Quantitative assessment of RUNX3 methylation in neoplastic and non-neoplastic gastric epithelia using a DNA microarray.

Silencing of the RUNX3 gene by hypermethylation of its promoter CpG island plays a major role in gastric carcinogenesis. To quantitatively evaluate RUNX3 methylation, a fiber-type DNA microarray was used on which methylated and unmethylated sequence probes were mounted. After bisulfite modification, a part of the RUNX3 promoter CpG island, at which methylation is critical for gene silencing, was amplified by polymerase chain reaction using a Cy5 end-labeled primer.

Multiple tumor suppressor genes are increasingly methylated with age in non-neoplastic gastric epithelia.

A number of tumor suppressor and tumor-related genes are silenced by promoter hypermethylation in gastric cancer. Hypermethylation is not restricted to cancer cells, but is also present in non-neoplastic cells during aging. Such age-related methylation in non-neoplastic gastric epithelia is postulated to constitute a field defect that increases the risk for development of gastric cancer.

Spreading of methylation within RUNX3 CpG island in gastric cancer.

RUNX3 is a novel tumor suppressor gene that is frequently silenced by promoter hypermethylation in gastric cancer. The methylation status of multiple regions within the RUNX3 promoter CpG island (3,478 bp) was examined in gastric cancer cell lines, primary gastric cancers and non-neoplastic gastric mucosa to clarify how methylation spreads within the CpG island. The critical regions for RUNX3 silencing were evaluated by analysis of cell lines.

Hypermethylation of Chfr and hMLH1 in gastric noninvasive and early invasive neoplasias.

Human tumors are genetically unstable, and the instability exists at two distinct levels-the chromosomal level and the nucleotide level. Chfr and hMLH1 hypermethylation, which may lead to chromosomal instability (CIN) and microsatellite instability (MSI), respectively, was analyzed in gastric noninvasive neoplasias (NIN, Padova international classification) and submucosal invasive adenocarcinomas and in their corresponding non-neoplastic gastric epithelia. Results were compared with microsatellite status, p53 immunoreactivity, and cellular phenotype.