title: Multiple tumor suppressor genes are increasingly methylated with age in non-neoplastic gastric epithelia.
abstract: 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. To quantitatively evaluate age-related methylation in non-neoplastic gastric epithelia, we used a fiber-type DNA microarray on which methylated and unmethylated sequence probes were mounted. After bisulfite modification, a part of the promoter CpG island of four tumor suppressor genes, lysyl oxidase (LOX), p16, RUNX3 and tazarotene-induced gene 1 (TIG1), were amplified by PCR using Cy5 end labeled primers. Methylation rates (MRs) were calculated as the ratio of the fluorescence intensity of a methylated sequence probe to the total fluorescence intensity of methylated and unmethylated probes. Non-neoplastic gastric mucosa was obtained from 24 non-cancer-bearing stomachs at autopsy. MRs ranged from 0.0% to 77.2% (mean, 15.8%) for LOX, 0.0% to 45.8% (mean, 10.0%) for p16, 0.0% to 83.8% (mean, 9.0%) for RUNX3, and 0.0% to 46.1% (mean, 6.6%) for TIG1, and significantly correlated with aging (P < 0.01). The regression curves were: y = 0.013x(2) - 0.6184x + 4.0512, R(2) = 0.5728 (P < 0.001) for LOX; y = 0.0107x(2) - 0.6055x + 5.2943, R(2) = 0.7891 (P < 0.00001) for p16; y = 0.0182x(2) - 1.2234x + 11.566, R(2) = 0.5595 (P < 0.001) for RUNX3; and y = 0.0068 x(2) - 0.3586 x + 2.4306, R(2) = 0.4670 (P < 0.01) for TIG1. Thus, our present results are consistent with the notion that age-related methylation is associated with cancer susceptibility in the elderly. Quantitative analysis of DNA methylation using DNA microarrays is a promising method for risk assessment in the development of gastric cancer.
authors.affiliation: Department of Pathology, Yamagata University School of Medicine, 2-2-2 Iida-nishi, Yamagata 990-9585, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: So
authors.forename: Gen
authors.initials: G
authors.lastname: Tamura
authors.forename: Teiichiro
authors.initials: T
authors.lastname: Honda
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Homma
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Waki
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Togawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nishizuka
authors.forename: Teiichi
authors.initials: T
authors.lastname: Motoyama
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D002648:Child; D002675:Child, Preschool; D018899:CpG Islands; D019175:DNA Methylation; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics*