• Bulletin of the Korean Chemical Society
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• 제30권11호
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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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• 제17권5호
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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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• 제19권2호
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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.

• 생명과학회지
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• 제17권4호
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• pp.522-528
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• 2007

본 연구에서 사용한 coffee에 다량 함유된 caffeic acid와 chlorogenic acid, 녹차에 함유된 EGCG 성분은 암세포의 증식을 억제하는데 중요한 기능을 담당하는 세포주기 조절인자인 p16 유전자의 DNA methylation 패턴을 유방암 T-47D 세포에서 유의하게 변화시켰다. MSP를 이용하여 p16 유전자의 promoter 지역에서의 methylation상태의 변화를 살펴본 결과 caffeic acid, chlorogenic acid, EGCG는 유전자의 hypermethylation을 감소시켰으며, 이로 인해 demethylation된 p16 유전자가 증가하는 경향을 보였다. 이러한 연구 결과는 coffee 폴리페놀인 caffeic acid, chlorogenic acid와 녹차 폴리페놀인 EGCG는 세포내의 DNA methylation을 억제하는 기능을 가지는데, 이는 coffee폴리페놀과 같이 COMT 효소에 의한 methylation 부산물인 SAH의 증가에 의한 DNMT의 억제이거나, EGCG와 같이 DNMT와 직접적으로 결합하여 methylation 반응을 억제하는 mechanism에 의한 것으로 사료된다. 따라서 앞으로 이미 개발된 항암제뿐만 아니라, 부작용과 독성이 적은 식이성분에 대한 연구가 좀 더 심도 있게 이루어 져야 할 것이며, 이러한 연구들은 암이 발생되고 난 후 치료 요법으로 사용됨은 물론, 암이 발생하기 전에 사전 예방법으로도 널리 적용하는데 있어 중요한 이론적 토대를 마련할 것으로 사료된다.

• Biomolecules & Therapeutics
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• 제2권1호
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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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• 제3권1호
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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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• 제24권3호
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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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• 제37권1호
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• pp.25-31
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• 2010

목 적: X 염색체 불활성화는 여성과 남성 사이에 X 염색체의 유전자 발현 유지를 위해 여성의 X 염색체 중 하나가 불활성화 되는 현상이다. 이러한 X 염색체 불활성화는 해독되지 않는 XIST 유전자에 의해 조절된다. XIST 유전자는 오직 불활성화된 X 염색체 에서만 발현되고, 활성화된 X 염색체 에서는 발현되지 않는다. 따라서 체세포에서 활성화된 X 염색체의 XIST 유전자는 promoter 부분이 메틸화 되어있고, 불활성화된 X 염색체에서는 메틸화가 거의 되어 있지 않다. 연구방법: 본 연구에서는 정상 여성과 정상 남성의 XIST 유전자의 promoter와 5'-end 지역의 메틸화 차이를 측정하기 위해 정상여성과 남성의 혈액에서 DNA를 추출하여 파이로시퀀싱 (Pyrosequencing) 방법을 통해 XIST 유전자의 총 8부분의 CpG 영역 (-1696, -1679, -1475, -1473, -1469, +947, +956, +971)을 분석하였다. 결 과: 총 8부분의 CpG 영역을 분석한 결과, promoter 부분인 CpG 1-5 영역 (-1696, -1679, -1475, -1473, -1469)에서는 여성과 남성의 메틸화 정도에 차이가 없었다. 그러나 5'-end 부분인 CpG6-8 영역 (+947, +956, +971)에서는 여성이 45.2% 49.9% 44.2%, 남성이 90.6%, 96.7%, 87.8%으로 메틸화 정도가 차이를 나타냈다. 결 론: 따라서 본 연구에 사용한 방법은 XIST 유전자의 메틸화 패턴의 차이를 기존의 방법보다 신속하고 정확하게 분석할 수 있다는 장점이 있기 때문에 유용하게 사용될 수 있을 것이다.

• Journal of Gastric Cancer
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• 제5권4호
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• pp.228-237
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• 2005

목적: 위암조직에서 P16과 hMLH1 유전자의 메틸화상태를 검사하여 위암의 발생과정에서의 작용과 유전자의 발현에 미치는 영향과 Helicobacter paylori균 감염여부 및 임상병리학적인자와의 연관성을 알아보고자 하였다. 대상 및 방법: 위암 신선 동결 절편조직 100예를 대상으로 유전자의 단백질 발현상태는 면역조직화학 염색을 시행하여 확인하였고. 메틸화 상태는 methylation-specific PCR(MSP)과 염기서열분석을 시행하였다. 결과: P16유전자의 메틸화는 19예(19%)에서 관찰되었고 이 중 18예(94.7%)에서 P16유전자의 단백질 발현 소실이 있어, P16 유전자의 단백질 발현 소실이 P16유전자의 메틸화와 연관이 있음을 알 수 있었다(kappa 계수=0.317, P=.0011). hMLH1 유전자의 메틸화는 27예(27%)에서 관찰되었고, 이 중 24예(8.8%)에서 hMLH1 단백의 소실이 hMLH1유전자의 메틸화와 연관이 있음을 보여주었다(kappa계수=0.675, p<0.0001). hMLH1 유전자의 메틸화는 나이, 암종의 크기, Lauren 분류와 연관성이 있었다. P16 유전자와 hMLH1 유전자 메틸화 모두 Helicobacter paylori균 감염여부와는 연관성이 없었다. 결론: 위암에서 P16 및 hMLH1 유전자의 불활성화에는 DNA 메틸화가 작용을 함을 알 수 있었고, hMLH1유전자의 메틸화는 나이, 암종의 크기, Lauren 분류와 연관이 있음을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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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.