DNA methylation of genes linked with retinoid signaling in gastric carcinoma: expression of the retinoid acid receptor beta, cellular retinol-binding protein 1, and tazarotene-induced gene 1 genes is associated with DNA methylation.

Hypermethylation of CpG islands has been associated with silencing of various tumor suppressor genes, and the retinoid acid receptor beta (RARbeta), cellular retinol-binding protein 1 (CRBP1), and tazarotene-induced gene 1 (TIG1) genes have been associated with retinoic acid signaling. To the authors' knowledge, little is known regarding the involvement of these three genes in gastric carcinoma (GC). In this study, the authors investigated the methylation status of these genes and analyzed the role of their DNA methylation in GC. DNA methylation of 3 retinoic acid-associated genes was analyzed in 42 samples of GC from 42 patients and in 8 GC cell lines by methylation-specific polymerase chain reaction (PCR) analysis. The mRNA expression levels for these three genes were measured by quantitative reverse transcription-PCR. In 7 of 8 GC cell lines, the CRBP1 gene was hypermethylated, and CRBP1 transcription was inactive. In 6 of 8 GC cell lines, the TIG1 gene was hypermethylated, and TIG1 transcription was inactive. Treatment with demethylating agent 5-aza-2'-deoxycytidine restored both CRBP1 and TIG1 transcription. DNA methylation of the RARbeta, CRBP1, and TIG1 genes was detected in 15 of 42 GC samples (36%), 14 of 42 GC samples (33%), and 4 of 42 GC samples (10%), respectively, and in 6 of 30 samples (20%), 0 of 30 samples (0%), and 1 of 30 samples (3%) of corresponding nonneoplastic mucosa. None of the 10 normal gastric mucosa samples from young, healthy individuals demonstrated hypermethylation of any of these genes. DNA methylation of each gene was associated significantly with low mRNA expression of the respective gene. Twenty-four of 42 GC samples (57%) demonstrated hypermethylation of at least 1 of the 3 genes. However, no significant, concordant hypermethylation of these genes was observed. The results suggested that gastric carcinogenesis involves transcriptional inactivation by aberrant DNA methylation of genes related to retinoid signaling.

Shutoh M ，Oue N ，Aung PP ，Noguchi T ，Kuraoka K ，Nakayama H ，Kawahara K ，Yasui W ... -  《CANCER》

Accumulation of DNA methylation is associated with tumor stage in gastric cancer.

The authors purpose in this study was to clarify the difference in terms of clinicopathologic features between gastric cancer (GC) with high numbers of DNA methylated genes and CpG island methylator phenotype (CIMP)-positive GC as originally defined. We analyzed DNA methylation of 12 tumor-related genes (hMLH1, MGMT, p16(INK4a), CDH1, RAR-beta, HLTF, RIZ1, TM, FLNc, LOX, HRASLS, HAND1) in 75 samples of GC from 75 patients, 25 samples of corresponding nonneoplastic mucosa from 25 patients, and 10 samples of normal gastric mucosa from 10 healthy young individuals by methylation-specific polymerase chain reaction (PCR) and bisulfite PCR. We also investigated CIMP status by examining the methylation of five MINT loci and p53 mutation status by PCR single-strand conformation polymorphism. We measured levels of expression of mRNAs for these 12 genes by quantitative reverse transcription PCR in 50 GC specimens. The average number of methylated genes per tumor was 4.83. DNA methylation of each gene was correlated with low expression of the respective mRNA. High methylation (GC with 5 or more methylated genes) was detected in 39 (52.0%) of 75 GCs. Twenty-nine (37.8%) of 75 GCs were CIMP-positive. DNA methylation of each of the 12 genes was observed more frequently in the high-methylation group than in the low-methylation group. Methylation of 6 specific genes occurred more frequently in CIMP-positive GC than in CIMP-negative GC. Methylation of the remaining 6 genes was not correlated with CIMP-status. High methylation was found more frequently in Stage III/IV GC (26 of 40 cases, 65.0%) than in Stage I/II GC (13 of 35 cases, 37.1%, P = 0.029).CONCLUSIONS.These findings indicate that GCs with higher numbers of methylated genes have more distinct DNA methylation profiles than the originally defined CIMP-positive GCs. DNA methylation of tumor-related genes accumulates in conjunction with tumor progression.

Oue N ，Mitani Y ，Motoshita J ，Matsumura S ，Yoshida K ，Kuniyasu H ，Nakayama H ，Yasui W ... -  《CANCER》

DNA methylation of genes linked to retinoid signaling in squamous cell carcinoma of the esophagus: DNA methylation of CRBP1 and TIG1 is associated with tumor stage.

Hypermethylation of CpG islands is associated with the silencing of various tumor suppressor genes. Retinoic acid receptor-beta (RAR-beta), cellular retinol-binding protein 1 (CRBP1), and tazarotene-induced gene 1 (TIG1) have been linked to retinoic acid signaling. Little is known about the involvement of these three genes in esophageal squamous cell carcinoma (ESCC). In this study, we investigated the methylation status of these genes and analyzed the role of methylation of their DNA in ESCC. Methylation-specific polymerase chain reaction (PCR) was performed to study the methylation of CpG islands in 28 ESCC (stages I, II, and III) and 10 samples of corresponding non-neoplastic mucosa. The mRNA expression levels of the three genes were measured by quantitative reverse transcription-PCR. DNA hypermethylation of RAR-beta was found in seven (25.0%) of the 28 ESCC, of CRBP1 in five (17.9%), and of TIG1 in five (17.9%). DNA methylation of RAR-beta was identified in one of 10 samples of corresponding non-neoplastic mucosa (10.0%), whereas no DNA methylation of CRBP1 or TIG1 was detected. In total, at least one of the three genes was hypermethylated in 12 (42.9%) ESCC. Reduced expression of RAR-beta, CRBP1, and TIG1 was found in 14 (50.0%), 15 (53.6%), and 13 (46.4%) ESCC, respectively. DNA methylation of each gene was significantly associated with reduced expression of the respective mRNA. No correlation was found between the DNA methylation status of RAR-beta and clinicopathological factors such as depth of invasion, lymph node metastasis, or tumor stage. In contrast, DNA methylation of both CRBP1 and TIG1 was observed only in stage III ESCC. These results show that inactivation of the retinoic acid signaling-associated genes RAR-beta, CRBP1, and TIG1 by DNA methylation occurs frequently in ESCC.

Mizuiri H ，Yoshida K ，Toge T ，Oue N ，Aung PP ，Noguchi T ，Yasui W ... -  《-》

Hypermethylation-associated Inactivation of the Cellular Retinol-Binding-Protein 1 Gene in Human Cancer.

Esteller M ，Guo M ，Moreno V ，Peinado MA ，Capella G ，Galm O ，Baylin SB ，Herman JG ... -  《CANCER RESEARCH》

Methylation-associated silencing of death-associated protein kinase gene in laryngeal squamous cell cancer.

Kong WJ ，Zhang S ，Guo C ，Zhang S ，Wang Y ，Zhang D ... -  《LARYNGOSCOPE》