Reduced expression of RASSF1A in esophageal and nasopharyngeal carcinomas significantly correlates with tumor stage

Analysis of salivary detection of P16INK4A and RASSF1A promoter gene methylation and its association with oral squamous cell carcinoma in a Colombian population

Background

Epigenetic factors play a fundamental role in the etiopathogenesis of oral squamous cell carcinoma (OSCC). This study evaluated if salivary detection of P16INK4A/RASSF1A gene promoter methylation might be linked to the clinical/histological features of OSCC in a Colombian population.

Material and Methods

Methylation-specific polymerase chain reaction (MSP-PCR) was used to detect the methylation frequency of P16INK4A/RASSF1A genes in DNA obtained from whole saliva collected of 40 healthy controls (HC) and 43 OSCC patients. Determination of the clinical performance of MSP-PCR assay was based on standard algorithms derived from two-way contingency table analysis. The association of methylation status of targeted genes with OSCC was analyzed in a multivariate binary logistic regression model.

Results

There were significantly higher proportions of promoter methylation of these target genes in OSCC patients when compared with HC. The analysis of single methylated genes showed high specificity, good positive and negative predictive values, but was accompanied by a low sensitivity. OSCC cases with clinical stage III/IV, poorly differentiated, and severe cellular atypia showed a significantly greater proportion of methylated than that of unmethylated targeted genes in saliva samples. Logistic regression analysis indicated an independent association of P16INK4A and RASSF1A promoter methylation with OSCC diagnosis. A significant interaction effect between ageing and P16INK4A promoter methylation was also detected.

Conclusions

Salivary detection of P16INK4A and RASSF1A promoter methylation appears to be independently associated with OSCC and may be linked to the tumor activity in the present population. Consequently, the targeting of these genes in saliva samples might constitute an important tool for diagnosis and prognosis purposes.

Key words:Gene methylation, oral squamous cell carcinoma, P16INK4A, RASSF1A, saliva.

Correlation Between β-Catenin Expression and Staging in Nasopharyngeal Carcinoma Patients

Nasopharyngeal carcinoma (NPC) is a malignant disease derived from nasopharyngeal epithelial cells that have a higher tendency for invasion and metastasis to the cervical lymph nodes than other head-neck malignancies. NPC patients with the same stages often show different progressions and prognoses. This suggests that clinical stages are not sufficient to predict progressivity, so biomarkers are required to provide better progression predictions. Some literature shows that the development and progression of NPC is a complex mechanism involving various components of signal paths, it plays a role in regulating the process of proliferation, angiogenesis and apoptosis. One of the most studied is β-catenin protein that is a key component of the canonical Wnt signal pathway. The β-catenin protein is reported to have roles in increasing the proliferative pathway of c-Myc and cyclin D1, increasing the expression of IL-8 proangiogenesis factor, decreasing expression of RASSF1A tumor suppressor and inhibiting apoptosis through the barriers of caspace-9 activity. To determine the association of β-catenin expression and staging in nasopharyngeal carcinoma patients. The research design used was analytic observational research with cross sectional approach. Samples were enrolled using consecutive sampling. The β-catenin expression was examined from the NPC tissue paraffin block with the immunohistochemical cracking technique, using an anti-β-catenin rabbit polyclonal antibody from Boster Biotechnology, California, USA. The β-catenin expression was assessed visually using a binocular light microscope and a scoring method according to the Allred scale index by an Anatomical Pathology consultant. Statistical analysis was performed using Spearman's test to determine the association between β-catenin expression and staging in NPC patients. The significance level was α = 0.05. The study was conducted from May to December 2015 at Otolaryngology Unit of Dr. Soetomo General Soetomo, Surabaya. There were 40 patients who fulfilled the inclusion criteria. Spearman test results obtained p value = 0.060. The correlation of β-catenin expression with staging in NPC patients was found to be non-significant (p > 0.05). There was no correlation between β-catenin expression and staging in NPC patients.

Metastasis-suppressing NID2, an epigenetically-silenced gene, in the pathogenesis of nasopharyngeal carcinoma and esophageal squamous cell carcinoma

Nidogen-2 (NID2) is a key component of the basement membrane that stabilizes the extracellular matrix (ECM) network. The aim of the study is to analyze the functional roles of NID2 in the pathogenesis of nasopharyngeal carcinoma (NPC) and esophageal squamous cell carcinoma (ESCC). We performed genome-wide methylation profiling of NPC and ESCC and validated our findings using the methylation-sensitive high-resolution melting (MS-HRM) assay. Results showed that promoter methylation of NID2 was significantly higher in NPC and ESCC samples than in their adjacent non-cancer counterparts. Consistently, down-regulation of NID2 was observed in the clinical samples and cell lines of both NPC and ESCC. Re-expression of NID2 suppresses clonogenic survival and migration abilities of transduced NPC and ESCC cells. We showed that NID2 significantly inhibits liver metastasis. Mechanistic studies of signaling pathways also confirm that NID2 suppresses the EGFR/Akt and integrin/FAK/PLCγ metastasis-related pathways. This study provides novel insights into the crucial tumor metastasis suppression roles of NID2 in cancers.

Genome-wide hypomethylation and specific tumor-related gene hypermethylation are associated with esophageal squamous cell carcinoma outcome

INTRODUCTION

Esophageal squamous cell carcinoma (ESCC) is a cancer of variable outcomes with limited effective treatments resulting in poor overall survival (OS). Epigenetic alterations contributing to this deadly cancer type that can be used as novel therapeutic or diagnostic targets are still poorly understood.

METHODS

We explored genome-wide DNA methylation data from The Cancer Genome Atlas project and identified a panel of tumor-related genes hypermethylated in ESCC. The methylation statuses of RASSF1, RARB, CDKN2A (p16INK4a, p14ARF), APC, and RUNX3 genes and long interspersed nucleotide element-1 (LINE-1) were validated in a large cohort (n = 140) of clinically well-annotated ESCC specimens and esophageal normal mucosa (n = 28) using a quantitative methylation-specific polymerase chain reaction.

RESULTS

Hypermethylation of RARB, p16INK4a, RASSF1, APC, RUNX3, and p14ARF were observed in 55%, 24%, 20%, 19%, 14%, and 8% of specimens, respectively. Hypermethylation of APC was significantly associated with tumor depth (p = 0.02) and American Joint Committee on Cancer stage (p = 0.03). Global DNA methylation level, assessed by LINE-1, was significantly lower in ESCC than in normal mucosa (p < 0.0001), and lower in greater than or equal to T2 (n = 69) than T1 tumors (n = 45; p = 0.03). There was a significant inverse correlation between LINE-1 and RARB methylation (p = 0.008). Importantly, hypermethylation of RASSF1 and APC genes was significantly associated with overall survival (OS; p = 0.006 and p = 0.007, respectively). In addition, patients with tumors containing a higher number of methylated genes (greater than two genes) presented worse OS (p = 0.003).

CONCLUSIONS

This study demonstrates that epigenetic alterations of a panel of tumor-related genes and the noncoding region LINE-1 can be used as prognostic indicators and help in clinical management of ESCC patients.

Transcriptome meta-analysis reveals dysregulated pathways in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant cancer arising from the epithelial surface of the nasopharynx that mostly appears in advanced stages of the disease, leading to a poor prognosis. To date, a number of mRNA profiling investigations on NPC have been reported in order to identify suitable biomarkers for early detection. However, the results may be specific to each study with distinct sample types. In this study, an integrative meta-analysis of NPC transcriptome data was performed to determine dysregulated pathways, potentially leading to identification of molecular markers. Ten independent NPC gene expression profiling microarray datasets, including 135 samples from NPC cell lines, primary cell lines, and tissues were assimilated into a meta-analysis and cross-validation to identify a cohort of genes that were significantly dysregulated in NPC. Bioinformatics analyses of these genes revealed the significant pathways and individual players involving in cellular metabolism, cell cycle regulation, DNA repair, as well as ErbB pathway. Altogether, we propose that dysregulation of these molecular pathways in NPC might play a role in the NPC pathogenesis, providing clues, which could eventually translate into diagnostic and therapeutic approaches.

RNAi-induced K-Ras gene silencing suppresses growth of EC9706 cells and enhances chemotherapy sensitivity of esophageal cancer

To analyze the growth, proliferation, apoptosis, invasiveness and chemotherapy sensitivity of EC9706 cells after K-Ras gene silencing, an expression carrier pSilencer-siK-Ras was constructed, and the EC9706 cell line was transfected using a liposome technique. Six groups were established: Control, siRNA NC (transfected with empty vector pSilencer2.1); Ras siRNA (transfected with pSilencer-siK-Ras2); Paclitaxel; Paclitaxel + siRNA NC; and Ras siRNA +Paclitaxel. After the treatment, RT-PCR, Western blotting, MTT assay, flow cytometry and the Transwell technique were used to assess expression of K-Ras mRNA and protein in EC9706 cells, as well as cell growth, proliferation, apoptosis and invasiveness. The effect of Paclitaxel chemotherapy was also tested. pSilencer-siK-Ras2 effectively down-regulated expression of K-Ras mRNA and protein in EC9706 cells, growth being significantly inhibited. Flow cytometry indicated obvious apoptosis of cells in the experimental group, with arrest in the G1 phase; cell migration ability was also reduced. After pSilencer-siK-Ras2 transfection or the addition of Paclitaxel, EC9706 cells were suppressed to different extents; the suppressive effect was strengthened by combined treatment. The results suggested that RNAi-induced K-Ras gene silencing could enhance chemotherapy sensitivity of esophageal cancer.

Loss of RASSF1A expression in colorectal cancer and its association with K-ras status

Background. The RAS-association domain family 1 A (RASSF1A) is a classical member of RAS effectors regulating cell proliferation and apoptosis. Loss of RASSF1A expression may shift the balance towards a growth-promoting effect without the necessity of activating K-ras mutations. Its potential association with K-ras mutations in colorectal cancer (CRC) is unclear. Methods. RASSF1A expression was examined in normal mucosa, adenoma, and tumor tissues of colon and rectum, respectively. We examined the association of RASSF1A expression, mutations of K-ras, and EGFR status in 76 primary CRCs. The relationship between clinicopathological characteristics and RASSF1A expression was also analyzed. Results. RASSF1A expression level decreased progressively in normal mucosa, adenoma and, tumor tissues, and the loss of RASSF1A expression occurred more frequently in tumor tissues. Of 76 primary CRCs, loss of RASSF1A expression and/or K-ras mutations were detected in 77% cases. Loss of RASSF1A expression was more frequent in K-ras wild-type than in mutation cases (63% versus 32%, P = 0.011). Conclusions. Our study indicates that loss of RASSF1A may be involved in pathogenesis of CRC, its expression was found predominantly in K-ras wild-type CRCs, suggesting that it may be another way of affecting RAS signaling, in addition to K-ras mutations.

Relationship between promoter methylation of the Runx3 and Rassf1a genes and Dnmt1 expression in gastric cancer

AIM: To analyze the promoter methylation of the human runt-related transcription factor 3 (Runx3) and ras-association domain family 1a (Rassf1a) genes and Dnmt1 protein expression in gastric cancer and to analyze their relationship with gastric carcinogenesis.

METHODS: Methylation status of the Runx3 and Rassf1a genes in 68 gastric carcinoma tissues and 68 paired surgical marginal normal gastric tissues was detected using methylation-specific PCR. Real-time RT-PCR was used to detect the expression of Runx3, Rassf1a, and Dnmt1 mRNAs, and immunohistochemistry was used to detect the expression of RUNX3, RASSF1a, and DNMT1 proteins in the above samples.

RESULTS: The positive rates of promoter methylation of the Runx3 and Rassf1a genes were significantly higher in gastric cancer than in normal tissue (45.59% vs 10.29%; 64.70% vs 7.35%; both P < 0.0001). The positive rates of Runx3 and Rassf1a mRNA expression in gastric cancer were significantly lower than those in normal tissue (36.76% vs 100%; 27.94% vs 97.06%; both P < 0.0001), while that of Dnmt1 mRNA expression was higher compared to normal tissue (80.88% vs 17.65%, P < 0.0001). The expression patterns of RUNX3, RASSF1a, and DNMT1 proteins were consistent with those of Runx3, Rassf1a, and Dnmt1 mRNAs. The negative rates of Runx3 and Rassf1a mRNA expression in gastric cancer were significantly higher in the methylation group than in the non-methylation group (72.09% vs 0%; 85.71% vs 2.94%; both P < 0.0001). There was a negative correlation between the expression of RUNX3 and RASSF1a proteins and that of DNMT1 protein in gastric cancer tissue (r = -0.627, P < 0.0001; r = - 0.477, P < 0.0001).

CONCLUSION: The promoter methylation of the Runx3 and Rassf1a genes and high expression of Dnmt1 may be associated with the occurrence of gastric cancer.

Clinical significance of TIMP-3 and RASSF1A expression in colorectal cancer

AIM: To investigate the correlation between TIMP-3 and RASSF1A expression and clinicopathologic features of colorectal cancer.

METHODS: The expression of TIMP-3 and RASSF1A was detected by immunohistochemistry in colorectal cancer, tumor-adjacent colorectal tissue and normal colorectal tissue specimens. The correlation between TIMP-3 and RASSF1A expression and clinicopathologic features, such as patient's age, gender, infiltration degree, and lymph node metastasis, was analyzed. The correlation between TIMP-3 and RASSF1A expression was also determined by spearman′s rank correlation analysis.

RESULTS: The positive rates of TIMP-3 expression in normal colorectal mucosa, tumor adjacent tissue and colorectal cancer were 90.0%, 70.0% and 16.7%, respectively, and those of RASSF1A were 83.3%, 63.3% and 23.3%. In colorectal cancer, the expression of TIMP-3 and RASSF1A was related to lymph node metastasis, depth of invasion, and degree of tumor differentiation (all P < 0.05). Spearman rank correlation analysis showed that there is a positive correlation between TIMP-3 and RASSF1A expression in colorectal adenocarcinoma (r = 0.256, P < 0.05).

CONCLUSION: The expression of TIMP-3 is significantly correlated with that of RASSF1A in colorectal cancer. The down-regulation of TIMP-3 and RASSF1A may be involved in the genesis of colorectal cancer and may be used as an index for evaluation of tumor malignancy.

Epstein-Barr virus-encoded latent membrane protein 1 (LMP1) and LMP2A function cooperatively to promote carcinoma development in a mouse carcinogenesis model

The Epstein-Barr virus (EBV) proteins latent membrane proteins 1 and 2 (LMP1 and LMP2) are frequently expressed in EBV-associated lymphoid and epithelial cancers and have complex effects on cell signaling and growth. The effects of these proteins on epithelial cell growth were assessed in vivo using transgenic mice driven by the keratin 14 promoter (K14). The development of papillomas and carcinomas was determined in the tumor initiator and promoter model using dimethyl benzanthracene (DMBA), followed by repeated treatments of 12-O-tetradecanoyl phorbol 13-acetate (TPA). In these assays, LMP1 functioned as a weak tumor promoter and increased papilloma formation. In contrast, mice expressing LMP2A did not induce or promote papilloma formation. Transgenic LMP1 mice had slightly increased development of squamous cell carcinoma; however, the development of carcinoma was significantly increased in the doubly transgenic mice expressing both LMP1 and LMP2A. DMBA treatment induces an activating mutation in the Harvey-ras (H-ras(61)) oncogene, and this mutation was identified in most papillomas and carcinomas although several papillomas and carcinomas in K14-LMP1 and K14-LMP1/LMP2A mice lacked the mutation. Analysis of signaling pathways that are known to be activated by LMP1 and/or LMP2 indicated that all genotypes had high levels of activated extracellular signal-regulated kinase (ERK) and Stat3 in carcinomas with significantly higher activation in the doubly transgenic carcinomas. These findings suggest that, in combination, LMP1 and LMP2 contribute to carcinoma progression and that this may reflect the combined effects of the proteins on activation of multiple signaling pathways. This study is the first to characterize the effects of LMP2 on tumor initiation and promotion and to identify an effect of the combined expression of LMP1 and LMP2 on the increase of carcinoma development.

Signaling Transduction Network Mediated by Tumor Suppressor/Susceptibility Genes in NPC

Nasopharyngeal carcinoma (NPC) is a polygenetic disease. SPLUNC1, UBAP1, BRD7, NAG7, NOR1, NGX6 and LTF genes were found to be tumor suppressor/susceptibility genes in different stages of NPC. SPLUNC1, an early warning molecular diagnosis marker, inhibits the bacteria clone formation, and is an innated immune molecule. SPLUNC1 can negatively regulate the ERK/MAPK signaling transduction pathway to inhibit NPC cell proliferation and induce apoptosis. BRD7, a transcript regulation factor, interacts with BRD2, and promotes apoptosis induced by BRD2. Its promoter is regulated by c-Myc and SP1. BRD7 inhibits NPC cell cycle progression, preventing passage through G0/G1 by suppressing ras/MEK/ERK, Rb/E2F and Wnt signaling pathways. Abnormal activation of BRD7 is crucial to cell cycle turbulence in NPC. NGX6, a metastasis-associated protein, can negative-regulate the EGF/Ras/MAPK signaling transduction pathway, and interacts with ezrin protein to inhibit NPC cell invasion and metastasis. LTF, also a metastasis-associated protein, can negatively regulate MAPK signal transduction pathways, such as JNK2 and ERK, to inhibit NPC cell proliferation and growth. Taken together, it was found that these tumor suppressor/susceptibility genes can regulate key molecules involved in cell signal pathways such as ras/MEK/ERK, Rb/E2F and EGFR ras/MEK/MAPK, and can regulate the expression of some adhesion molecules such as ezrin, nm23 and α-catenin. According to functional genomics and signaling transduction pathways, we have described a signaling cross-talk network between the tumor suppressor/susceptibility genes involved in NPC. These tumor suppressor/susceptibility genes may be potential treatment targets for NPC in the future.

Correlation between hMLH1 and RASSF1A expression and prognosis of esophageal carcinoma

AIM: To investigate the expression of human mutL homologue 1 (hMLH1) and Ras association domain family 1A (RASSF1A) in esophageal squamous cell carcinoma (ESCC) and to analyze their prognostic value.

METHODS: The expression of hMLH1 mRNA and RASSF1A protein in 60 specimens of esophageal cancer was detected by in situ hybridization (ISH) and immunohistochemistry, respectively. The relationship of hMLH1 and RASSF1A expression with ESCC prognosis was evaluated using Cox regression model and Kaplan-Meier survival curve analysis.

RESULTS: The positive rates of hMLH1 and RASSF1A expression in esophageal carcinoma were significantly lower than those in normal esophageal tissue (41.67% vs 90.00%, 80.00% vs 100.00%; both P < 0.05). The expression of hMLH1 and RASSF1A was correlated with tumor TNM stage, invasion depth, lymph node metastasis, and tumor size (all P < 0.05), but not with patient's nationality (P > 0.05). The expression of RASSF1A was positively correlated with that of hMLH1 (r = 0.338, P < 0.01). The five-year overall survival rate for all the patients was 35% (21/60). Univariate survival analysis suggested that the five-year survival rate for patients with positive expression of RASSF1A was higher than that for patients with negative expression of RASSF1A though the difference was not significant (P > 0.05). Patients with positive expression of hMLH1 had a significantly higher survival rate compared to those with negative expression of hMLH1 (P < 0.05). Cox multivariate analysis indicated that tumor invasion depth and TNM stage were independent prognostic factors affecting survival of ESCC patients (both P < 0.05).

CONCLUSION: Both hMLH1 and RASSF1A were weakly expressed in ESCC. The expression of hMLH1 and RASSF1A was positively correlated with ESCC progression. Expression of hMLH1 and RASSF1A might be used as a prognostic parameter in ESCC patients.

Clinical significance of RASSF1A promoter methylation in gastric cardiac carcinoma and esophageal squamous cell carcinoma

AIM: To investigate the methylation status of the promoter region of the RASSF1A gene in gastric cardiac adenocarcinoma (GCA) and esophageal squamous cell carcinoma (ESCC) in the distal esophagus and to analyze their clinical significance.

METHODS: Thirty-three GCA patients and 36 ESCC patients who came from a high-incidence region of ESCC in Linzhou, Henan and were treated at Yaocun Esophageal Cancer Hospital and Linzhou Center Hospital were enrolled in this study. No statistical differences were found in sex, age, and tumor differentiation between GCA and ESCC patients. No patients received chemotherapy or radiotherapy before operation. Methylation-specific polymerase chain reaction (MSP) was used to investigate the methylation status of the promoter region of the RASSF1A gene in the two groups of patients.

RESULTS: For GCA patients, the frequencies of RASSF1A promoter methylation in cancer tissue (CA), matched dysplasia tissue (DYS) and normal tissue (NOR) were 63.6%, 20% and 4.2%, respectively. For ESCC patients, the frequencies of RASSF1A promoter methylation in tumor tissue, matched dysplasia tissue and normal tissue were 66.7%, 25% and 16.7%, respectively. High methylation frequency was found in both types of cancer tissue. With the evolution of lesions (NOR-DYS-CA), the frequency of RASSF1A promoter methylation showed an increasing tendency in both GCA (χ² = 22.173, P < 0.001) and ESCC patients (χ² = 19.324, P < 0.001). The frequency of RASSF1A promoter methylation in normal tissue from GCA patients was lower than that from ESCC patients.

CONCLUSION: RASSF1A promoter hypermethylation is a molecular event that occurs in both GCA and ESCC patients. RASSF1A is a potential candidate biomarker for early detection of carcinoma of the esophagogastric junction.

DNA methylation in thoracic neoplasms

Thoracic neoplasms, which include lung cancers, esophageal carcinoma, and thymic epithelial tumors, are the leading causes of tumor-related death and a major health concern worldwide. The development of neoplasms is a multistep process involving both genetic and epigenetic alterations. A growing body of research provides evidence that aberrant DNA methylation, including DNA hypermethylation in promoter regions, global DNA hypomethylation and the overexpression of DNA methyltransferases, plays an important role in tumorigenesis. In this review, we summarize published observations of methylation pattern disruptions in thoracic tumors, and discuss how these abnormalities contribute to the development of cancers. We review recent findings showing that suppressing the activity of the DNA methylating enzymes DNMTs can have potent anti-cancer effects, and discuss the possibility of developing novel therapies for thoracic tumors based on DNMT inhibition.

Decreased expression of updated NESG1 in nasopharyngeal carcinoma: its potential role and preliminarily functional mechanism

Human NESG1 (CCDC19) gene was originally isolated in our laboratory from human nasopharynx tissue. However, the biological and clinical significances of this gene remain largely unknown. In this report, two errors in the originally submitted sequence of human NESG1 gene were found, and the open reading frame sequence of NESG1 (Accession number: NM_012337.1) was revised and updated in the NCBI database (Accession number: NM_012337.2). The antibody raised against the revised sequence of NESG1 detected a single band of 66 kD in human nasopharynx tissues. NESG1 transcripts were specifically expressed in the nasopharynx epithelium. Expression of NESG1 transcripts and protein was downregulated or absent in nasopharyngeal carcinoma (NPC) tissues and cell lines in comparison to that in the normal nasopharynx tissues. The levels of NESG1 protein were significantly greater in the low-grade NPC tissues than that in the high-grade NPC tissues. Induced expression of NESG1 in otherwise NESG1-negative 5-8F cells not only significantly decreased cell proliferation, G1-S phase transition, but also markedly inhibited the ability of cell migration and invasion as well as in vivo tumorigenesis. Furthermore, NESG1 also significantly regulated the expression of cell cycle regulator CCNA1 and p21. Our findings first provided evidence that NESG1 may act as a tumor suppressor by inhibiting cell proliferation, invasion and migration of NPC cells.

Prognostic significance of RASSF1A expression and methylation status in esophageal squamous cell carcinoma

AIM: To investigate the expression and methylation status of the RASSF1A gene in esophageal squamous cell carcinoma (ESCC) and to analyze their prognostic significance.

METHODS: The mRNA expression and DNA methylation of the promoter region of the RASSF1A gene in normal esophageal tissue samples and ESCC tissue samples taken from 49 ESCC patients were detected by real-time RT-PCR and real-time methylation-specific PCR (qMSP), respectively.

RESULTS: RASSF1A mRNA expression was down-regulated in 53.06% (26/49) of ESCC tissue samples. The level of RASSF1A mRNA expression in ESCC was significantly lower than that in adjacent normal tissue (P < 0.05). Down-regulation of RASSF1A mRNA expression was correlated with TNM stage, lymph node metastasis and poor prognosis in ESCC patients (all P < 0.05). Hypermethylation of the RASSF1A gene promoter region was detected in 77.60% (38/49) of ESCC patients. RASSF1A gene promoter hypermethylation was correlated with TNM stage, lymph node metastasis and poor prognosis in ESCC patients (all P < 0.05).

CONCLUSION: RASSF1A gene promoter hypermethylation is a very common molecular event in ESCC and may be responsible for the down-regulation of RASSF1A mRNA expression. Down-regulation of RASSF1A mRNA expression and hypermethylation of RASSF1A gene promoter region were significantly correlated with lymph node metastasis, TNM stage and poor prognosis in ESCC patients.

Extracellular protease ADAMTS9 suppresses esophageal and nasopharyngeal carcinoma tumor formation by inhibiting angiogenesis

ADAMTS metalloprotease family member ADAMTS9 maps to 3p14.2 and shows significant associations with the aerodigestive tract cancers esophageal squamous cell carcinoma (ESCC) and nasopharyngeal carcinoma (NPC). However, the functional impact of ADAMTS9 on cancer development has not been explored. In this study, we evaluated the hypothesized antiangiogenic and tumor-suppressive functions of ADAMTS9 in ESCC and NPC, in stringent tumorigenicity and Matrigel plug angiogenesis assays. ADAMTS9 activation suppressed tumor formation in nude mice. Conversely, knockdown of ADAMTS9 resulted in clones reverting to the tumorigenic phenotype of parental cells. In vivo angiogenesis assays revealed a reduction in microvessel numbers in gel plugs injected with tumor-suppressive cell transfectants. Similarly, conditioned medium from cell transfectants dramatically reduced the tube-forming capacity of human umbilical vein endothelial cells. These activities were associated with a reduction in expression levels of the proangiogenic factors MMP9 and VEGFA, which were consistently reduced in ADAMTS9 transfectants derived from both cancers. Taken together, our results indicate that ADAMTS9 contributes an important function in the tumor microenvironment that acts to inhibit angiogenesis and tumor growth in both ESCC and NPC.

Clinicopathological significance of RASSF1A reduced expression and hypermethylation in hepatocellular carcinoma

PURPOSE

Protein downregulation and hypermethylation of Ras association domain family 1A (RASSF1A) has been recognized as an important early event in different classes of carcinogenesis, but clinicopathological significance of RASSF1A protein expression and methylation in hepatocellular carcinoma (HCC) remains largely unknown. The aim of the study was to investigate the expression of RASSF1A protein and methylation in HCC and their clinical significance.

METHODS

Immunohistochemistry was employed to detect the expression of RASSF1A proteins in liver tissue microarrays. Aberrant promoter hypermethylation of RASSF1A was investigated in DNA from HCC, matching noncancerous tissues and serum of 35 HCC patients by methylation-specific PCR.

RESULTS

RASSF1A protein expression in HCC was significantly lower than that in noncancerous (p = 0.015) and paracancerous tissues (p = 0.017). In addition, reduced RASSF1A protein expression is related to TNM stage, metastasis, alpha-fetoprotein, portal vein embolus, capsular infiltration, and multiple tumor nodes. Furthermore, RASSF1A promoter methylation in HCC was significantly higher than that in noncancerous liver tissues (p < 0.05). Meanwhile, RASSF1A promoter hypermethylation was detected in 14 in the serum DNA from HCC patients, whereas no hypermethylation was detected in the normal controls. Hypermethylation of RASSF1A in HCC serum and tissues was negatively correlated with the expression of RASSF1A protein expression (p < 0.05).

CONCLUSIONS

The loss or abnormal protein downregulation and the promoter hypermethylation of RASSF1A could play important roles in the tumorigenesis development and metastases of HCC. The detection of the promoter hypermethylation of RASSF1A in serum DNA could be a valuable biomarker for early-stage diagnosis in populations at high risk of HCC.

Methylation associated inactivation of RASSF1A and its synergistic effect with activated K-Ras in nasopharyngeal carcinoma

Background

Epigenetic silencing of tumor suppressor genes associated with promoter methylation is considered to be a hallmark of oncogenesis. RASSF1A is a candidate tumor suppressor gene which was found to be inactivated in many human cancers. Although we have had a prelimilary cognition about the function of RASSF1A, the exact mechanisms about how RASSF1A functions in human cancers were largely unknown. Moreover, the effect of mutated K-Ras gene on the function of RASSF1A is lacking. The aim of this study was to investigate the expression profile and methylation status of RASSF1A gene, and to explore its concrete mechanisms as a tumor suppressor gene in Nasopharyngeal Carcinoma.

Methods

We examined the expression profile and methylation status of RASSF1A in two NPC cell lines, 38 primary nasopharyngeal carcinoma and 14 normal nasopharyngeal epithelia using RT-PCR and methylated specific PCR(MSP) respectively. 5-aza-dC was then added to confirm the correlation between hypermethylation status and inactivation of RASSF1A. The NPC cell line CNE-2 was transfected with exogenous pcDNA3.1(+)/RASSF1A plasmid in the presence or absence of mutated K-Ras by liposome-mediated gene transfer method. Flow cytometry was used to examine the effect of RASSF1A on cell cycle modulation and apoptosis. Meanwhile, trypan blue dye exclusion assays was used to detect the effect of RASSF1A transfection alone and the co-transfection of RASSF1A and K-Ras on cell proliferation.

Results

Promoter methylation of RASSF1A could be detected in 71.05% (27/38) of NPC samples, but not in normal nasopharyngeal epithelia. RASSF1A expression in NPC primary tumors was lower than that in normal nasopharyngeal epithelial (p < 0.01). Expression of RASSF1A was down-regulated in two NPC cell lines. Loss of RASSF1A expression was greatly restored by the methyltransferase inhibitor 5-aza-dC in CNE-2. Ectopic expression of RASSF1A in CNE-2 could increase the percentage of G0/G1 phase cells (p < 0.01), inhibit cell proliferation and induce apoptosis (p < 0.001). Moreover, activated K-Ras could enhance the growth inhibition effect induced by RASSF1A in CNE-2 cells (p < 0.01).

Conclusion

Expression of RASSF1A is down-regulated in NPC due to the hypermethylation of promoter. Exogenous expression of RASSF1A is able to induce growth inhibition effect and apoptosis in tumor cell lines, and this effect could be enhanced by activated K-Ras.

Aberrant methylation and reduced expression of RASSF1A in Ewing sarcoma

BACKGROUND

Ewing sarcoma (ES) is the second most common solid bone and soft tissue malignancy in children and young adults with low cure rates indicating the need to identify further prognostic markers. The importance of methylation in the inactivation of key tumor suppressor genes including RASSF1A has begun to be appreciated in context of cancer development, prognosis and therapy. However there is lack of similar broad based studies in ES. The objective of this study was to analyze RASSF1A methylation and assess its clinical significance in ES.

PROCEDURE

The methylation of RASSF1A was determined 31 ES tumor samples and 4 ES cell lines. ES cell lines were also treated with demethylating agent 5-aza-2'-deoxycytidine to ascertain its effect on methylation. RASSF1A expression was studied in 12 ES tumors. The association between RASSF1A methylation, clinical parameters and outcome was also analyzed.

RESULTS

Methylation of RASSF1A was observed in 21/31 (68%) tumors and in 3/4 ES cell lines. A significant correlation of methylation to reduced expression of RASSF1A was observed in 12 ES tumors analyzed (P = 0.0013) and in all cell lines. ES patients with methylated RASSF1A had worse prognosis compared to the unmethylated group (P = 0.049). Treatment with 5-aza-2'-deoxycytidine resulted in the re-expression of the unmethylated form of RASSF1A in two ES cell lines.

CONCLUSION

RASSF1A is frequently methylated in ES.

Expression of RASSF1A and CyclinD1 in gastric mucosal lesions and their correlations

AIM: To investigate the expression of Ras association domain family 1A gene (RASSF1A) and CyclinD1 as well as their correlations in gastric mucosal lesions.

METHODS: We detected the expression of RASSF1A and CyclinD1 in tissue specimens of gastric cancer (n = 69), chronic superficial gastritis (n = 45), chronic atrophic gastritis (n = 45), chronic gastritis accompanied with intestinal metaplasia (n = 45) and chronic gastritis accompanied with atypical hyperplasia (n = 47) using SP immunohistochemistry.

RESULTS: The positive rate of RASSF1A expression was significantly lower in gastric carcinoma than that in chronic superficial gastritis (χ² = 10.4, P < 0.05); In the mucosa of precancerous lesions, the expression of RASSF1A protein was decreased gradually (χ² = 28.7, P < 0.05), and obviously correlated with the degrees of tumor differentiation (P < 0.05). CyclinD1 protein was hardly expressed in chronic superficial gastritis, but its expression was significantly elevated in gastric cancer (84.1%). The expression of CyclinD1 was increased gradually in the mucosa of precancerous lesions (χ² = 11.9, P < 0.05), and it was markedly higher in gastric carcinoma than that in the other lesions (χ² = 22.0, 19.6, 29.4; all P < 0.01). There was a negative correlation between the expression of RASSF1A and CyclinD1 protein in gastric carcinoma (r_s = -0.323, P < 0.05).

CONCLUSION: RASSF1A expression is down-regulated while CyclinD1 expression is up-regulated in gastric mucosa during the evolution process of chronic superficial gastritis→chronic atrophic gastritis→intestinal metaplasia→gastric dysplasia→gastric carcinoma. Combined detection of the two markers may help to study the mechanism of gastric cancer pathogenesis and development.