The Expression of Melanoma-Antigen Gene A1-6 during the Carcinogenesis of the Colon

Um, Jung Sup; Park, Jeen Kyung; Park, Moo In; Koo, Ja Young; Jeong, Min Jung; Park, Hee Sung; Chang, Hee Kyung

Abstract

BACKGROUND/AIMS
Melanoma antigen gene (MAGE)-A which have more than 12 subtypes is a gene family for tumor specific shared antigens, recognized by the cytotoxic T cell. Since these genes are expressed only in tumor cells and silent in normal adult tissues except in the male germ line, they may be used as diagnostic markers in detecting malignancy. During the carcinogenesis of gastrointestinal tract, the hyperplastic epithelium-adenoma-adenocarcinoma sequence is largely accepted and the molecular studies on each step have been issued. However, in the aspect of carcinogenesis in the gastrointestinal tract, MAGE genes have not studied yet. To explore the functional role and clinical significance of MAGE-A genes in the carcinogenesis of the colon, mRNA expression of MAGE-A1 to -A6 in the mucosal tissues obtained from the colonoscopy was investigated and the relationship between their expressions and clinicopathologic parameters was analysed.
METHODS
We investigated the expression of MAGE 1~6 in 65 endoscopically biopsied samples of neoplastic and nonneoplastic tissues from the colon, using a MAGE common primer by the reverse transcription-nested polymerase chain reaction and DNA sequencing.
RESULTS
Of the 31 colorectal adenocarcinoma specimens examined, MAGE genes were expressed in 11 cases (36%). In contrast, no expression of these genes was observed in any of the 12 samples of tubular adenoma and 12 of non-specific colitis and 5 cases of normal colonic tissues. There was no significant correlation between the expression of the MAGE genes and clinicopathologic factors, such as gender, disease stage, lymph node metastasis and perineural and vascular invasion in colonic carcinoma.
CONCLUSIONS
It is postulated that the expression of MAGE genes could reflect the late event of oncogenesis of the colon because no MAGE expression was noticed in chronic inflamamtion and adenomas which might have the important role in the process of malignant transformation.