Biological significance of the CpG island methylator phenotype

•CIMP represents a subtype of cancers with multiple CpG island hypermethylation.•CIMP-positive tumors are found in a wide variety of human malignancies.•CIMP tumors show characteristic molecular and clinicopathological features.•CIMP is associated with clinical outcome and it could be a predictive biomarker.

Cancers exhibiting the CpG island methylator phenotype (CIMP) are found among a wide variety of human malignancies and represent a subclass of tumors showing concurrent hypermethylation of multiple CpG islands. These CIMP-positive tumors often exhibit characteristic molecular and clinicopathological features, suggesting CIMP represents a distinct carcinogenic pathway. However, marker genes to define CIMP have been largely inconsistent among studies, which has caused results to vary. Nonetheless, recent advances in genome-wide methylation analysis have enabled the existence of CIMP to be confirmed, and large-scale cancer genome analyses have begun to unravel the previously unknown molecular basis of CIMP tumors. CIMP is strongly associated with clinical outcome, suggesting it may be a predictive biomarker.