MUC2 gene promoter methylation in mucinous and non-mucinous colorectal cancer tissues

Abstract

Abundant mucin production and MUC2 expression is the key feature ofmucinous colorectal cancer (CRC). Although MUC2 gene methylation hasbeen thought to play ail important role in loss of MUC2 expression, thetissues are difficult to analyze because of the cellular heterogencityof tissue samples. In the present Study, we determined the role ofregion-specific methylation in the MUC2 promoter in MUC2 expression inCRC. Additionally. we optimized the conditions for quantification ofmethylation analysis in mucinous and non-mucinous CRC tissues. Weidentified two regions in MUC2 promoter, region A (-289 and -274) andregion C (-193 and -160), that correlated with loss of MUC2 expressionby comparing the methylation status in 13 CRC cell lines with no or lowMUC2 expression and those in 4 cell lines with high MUC2 expression. Toprove the correlation of MUC2 methylation status and loss of expressionin CRC tissues, MUC2 methylation status in tumors, needs to bedetermined. Since the critical CpG sites have been identified in celllines by sequencing, a more rapid and sensitive methylation specific PCR(MSP) was used. We conducted MSP at 3 CpG sites (-289, -274, -193) in 19mucinous and 34 non-mucinous CRC tissues because this analysis worked atonly these sites in the preliminary cell line experiments. Our resultsshowed that methylation status of mucinous CRC was significantly lowerthan that of non-mucinous CRC at 3 sites (-289; p=0.001, -274; p=0.013,-193; p=0.001), and correlated with high level of MUC2 expression asdetermined by immunohistochemistry. Besides, these results indicatedthat MUC2 expression and mucin contents decreased in accordance with theincrease of methylation status. We concluded that low methylation statusof MUC2 gene plays a predominant role in high level MUC2 expression inmucinous CRC.