The CpG island methylator phenotype (CIMP), characterized by an exceptionally 
high frequency of methylation of discrete CpG islands, is observed in 18% to 25% 
of sporadic colorectal cancers. Another hypermethylation pattern found in 
colorectal cancers, termed long-range epigenetic silencing, is associated with 
DNA/histone methylation in three distinct gene clusters at chromosome 2q14.2, 
showing that DNA hypermethylation can span larger chromosomal domains and lead 
to the silencing of flanking, unmethylated genes. We investigated whether these 
two phenotypes are interrelated in colorectal cancers. The CIMP status of 148 
sporadic colorectal cancers was determined by methylation-specific PCR. We 
determined the BRAF V600E mutation by mutant allele-specific PCR amplification. 
The methylation status of the MLH1 gene and of three CpG islands (EN1, SCTR, and 
INHBB), corresponding to three distinct clusters along 2q14.2, was determined by 
methylation-specific PCR. The average number of sites showing methylation in 
CIMP+ tumors was 2.21, compared with 1.22 for CIMP- individuals, and this 
difference was highly significant (P = 3.6 x 10(-8), Mann-Whitney test). 
Moreover, all CIMP+ tumors showed hypermethylation of at least one of these 
loci, in contrast to CIMP- tumors, where 18 (16%) samples remained unmethylated. 
The mean number of simultaneously hypermethylated CpG islands at 2q14.2 differs 
significantly between CIMP- and CIMP+ tumors, suggesting varying effects of 
domain silencing in this region. Given that the number of hypermethylated loci 
at 2q14.2 likely affects the range of silenced flanking genes, high frequency of 
simultaneous hypermethylation of three CpG islands (EN1, SCTR, and INHBB) may 
have potential influence on specific characteristics of CIMP+ colorectal 
cancers.