Methylation of CpG sites in exon 2 of the Bcl-2 gene occurs in colorectal carcinoma

Abstract

<h4>Background</h4>Aberrant bcl-2 expression frequently occurs in colorectal carcinoma. The current study investigated if CpG sites in bcl-2 were methylated in colorectal carcinoma and if methylation correlated with loss of expression of bcl-2 mRNA.<h4>Methods</h4>Methylation was assessed in 23 matched normal mucosae and colonic carcinomas by Southern blotting with methylation-sensitive enzymes. Expression of bcl-2 mRNA was assessed by Northern blotting.<h4>Results</h4>A SacII site in exon 2 of the bcl-2 gene was methylated in 5 carcinomas, plus an adjacent HpaII sites in 1 tumour. SacII site in the bcl-2 promoter were not methylated. Elevated levels of bcl-2 mRNA were detected in 3 carcinomas, 5 showed decreased expression and 4 were unchanged.<h4>Conclusions</h4>De novo methylation of CpG sites in exon 2 of the bcl-2 gene occurs during the development of colorectal carcinoma. However, there was no relationship between expression of bc1-2 mRNA and methylation of specific CpG sites.