BACKGROUND:In colorectal cancer (CRC), DNA methylation anomalies define distinct subgroups termed CpG island methylator phenotype 1 (CIMP1), CIMP2, and CIMP-negative. The role of this classification in predicting recurrence and disease-free survival (DFS) in resected stage III CRC was evaluated. METHODS: Sporadic cancers from 161 patients were analyzed. Bisulfite pyrosequencing was used to examine the methylation of 2 global DNA methylation markers (LINE-1, Alu) and 9 loci (MINT1, MINT2, MINT31, P16, hMLH1, P14, SFRP1, SFRP2, and WNT5A). Mutations in BRAF and KRAS were assayed. RESULTS: Gene hypermethylation clustered in discrete groups of patients, indicating the presence of CIMP. K-means clustering analysis identified 3 discrete subgroups: CIMP1 (n ¼ 22, 13.7%), associated with proximal location and BRAF mutations; CIMP2 (n ¼ 40, 24.8%), associated with KRAS mutations; and CIMP-negative (n ¼ 99, 61.5%), associated with distal location. In proximal CRC, CIMP1 was correlated with a higher recurrence rate (53% for CIMP1, 18% for CIMP2, and 26% for CIMP-negative) and a worse DFS (P ¼ .015). Also in proximal CRC, LINE-1 methylation was lower in patients whose cancer recurred compared with those whose cancer did not recur (P ¼ .049). In multivariate analysis, CIMP1 and low LINE1 methylation were independent prognostic factors for DFS in proximal CRC (P ¼ .008 for classification by K-means clustering analysis; P ¼ .040 for LINE-1 methylation status). CONCLUSIONS: DNA methylation is a useful biomarker of recurrence in resected stage III proximal but not distal CRC. However, as the number of CIMP1 cases was small in distal CRC, further study is required to validate our findings.

The hypermethylation of the CpG islands is a common mechanism for the inactivation of tumor-related genes. In the present study, we analyzed the methylation status of genes for cell repair such as hMLH1, MGMT, and GSTP1, and a gastric cancer-specifically methylated DNA fragment, MINT 25 in gastric cancer cases and control groups. The study population consisted of 100 gastric cancer patients (50 distal and 50 proximal carcinomas), and 238 healthy controls. All genes showed more frequent hypermethylation in the cases than in the control group (p<0.0001). We investigated the association between promoter hypermethylation and relevant parameters including age, gender, alcohol consumption, smoking, and family history. There was a common hypermethylation of hMLH1 (p=0.008), MGMT (p=0.0001), and GSTP1 (p=0.0003) in females. This study also demonstrates that hypermethylation was strongly associated with non-drinkers (MGMT, p=0.046 and MINT 25, p=0.049) and non-smokers (hMLH1, p=0.044; MGMT, p=0.0003; MINT 25, p=0.029). Moreover, the frequency of MINT 25 hypermethylation increased with age (p=0.037), and MGMT methylation was frequently detected in distal gastric cancer than in proximal type (p=0.038). Our study suggested that promoter hypermethylation of the genes involved in cell repair system and MINT 25 is associated strongly with some subgroups of primary gastric carcinoma.

Hypermethylation of CpG island is a common mechanism for the inactivation of tumor-related genes. In the present study, we analyzed 13 genitourinary cancer cell lines for aberrant DNA methylation of 5 tumor-related genes using methylation- specific polymerase chain reaction (MSP). GSTP1 was methylated in 5 (38.5%), E-cadherin in 1 (8%), VHL in 1 (8%), and MGMT and hMLH1 in none (0%). Six out of thirteen genitourinary cancer cell lines had methylation of at least one of five genes; 5 had one gene methylated, and, 1 had two genes methylated. Methylation of these 5 genes was not detected in any of the bladder cancer cell lines. GSTP1 was methylated in all of the 3 prostate cancer cell lines. We conclude that aberrant hypermethylation may be an important mechanism for the inactivation of cancer-related genes in kidney and prostate cancer cell lines.