CpG island methylator phenotype in colorectal cancers: comparison of the new and classic CpG island methylator phenotype marker panels.
BACKGROUND
CpG island methylator phenotype (CIMP) designates a subset of colorectal cancers featuring concordant hypermethylation of multiple promoter CpG islands. Little is known about the clinical outcome or histologic characteristics of CIMP-positive colorectal cancers defined by recently identified CpG island methylator phenotype panels.


OBJECTIVE
To investigate and compare the molecular and clinicopathologic features of CIMP-positive colorectal cancers defined by classic (p16, hMLH1, MINT1, MINT2, MINT31) and new (CACNA1G, IGF2, NEUROG1, RUNX3, SOCS1) CIMP panels.


METHODS
We analyzed 130 colorectal cancers for hypermethylation of both panels using methylation-specific polymerase chain reaction.


RESULTS
With at least 2 markers methylated, both classic (39/130; 23.1%) and new (23.1%) CIMP-positive colorectal cancers were significantly associated with proximal tumor location, microsatellite instability, and BRAF mutation (all P values were less than .05). The new panel outperformed the classic panel in detecting these features. With at least 3 markers methylated, new CIMP-positive colorectal cancers (16.9%) were closely associated with proximal tumor location, low frequency of KRAS mutation, and high frequency of BRAF mutation (all P values were less than .05), whereas classic CIMP-positive colorectal cancers (18.5%) were closely associated with proximal tumor location, frequent microsatellite instability, and frequent BRAF mutation (all P values were less than .05). Analyzing a combination of CIMP and microsatellite instability status, CIMP-positive/microsatellite instability-negative colorectal cancers had the worst clinical outcomes.


CONCLUSIONS
Whereas the classic panel outperformed in predicting clinical outcome, the new panel was superior in detecting known clinicopathologic features of CIMP but inferior in prognostication power.
Lee
Sun
S
Department of Pathology, Kyung Hee University College of Medicine, Seoul, Korea.
Cho
Nam-Yun
NY
Yoo
Eun Joo
EJ
Kim
Jung Ho
JH
Kang
Gyeong Hoon
GH
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D014408:Biomarkers, Tumor / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins / Q000235:genetics
D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins