sodium-bisulfite and Stomach-Neoplasms

Genome-wide DNA hypomethylation plays an important role in genomic instability and carcinogenesis. DNA methylation in the long interspersed nucleotide element-1, L1 (LINE-1) repetitive element is a good indicator of the global DNA methylation level. In some types of human neoplasms, LINE-1 methylation level is attracting interest as a predictive marker for patient prognosis. However, the prognostic significance of LINE-1 hypomethylation in gastric cancer remains unclear.. Using 203 resected gastric cancer specimens, we quantified LINE-1 methylation using bisulfite-pyrosequencing technology. A Cox proportional hazards model was used to calculate the hazard ratio (HR), adjusted for the clinical and pathological variables.. Gastric cancers showed significantly lower LINE-1 methylation levels compared to matched normal gastric mucosa (p < 0.0001; n = 74). Tumoral LINE-1 methylation range was 11.6-97.5 on a 0-100 scale (n = 203; mean 71.4, median 74.4, standard deviation 12.9). LINE-1 hypomethylation was significantly associated with shorter overall survival [log-rank p = 0.029; univariate HR 2.01, 95 % confidence interval (CI) 1.09-3.99, p = 0.023; stage-matched HR 1.88, 95 % CI 1.02-3.74, p = 0.041; multivariate HR 1.98, 95 % CI 1.04-4.04, p = 0.036]. No significant effect modification was observed by any of the covariates in survival analysis (all p interaction >0.25).. LINE-1 hypomethylation in gastric cancer is associated with shorter survival, suggesting that it has potential for use as a prognostic biomarker.

Topics: Aged; Biomarkers, Tumor; DNA Methylation; Female; Follow-Up Studies; Genomic Instability; Humans; Long Interspersed Nucleotide Elements; Male; Neoplasm Staging; Polymerase Chain Reaction; Prognosis; Sequence Analysis, DNA; Stomach Neoplasms; Sulfites; Survival Rate

Aberrant DNA methylation of a CpG site is among the earliest and most frequent alterations in various tumors including gastric carcinoma. The aim of this study is to detect tumor-associated aberrant hypermethylation of the p16 gene from 60 gastric tumor and corresponding normal tissues using a seminested methylation-specific PCR (MSP). The results indicated that hypermethylation of the p16 gene could be detected in 80% (48/60) of the gastric tumor samples from the first PCR. However, the frequency increased significantly to 86.7% (52/60) of the gastric tumor samples after the second PCR. These results show that this technique increases the sensitivity of detecting p16 hypermethylation from tumor samples. Furthermore, the aberrant methylation of p16 was observed in all of the stages, confirming that this epigenetic alteration is an early event during gastric carcinogenesis. Clinicopathologic parameters such as age, sex, and histological differentiation of GC were not significantly associated with the methylation status.

Topics: Cyclin-Dependent Kinase Inhibitor p16; DNA Methylation; DNA, Neoplasm; Female; Genes, p16; Humans; Male; Middle Aged; Polymerase Chain Reaction; Sensitivity and Specificity; Stomach Neoplasms; Sulfites

The proportion of gastric cancers positive for estrogen receptor (ER)-alpha expression is reported to be between 0-67%, depending upon the study. The role of ER-alpha in gastric carcinogenesis is unclear. The ER-alpha gene is located at chromosome 6q25.1, and the long arm of chromosome 6 has been known as a site with frequent loss of heterozygosity (LOH) in gastric cancer. ER expression is linked to suppression of cell proliferation in vitro. Epigenetic inactivation might explain the loss of ER-alpha gene expression in gastric cancer. Given there is no information available regarding the methylation status of the ER-alpha gene promoter region in gastric cancer, we investigated such methylation in 13 gastric cancer cell lines. Western blot analysis, reverse transcription-polymerase chain reaction (PCR), methylation-specific PCR (MS-PCR) and bisulfite sequencing analyses were used. ER-alpha protein was not detected in any cell line, although ER-alpha mRNA was detected in 1 of 13 gastric cancer cell lines. MS-PCR and bisulfite sequencing showed all 13 gastric cancer cell lines had methylated CpG regions in their ER-alpha gene promoters. In conclusion, inactivation of ER-alpha gene expression in gastric cancer cell lines appears associated with CpG island methylation near the TGA initiation codon of the ER-alpha gene.

Topics: Base Sequence; Blotting, Western; Cell Line, Tumor; Chromosomes, Human, Pair 6; Codon, Initiator; CpG Islands; DNA Methylation; Epigenesis, Genetic; Estrogen Receptor alpha; Gene Silencing; Humans; Molecular Sequence Data; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Biosynthesis; Receptors, Estrogen; Stomach Neoplasms; Sulfites

Whereas synuclein gamma (SNCG) gene expression is usually highly tissue-specific and restricted to the nervous system, SNCG is expressed in advanced-stage breast and ovarian cancers. When overexpressed, SNCG stimulates cancer cell proliferation and metastasis. It is thought that the molecular mechanism of CpG island demethylation may underlie aberrant SNCG expression. To determine whether aberrant SNCG expression and demethylation play a role in gastric carcinogenesis, we examined the expression and methylation status of SNCG in primary gastric cancers, gastric cancer cell lines, and non-neoplastic gastric mucosal tissues.. Ten gastric cancer cell lines, 105 primary gastric cancers, and 10 non-neoplastic gastric mucosal tissues were examined. SNCG expression and methylation status were examined by reverse transcription-PCR and bisulfite-single-strand conformational polymorphism followed by direct sequencing, respectively. The relationship between SNCG methylation status and various clinicopathological factors of the primary gastric cancers was then analyzed.. SNCG mRNA expression was observed in 5 of 10 cell lines. Analysis of cell lines positive for SNCG expression revealed that most of the SNCG CpGs were demethylated. SNCG mRNA was not expressed in the 10 non-neoplastic gastric mucosal tissues, although several CpGs were demethylated. Of the 105 primary gastric cancers, 40 (38.1%) showed apparent SNCG demethylation, similar to the result obtained using cell lines. SNCG demethylation was more frequent in primary gastric cancers positive for lymph node metastasis (51%; 26 of 51) than in cancers without lymph node involvement (26%; 14 of 54; P < 0.05), and also more common in stage II-IV (48%; 27 of 56) than in stage I (27%; 13 of 49) cancers (P < 0.05).. Aberrant SNCG gene expression can occur via CpG island demethylation, and tends to occur during the more progressive stages of gastric carcinogenesis.

Topics: Adult; Aged; Aged, 80 and over; Azacitidine; Cell Division; Cell Line, Tumor; CpG Islands; Decitabine; Disease Progression; DNA Methylation; DNA, Complementary; Exons; Female; Gastric Mucosa; Gene Expression Regulation, Neoplastic; Humans; Male; Middle Aged; Neoplasm Metastasis; Nerve Tissue Proteins; Polymorphism, Single-Stranded Conformational; Prognosis; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stomach Neoplasms; Sulfites; Synucleins; Time Factors

The Arp2/3 complex and filamins play important roles in organization of actin cytoskeleton, and thus in cellular morphology and locomotion. We recently identified decreased expression of a gene for one of seven subunits of the Arp2/3 complex, the p41-Arc gene, and silencing of a filamin gene, the FLNc gene, in human gastric cancers. In this study, gene expressions of the seven subunits of the Arp2/3 complex, including p41-Arc, and their methylation statuses were analyzed in human gastric cancers. Quantitative real-time RT-PCR analysis of 32 primary gastric cancer samples and eight gastric cancer cell lines revealed that expressions of all the seven genes were significantly decreased. All the 32 primary cancer samples showed decreased expression of at least one subunit, and 25 samples showed decreased expressions of four or more of the seven subunits. Methylation-specific PCR analysis showed that none of the CpG islands in the 5' regions of the six genes other than p41-Arc were methylated in primary gastric cancers or cell lines. The consistent decrease of the Arp2/3 complex genes and its important role in actin organization suggested that the decrease could be involved in cancer phenotypes, such as dysplastic morphology.

Topics: Actin-Related Protein 2; Actin-Related Protein 2-3 Complex; Actin-Related Protein 3; Actins; Cell Line, Tumor; CpG Islands; Cytoskeletal Proteins; DNA; DNA Methylation; DNA Primers; Gene Silencing; Humans; Models, Genetic; Phenotype; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Structure, Tertiary; Reverse Transcriptase Polymerase Chain Reaction; Stomach Neoplasms; Sulfites

Silencing of tumor suppressor and tumor-related genes by hypermethylation at promoter CpG islands is frequently found in human tumors, including gastric cancer. Promoter methylation is not restricted to cancer cells, and is also present in non-neoplastic cells as an age-related tissue-specific phenomenon. To clarify the physiological consequence of DAP-kinase and RUNX3 age-related methylation in gastric epithelia, we investigated the promoter methylation status of these genes in both neoplastic and non-neoplastic gastric epithelia obtained at autopsy and surgery, as well as in 10 gastric cancer cell lines. Methylation of DAP-kinase and RUNX3 was detected in 10% (1/10) and 70% (7/10) of the cell lines, respectively, and was almost concordant with their expression status. Among autopsy samples, methylation of these genes was not seen in non-neoplastic gastric epithelia from persons who were aged 22 years and below (0%; 0/4). DAP-kinase was methylated in 87% (13/15) of non-neoplastic gastric epithelia of persons who were aged 45 years or older, while RUNX3 methylation in non-neoplastic gastric epithelia was restricted to individuals who were aged 77 years or older. Among samples obtained from patients with stomach cancer, methylation was observed in both the neoplastic and the corresponding non-neoplastic gastric epithelia; 43% (40/93) and 73% (68/93) for DAP-kinase, and 45% (42/93) and 8% (7/93) for RUNX3, respectively. Frequencies of DAP-kinase and RUNX3 methylation differed significantly in non-neoplastic gastric epithelia (P < 0.01), although those in gastric cancers were almost the same. RUNX3 methylation is mostly cancer-specific, except for very old individuals, and therefore may be a possible molecular diagnostic marker and malignancy predictor.

Topics: Adenocarcinoma; Adolescent; Adult; Aged; Aged, 80 and over; Apoptosis Regulatory Proteins; Calcium-Calmodulin-Dependent Protein Kinases; Child; Child, Preschool; Core Binding Factor Alpha 3 Subunit; Death-Associated Protein Kinases; DNA Methylation; DNA-Binding Proteins; DNA, Neoplasm; Epithelial Cells; Female; Gastric Mucosa; Humans; Infant; Male; Middle Aged; Promoter Regions, Genetic; Stomach Neoplasms; Sulfites; Transcription Factors; Tumor Cells, Cultured

Promoter hypermethylation of CpG islands in tumour suppressor genes can lead to transcriptional inactivation. To investigate the association between methylation and expression at O6-methylguanine-DNA methyltransferase, we performed methylation-specific PCR and immunohistochemistry in 149 gastric carcinomas. Promoter methylation was found in 14.1% of tumours and loss of expression was detected in 11.4% of tumours. To examine correlation between the O6-methylguanine-DNA methyltransferase expression and the clinical data, we investigated O6-methylguanine-DNA methyltransferase expression in 315 consecutive gastric carcinomas. A similar frequency of loss of O6-methylguanine-DNA methyltransferase expression was confirmed in these cases. The loss of O6-methylguanine-DNA methyltransferase expression was significantly associated with pTNM stage (P=0.037), tumour invasion (P=0.02), microsatellite instability (P=0.041) and overall survival (P=0.01). Among 11 gastric cancer cell lines, SNU-620 showed the loss of O6-methylguanine-DNA methyltransferase expression as well as promoter methylation. After treatment with 5-aza-2-deoxycytidine, a demethylating agent, SNU-620 re-expressed O6-methylguanine-DNA methyltransferase mRNA. In summary, we suggest that during gastric carcinogenesis, the loss of O6-methylguanine-DNA methyltransferase expression frequently occurs via the hypermethylation of the CpG islands of the promoter region, and that this is significantly associated with the clinicopathological characteristics.

Topics: Antimetabolites, Antineoplastic; Azacitidine; Carcinoma; CpG Islands; Decitabine; DNA Methylation; DNA Modification Methylases; DNA Primers; Down-Regulation; Enzyme Inhibitors; Humans; Microsatellite Repeats; Mutation; Neoplasm Invasiveness; Neoplasm Staging; O(6)-Methylguanine-DNA Methyltransferase; Prognosis; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Analysis, DNA; Stomach; Stomach Neoplasms; Sulfites; Survival Rate; Transcription, Genetic; Tumor Cells, Cultured

Silencing of p16(INK4a) by methylation of the CpG islands in the promoter region has been found to be an alternative mechanism of inactivation in several tumors. However, in gastric carcinoma, the relationship between methylation status and the transcriptional silencing of the p16 gene remains to be clarified. In this study, we investigated whether methylation of a few specific CpG sites in the promoter region could significantly down-regulate p16 activity in the tumorigenesis of gastric carcinoma. By Southern analysis and bisulfite-modified genomic sequencing of 9 gastric-carcinoma cell lines, we found that the 5 cell lines (55.5%) not expressing p16 mRNA had methylated CpG sites at the promoter region of p16. In addition, we analyzed the p16-protein expression of 28 primary gastric carcinomas and their normal counterparts by immunohistochemical staining (IHC) on paraffin sections. Loss of p16 expression was detected in 6 cases (22%). In 5 out of these 6 (83%), the actual p16 gene was inactivated by de novo methylation of the promoter sites. Taken together, these results suggest a strong correlation between de novo methylation of a few specific CpG sites and transcriptional silencing of the p16 gene in gastric carcinoma.

Topics: Adenocarcinoma; Adult; Aged; Antimetabolites, Antineoplastic; Azacitidine; Blotting, Northern; Blotting, Southern; Carrier Proteins; CpG Islands; Cyclin-Dependent Kinase Inhibitor p16; Decitabine; DNA Methylation; Down-Regulation; Female; Humans; Immunohistochemistry; Male; Middle Aged; Models, Genetic; Mutagens; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Analysis, DNA; Stomach Neoplasms; Sulfites; Tumor Cells, Cultured