e14503 Background: Data on the prognostic significance of promoter CpG island methylation in colorectal cancer (CRC) are conflicting, possibly due to associations between methylation and other factors affecting survival such as genetic alterations and use of adjuvant therapy. Here we examine the prognostic impact of promoter methylation in CRC patients treated with surgery alone in the context of microsatellite instability (MSI), BRAF- and KRAS mutations. Methods: 173 CRCs were analyzed for promoter methylation of 19 tumor suppressor- and DNA repair genes, the CpG island methylator phenotype (CIMP), MSI, the exon 15 V600E BRAF mutation and KRAS codon 12 and 13 mutations. Results: Unsupervised hierarchical clustering based on methylation status of 19 genes revealed three subgroups: cluster 1 (CL1, 57% (98/173) of CRCs), cluster 2 (CL2, 25% (43/173) of CRCs) and cluster 3 (CL3, 18% (32/173) of CRCs). CL3 had the highest methylation index (0.25, 0.49 and 0.69 respectively, p=<0.01) and was strongly associated with CIMP (p<0.01). After stratification for tumor stage, MSI and BRAF status, no statistically significant differences in survival between CL1, CL2 and CL3 nor between CIMP and non-CIMP CRCs were detected. Analyzing genes separately revealed that CHFR promoter methylation was associated with a poor prognosis in stage II, MSS, BRAF wild-type CRCs: HR=3.89 (95% CI =1.58-9.60, p=0.003) and HR=2.21 (95% CI =1.09-4.48, p=0.03) in a second population-based study (n=151). Conclusions: CHFR promoter CpG island methylation, which is associated with MSI, also occurs frequently in MSS CRCs and is a promising prognostic marker in stage II, MSS, BRAF wild-type CRCs.
MAPT promoter CpG island hypermethylation is associated with poor prognosis in patients with stage II colorectal cancer