Age-related methylation patterning of housekeeping genes and tissue-specific genes is distinct between the stomach antrum and body.

Aim: The methylation-variable sites around CpG islands are frequently overmethylated in Helicobacter pylori-infected stomachs. Age-related patterns of the overmethylation changes were compared between the fast-growing antrum cells and the slow-growing body cells.

Materials & Methods: A total of 316 H. pylori-positive tissues and 380 H. pylori-negative tissues were obtained by endoscopic biopsy. The methylation-variable sites of ten housekeeping genes and nine tissue-specific genes were semiquantitatively analyzed, based on the ten-level classification of methylation-specific PCR intensity. The overmethylated genes were scored when their methylation levels were higher than an intermediate level of each gene common in the H. pylori-negative mucosa.

Results: The age-dependent methylation level of the inactive APC gene observed similarly in the antrum and the body was used as an age standard of methylation variation in a biopsy tissue. The overmethylation of housekeeping genes and stomach-specific genes rapidly increased to a high plateau frequency in the young-aged APC methylation cases (mean age: 43 years) in the H. pylori-positive antrum. In the H. pylori-positive body, most of the overmethylated housekeeping genes slowly increased to a peak frequency in the middle-aged APC methylation cases (mean age: 53 years). The housekeeping gene pairs showed high correlations (Spearman's correlation coefficient > 0.4) in both the antrum and the body.

Conclusion: The overmethylation of housekeeping genes rapidly and slowly increased to a high frequency in concordance with a rapid and slow growth of epithelial cells in the H. pylori-infected stomach.