The average methylation across http://www.selleckchem.com/products/ldk378.html all sites was 8.3% in normal mucosa and 17.6% in colorectal cancer. The percent-methylation at each CpG … Methylation differences between tumor and normal mucosa The distribution of CDKN2A methylation differences between tumor and normal mucosa are shown in Figure Figure3B.3B. Considering a background methylation rate of 10%, (see 2.7), 92.2% of all cases had equal or greater methylation in tumor compared to normal tissue, while 33 cases (7.8%) were more highly methylated in normal mucosa. Using a threshold value of 20% difference between tumor and normal tissue, 87 patients (20.6%) were considered methylation-positive. CDKN2A methylation and clinico-pathological and molecular data Methylation of CDKN2A in colorectal cancers was significantly more frequent in right-sided colon cancers (p < 0.

0001), as well as those with mucinous histology (p = 0.0209), higher tumor grade (p < 0.0001) and lymph node metastasis (p = 0.0335). Although methylation was not associated with KRAS mutation (p = 0.565), a strong relationship between BRAF mutation and CDKN2A methylation was observed (p < 0.0001). Specifically 31.2% of methylated cases showed BRAF mutation in comparison to only 5.9% of negative cases. In addition, methylation was found more frequently in MSI-H (23.5%) than MSS/MSI-L (13.4%) cancers (p = 0.0252) (Table (Table22). Table 2 Association ofCDKN2Amethylation and clinico-pathological features in colorectal cancers (n = 422) Effect of CDKN2A methylation on survival The prognostic effect of CDKN2A could be assessed in all 422 patients.

Methylation led to a strong negative effect on survival time (p = 0.0003, log-rank; Figure Figure4A).4A). This is additionally highlighted by a HR (95%CI) of 1.6 (1.2-2.1) indicating that patients with methylation-positive tumors have a 60% increased risk of death in comparison to methylation-negative patients. This association is maintained in patients with MSS/MSI-L cancers (p = 0.0001; Figure Figure4B)4B) whereas the effect was non-significant in patients with MSI-H tumors (p = 0.095; Figure Figure4C).4C). However, of the 19 patients with MSI-H/CDKN2A methylation positive cancers, 14 (74%) died of disease, in comparison to 20/42 (47.6%) of patients with MSI-H/CDKN2A methylation negative cancers.

Figure 4 Kaplan-Meier survival curves showing the unfavorable prognostic impact of CDKN2A methylation positivity in (A) all patients and in cases with (B) microsatellite stable (MSS/MSI-L), (C) microsatellite instability-high (MSI-H), (D) BRAF wild-type (WT) and … Next we stratified the survival effect of CDKN2A methylation by Dacomitinib BRAF status. In both BRAF WT (p = 0.0291) and BRAF mutated (p = 0.0121) tumors, CDKN2A methylation positivity had a significant and unfavourable effect on survival time (Figure (Figure44 D, E). We further performed multivariate analysis of CDKN2A using two different models.