Gastric Cancer Open Access
Copyright ©The Author(s) 2004. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 1, 2004; 10(23): 3394-3398
Published online Dec 1, 2004. doi: 10.3748/wjg.v10.i23.3394
Expression of Dnmt1, demethylase, MeCP2 and methylation of tumor-related genes in human gastric cancer
Jing-Yuan Fang, Zhong-Hua Cheng, Ying-Xuan Chen, Rong Lu, Li Yang, Hong-Yin Zhu, Lun-Gen Lu, Shanghai Institute of Digestive Disease, Shanghai Second Medical University Renji Hospital, Shanghai 200001, China
Author contributions: All authors contributed equally to the work.
Supported by National Natural Science Foundation of China, No. 30170413; Foundation for the Author of National Excellent Doctoral Dissertation of China, No.199946 and the Key Project Funds of Shanghai Education Committee
Correspondence to: Dr. Jing-Yuan Fang, Shanghai Institute of Digestive Disease, 145 Shandong Zhong Road, Shanghai 200001, China.
Telephone: +86-21-63200874 Fax: +86-21-63266027
Received: March 27, 2004
Revised: April 3, 2004
Accepted: April 16, 2004
Published online: December 1, 2004


AIM: To explore the effect of DNA methyltransferase, demethylase and methyl-CpG binding protein MeCP2 on the expressions and methylation of hMSH2 and proto-oncogene in human gastric cancer.

METHODS: Paired samples of primary gastric cancer and corresponding para-cancerous, non-cancerous gastric mucosae were obtained from surgically resected specimens of 28 patients. Transcription levels of Dnmt1, mbd2, MeCP2, p16INK4A, hMSH2 and c-myc were detected by using real-time PCR or RT-PCR. Promoter methylation of p16INK4A, c-myc and hMSH2 genes was assayed by methylation-specific PCR (MSP) and sequencing (mapping). Their relationships were analyzed by Fisher’s exact test using the software SPSS.

RESULTS: The average mRNA level of Dnmt1 gene from cancerous tissue was higher and that of mbd2 gene from cancerous tissue was lower than that from non-cancerous tissue, respectively. mbd2 was lower in cancerous tissue than in non-cancerous tissue in 14 (50.0%) of patients but higher in 3 cases (10.7%) of non-cancerous gastric tissue (P < 0.001). c-myc expression was up-regulated in cancer tissues (P < 0.05). The up-regulation of mbd2 was found in all patients with hypomethylated c-myc. The transcriptional levels of p16INK4A and MeCP2 genes did not display any difference between gastric cancerous and matched non-cancerous tissues. There were down-regulation and hypermethylation of hMSH2 in cancer tissues, and the hypermethylation of hMSH2 coexisted with down-regulated transcription. However, the transcription level of the above genes was not associated with biological behaviours of gastric cancers.

CONCLUSION: The up-regulation of proto-oncogene may be the consequence of epigenetic control of gene expression by demethylase, and mbd2 is involved in the regulation of hMSH2 expression in human gastric cancer.


Methylation of gene regulatory elements, a well-known epigenetic change, acts as an important alternative to genetic alteration for gene inactivation. DNA methyltransferase (Dnmt) and DNA demethylase are the enzymes potentially affecting promoter methylation status. Human DNA demethylase has been cloned[1]. The inactivity of demethylase may play a role in production and maintenance of regional DNA hypermethylation, which frequently results in reduced expression of tumor suppressor genes in human cancers.

Gastric cancer is the second most common malignant tumor in Asia, with a much higher incidence than in Western countries. During gastric carcinogenesis, hypomethylation of c-myc and c-Ha-ras proto-oncogenes was frequently seen[2,3], however the average level of mRNA for Dnmt1 was significantly higher in gastric cancers than in corresponding non-cancerous mucosa[4]. mbd2 has been proposed to be a DNA demethylase, and the average level of mbd2 mRNA was significantly lower in gastric cancer than in non-cancerous mucosa. But there was no significant association between DNA demethylase mRNA level and malignant potential in gastric cancers[5]. The mRNA expression levels for pro-methylation of Dnmt1, Dnmt3a and Dnmt3b and mbd2 are not the critical determinant of tumor-specific promoter hypermethylation of hMLH1, p16INK4A or CDH1 in gastric cancer[6]. However, little is known about the relationship between mbd2 or Dnmt1 and the methylation status of proto-oncogene or hMSH2, another important mismatch repair (MMR) gene. Furthermore, up-to date, there has not been any report about methyl-CpG binding protein MeCP2 associated with tumor-related genes in gastric cancer.

In the present study, we examined the methylation and transcriptional level of tumor-related genes including p16INK4A, hMSH2 and c-myc, and detected the expression of Dnmt1, mbd2 and MeCP2. We therefore analyzed their relationship in normal and cancerous stomach tissues.


Paired samples of histologically verified primary gastric cancer and corresponding para-cancerous (3-5 cm from cancer margin) and non-cancerous gastric mucosae were obtained immediately from surgically resected specimens of 28 patients (C1-C28) treated at Renji Hospital, Shanghai, China. A complete written informed consent was obtained from all patients. They were all diagnosed pathologically by HE-stained sections and classified according to WHO’s histological classifications of gastric carcinoma. The histological characteristics in para-cancerous area were chronic gastritis or intestinal metaplasia, and dysplasia was present in ten cases. The clinico-pathological features of each patient were reviewed and recorded (Table 1). The mean age of patients (19 men and 9 women) at resection was 58 (range 45-79) years. A portion of the tissues (approximately 1-3 g) was snap-frozen on dry ice and kept in liquid nitrogen until used for DNA or RNA extraction. Other portions were used for histological examination.

Table 1 Relationship between Dnmt1 and pathological change in patients with gastric cancer (case number, %).
SubtotalDnmt1 transcription
Total or subtotal28 (100.0)9 (32.14)9 (32.14)10 (35.72)
Age (yr) > 5018 (64.30)7 (38.89)4 (22.22)7 (38.89)0.30
< 5010 (35.70)2 (20.00)5 (50.00)3 (30.00)
Size of tumor >5 cm14 (50.00)4 (28.57)5 (35.71)5 (35.71)0.88
<5 cm14 (50.00)4 (28.57)5 (35.71)5 (35.71)
Borrmann II6 (21.43)2 (33.33)0 (0.00)4 (66.67)0.34
III15 (53.57)5 (33.33)6 (40.00)4 (26.67)
IV7 (25.00)2 (28.57)3 (42.86)2 (28.57)
Lymph node Positive21 (75.00)6 (28.57)8 (38.10)7 (33.33)0.49
invasion Negative7 (25.00)3 (42.86)1 (14.29)3 (42.86)
RNA extraction and reverse-transcription polymerase chain reaction (RT-PCR)

First, mRNA expression of tumor-related genes in cancerous, para-cancerous and non-cancerous tissues from each patient was detected by using RT-PCR and real-time PCR. Total RNA was extracted using a commercial kit (Trizol) according to the manufacturer’s instructions (Gibco BRL). RT reactions using 5 μg of total RNA in 20 μL of reaction buffer were performed with Superscript II reverse transcriptase (Life Technologies, Inc). mRNA transcription levels of mbd2, MeCP2, p16INK4A and c-myc genes were evaluated by using RT-PCR. The sequence and PCR reaction for each primer are shown in Table 2. For control of RT-PCR, a 612 bp fragment of β -actin cDNA was also amplified. At the end of 40 cycles, reaction products were separated electrophoretically on a 3% agarose gel and stained with ethidium bromide for visual confirmation of PCR products. The density of bands in RT-PCR in each lane was normalized to the amount of total RNA as determined by the density of the band in RT-PCR for β -actin[7]. RT-PCR analysis was repeated at least thrice.

Table 2 Primer sequences and PCR conditions for RT-PCR, MSP and sequencing.
PrimersSense (5’→3’)Antisense (5’→3’)Product size (bp) PCR programGenBank accession number
β -ActinGGA GTC CTG TGG CAT CCA CGCTA GAA GCA TTT GCG GTG GA322 bp 94 °C 30 s, 60 °C 1 min, 72 °C 1 min, 27 cyclesBC023204
p16INK4A RT-PCRCCC GCT TTC GTA GTT TTC ATTTA TTT GAG CTT TGG TTC TG355 bp 94 °C 1 min, 58 °C 1 min, 72 °C, 1 min, 35 cyclesL27211
c-myc RT-PCRCCA ACA GGA GCT ATG ACC TCCTC GGT CAC CAT CTC CAG CT290 bp 94 °C 1 min, 52 °C 1 min, 72 °C, 1 min, 35 cyclesV00568
MeCP2 RT-PCRACT CCT CAG AAT ACA CCT TGC TTTGA GGC CCT GGA GGT CCT112 bp 95 °C 1 min, 50 °C 1 min, 72 °C, 1 min, 35 cyclesMCB, 2000; 20: 3316
mbd2 RT-PCRAAC CCT GCT GTT TGC TTA ACCGT ACT TGC TGT ACT CGC TCT TC101 bp 94 °C 1 min, 60 °C 1 min, 72 °C, 1 min, 40 cyclesAF072242
p16INK4A M-MSPTTA TTA GAG GGT GGG GCG GAT CGCGAC CCC GAA CCG CGA CCG TAA150 bp 95 °C 30 s, 65 °C 30 s, 72 °C, 1 min, 40 cyclesX94154
p16INK4A UM-MSPTTA TTA GAG GGT GGG GTG GAT TGTCAA CCC CAA ACC ACA ACC ATA A151 bp 95 °C 30 s, 60 °C 30 s, 72 °C, 1 min, 40 cyclesX94154
c-myc M-MSPTAG AAT TGG ATC GGG GTA AACGA CCG AAA ATC AAC GCG AAT131 bp 95 °C 30 s, 56 °C 30 s, 72 °C, 1 min, 40 cyclesAF002859
c-myc UM-MSPTAG AAT TGG ATT GGG GTA AACCA ACC AAA AAT CAA CAT GAA T132 bp 95 °C 30 s, 56 °C 30 s, 72 °C, 1 min, 40 cyclesAF002859
hMSH2 sequencing 1st roundTGT TTA GAA AGA AAA AGG GAAAA CCT CCT CAC CTC CT94 °C 1 min, 55 °C 1 min, 72 °C, 1 min, 35 cyclesAB006445
hMSH2 sequencing 2nd roundAAA TAT TGG GAG GAG GAG GAACC CAC TAA ACT ATT TCC CA327 bp 94 °C1 min,, 55 °C 1 min, 72 °C, 1 min, 35 cyclesAB006445
Real-time quantitative PCR for Dnmt1 and hMSH2

mRNA levels of Dnmt1 and hMSH2 were measured using a real-time quantitative PCR system. Relative quantitation using the comparative Ct method with the data from ABI PRISM 7700 sequence detection system (version 1.6 software) was performed according to the manufacturer’s protocol.

Real-time PCR was also performed with Taqman β -actin to normalize each of the extracts for amplifiable human DNA. The results were expressed as the ratio of copies of each gene to β -actin, respectively. The Ct values were measured, and the average Ct value of triplicate samples was calculated. Alteration of mRNA expression was defined as a 3-fold difference in the expression level[8]. The primers and the Taqman fluorogenic probes for Dnmt1, hMSH2 and β -actin were provided by Jikang Company, Shanghai, China.

The sequences of all primers and probes, as well as PCR programs are shown in Table 3.

Table 3 Sequence of primers and probes for real-time PCR.
GeneSense (5’→3’)Antisense (5’→3’)ProbeGenBank No
Methyl-specific PCR (MSP) for p16INK4A and c-myc genes

To amplify the promoters of p16INK4A and c-myc genes, we carried out bisulfite modification[9] and MSP.

Bisulfite could convert unmethylated cytosine residues to uracil, but methylated cytosines remained non-reactive. PCR amplified uracil as thymine while methylated cytosines were only amplified as cytosines. Two micrograms of total genomic DNA (from at least two independent treatments corresponding to RT-PCR experiments) were isolated by using QIAamp DNA blood mini kit (QIAGEN Inc.), then denatured by NaOH and modified by sodium bisulfite solution (2.35 mol/L) containing hydroquinone (40 mmol/L) freshly prepared. The bisulfite-treated DNA was desalted using Wizard DNA clean up kit (Promega) and amplified by PCR using primers specific for methylated and unmethylated p16INK4A and c-myc promoters. PCR reaction buffer contained 0.1 mmol/L dNTP, 2.0 mmol/L MgCl2, and 0.5 μmol/L primers. PCR products were directly loaded onto 3% agarose gels and electrophoresed. The gel was stained with ethidium bromide and directly visualized under UV illumination. Furthermore, the primers for wild-type p16INK4A and c-myc were used to monitor complete conversion of DNA obtained in the bisulfite reaction.

Bisulfite modification and sequencing (mapping) for hMSH2

Primers were designed in the region without CpG dinucleotides to amplify both methylated and unmethylated alleles in hMSH2. The PCR products were recovered using QIA quick gel extraction kit (Gibco). Direct sequencing was performed by using ABI PRISM BigDye terminator kit (PE Biosystems, Foster City, CA). The products of sequencing PCR included 22 CpG sites in promoter of hMSH2 gene.

The sequences of all primers and PCR programs are shown in Table 2.

Statistical analysis

Results were representative of at least three independent experiments performed in triplicate and presented as mean±SD. Comparisons between groups were made using Student’s paired t test. Their relationship was analyzed by Fisher’s exact test using the software SPSS.

Expressions of Dnmt1, mbd2 and MeCP2 genes in cancerous and non-cancerous gastric tissues

After quantitative PCR, the specific products visually confirmed on agarose gels were about 101- and 96 bp, and no non-specific products were obtained upon amplification of Dnmt1 and β -actin, respectively. In all cancerous, para-cancerous and non-cancerous tissues, their mRNA expressions were detected, and 32.2% (9/28) of cancerous tissues over-expressed Dnmt1, and the copies of Dnmt1 were higher than in non-cancerous tissues (5.08 vs 1).

mbd2 was expressed in all samples. However, mbd2 was down-regulated in 50% (14/28) of gastric cancer tissues, up-regulated in 10.7% (3/28) cases, and no significant change in 3.39% (11/28), respectively. Average value of mbd2 mRNA expression was lower in cancerous tissues than in non-cancerous tissue (Figure 1, Figure 2). In 11 patients, mbd2 mRNA level in gastric cancer was particularly low, being reduced by 50% or more when compared with that in the corresponding non-cancerous mucosae. However, we did not find association between expressions of MeCP2 and Dnmt1 and mbd2.

Figure 1
Figure 1 mRNA expression of p16INK4A, c-myc, mbd2 and MeCP2 in cancerous (lanes 1, 4, 7 and 10), para-cancerous (lanes 2, 5, 8 and 11) and non-cancerous (lanes 3, 6, 9 and 12) tissues from patients with gastric cancer by using RT-PCR.
Figure 2
Figure 2 Density of bands from RT-PCR in each lane normalized to the total RNA as determined by the density of bands in RT-PCR for β -actin. Assuming β -actin was 4 562.39 units (pixels of brightness), the calculation [4 562.39/(density of actin)] × (density of each gene) equals each gene normalized to β -actin. Data shown are representative of three separate experiments. aP < 0.05.

In addition, we did not find the association of overall aberrant methylation and expressions of Dnmt1, MeCP2, mbd2 with the age of patients.

Examination of mRNA expression of tumor-related genes and status of promoter methylation in primary gastric cancers

Figure 1 shows the results from RT-PCR and real-time PCR, and Figure 2 shows the relative mRNA levels of each gene after normalization with the signal of β -actin. These data demonstrated that the expressions of p16INK4A and hMSH2 (data not shown) were down-regulated in cancerous tissues from 11 cases (39.3%) and 10 cases (35.7%) respectively, but there was no significant difference between cancerous and non-cancerous tissues. As shown in Figure 2, c-myc transcription level was up-regulated in 14 patients with gastric cancer, and the mean value of expression in cancerous tissues was greater than that in non-cancerous tissues (P < 0.05).

To determine whether the expression of p16INK4A, hMSH2 and c-myc genes in gastric cancer was associated with methylation, we selected the samples from cancerous, para-cancerous and non-cancerous tissues in ten patients for MSP or genomic bisulfite sequencing. Each tissue showed a positive 150 bp and a 151 bp band for methylated and unmethylated specific primer sets for p16INK4A, indicating that the p16INK4A gene was partially methylated in human gastric cancer. The methylated bands for the p16INK4A gene in the cancerous and para-cancerous tissues were consistently stronger than the products of non-cancerous tissues (Figure 3A). Regarding c-myc gene, the methylated product (131 bp) was significantly lower and the unmethylated product (132 bp) was higher in cancerous and para-cancerous tissues than in non-cancerous tissues. Figure 3B displays representative examples of MSP products analyzed by electrophoresis on an agarose gel.

Figure 3
Figure 3 Hypermethylation of p16INK4A promoter (A) and hypomethylation of proto-oncogene c-myc promoter (B) in gastric cancer tissue indicated by MSP. U: unmethylation-spe-cific PCR; M: methylation-specific PCR.

Bisulfite genomic sequencing of the representative PCR products of hMSH2 showed that all cytosines at non-CpG sites were converted to thymine. This excluded the possibility that successful amplification could be attributable to incomplete bisulfite conversion. Interestingly, methylation occurred at the -166 CpG site only (Figure 4).

Figure 4
Figure 4 Methylation analysis of hMSH2 gene promoter by bisulfite sequencing. The arrows indicate the changes of CG to TG in promoters of non-cancerous and para-cancerous tissue, but CG remained in cancerous tissues.

Taken together, the results from MSP, sequencing, RT-PCR and real-time PCR indicated that hypermethylation of hMSH2 might be induced, inactivation and activation of c-myc were associated with its hypomethylation in human gastric cancer.

Correlation between mRNA expression of Dnmt1, mbd2 and DNA methylation

Dnmt1 was not associated with the methylation status of p16INK4A or c-myc gene.

Among Dnmt1 down-regulated cases, 6 (60%) had over-expression of c-myc in cancerous tissues. In the cancer cases with up-regulated mbd2, all 3 had an expression of c-myc. We also found that there was a positive correlation in the expression of c-myc and mbd2 (r = 0.59, P = 0.026), MeCP2 (r = 0.64, P = 0.02), but c-myc had no positive correlation with Dnmt1.

In contrast to cancer tissues, all normal tissues had a positive association of p16INK4A with MeCP2 (r = 0.483, P = 0.02) or mbd2 (r = 0.483, P = 0.027).

Among the 10 cases with down-regulated hMSH2, 6 cases had a decreased mbd2 mRNA, but there was no significant association between expressions of Dnmt1 and hMSH2.

Association of Dnmt1, mbd2 and histological change

There was no significant association between Dnmt1, mbd2 mRNA level and clinico-pathological parameters of the tumors, such as histological differentiation, size of tumor and lymph node metastasis. These data failed to indicate their aberrant expression as an early event in gastric cancer.


Generally, the global DNA methylation level is lower in cancer cells than in normal cells, and some loci tend to show hypomethylation of proto-oncogene in human gastrointestinal cancers[10]. Recent studies demonstrated that DNA methylation could contribute to inactivation of tumor suppressor genes, a key event in tumorigenesis of a wide spectrum of human tumors[11,12].

Three enzymes are responsible for DNA methylation. The carboxy-terminal domain of Dnmt1 could catalyse the methylation of DNA containing hemi-methylated CpG dinucleotides more efficiently than unmethylated DNA in vitro[13]. DNA demethylase was first identified by Szyf’s group, and they demethylated both fully methylated and hemimethylated DNA, showing dinucleotide specificity, and could demethylate mCpG in different sequence contexts[5]. The shortest form of methyl- CpG binding domain (MBD)2, mbd2b, has been proposed to be a DNA demethylase which has been cloned and characterized[14]. MeCP2 is the first true member of the family of proteins that could selectively recognize methylated CpG[15]. It is a single polypeptide characterized by an MBD and a transcriptional repression domain[16,17]. Aberrant methylation in tumor-related genes was frequently detected in gastric intestinal metaplasia of both cancer and non-cancer patients, suggesting their early involvement in the multi-step progression of gastric carcinogenesis[18]. However, little is known about the relationship of Dnmt1, demethylase, MeCP2 with tumor-related genes.

We found that the average mRNA level of Dnmt1 gene in cancerous tissue was higher and that of mbd2 gene was lower than that in non-cancerous tissue. Regarding Dnmt1 expression, these results are consistent with a study by Kanai[4]. On the other hand, Patra found that MBD2 protein expression was significantly higher in benign prostatic hyperplasia BPH-1 cells and deficient in prostate cancer cell lines and in BPH tissues[19]. For mbd2, our result is consistent with another experiment of gastrointestinal cancer[3]. They suggested that the average levels of demethylase mRNA expression normalized to GAPDH mRNA were significantly lower in colorectal (0.81 ± 0.55) and gastric (2.88 ± 0.23) cancers than in the non-cancerous mucosae (1.90 ± 0.16 and 5.11 ± 0.34, respectively, P < 0.0001). However, up to date, we have not found any report about the expression of MeCP2 in gastric cancer. Darwanto found that colonic mucinous adenocarcinomas showed a strong MeCP2 expression[20], and Muller observed a higher expression level of MeCP2 mRNA in breast cancer tissues than in non-cancerous tissues[21].

Previous studies indicated that the mRNA expression level for Dnmt1 and mbd2 was not a critical determinant of promoter hypermethylation of tumor-suppressor gene p16INK4A in gastric cancer[6,22]. Regarding the hMLH1, the result was different in different studies[6,23]. During gastric carcinogenesis, hypomethylation of c-myc proto-oncogene is common, and it has not been linked to Dnmt1, mbd2 or MeCP2, or hMSH2. In the present study, we demonstrated that there was a positive association of mbd2 and c-myc proto-oncogene in gastric cancerous tissues. The up-regulation of mbd2 was found in all patients with hypomethylated c-myc. The correlation of mbd2 expression with unmethylation of c-myc promoter suggests that c-myc may be a target for demethylation by the enzymes.

Another interesting gene we tested was hMSH2. The second important finding in this study was the decrease of mbd2 mRNA in most patients with down-regulated hMSH2, but we did not find any correlation between hMSH2 and Dnmt1 or MeCP2. It suggests that mbd2 is also involved in the regulation of hMSH2 expression in human gastric cancer. We did not test the promoter region of hMLH1 gene, because the promoter was not associated with Dnmt1[6,23] and mbd2[6] in human gastric cancer.

In addition, the data from our study demonstrated that the transcription level of Dnmt1, mbd2 and MeCP2 might not be associated with biological behaviours in human gastric cancer. Kanai also suggested there was no significant association between DNA demethylase mRNA level and malignant potential in gastric cancers[5]. Although the mbd2 expression was lower both in early and in advanced cancers, we could not demonstrate a definitive relationship between the histology and mbd2 expression due to the small number of patients studied.

In conclusion, the up-regulation of proto-oncogene may be the consequence of epigenetic control of gene expression by demethylase, and mbd2 is also involved in the regulation of hMSH2 expression in human gastric cancer.


Thanks are given to Dr. Yao Shi and Xiao-Yu Chen, Ms. Hong-Yin Zhu and Ms. Wei-Qi Gu for performing the diagnosis of pathology, MSP and real-time PCR.


Edited by Wang XL Proofread by Zhu LH and Xu FM

1.  Bhattacharya SK, Ramchandani S, Cervoni N, Szyf M. A mammalian protein with specific demethylase activity for mCpG DNA. Nature. 1999;397:579-583.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 464]  [Cited by in F6Publishing: 487]  [Article Influence: 20.3]  [Reference Citation Analysis (0)]
2.  Fang JY, Zhu SS, Xiao SD, Jiang SJ, Shi Y, Chen XY, Zhou XM, Qian LF. Studies on the hypomethylation of c-myc, c-Ha-ras oncogenes and histopathological changes in human gastric carcinoma. J Gastroenterol Hepatol. 1996;11:1079-1082.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 28]  [Cited by in F6Publishing: 33]  [Article Influence: 1.2]  [Reference Citation Analysis (0)]
3.  Fang J, Zhu S, Xiao S, Shi Y, Jiang S, Zhou X, Qian L. Alterations of level of total genomic DNA methylation and pattern of c-myc, c-Ha-ras oncogene methylation in human gastric carcinogenesis. Chin Med J (Engl). 1996;109:787-791.  [PubMed]  [DOI]  [Cited in This Article: ]
4.  Kanai Y, Ushijima S, Kondo Y, Nakanishi Y, Hirohashi S. DNA methyltransferase expression and DNA methylation of CPG islands and peri-centromeric satellite regions in human colorectal and stomach cancers. Int J Cancer. 2001;91:205-212.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in F6Publishing: 1]  [Reference Citation Analysis (0)]
5.  Kanai Y, Ushijima S, Saito Y, Nakanishi Y, Sakamoto M, Hirohashi S. MRNA expression of genes altered by 5-azacytidine treatment in cancer cell lines is associated with clinicopathological parameters of human cancers. J Cancer Res Clin Oncol. 2001;127:697-706.  [PubMed]  [DOI]  [Cited in This Article: ]
6.  Oue N, Shigeishi H, Kuniyasu H, Yokozaki H, Kuraoka K, Ito R, Yasui W. Promoter hypermethylation of MGMT is associated with protein loss in gastric carcinoma. Int J Cancer. 2001;93:805-809.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 64]  [Cited by in F6Publishing: 69]  [Article Influence: 3.1]  [Reference Citation Analysis (0)]
7.  Fang JY, Mikovits JA, Bagni R, Petrow-Sadowski CL, Ruscetti FW. Infection of lymphoid cells by integration-defective human immunodeficiency virus type 1 increases de novo methylation. J Virol. 2001;75:9753-9761.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 63]  [Cited by in F6Publishing: 69]  [Article Influence: 3.1]  [Reference Citation Analysis (0)]
8.  Scanlan MJ, Welt S, Gordon CM, Chen YT, Gure AO, Stockert E, Jungbluth AA, Ritter G, Jäger D, Jäger E. Cancer-related serological recognition of human colon cancer: identification of potential diagnostic and immunotherapeutic targets. Cancer Res. 2002;62:4041-4047.  [PubMed]  [DOI]  [Cited in This Article: ]
9.  Xiong Z, Laird PW. COBRA: a sensitive and quantitative DNA methylation assay. Nucleic Acids Res. 1997;25:2532-2534.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 913]  [Cited by in F6Publishing: 953]  [Article Influence: 36.7]  [Reference Citation Analysis (0)]
10.  Fang JY, Xiao SD. Alteration of DNA methylation in gastrointestinal carcinogenesis. J Gastroenterol Hepatol. 2001;16:960-968.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 36]  [Cited by in F6Publishing: 37]  [Article Influence: 1.7]  [Reference Citation Analysis (0)]
11.  Jones PA, Takai D. The role of DNA methylation in mammalian epigenetics. Science. 2001;293:1068-1070.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1432]  [Cited by in F6Publishing: 1485]  [Article Influence: 67.5]  [Reference Citation Analysis (0)]
12.  Baylin SB, Herman JG. DNA hypermethylation in tumorigenesis: epigenetics joins genetics. Trends Genet. 2000;16:168-174.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 1168]  [Cited by in F6Publishing: 1242]  [Article Influence: 54.0]  [Reference Citation Analysis (0)]
13.  Bestor TH. Activation of mammalian DNA methyltransferase by cleavage of a Zn binding regulatory domain. EMBO J. 1992;11:2611-2617.  [PubMed]  [DOI]  [Cited in This Article: ]
14.  Ramchandani S, Bhattacharya SK, Cervoni N, Szyf M. DNA methylation is a reversible biological signal. Proc Natl Acad Sci U S A. 1999;96:6107-6112.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 246]  [Cited by in F6Publishing: 258]  [Article Influence: 10.8]  [Reference Citation Analysis (0)]
15.  Nan X, Meehan RR, Bird A. Dissection of the methyl-CpG binding domain from the chromosomal protein MeCP2. Nucleic Acids Res. 1993;21:4886-4892.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 412]  [Cited by in F6Publishing: 448]  [Article Influence: 14.9]  [Reference Citation Analysis (0)]
16.  Ng HH, Zhang Y, Hendrich B, Johnson CA, Turner BM, Erdjument-Bromage H, Tempst P, Reinberg D, Bird A. MBD2 is a transcriptional repressor belonging to the MeCP1 histone deacetylase complex. Nat Genet. 1999;23:58-61.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 636]  [Cited by in F6Publishing: 707]  [Article Influence: 29.5]  [Reference Citation Analysis (0)]
17.  Nan X, Campoy FJ, Bird A. MeCP2 is a transcriptional repressor with abundant binding sites in genomic chromatin. Cell. 1997;88:471-481.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 908]  [Cited by in F6Publishing: 977]  [Article Influence: 37.6]  [Reference Citation Analysis (0)]
18.  To KF, Leung WK, Lee TL, Yu J, Tong JH, Chan MW, Ng EK, Chung SC, Sung JJ. Promoter hypermethylation of tumor-related genes in gastric intestinal metaplasia of patients with and without gastric cancer. Int J Cancer. 2002;102:623-628.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 98]  [Cited by in F6Publishing: 104]  [Article Influence: 5.0]  [Reference Citation Analysis (0)]
19.  Patra SK, Patra A, Zhao H, Dahiya R. DNA methyltransferase and demethylase in human prostate cancer. Mol Carcinog. 2002;33:163-171.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 156]  [Cited by in F6Publishing: 160]  [Article Influence: 7.6]  [Reference Citation Analysis (0)]
20.  Darwanto A, Kitazawa R, Maeda S, Kitazawa S. MeCP2 and promoter methylation cooperatively regulate E-cadherin gene expression in colorectal carcinoma. Cancer Sci. 2003;94:442-447.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 39]  [Cited by in F6Publishing: 41]  [Article Influence: 2.1]  [Reference Citation Analysis (0)]
21.  Müller HM, Fiegl H, Goebel G, Hubalek MM, Widschwendter A, Müller-Holzner E, Marth C, Widschwendter M. MeCP2 and MBD2 expression in human neoplastic and non-neoplastic breast tissue and its association with oestrogen receptor status. Br J Cancer. 2003;89:1934-1939.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 53]  [Cited by in F6Publishing: 55]  [Article Influence: 2.9]  [Reference Citation Analysis (0)]
22.  Sato M, Horio Y, Sekido Y, Minna JD, Shimokata K, Hasegawa Y. The expression of DNA methyltransferases and methyl-CpG-binding proteins is not associated with the methylation status of p14(ARF), p16(INK4a) and RASSF1A in human lung cancer cell lines. Oncogene. 2002;21:4822-4829.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 62]  [Cited by in F6Publishing: 68]  [Article Influence: 3.2]  [Reference Citation Analysis (0)]
23.  Etoh T, Kanai Y, Ushijima S, Nakagawa T, Nakanishi Y, Sasako M, Kitano S, Hirohashi S. Increased DNA methyltransferase 1 (DNMT1) protein expression correlates significantly with poorer tumor differentiation and frequent DNA hypermethylation of multiple CpG islands in gastric cancers. Am J Pathol. 2004;164:689-699.  [PubMed]  [DOI]  [Cited in This Article: ]  [Cited by in Crossref: 207]  [Cited by in F6Publishing: 184]  [Article Influence: 9.7]  [Reference Citation Analysis (0)]