Expression of beta-catenin, hMLH1, p53, Bcl-2, Bax and COX-2 in Serrated Adenomas of Colon

Choi, Kyo Won; Jang, Byung Ik; Eun, Jong Ryul; Lee, Jung Hoon; Bae, Young Kyung; Kim, Tae Nyun

Abstract

BACKGROUND/AIMS: Serrated adenoma of the colorectum is a recently proposed entity that is characterized by a saw-toothed structure of hyperplastic polyp and also the cytologic atypia of conventional adenoma. In contrast to conventional adenomas, the molecular features of serrated adenomas have been poorly studied.
METHODS
The expression of beta-catenin and the DNA mismatch repair protein hMLH1, apoptosis regulating protein Bcl-2, Bax, p53 and COX-2 were analyzed in 28 serrated adenoma specimens and 28 tubular adenoma specimens.
RESULTS
No differences were observed in the frequency of beta-catenin loss in the cell membrane between the serrated and tubular adenoma specimens. The frequency of hMLH1 loss was significantly higher in the serrated adenomas than in tubular adenomas (p < 0.05). The frequency of p53 overexpression was not significantly different between the serrated and tubular adenoma specimens. The frequencies of the Bax and Bcl-2 overexpressions were significantly lower in the serrated adenomas than in the tubular adenomas. The COX-2 levels were not different between the serrated and tubular adenomas. In the serrated adenoma specimens, the frequency of Bax overexpression was reduced in the older age group (> 60 years old). In the tubular adenoma specimens, the frequency of p53 overexpression was increased in the dysplastic epithelium.
CONCLUSIONS
The expressions of hMLH1, Bax and Bcl-2 were decreased in the serrated adenoma than in the tubular adenoma. Our data suggest that the serrated adenoma and tubular adenoma may have different pathway in their development. However, further studies including normal mucosa, hyperplastic polyp and cancer specimens are needed.