression of RASSF3 inhibited cell proliferation in HER2/neu positive human and mouse breast cancer cell lines, possibly through induction of apoptosis. A novel MMTV/Rassf3-neu bi-transgenic mouse line, overexpressing Rassf3 and neu genes in mammary glands, was established. Mammary tumor incidence in bi-transgenic mice was delayed compared to their MMTV/neu+/- littermates. These data suggest that Rassf3 may influence mammary tumor incidence in MMTV/neu transgenic mice.

Macheiner D, Gauglhofer C, Rodgarkia-Dara C, et al.
NORE1B is a putative tumor suppressor in hepatocarcinogenesis and may act via RASSF1A.
Cancer Res. 2009; 69(1):235-42 [PubMed] Related Publications
Recently, we found epigenetic silencing of the Ras effector genes NORE1B and/or RASSF1A in 97% of the hepatocellular carcinoma (HCC) investigated. This is strong evidence that the two genes are of major significance in hepatocarcinogenesis. Although RASSF1A serves as a tumor suppressor gene, the functions of NORE1B are largely unknown. Here, we studied the role of NORE1B for growth and transformation of cells. To understand the molecular mechanisms of action of the gene, we used the wild-type form and deletion mutants without the NH(2) terminus and CENTRAL domain, the Ras association (RA) domain, or the COOH-terminal SARAH-domain. Intact RA and SARAH-domains were found to be necessary for NORE1B (a) to increase the G(0)-G(1) fraction in hepatoma cells, (b) to suppress c-Myc/Ha-Ras-induced cell transformation, and (c) to interact closely with RASSF1A, as determined with fluorescence resonance energy transfer. In further studies, cell cycle delay by NORE1B was equally effective in hepatocyte cell lines with wild-type or mutant Ras suggesting that NORE1B does not interact with either Ras. In conclusion, NORE1B suppresses replication and transformation of cells as effectively as RASSF1A and thus is a putative tumor suppressor gene. NORE1B interacts physically with RASSF1A and functional loss of one of the interacting partners may lead to uncontrolled growth and transformation of hepatocytes. This may explain the frequent epigenetic silencing of NORE1B and/or RASSF1A in HCC.

Kuznetsov S, Khokhlatchev AV
The growth and tumor suppressors NORE1A and RASSF1A are targets for calpain-mediated proteolysis.
PLoS One. 2008; 3(12):e3997 [PubMed] Article available free on PMC after 05/04/2015 Related Publications
BACKGROUND: NORE1A and RASSF1A are growth and tumour suppressors inactivated in a variety of cancers. Methylation of NORE1A and RASSF1A promoters is the predominant mechanism for downregulation of these proteins; however, other mechanisms are likely to exist.
METHODOLOGY/PRINCIPAL FINDINGS: Here we describe a proteolysis of NORE1A and RASSF1A by calpains as alternative mechanism of their downregulation. Extracts of H358 cell line, a human bronchoalveolar carcinoma, and H460, a large cell carcinoma, were capable of proteolysis of NORE1A protein in the calpain-dependent manner. Likewise, RASSF1A tumor suppressor was proteolyzed by the H358 cell extract. Addition of calpain inhibitor to H358 and H460 cells growing in tissue culture resulted in re-expression of endogenous NORE1A. A survey of 10 human lung tumours revealed that three of them contain an activity capable of inducing NORE1A degradation.
CONCLUSIONS/SIGNIFICANCE: Thus, degradation by calpains is a novel mechanism for downregulation of NORE1A and RASSF1A proteins and might be the mechanism allowing cancer cells to escape growth suppression.

Lorente A, Mueller W, Urdangarín E, et al.
RASSF1A, BLU, NORE1A, PTEN and MGMT expression and promoter methylation in gliomas and glioma cell lines and evidence of deregulated expression of de novo DNMTs.
Brain Pathol. 2009; 19(2):279-92 [PubMed] Related Publications
Methylation of CpG islands in gene promoters can lead to gene silencing. Together with deletion or mutation, it may cause a loss of function of tumor suppressor genes. RASSF1A (3p21.3), NORE1A (1q32.1) and BLU (3p21.3) have been shown to be downregulated by methylation in cancer, and PTEN (10q23.3) and MGMT (10q26.1) are located in areas commonly deleted in astrocytomas. MGMT methylation predicts a better response and a longer overall survival in patients with glioblastomas treated with temozolomide. We analyzed 53 astrocytoma samples and 10 high-grade glioma cell lines. Gene expression was assessed by RT-PCR. Bisulfite sequencing, MSP and a melting curve analysis-based real-time PCR were performed to detect promoter methylation. Treatments with 5'-aza-2'-deoxicitidine were applied to restore gene expression in cell lines. Ninety-two percent of tumor samples were methylated for RASSF1A, 30%-57% for BLU and 47% for MGMT, suggesting promoter methylation of these genes to be a common event in glioma tumorigenesis. Only 4% of the tumors revealed a methylated promoter for NORE1A. No association between methylation and loss of expression could be established for PTEN. We identified de novo DNMTs overexpression in a subset of tumors which may explain the methylation phenotype of individual gliomas.

Geli J, Kogner P, Lanner F, et al.
Assessment of NORE1A as a putative tumor suppressor in human neuroblastoma.
Int J Cancer. 2008; 123(2):389-94 [PubMed] Related Publications
The putative tumor suppressor NORE1A (RASSF5) is a member of the Ras association domain family and is commonly inactivated in human cancer. The closely related gene family member and functional collaborator RASSF1A is a bona fide tumor suppressor and is frequently involved in neuroblastoma. In the present study, we sought to investigate the role of NORE1A in human neuroblastoma. A panel of tumors (36 neuroblastomas and 4 ganglioneuromas) and neuroblastoma cell lines was assessed for NORE1A gene expression by Taqman quantitative RT-PCR. Promoter methylation was quantitatively determined by methylation sensitive pyrosequencing. The antitumourigenic role was functionally investigated in Nore1a transfected SK-N-BE (2) cells by fluorescent inhibition of caspase activity and BrdU incorporation assays. Neuroblastoma cells showed very low or absent NORE1A mRNA expression, which could not be reversed by trichostatin A or 5-aza-cytidine treatments. Neuroblastoma tumors showed suppressed NORE1A gene expression that was particularly pronounced in cases without MYCN amplification or 1p loss. Methylation of the NORE1A promoter was not observed in primary tumors and only one out of seven neuroblastoma cell lines displayed weak partial methylation. Transient expression of Nore1a resulted in enhanced apoptosis and delayed cell cycle progression. In conclusion NORE1A appears to be strongly suppressed in neuroblastic tumors and reconstitution of its expression diminishes the tumorigenic phenotype. Promotor methylation is not a common mechanism responsible for NORE1A transcriptional suppression in this tumor type.

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