Table 3

Geometric means (95% confidence intervals) of percentage methylation for selected genes in colon tumor tissue by MSI+ status and by high vs. low levels of MLH1 methylation

CpG islandMSI statusPaMLH1 methylationbPc
MSI+ (n = 15)MSI− (n = 47)Low (< median) (n = 31)High (> median) (n = 31)
APC 7.1 (3.9, 12.3)7.4 (5.0, 10.9)0.886.6 (3.8, 10.9)8.2 (5.5, 12.1)0.38
CDKN2A promoter3.9 (1.9, 7.3)3.8 (2.8, 5.1)0.77d2.9 (1.9, 4.3)4.9 (3.3, 7.1)0.11e
CDKN2A exon 232.5 (29.1, 36.3)31.0 (27.9, 34.5)0.60d29.0 (26.0, 32.3)34.0 (29.9, 38.5)0.03e
ESR1 22.6 (14.3, 35.4)30.1 (23.9, 37.9)0.3426.3 (18.7, 36.9)29.9 (23.5, 38.1)0.42
MLH1 16.7 (9.0, 30.2)7.5 (5.8, 9.6)0.02NAfNANA
  • a Ps for differences in methylation percentages between MSI+ and MSI− colon cancers were based on the Wilcoxon rank-sum test.

  • b Low MLH1 methylation status is defined as below median methylation levels (below 8%) and high MLH1 methylation is defined as above median MLH1 methylation levels (8% and above).

  • c Ps for differences in methylation percentages between low MLH1 methylation and high MLH1 colon cancers were based on the Wilcoxon rank-sum test.

  • d The Ps for difference in the combined methylation score for CDKN2A (see “Materials and Methods”) between MSI+ versus MSI− tumors was P = 0.95.

  • e The Ps for difference in the combined methylation score for CDKN2A (see “Materials and Methods”) between low (below median) versus high (above median) MLH1 methylation levels was P = 0.03.

  • f NA, not applicable.