Fig. 3

Methylation analysis of the promoter region in the MLH1 gene. a Schematic depiction of two regions (AB and C region) of the MLH1 promoter for methylation, and results of a panel of representative fluorescent bisulphite PCR following restriction enzyme analysis. AB and C region in this study link to A plus B and C plus D region, defined by Deng and colleagues [18], respectivily.  Methylated samples had the new fragment cleaved by the restriction enzyme (black triangles). White triangles represent unmethylated alleles. M and U denote methylated and unmethylated, respectively. A grey bar denotes an untranslated exon. b The frequencies of MLH1 promoter methylation status among the POLE, MSI, and non-MSI groups. Extensive methylation is defined as 5.0% or more methylation on both AB and C regions. Partial methylation is defined as 5.0% or more methylation on AB region only. c The frequencies of MLH1 promoter methylation status according to MMR protein expression status. dMLH1, dMSH2, and dMSH6 denote deficiency of MLH1, MSH2, and MSH6, respectively. pMMR denotes proficiency of all MMR proteins. d The final classification of 1,013 CRCs according to POLE mutation, MSI, and MLH1 promoter methylation status. MSI-M denotes MSI tumours with extensive MLH1 methylation. MSI-U denotes MSI tumours without extensive MLH1 methylation. The number in each column denotes the number of samples classified in each category divided by MLH1 methylation status