Gene Summary

Gene:RASSF2; Ras association (RalGDS/AF-6) domain family member 2
Aliases: CENP-34, RASFADIN
Summary:This gene encodes a protein that contains a Ras association domain. Similar to its cattle and sheep counterparts, this gene is located near the prion gene. Two alternatively spliced transcripts encoding the same isoform have been reported. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:ras association domain-containing protein 2
Source:NCBIAccessed: 25 February, 2015


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 25 February 2015 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 25 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

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

Entity Topic PubMed Papers
Colorectal CancerRASSF2 and Colorectal Cancer View Publications11
Stomach CancerRASSF2 and Stomach Cancer View Publications5
-RASSF2 and Adenoma View Publications5
Ovarian CancerRASSF2 and Ovarian Cancer View Publications5
Cervical CancerRASSF2 and Cervical Cancer View Publications1
Thyroid CancerInactivation of RASSF2 in thyroid cancer Epigenetics
In a study of the RASSF family of genes in Thyroid Cancers, Schagdarsurengin et al (2010) found that RASSF2 methylation was significantly increased in primary thyroid carcinoma compared to normal thyroid, goiter and follicular adenoma. They found that RASSF2 interacts with the proapoptotic kinases MST1 and MST2 and deletion of the MST interaction domain of RASSF2 reduced apoptosis significantly (p < 0.05). Together these results suggest that RASSF2 is an epigenetically inactivated candidate tumor suppressor gene in thyroid carcinogenesis.
View Publications1

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

Latest Publications: RASSF2 (cancer-related)

Ren F, Wang DB, Li T, et al.
Identification of differentially methylated genes in the malignant transformation of ovarian endometriosis.
J Ovarian Res. 2014; 7:73 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Key roles for epigenetic mechanisms in tumorigenesis are well accepted, while the relationship between gene methylation and malignant transformation of ovarian endometriosis (EMS) was seldom reported. In this study, we aimed to screen for aberrantly methylated genes associated with the malignant transformation of ovarian EMS and to preliminarily verify the reliability of screened results by detecting the methylation status and protein expression of the candidate gene in a larger scale of formaldehyde-fixed and paraffin-embedded (FFPE) samples.
METHODS: Methylated CpG island amplification coupled with representational difference analysis (MCA-RDA) was performed on 3 couples of endometriosis-associated ovarian carcinoma (EAOC) fresh samples to identify differentially methylated candidate genes related to malignant transformation of ovarian EMS; Methylation-specific PCR (MSP) and immunohistochemistry were performed in 30 EAOC samples to detected the methylation status and protein expression of RASSF2 gene to verify the reliability of MCA-RDA results.
RESULTS: Nine differentially methylated genes were obtained by MCA-RDA as candidate genes for malignant transformation of EMS; Methylation frequency of RASSF2 in the neoplastic tissues of EAOC group was higher than that in the ectopic endometria (p < 0.05). While protein expression of RASSF2 in the neoplastic tissues was lower than that in the ectopic endometria of the EAOC group (p < 0.05) Absence of protein expression of RASSF2 was significantly correlated with the promoter methylation of the gene (p < 0.05).
CONCLUSIONS: RASSF2, RUNX3, GSTZ1, CYP2A, GBGT1, NDUFS1, SPOCK2, ADAM22, and TRIM36 were candidate genes for malignant transformation of ovarian EMS and epigenetic inactivation of RASSF2 by promoter hypermethylation is an early event in malignant transformation of ovarian EMS. The screen results were reliable and worthy of further study.

Wu Y, Zhang X, Lin L, et al.
Aberrant methylation of RASSF2A in tumors and plasma of patients with epithelial ovarian cancer.
Asian Pac J Cancer Prev. 2014; 15(3):1171-6 [PubMed] Related Publications
OBJECTIVE: The tumor suppressor gene, Ras-association domain family (RASSF)2A, is inactivated by promoter hypermethylation in many cancers. The current study was performed to evaluate the methylation status of RASSF2A in epithelial ovarian cancer (EOC) tissues and plasma, and correlations with gene expression and clinicopathologic characteristics.
METHOD: We detected methylation of the RASSF2A gene in tissues and corresponding plasma samples from 47 EOC patients and 14 patients with benign ovarian tumors and 10 with normal ovarian tissues. The methylation status was determined by methylation-specific PCR while gene expression of mRNA was examined by RT-PCR. The EOC cell line, SKOV3, was treated with 5-aza-2'-deoxycytidine (5-aza- dC).
RESULTS: RASSF2A mRNA expression was significantly low in EOC tissues. The frequency of aberrant methylation of RASSF2A was 51.1% in EOC tissues and 36.2% in corresponding plasma samples, whereas such hypermethylation was not detected in the benign ovarial tumors and normal ovarian samples. The expression of RASSF2A mRNA was significantly down-regulated or lost in the methylated group compared to the unmethylated group (p<0.05). After treatment with 5-aza-dC, RASSF2A mRNA expression was significantly restored in the Skov3 cell line.
CONCLUSION: Epigenetic inactivation of RASSF2A through aberrant promoter methylation may play an important role in the pathogenesis of EOC. Methylation of the RASSF2A gene in plasma may be a valuable molecular marker for the early detection of EOC.

Alholle A, Brini AT, Gharanei S, et al.
Functional epigenetic approach identifies frequently methylated genes in Ewing sarcoma.
Epigenetics. 2013; 8(11):1198-204 [PubMed] Related Publications
Using a candidate gene approach we recently identified frequent methylation of the RASSF2 gene associated with poor overall survival in Ewing sarcoma (ES). To identify effective biomarkers in ES on a genome-wide scale, we used a functionally proven epigenetic approach, in which gene expression was induced in ES cell lines by treatment with a demethylating agent followed by hybridization onto high density gene expression microarrays. After following a strict selection criterion, 34 genes were selected for expression and methylation analysis in ES cell lines and primary ES. Eight genes (CTHRC1, DNAJA4, ECHDC2, NEFH, NPTX2, PHF11, RARRES2, TSGA14) showed methylation frequencies of>20% in ES tumors (range 24-71%), these genes were expressed in human bone marrow derived mesenchymal stem cells (hBMSC) and hypermethylation was associated with transcriptional silencing. Methylation of NPTX2 or PHF11 was associated with poorer prognosis in ES. In addition, six of the above genes also showed methylation frequency of>20% (range 36-50%) in osteosarcomas. Identification of these genes may provide insights into bone cancer tumorigenesis and development of epigenetic biomarkers for prognosis and detection of these rare tumor types.

Guerrero-Setas D, Pérez-Janices N, Ojer A, et al.
Differential gene hypermethylation in genital lichen sclerosus and cancer: a comparative study.
Histopathology. 2013; 63(5):659-69 [PubMed] Related Publications
AIMS: Lichen sclerosus (LS) is a chronic inflammatory disease of the genital skin of unknown aetiology. The role of LS in penile squamous cell carcinogenesis is not well characterized. HPV has been implicated in both, as have epigenetic changes. The presence of HPV and hypermethylation of the MGMT, p16, RASSF1, RASSF2, TSLC1 and TSP1 genes were studied in penile LS; MGMT, RASSF2 and TSLC1 hypermethylation in penile cancer and TSLC1 hypermethylation in vulvar LS and cancer extends previous results reported by our group.
METHODS AND RESULTS: Thirty-seven HPV genotypes and hypermethylation were evaluated by PCR/reverse-line-blot and methylation-specific PCR respectively, in 27 preputial LS, 24 penile SCC, 30 vulvar SCC, 21 vulvar LS and 22 normal skin cases. HPV66 was present in 3.7% of penile LS cases, and p16 and RASSF2 hypermethylation were more frequent in penile cancer than in penile LS. p16, RASSF1, RASSF2 and TSP1 hypermethylation were similar in penile and vulvar LS.
CONCLUSIONS: Gene hypermethylation is a common event in penile LS, and occurs approximately as frequently as in vulvar LS. Certain genes can be hypermethylated as an early or late event in LS or cancer, respectively. This suggests a possible sequential role for these alterations in the transition from benign to malignant lesions.

Gharanei S, Brini AT, Vaiyapuri S, et al.
RASSF2 methylation is a strong prognostic marker in younger age patients with Ewing sarcoma.
Epigenetics. 2013; 8(9):893-8 [PubMed] Free Access to Full Article Related Publications
Ras-association domain family of genes consist of 10 members (RASSF1-RASSF10), all containing a Ras-association (RA) domain in either the C- or the N-terminus. Several members of this gene family are frequently methylated in common sporadic cancers; however, the role of the RASSF gene family in rare types of cancers, such as bone cancer, has remained largely uninvestigated. In this report, we investigated the methylation status of RASSF1A and RASSF2 in Ewing sarcoma (ES). Quantitative real-time methylation analysis (MethyLight) demonstrated that both genes were frequently methylated in Ewing sarcoma tumors (52.5% and 42.5%, respectively) as well as in ES cell lines and gene expression was upregulated in methylated cell lines after treatment with 5-aza-2'-deoxcytidine. Overexpression of either RASSF1A or RASSF2 reduced colony formation ability of ES cells. RASSF2 methylation correlated with poor overall survival (p = 0.028) and this association was more pronounced in patients under the age of 18 y (p = 0.002). These results suggest that both RASSF1A and RASSF2 are novel epigenetically inactivated tumor suppressor genes in Ewing sarcoma and RASSF2 methylation may have prognostic implications for ES patients.

Yang J, Du X
Genomic and molecular aberrations in malignant peripheral nerve sheath tumor and their roles in personalized target therapy.
Surg Oncol. 2013; 22(3):e53-7 [PubMed] Related Publications
Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors with a high rate of local recurrence and a significant tendency to metastasize. Its dismal outcome points to the urgent need to establish better therapeutic strategies for patients harboring MPNSTs. The investigations of genomic and molecular aberrations in MPNSTs which detect many chromosomal aberrations, pathway abnormalities, and specific molecular aberrant events would supply multiple potential therapy targets and contribute to achievement of personalized medicine. The involved genes in the significant gains aberrations include BIRC5, CCNE2, DAB2, DDX15, EGFR, DAB2, MSH2, CDK6, HGF, ITGB4, KCNK12, LAMA3, LOXL2, MET, and PDGFRA. The involved genes in the significant deletion aberrations include CDH1, GLTSCR2, EGR1, CTSB, GATA3, SULT2A1, GLTSCR2, HMMR/RHAMM, LICAM2, MMP13, p16/INK4a, RASSF2, NM-23H1, and TP53. These genetic aberrations involve in several important signaling pathways such as TFF, EGFR, ARF, IGF1R signaling pathways. The genomic and molecular aberrations of EGFR, IGF1R, SOX9, EYA4, TOP2A, ETV4, and BIRC5 exhibit great promise as personalized therapeutic targets for MPNST patients.

Qiu JJ, Guo JJ, Lv TJ, et al.
Prognostic value of centromere protein-A expression in patients with epithelial ovarian cancer.
Tumour Biol. 2013; 34(5):2971-5 [PubMed] Related Publications
Altered expression of centromere protein-A (CENP-A) is observed in various types of human cancers. However, the clinical significance and pathological role of CENP-A in epithelial ovarian cancer (EOC) remains unclear. The main objective of this investigation was to clarify the relationships between CENP-A expression and the clinicopathological features of patients with EOC. Real-time quantitative PCR and Western blot were performed to examine CENP-A expression in 20 pairs of fresh-frozen EOC tissues and corresponding noncancerous tissues. Using immunohistochemistry, we performed a retrospective study of the CENP-A expression levels on 120 archival EOC paraffin-embedded samples. Prognostic outcomes correlated with CENP-A were examined using Kaplan-Meier analysis and Cox proportional hazards model. Our results showed that the expression levels of CENP-A mRNA and protein in EOC tissues were both significantly higher than those in noncancerous tissues. By immunohistochemistry, the data revealed that high CENP-A expression was significantly correlated with pathological grade (P = 0.02) and International Federation of Gynecology and Obstetrics stage (P = 0.006). Consistent with these results, we found that high expression of CENP-A was significantly correlated with poor survival in EOC patients (P < 0.001). Furthermore, Cox regression analyses showed that CENP-A expression was an independent predictor of overall survival. Our data suggest that CENP-A could play an important role in EOC and might serve as a valuable prognostic marker and potential target for gene therapy in the treatment of EOC.

Qu Y, Dang S, Hou P
Gene methylation in gastric cancer.
Clin Chim Acta. 2013; 424:53-65 [PubMed] Related Publications
Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field.

Guerrero-Setas D, Pérez-Janices N, Blanco-Fernandez L, et al.
RASSF2 hypermethylation is present and related to shorter survival in squamous cervical cancer.
Mod Pathol. 2013; 26(8):1111-22 [PubMed] Related Publications
Ras association (RalGDS/AF-6) domain family member 2 (RASSF2) is a gene involved in the progression of several human cancers, including breast, colorectal and lung cancer. The aims of this study were to determine the hypermethylation of the gene in squamous cervical cancer and precursor lesions, along with that of RASSF1 and the recently described EPB41L3, and to analyze the potential prognostic role of these genes. Methylation-specific PCR and bisulfite sequencing were used to analyze the methylation status of RASSF2 and EPB41L3 gene in 60 squamous cervical cancer, 76 cervical intraepithelial neoplasias grade III, 16 grade II, 14 grade I and 13 cases of normal tissue adjacent to cervical intraepithelial neoplasia. RASSF2 expression was evaluated by immunohistochemistry and the re-expression of RASSF2 and EPB41L3 was analyzed by quantitative reverse-transcription PCR in HeLa, SiHa, C33A and A431 cell lines treated with 5-aza-2'-deoxycytidine and/or trichostatin. RASSF1 hypermethylation and human papillomavirus type were also analyzed in all the cases by methylation-specific PCR and reverse line blot, respectively. RASSF2 hypermethylation was predominant in squamous cervical cancer (60.9%) compared with cervical intraepithelial neoplasias (4.2%) and was associated with a lower level of RASSF2 expression and vascular invasion in squamous cervical cancer. EPB41L3 and RASSF1 hypermethylations were also more frequent in cancer than in precursor lesions. Patients with RASSF2 hypermethylation had shorter survival time, independent of tumor stage (hazard ratio: 6.0; 95% confidence interval: 1.5-24.5). Finally, the expressions of RASSF2 and EPB41L3 were restored in several cell lines treated with 5-aza-2'-deoxycytidine. Taken together, our results suggest that RASSF2 potentially functions as a new tumor-suppressor gene that is inactivated through hypermethylation in cervical cancer and is related to the bad prognosis of these patients.

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] Free Access to Full Article 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] Free Access to Full Article 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.

Helmbold P, Richter AM, Walesch S, et al.
RASSF10 promoter hypermethylation is frequent in malignant melanoma of the skin but uncommon in nevus cell nevi.
J Invest Dermatol. 2012; 132(3 Pt 1):687-94 [PubMed] Related Publications
The Ras association domain family (RASSF) consists of several tumor suppressor genes, which are frequently silenced in human cancers. We analyzed the epigenetic inactivation of RASSF2 and RASSF10 in malignant melanoma (MM) of the skin, including 5 MM cell lines, 28 primary MM, 33 metastases of MM, 47 nevus cell nevi (NCN), and 22 control tissues. The RASSF2 promoter was epigenetically downregulated in two MM cell lines only, but not in any of the investigated tumor samples. In contrast, hypermethylation of the RASSF10 promoter was found in all investigated cell lines, 19/28 (68%) of the primary MM and 30/33 (91%) of the MM metastases, 2/18 (11%) of the dysplastic NCN, and 0/29 (0%) of the non-dysplastic NCN (difference between MM and all nevi, P<0.001). RASSF10 promoter hypermethylation correlated with a reduced RASSF10 mRNA expression in 3/4 MM cell lines, and treatment with a DNA methylation inhibitor reactivated RASSF10 transcription. Furthermore, immunohistological RASSF10 expression corresponds negatively to its promoter methylation state. In summary, RASSF10 proved to be a characteristically epigenetically silenced tumor suppressor in melanomagenesis, and analysis of RASSF10 methylation status represents a new candidate tool to assist in discrimination between MM and NCN.

Zhao L, Cui Q, Lu Z, Chen J
Aberrant methylation of RASSF2A in human pancreatic ductal adenocarcinoma and its relation to clinicopathologic features.
Pancreas. 2012; 41(2):206-11 [PubMed] Related Publications
OBJECTIVES: Tumor suppressor gene Ras-association domain family 2A (RASSF2A) is inactivated by promoter hypermethylation in many cancers. The study was performed to evaluate the methylation status of RASSF2A in pancreatic ductal adenocarcinoma and cell lines and its relation to clinicopathologic features.
METHODS: The RASSF2 expression in 8 pancreatic carcinoma cell lines and 1 normal pancreatic tissue was detected. The methylation status of RASSF2A in 8 pancreatic carcinoma cell lines, 41 cases of pancreatic ductal adenocarcinoma, and corresponding normal pancreatic tissue was also examined by methylation-specific PCR. BxPC-3 and AsPC-1 cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC), and RASSF2 expression was determined by quantitative real-time reverse transcriptase-polymerase chain reaction.
RESULTS: The expression of RASSF2 was down-regulated in all cell lines. Hypermethylation of RASSF2A was detected in all cell lines and 9 of 41 pancreatic ductal adenocarcinomas. Whereas none of hypermethylation of RASSF2A was found in the normal pancreatic tissue. The expression of RASSF2 could be restored by 5-aza-dC in cell lines.
CONCLUSIONS: Promoter hypermethylation of RASSF2A is observed in pancreatic ductal adenocarcinoma, while not in normal pancreatic tissue. RASSF2A is inactivated in pancreatic ductal adenocarcinoma by CpG island promoter hypermethylation and may play a role in pancreatic carcinogenesis.

Hiraki M, Kitajima Y, Koga Y, et al.
Aberrant gene methylation is a biomarker for the detection of cancer cells in peritoneal wash samples from advanced gastric cancer patients.
Ann Surg Oncol. 2011; 18(10):3013-9 [PubMed] Related Publications
PURPOSE: To assess whether gene methylation in peritoneal fluid (PF) is clinically feasible for determining micrometastasis to the peritoneum in gastric cancer.
METHODS: The gene methylation of BNIP3, CHFR, CYP1B1, MINT25, SFRP2, and RASSF2 were analyzed in 107 specimens of PF by quantitative methylation-specific polymerase chain reaction. All patients were placed into one of 3 groups: group A (n = 42), patients with depth of cancer invasion at muscularis propria (MP) or less than MP; group B (n = 45), depth of cancer invasion beyond the MP; and group C (n = 20), histologically diagnosed peritoneal metastasis or cancer cells cytologically defined in the peritoneal cavity. Patients in both groups A and B were diagnosed as having no cancer cells by peritoneal cytology and histology.
RESULTS: The methylation status of the 6 genes was found to be significantly different among the 3 groups (group A, 0-5%; group B, 0-15%; group C, 15-45%; P < 0.01). Furthermore, the rate of positive methylation in any of the 6 genes was significantly different in each group (group A, 7%; group B, 20%; group C, 75%; P < 0.001). Three of 9 patients in group B with positive methylation in any of 6 genes experienced peritoneal recurrence. On the other hand, only 1 of 36 patients without gene methylation experienced peritoneal recurrence (P < 0.05).
CONCLUSIONS: DNA methylation in PFs is a possible marker detecting occult neoplastic cells on the peritoneum. Methylation analysis along with a cytological examination might therefore improve the positive detection of cancer cells in PF of gastric cancer.

Underhill-Day N, Hill V, Latif F
N-terminal RASSF family: RASSF7-RASSF10.
Epigenetics. 2011; 6(3):284-92 [PubMed] Free Access to Full Article 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.

Igarashi S, Suzuki H, Niinuma T, et al.
A novel correlation between LINE-1 hypomethylation and the malignancy of gastrointestinal stromal tumors.
Clin Cancer Res. 2010; 16(21):5114-23 [PubMed] Related Publications
PURPOSE: Gastrointestinal stromal tumors (GIST) are the most important mesenchymal tumors of the gastrointestinal tract. The vast majority of GISTs exhibit activating mutations of KIT or PDGFRA, but epigenetic alteration of GISTs is largely unknown. In this study, we aimed to clarify the involvement of DNA methylation in GIST malignancy.
EXPERIMENTAL DESIGN: A total of 106 GIST specimens were studied. Levels of LINE-1 methylation were analyzed using bisulfite pyrosequencing. In addition, methylation of three other repetitive sequences (Alu Yb8, Satellite-α, and NBL2) was similarly analyzed, and CpG island hypermethylation was analyzed using MethyLight. Array-based comparative genomic hybridization (array CGH) was carried out in 25 GIST specimens.
RESULTS: LINE-1 hypomethylation was significantly correlated with risk, and high-risk GISTs exhibited significantly lower levels of LINE-1 methylation than low-risk (61.3% versus 53.2%; P = 0.001) or intermediate-risk GISTs (60.8% versus 53.2%; P = 0.002). Hypomethylation of Satellite-α and NBL2 was also observed in high-risk GISTs. By contrast, promoter hypermethylation was relatively infrequent (CDH1, 11.2%; MLH1, 9.8%; SFRP1, 1.2%; SFRP2, 11.0%; CHFR, 9.8%; APC, 6.1%; CDKN2A, 0%; RASSF1A, 0%; RASSF2, 0%) and did not correlate with LINE-1 methylation or risk. Array CGH analysis revealed a significant correlation between LINE-1 hypomethylation and chromosomal aberrations.
CONCLUSIONS: Our data suggest that LINE-1 hypomethylation correlates significantly with the aggressiveness of GISTs and that LINE-1 methylation could be a useful marker for risk assessment. Hypomethylation may increase the malignant potential of GISTs by inducing accumulation of chromosomal aberrations.

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] Free Access to Full Article 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.

Sandgren J, Andersson R, Rada-Iglesias A, et al.
Integrative epigenomic and genomic analysis of malignant pheochromocytoma.
Exp Mol Med. 2010; 42(7):484-502 [PubMed] Free Access to Full Article Related Publications
Epigenomic and genomic changes affect gene expression and contribute to tumor development. The histone modifications trimethylated histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3) are epigenetic regulators associated to active and silenced genes, respectively and alterations of these modifications have been observed in cancer. Furthermore, genomic aberrations such as DNA copy number changes are common events in tumors. Pheochromocytoma is a rare endocrine tumor of the adrenal gland that mostly occurs sporadic with unknown epigenetic/genetic cause. The majority of cases are benign. Here we aimed to combine the genome-wide profiling of H3K4me3 and H3K27me3, obtained by the ChIP-chip methodology, and DNA copy number data with global gene expression examination in a malignant pheochromocytoma sample. The integrated analysis of the tumor expression levels, in relation to normal adrenal medulla, indicated that either histone modifications or chromosomal alterations, or both, have great impact on the expression of a substantial fraction of the genes in the investigated sample. Candidate tumor suppressor genes identified with decreased expression, a H3K27me3 mark and/or in regions of deletion were for instance TGIF1, DSC3, TNFRSF10B, RASSF2, HOXA9, PTPRE and CDH11. More genes were found with increased expression, a H3K4me3 mark, and/or in regions of gain. Potential oncogenes detected among those were GNAS, INSM1, DOK5, ETV1, RET, NTRK1, IGF2, and the H3K27 trimethylase gene EZH2. Our approach to associate histone methylations and DNA copy number changes to gene expression revealed apparent impact on global gene transcription, and enabled the identification of candidate tumor genes for further exploration.

Donninger H, Hesson L, Vos M, et al.
The Ras effector RASSF2 controls the PAR-4 tumor suppressor.
Mol Cell Biol. 2010; 30(11):2608-20 [PubMed] Free Access to Full Article Related Publications
RASSF2 is a novel proapoptotic effector of K-Ras. Inhibition of RASSF2 expression enhances the transforming effects of K-Ras, and epigenetic inactivation of RASSF2 is frequently detected in mutant Ras-containing primary tumors. Thus, RASSF2 is implicated as a tumor suppressor whose inactivation facilitates transformation by disconnecting apoptotic responses from Ras. The mechanism of action of RASSF2 is not known. Here we show that RASSF2 forms a direct and endogenous complex with the prostate apoptosis response protein 4 (PAR-4) tumor suppressor. This interaction is regulated by K-Ras and is essential for the full apoptotic effects of PAR-4. RASSF2 is primarily a nuclear protein, and shuttling of PAR-4 from the cytoplasm to the nucleus is essential for its function. We show that RASSF2 modulates the nuclear translocation of PAR-4 in prostate tumor cells, providing a mechanism for its biological effects. Thus, we identify the first tumor suppressor signaling pathway emanating from RASSF2, we identify a novel mode of action of a RASSF protein, and we provide an explanation for the extraordinarily high frequency of RASSF2 inactivation we have observed in primary prostate tumors.

Song H, Oh S, Oh HJ, Lim DS
Role of the tumor suppressor RASSF2 in regulation of MST1 kinase activity.
Biochem Biophys Res Commun. 2010; 391(1):969-73 [PubMed] Related Publications
The tumor suppressor, RASSF2 (Ras association domain family 2), is frequently downregulated in a number of cancers. Although exogenously expressed RASSF2 induces apoptotic cell death, the precise roles of RASSF2 under pro-apoptotic conditions remain largely unknown. Here, we demonstrate that MST1 (mammalian sterile 20-like kinase 1) regulates RASSF2 protein stability. Knockdown of MST1 in cancer cells markedly destabilizes RASSF2, and Mst1-deficient mice show reduced Rassf2 protein levels in several organs. Conversely, RASSF2 activates MST1 kinase activity through formation of a RASSF2-MST1 complex, which inhibits the MST-FOXO3 signaling pathway. RASSF2 also engages the JNK pathway and induces apoptosis in an MST1-independent manner. Collectively, these findings indicate that MST1 is a major determinant of RASSF2 protein stability, and suggest that RASSF2 acts in a complex manner that extends beyond simple protein-protein association to play an important role in MST1 regulation.

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.

Lee BB, Lee EJ, Jung EH, et al.
Aberrant methylation of APC, MGMT, RASSF2A, and Wif-1 genes in plasma as a biomarker for early detection of colorectal cancer.
Clin Cancer Res. 2009; 15(19):6185-91 [PubMed] Related Publications
PURPOSE: To identify epigenetic molecular makers in plasma for the early detection of colorectal cancer.
EXPERIMENTAL DESIGN: We retrospectively analyzed the methylation status of 10 genes in fresh-frozen tissues and corresponding plasma samples from 243 patients with stage I and II sporadic colorectal cancer, 276 healthy individuals, and plasma from 64 colorectal adenoma patients using methylation-specific PCR. The methylation score (Mscore) was used to find molecular markers with high sensitivity and specificity.
RESULTS: Of the 243 colorectal cancer tissues, methylation was detected in 18% for p14, 34% for p16, 27% for APC, 34% for DAPK, 32% for HLTF, 21% for hMLH1, 39% for MGMT, 24% for RARbeta2, 58% for RASSF2A, and 74% for Wif-1. Receiver operator characteristic curve analysis in plasma from 243 patients with cancer and 276 healthy individuals showed that the M score of any single gene had a sensitivity of <40% after controlling for age, sex, and tumor location. The specificity of the M score was not different between multigene and single gene analyses, but the sensitivity of the M score was significantly increased by multigene analysis. For all patients, the M score in a model including APC, MGMT, RASSF2A, and Wif-1 genes had a sensitivity of 86.5% and a specificity of 92.1% when 1.6 was used as a cutoff. In this model, the M score had a positive predictive value of 90.6% and a negative predictive value of 88.8%.
CONCLUSION: The present study suggests that tumor-specific methylation of APC, MGMT, RASSF2A, and Wif-1 genes might be a valuable biomarker in plasma for the early detection of colorectal cancer.

Nagasaka T, Tanaka N, Cullings HM, et al.
Analysis of fecal DNA methylation to detect gastrointestinal neoplasia.
J Natl Cancer Inst. 2009; 101(18):1244-58 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The development of noninvasive screening tests is important to reduce mortality from gastrointestinal neoplasia. We sought to develop such a test by analysis of DNA methylation from exfoliated cancer cells in feces.
METHODS: We first analyzed methylation of the RASSF2 and SFRP2 gene promoters from 788 primary gastric and colorectal tissue specimens to determine whether methylation patterns could act as stage-dependent biomarkers of gastrointestinal tumorigenesis. Next, we developed a novel strategy that uses single-step modification of DNA with sodium bisulfite and fluorescence polymerase chain reaction methodology to measure aberrant methylation in fecal DNA. Methylation of the RASSF2 and SFRP2 promoters was analyzed in 296 fecal samples obtained from a variety of patients, including 21 with gastric tumors, 152 with colorectal tumors, and 10 with non-neoplastic or inflammatory lesions in the gastrointestinal lumen.
RESULTS: Analysis of DNA from tissues showed presence of extensive methylation in both gene promoters exclusively in advanced gastric and colorectal tumors. The assay successfully identified one or more methylated markers in fecal DNA from 57.1% of patients with gastric cancer, 75.0% of patients with colorectal cancer, and 44.4% of patients with advanced colorectal adenomas, but only 10.6% of subjects without neoplastic or active diseases (difference, gastric cancer vs undiseased = 46.5%, 95% confidence interval (CI) = 24.6% to 68.4%, P < .001; difference, colorectal cancer vs undiseased = 64.4%, 95% CI = 53.5% to 75.2%, P < .001; difference, colorectal adenoma vs undiseased = 33.8%, 95% CI = 14.2% to 53.4%, P < .001).
CONCLUSIONS: Methylation of the RASSF2 and SFRP2 promoters in fecal DNA is associated with the presence of gastrointestinal tumors relative to non-neoplastic conditions. Our novel fecal DNA methylation assay provides a possible means to noninvasively screen not only for colorectal tumors but also for gastric tumors.

Ren J, He W, Zhang R, et al.
RASSF2A promoter methylation in hepatitis B virus-related hepatocellular carcinogenesis and its correlation with elevated serum alpha-fetoprotein level.
J Huazhong Univ Sci Technolog Med Sci. 2009; 29(3):309-12 [PubMed] Related Publications
Loss of the RASSF2A expression induced by methylation-mediated silencing has been reported in several human cancers, but the methylation status of RASSF2A in hepatocellular carcinoma (HCC) is rarely studied so far. In this study, we investigated the RASSF2A expression and its methylation status in a cohort of 45 hepatitis B virus-associated HCC tissues and their adjacent non-carcinoma tissues by using RT-PCR and MS-PCR. Promoter methylation of RASSF2A was found in 31 (68.9%) out of 45 HCC tissues and 12 (40%) out of 30 adjacent normal tissues, respectively (P<0.05). The methylation status of PASSF2A was closely associated with the loss of RASSF2A expression and elevated serum alpha-fetoprotein level, but not significantly with clinical stage, hepatic fibrosis and K-ras mutation. It was concluded that aberrant methylation of the RASSF2A gene with the subsequent loss of RASSF2A expression plays an important role in the pathogenesis of HCC.

Huang KH, Huang SF, Chen IH, et al.
Methylation of RASSF1A, RASSF2A, and HIN-1 is associated with poor outcome after radiotherapy, but not surgery, in oral squamous cell carcinoma.
Clin Cancer Res. 2009; 15(12):4174-80 [PubMed] Related Publications
PURPOSE: Radiotherapy is the standard adjuvant treatment for oral squamous cell carcinoma (OSCC). The Ras/PI3K/AKT pathway is the major mechanism associated with radioresistance. To evaluate the potential significance on the outcome of radiotherapy in OSCC of the Ras/PI3K/AKT pathway with respect to methylation of negative regulators, we examined the methylation status of genes known to be involved in Ras/PI3K/AKT pathway and aberrantly methylated in human cancers together with the mutation status of K-ras/H-ras.
EXPERIMENTAL DESIGN: PCR--denaturing high-performance liquid chromatography was used to examine the methylation status of the RASSF1A, RASSF2A, PTEN, and HIN-1 genes, and PCR-RFLP was used to determine the mutation status of K-ras/H-ras in 482 OSCCs. Associations between mutation, methylation, clinicopathologic parameters, and outcome were evaluated.
RESULTS: The frequencies of K-ras/H-ras mutation and promoter methylation of the RASSF1A, RASSF2A, PTEN, and HIN-1 genes were 6.6%, 22.4%, 27.8%, 1.2%, and 7.3%, respectively. A combination of RASSF1A and RASSF2A methylation was found to be significantly associated with poor disease-free survival (DFS). Furthermore, a gene dosage effect of the activated Ras/PI3K/AKT signal on DFS was observed in patients treated with radiotherapy after surgery but not in patients treated with surgery alone. The Ras/PI3K/AKT pathway was activated in 140 primary OSCCs among 286 patients treated with radiotherapy after surgery and methylation of RASSF1A/RASSF2A (75.7%) was the most common mechanism.
CONCLUSION: Our study indicates that epigenetic silencing of tumor suppressor genes involved in the Ras/PI3K/AKT pathway plays an important role in OSCC radioresistance and this provides a rationale for exploring novel treatment strategies.

Payne SR, Serth J, Schostak M, et al.
DNA methylation biomarkers of prostate cancer: confirmation of candidates and evidence urine is the most sensitive body fluid for non-invasive detection.
Prostate. 2009; 69(12):1257-69 [PubMed] Related Publications
BACKGROUND: A prostate cancer (PCa) biomarker with improved specificity relative to PSA is a public health priority. Hypermethylated DNA can be detected in body fluids from PCa patients and may be a useful biomarker, although clinical performance varies between studies. We investigated the performance of candidate PCa DNA methylation biomarkers identified through a genome-wide search.
METHODS: Real-time PCR was used to measure four DNA methylation biomarkers: GSTP1 and three previously unreported candidates associated with the genes RASSF2, HIST1H4K, and TFAP2E in sodium bisulfite-modified DNA. Matched plasma and urine collected prospectively from 142 patients referred for prostate biopsy and 50 young asymptomatic males were analyzed.
RESULTS: Analysis of all biomarkers in urine DNA significantly discriminated PCa from biopsy negative patients. The biomarkers discriminated PCa from biopsy negative patients with AUCs ranging from 0.64 for HIST1H4K (95% CI 0.55-0.72, P < 0.00001) to 0.69 for GSTP1 (95% CI 0.60-0.77, P < 0.00001). All biomarkers showed minimal correlation with PSA. Multivariate analysis did not yield a panel that significantly improved performance over that of single biomarkers. All biomarkers showed greater sensitivity for PCa in urine than in plasma DNA.
CONCLUSIONS: Analysis of the biomarkers in urine DNA significantly discriminated PCa from biopsy negative patients. The biomarkers provided information independent of PSA and may warrant inclusion in nomograms for predicting prostate biopsy outcome. The biomarkers' PCa sensitivity was greater for urine than plasma DNA. The biomarker performances in urine DNA should next be validated in formal training and test studies.

Li Z, Luo RT, Mi S, et al.
Consistent deregulation of gene expression between human and murine MLL rearrangement leukemias.
Cancer Res. 2009; 69(3):1109-16 [PubMed] Free Access to Full Article Related Publications
Important biological and pathologic properties are often conserved across species. Although several mouse leukemia models have been well established, the genes deregulated in both human and murine leukemia cells have not been studied systematically. We performed a serial analysis of gene expression in both human and murine MLL-ELL or MLL-ENL leukemia cells and identified 88 genes that seemed to be significantly deregulated in both types of leukemia cells, including 57 genes not reported previously as being deregulated in MLL-associated leukemias. These changes were validated by quantitative PCR. The most up-regulated genes include several HOX genes (e.g., HOX A5, HOXA9, and HOXA10) and MEIS1, which are the typical hallmark of MLL rearrangement leukemia. The most down-regulated genes include LTF, LCN2, MMP9, S100A8, S100A9, PADI4, TGFBI, and CYBB. Notably, the up-regulated genes are enriched in gene ontology terms, such as gene expression and transcription, whereas the down-regulated genes are enriched in signal transduction and apoptosis. We showed that the CpG islands of the down-regulated genes are hypermethylated. We also showed that seven individual microRNAs (miRNA) from the mir-17-92 cluster, which are overexpressed in human MLL rearrangement leukemias, are also consistently overexpressed in mouse MLL rearrangement leukemia cells. Nineteen possible targets of these miRNAs were identified, and two of them (i.e., APP and RASSF2) were confirmed further by luciferase reporter and mutagenesis assays. The identification and validation of consistent changes of gene expression in human and murine MLL rearrangement leukemias provide important insights into the genetic base for MLL-associated leukemogenesis.

Liao X, Siu MK, Chan KY, et al.
Hypermethylation of RAS effector related genes and DNA methyltransferase 1 expression in endometrial carcinogenesis.
Int J Cancer. 2008; 123(2):296-302 [PubMed] Related Publications
Epigenetic aberration is known to be important in human carcinogenesis. Promoter methylation status of RAS effector related genes, RASSF1A, RASSF2A, hDAB2IP (m2a and m2b regions) and BLU, was evaluated in 76 endometrial carcinomas and their non-neoplastic endometrial tissue by methylation specific PCR. Hypermethylation of at least one of the 5 genes was detected in 73.7% of carcinomas. There were significant correlations between methylation of hDAB2IP and RASSF1A, RASSF2A (p = 0.042, p = 0.012, respectively). Significantly, more frequent RASSF1A hypermethylation was found in Type I endometrioid carcinomas than Type II carcinomas (p = 0.049). Among endometrioid cancers, significant association between RASSF1A hypermethylation and advanced stage, as well as between methylation of hDAB2IP at m2a region with deep myometrial invasion (p < 0.05) was observed. mRNA expression of RASSF1A, RASSF2A and BLU in endometrial cancer cell lines significantly increased after treatment with the demethylating agent 5-Aza-2'-deoxycytidine supporting the repressive effect of hypermethylation on their transcription. Immunohistochemical study of DNMT1 on eight normal endometrium, 16 hyperplastic endometrium without atypia, 40 atypical complex hyperplasia and 79 endometrial carcinomas showed progressive increase in DNMT1 immunoreactivity from normal endometrium to endometrial hyperplasia and endometrioid carcinomas (p = 0.001). Among carcinomas, distinctly higher DNMT1 expression was observed in Type I endometrioid carcinomas (p < 0.001). DNMT1 immunoreactivity correlated with RASSF1A and RASSF2A methylation (p < 0.05). The data suggested that hypermethylation of RAS related genes, particularly RASSF1A, was involved in endometrial carcinogenesis with possible divergent patterns in different histological types. DNMT1 protein overexpression might contribute to such aberrant DNA hypermethylation of specific tumor suppressor genes in endometrial cancers.

Maruyama R, Akino K, Toyota M, et al.
Cytoplasmic RASSF2A is a proapoptotic mediator whose expression is epigenetically silenced in gastric cancer.
Carcinogenesis. 2008; 29(7):1312-8 [PubMed] Free Access to Full Article Related Publications
Gastric cancer cells often show altered Ras signaling, though the underlying molecular mechanism is not fully understood. We examined the expression profile of eight ras-association domain family (RASSF) genes plus MST1/2 and found that RASSF2A is the most frequently downregulated in gastric cancer. RASSF2A was completely silenced in 6 of 10 gastric cancer cell lines as a result of promoter methylation, and expression was restored by treating the cells with 5-aza-2'-deoxycytidine. Introduction of RASSF2A into non-expressing cell lines suppressed colony formation and induced apoptosis. These effects were associated with the cytoplasmic localization of RASSF2A and morphological changes to the cells. Complementary DNA microarray analysis revealed that RASSF2A suppresses the expression of inflammatory cytokines, which may in turn suppress angiogenesis and invasion. In primary gastric cancers, aberrant methylation of RASSF2A was detected in 23 of 78 (29.5%) cases, and methylation correlated significantly with an absence of the lymphatic invasion, absence of venous invasion, absence of lymph node metastasis, less advanced stages, Epstein-Barr virus, absence of p53 mutations and the presence of the CpG island methylator phenotype-high. These results suggest that epigenetic inactivation of RASSF2A is required for tumorigenesis in a subset of gastric cancers.

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