Table 1.

Summary of epigenetic, genetic, and associated phenotypic alterations

Site and type of alterationPercentage of tumorsNo. tumorsTotal tumors evaluated
APC gene
    APC gene alteration identified70.2146208
    APC promoter hypermethylation31.764202
Mutation in APC mutation cluster region62.0129208
        Point mutation87 (136)*
            G-to-A transition19 (25)*
            C-to-T transition30 (32)*
        Frameshift mutation57 (59)*
MGMT gene and MGMT expression
    MGMT promoter hypermethylation27.457208
    Loss of MGMT protein expression24.551208
    Concordance of MGMT methylation status with MGMT protein expression status82.7172208
hMLH1 gene and microsatellite instability
    hMLH1 promoter hypermethylation9.219207
    Loss of hMLH1 protein expression9.820204
    Concordance of hMLH1 methylation status with hMLH1 protein expression status94.6192203
    High levels of microsatellite instability (MSI-H)10.622208
    Concordance of hMLH1 methylation status with MSI status92.6187202
CpG island methylation of additional markers
    Frequency of hypermethylation
        P16 gene19.539200
        N33 gene93.8180192
    CIMP with three markers (≥60%)10.121208
KRAS proto-oncogene/BRAF gene
    KRAS codon 12 or 13 mutation39.280204
    KRAS codon 12 or 13 G-to-A transition56
        Codon 12a G-to-A5
        Codon 12b G-to-A26
        Codon 13b G-to-A25
    BRAF mutation6.513199
    BRAF V600E nt 1799 T-to-A transversion4.59199
    Discordant KRAS and BRAF V600E mutation status10099
P53 gene
    Exon 5-8 mutation55.2112203
        G-to-A transition40
        C-to-T transition31
  • * Number in parenthesis is the number of APC mutations. The total number of APC mutations exceeds the number of tumors due to the occurrence of multiple mutations in 41 tumors. The total number of point mutations includes the number of G-to-A transition mutations.

  • Five markers used to define CIMP based on cluster analysis (see Fig. 2).