Characterisation of colorectal cancers showing hypermethylation at multiple CpG islands

Background and aims: A subgroup of colorectal cancers (CRC) referred to as the CpG island methylator phenotype (CIMP+) shows simultaneous methylation of multiple CpG islands. The clinicopathological and molecular characteristics of this phenotype remain uncertain however.Methods: We analysed methylation of CpG islands in the p 16 and MDR1 genes and MINT-2 clone in 275 stage II/III CRCs.Results: Concurrent methylation of two or more CpG islands was observed in 32% of cases and was considered to represent CIMP+. These were often poorly differentiated, had less TP53 mutations, and originated frequently in the proximal or higher stage CRC compared with CIMP- tumours (p