• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2542-2548
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• 2009

Direct methylation behaviors of 20 amino acids with tetramethylammonium hydroxide (TMAH) were studied under diluted conditions with silica. Amino acid concentration was controlled by dilution with silica ($SiO_2$) and the molar ratios of amino acid/silica were 0.20, 0.50, and 2.0. The molar ratios of amino acid/TMAH (0.51 - 4.64) also varied. It was found that arginine, asparagine, aspartic acid, cysteine, glutamic acid, and glutamine did not generate any directly methylated pyrolysis products, whereas alanine, glycine, isoleucine, leucine, methionine, phenylanaline, valine, and proline generated all the directly methylated pyrolysis products. Tri- and tetra methylated products of lysine consisted of two types. Histidine and threonine hardly generated the partly methylated products. Mono- and dimethylated products of serine, tryptophan, and tyrosine were not observed. Relative intensities of the methylated products varied with the amino acid concentration, TMAH concentration, and pyrolysis temperature. Direct methylation behaviors of amino acids were explained by the structural characteristics of amino acids.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.5
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• pp.2499-2506
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• 2016

Background: Gastric cancer (GC) is the second leading cause of cancer-related death worldwide. Several environmental, genetic and epigenetic factors have been suggested to have a role in GC development. Epigenetic mechanisms like histone changes and promoter hyper-methylation are now being increasingly studied. Associations between methylation of many gene promoters with the risk of gastric cancer have been investigated worldwide. Such aberrant methylation may result in silencing of specific genes related to cell cycling, cell adhesion, apoptosis and DNA repair. Thus this molecular mechanism might have a key role in proliferation and migration of cancerous cells. Materials and Methods: In this review article we included studies conducted on DNA methylation and gastric cancer in Iranian populations. Using Science direct, Pubmed/PMC, Springer, Wiley online library and SciELO databases, all published data until 31 January 2016 were gathered. We also searched Science direct data base for similar investigations around the world to make a comparison between Iran and other countries. Results: By searching these databases, we found that the association between methylation of seven gene promoters and gastric cancer had been studied in Iran until 31 January 2016. These genes were p16, hLMH1, E-cadherin, CTLA4, $THR{\beta}$, mir9 and APC. Searching in science direct database also showed that 92 articles had been published around the world till January 2016. Our investigation revealed that despite the importance of GC and its high prevalence in Iran, the methylation status of only a few gene promoters has been studied so far. More studies with higher sample numbers are needed to reveal the relation of methylation status of gene promoters to gastric cancer in Iran. Conclusions: Further studies will be helpful in identifying associations of DNA methylation in candidate genes with gastric cancer risk in Iranian populations.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.164-169
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• 1998

Vulcanized rubber containing three kinds of oligomeric resins such as cashew resin, t-octylphenol formaldehyde resin and terpene modified wood rosin has been characterized by simultaneous pyrolysis methylation-gas chromatography/mass spectrometry (SPM-GC/MS). After methylation by the SPM method using tetramethylammonium hydroxide, the methylated pyrolyzates of the corresponding resins were detected with higher sensitivity than underivatized pyrolyzates without any interferences from other ingredients of vulcanized rubber.

• Journal of Life Science
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• v.17 no.4 s.84
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• pp.522-528
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• 2007

In the present investigation, we studied the modulating effects of caffeic acid, chlorogenic acid, and (-)-epigallocatechin-3-gallate(EGCG) on the methylation status of promoter regions of cell cycle regulator, p16, in human breast cancer T-47D cells. We demonstrated that treatment of T-47D cells with caffeic acid, chlorogenic acid, or EGCG partially inhibited the methylation status of the promoter regions of p16 genes determined by methylation-specific PCR. In contrast, unmethylated p16 genes were increased with the treatment of T-47D cells with $20{\mu}M$ of caffeic acid or chlorogenic acid for 6 days. Treatment of T-47D cells with 5, 20 or $50{\mu}M$ of EGCG increased the unmethylation status of p16 gene up to 100%, and the methylation-specific bands of this gene were decreased up to 50% in a concentration-dependent manner. The finding of present study demonstrated that coffee polyphenols and EGCG have strong inhibitory effects of the cellular DNA methylation process through increased formation of S-adenosyl-homocysteine(SAH) during the catechol-O-methyltransferase (COMT)- mediated O-methylation of these dietary chemicals or an direct inhibition of the DNA methyltransferases. In conclusion, various dietary polyphenols could reverse the methylation status of p16 gene in human breast T-47D cells.

• Biomolecules & Therapeutics
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• v.2 no.1
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• pp.47-53
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• 1994

The methylation response as well as the level of methyl donor substance, 5-adenosyl-L-methionine (SAM) has been suggested to be related to hepatotoxicity including hepatocarcinogenesis. But direct correlation between protein methylation and hepatotoxicity has not been established to the present. To observe relationship between protein methylation and short-term hepatotoxicity induced by chemical substances, the activities of protein methylase I and II (PM I, PM II) were examined in cytosolic fraction of SD rat treated orally with acetaminophen(AA), $\alpha$-naphtyl-isothiocyanate (ANIT) and tetracycline (TC) that was known to produce necrosis, cholestasis and steatosis respectively. To evaluate the degree of hepatotoxicity induced by each chemicals, we observed the serum levels of indicative parameters and histopathological alteration. In AA treated group, the activities of PM I were increased at 6, 12 hours after administration, prior to the appearance of the hepatotoxicity by clinical parameters. It was suggested that the levels of PM I were related with the initial stage of hepatotoxic mechanism induced by AA. In ANIT treated group, though most of clinical parameters were significantly increased at 24, 48 hours after administration, the activity of PM I was not changed, indicating that ANIT induced hepatotoxicity was not coupled to protein methylation.

• Journal of Gastric Cancer
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• v.3 no.1
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• pp.50-55
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• 2003

Background: An aberrant function of the mismatch repair system has been reported to underlie carcinogenesis in several tumors, including colorectal and gastric carcinomas, and to induce the typical genotype of microsatellite instability (MSI). Purpose: We aimed to determine the frequency of MSI in early-onset sporadic gastric carcinoma and elucidate the role of promoter methylation in hMLH1 as the mechanism of MSI. Materials and Methods: Thirty-six early-onset sporadic gastric carcinomas were analyzed to determine the status of MSI and the frequency of methylation of the promoter region in hMLH1. MSI was determined using five markers recommended by NCI: MSI-H (high), MSI-L (low), and MSS (Microsatellite stable). Methylation specific PCR (MSP) and direct automated genomic sequencing analysis with DNA modified by sodium bisulfite have been performed to confirm promoter region methylation. All the data were analyzed regarding characteristics of molecular changes, and clinicopathologic variables. Results: The microsatellite status was determined as MSI-H in five cases ($13.8\%$), MSI-L in 13 cases ($36.1\%$), and MSS in 18 cases ($50.0\%$). hMLH1 was methylated in seven cases ($19.4\%$). In all cases of MSI-H, promoter of hMLH1 was methylated, and in two of the 13 cases of MSI-L, hMLH1 promoter methylation was identified. Methylation was not found in any cases of MSS. Promoter methylation in hMLH1 was significantly correlated with MSI status (P<0.001). We could not find any relationship between MSI and clinicopathologic parameters. Conclusion: These results suggest that an abnormal function of the mismatch repair system may be associated with gastric carcinogenesis in more than $10\%$ of early-onset gastric carcinomas and MSI appeared to be closely related to the promoter methylation in hMLH1.

• Molecules and Cells
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• v.24 no.3
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• pp.364-371
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• 2007

The tumor suppressor gene Ras association domain family 1A (RASSF1A) is highly methylated in a wide range of human sporadic tumors. The current study investigated the hypermethylation of RASSF1A, the expression of RASSF1A protein, and the correlation between these and the clinicopathological features of gallbladder (GB) cancer in Korean patients. Formalin-fixed, paraffin-embedded tumors and non-neoplastic GB tissues (22 carcinomas, 8 adenomas, 26 normal epithelia) were collected from patients who had undergone surgical resection. The methylation status of two regions of the RASSF1A CpG island was determined by methylation-specific PCR (MSP), and the expression of RASSF1A protein was examined by immunohistochemistry using tissue microarrays. The K-RAS mutation was analyzed by direct sequencing. Methylation of the RASSF1A promoter (region 1) was detected in 22.7% (5/22) of carcinomas, 12.5% (1/8) of adenomas, and 0% (0/26) of normal gallbladder epithelia (P = 0.025). Methylation of the first exon (region 2) was found in 36.4% (8/22) of carcinomas, 25.0% (2/8) of adenomas, and 8.0% (2/26) of normal gallbladder epithelia (P = 0.038). K-RAS mutations were present in 4.5% (1/22) of carcinomas and 25% (2/8) of adenomas. RASSF1A methylaton was not associated with clinicopathological factors or K-ras mutation. Reduction or loss of RASSF1A expression was observed in most methylated adenocarcinomas. Three RASSF1A-expressing human biliary tract cancer cell lines examined contained unmethylated promoters and exons 1. These results suggest that downregulation of RASSF1A expression by DNA hypermethylation may be involved in GB carcinogenesis.

• Clinical and Experimental Reproductive Medicine
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• v.37 no.1
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• pp.25-31
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• 2010

Objective: X inactivation is the silencing one of the two X chromosomes in female mammals for gene dosage on the X-chromosome between female and male. X inactivation is controlled by X inactive-specific transcript (XIST) gene, untranslated RNA. XIST is expressed only from the inactive X (Xi), not expressed from the active X (Xa). The Xist promoter is methylated on the silent Xist allele on the Xa in somatic cells, and less methylated on the Xist-expressing Xi. We investigated the difference of XIST methylation pattern of the promoter and 5'-region of XIST from male (XY) and female (XX) subjects. Methods: The direct quantification of XIST methylation is required for clinical application of normal XX and XY blood. Methylation percentage of eight CpG sites (-1696, -1679, -1475, -1473, -1469, +947, +956, +971) of XIST gene were diagnosed by pyrosequencing. Results: We directly quantitated the methylation percentage of the promoter and 5'-end of XIST by pyrosequencing. The average methylation percentages at CpG6-8 sites (+947, +956, +971) were 45.2% at CpG6, 49.9% at CpG7, and 44.2% at CpG8 from normal female and normal male were 90.6%, 96.7%, 87.8%, respectively. Nether CpG 1-5sites (-1696, -1679, -1475, -1473, -1469) had any effect on XX and XY. Conclusion: This method is sensitive for quantifying the small percentage change in the methylation status of XIST, and may be used for diagnosis.

• Journal of Gastric Cancer
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• v.5 no.4 s.20
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• pp.228-237
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• 2005

Purpose: We investigated the impacts of the methylation states of the P16 and the hMLH1 genes on pathogenesis and genetic expression of stomach cancer and their relationships with Helicobater pylori infection, and with other clinico-pathologic factors. Material and Methods: In our study, to detect protein expression and methylation status of the P16 and the hMLH1 genes in 100 advanced gastric adenocarcinomas, used immunohistochemical staining and methylation-specific PCR (MSP) and direct automatic genetic sequencing analysis. Results: Methylation of the P16 gene was observed in 19 out of 100 cases (19%) and in the 18 of those cases (94.7%) loss of protein expression was seen. We were sble to show that loss of P16 gene expression was related to methylation of the P16 gene (kappa coefficient=0.317, p=0.0011). Methylation of the hMLH1 gene was observed in 27 cases (27%), and in 24 cases of those 27 cases (88.8%), loss of protein expression was seen, which suggested that loss of protein expression in the hMLH1 gene is related to methylation of hMLH1 gene (kappa coefficient=0.675, P<0.0001). Also methylation of the hMLH1 gene was related to age, size of the mass, and lauren's classification. Conclusion: We found that methylation of DNA plays an important role in inactivation of the P16 and the hMLH1 genes. The methylation of the hMLH1 genes is significantly related to age, size of the mass, and lauren's classification.

• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.