CpG Island Methylation According to the Histologic Patterns of Early Gastric Adenocarcinoma

Background: Although the importance of aberrant DNA methylation in the development of gastric adenocarcinoma has been described, the mechanism of pathogenesis has not been revealed yet. We quantitatively analyzed methylation of four CpG islands and one repetitive DNA element, according to the histologic features of adenocarcinoma with precursor lesions. Methods: We divided the cases as adenocarcinoma with intestinal type precursors (type A, n = 19 cases) and adenocarcinoma with diffuse type precursors (type B, n = 19 cases). We micro-dissected tumor cells and matched non-neoplastic gastric mucosa from the hematoxylin and eosin-stained slides. Results: A total of 20 CpG sites of long interspersed nucleotide element-1 (LINE1), RAR-related orphan receptor alpha (RORA), Kruppel-like factor 7 (KLF7), mutL homolog 1 (MLH1), MINT25, and CD133 were analyzed. Methylation was determined by bisulfate-pyro-sequencing, and hypomethylation of LINE1 and CD133 was noted in the tumors, compared to the levels in the non-neoplastic gastric mucosa (p = 0.014 and p = 0.015, respectively). A statistically different methylation pattern of CpG sites at CD133 and KLF7 was noted only in type B lesions, compared to that in mat-ch-ed non-neoplastic gastric mucosa (p = 0.027 and p = 0.043, respectively). Conclusions: Given that aberrant methylation occurs in a relatively early phase of carcinogenesis, different patterns of me-thylation may determine the carcinoma phenotype. However, further large-scale study is required to clarify the significance of this difference.