Aberrant DNA methylation of CpG islands occurred frequently in CRC and associated with transcriptional silencing of key genes. In this study, the CIMP combined with MLH1 or p16 methylation status was determined in CRC patients and correlated with clinicopathological parameters and overall survival. Our data showed that CIMP+ CRCs were identified in 32.9% of cases and that CACNAG1 is the most frequently methylated promoter. When we combined the CIMP with the MLH1 or the p16 methylation status, we found that CIMP-/MLH1-U (37.8%) and CIMP-/p16 -U (35.4%) tumors were the most frequent among the four subtypes. Statistical analysis showed that tumor location, lymphovascular invasion, TNM stage, and MSI differed among the group of patients. Kaplan-Meier analyses revealed differences in overall survival according to the CIMP combined with MLH1 or p16 methylation status. In a multivariate analysis, CIMP/MLH1 and CIMP/p16 methylation statuses were predictive of prognosis, and the OS was longer for patients with tumors CIMP-/MLH1-M, as well as CIMP-/p16 -M. Furthermore, DNMT1 is significantly overexpressed in tumors than in normal tissues as well as in CIMP+ than CIMP- tumors. Our results suggest that tumor classification based on the CIMP status combined with MLH1 or p16 methylation is useful to predict prognosis in CRC patients.

Objective To determine the correlation between DNA methylation of p66Shc promoter and some markers of inflammatory and oxidative stress in chronic renal failure (CRF) patients compared with healthy subjects. Methods An observational cross-sectional study was conducted in the nephrology department at Sidi Bouzid Regional Hospital (Tunisia). In total, 39 patients with CRF and 37 healthy subjects were included. Several biochemical parameters were measured. Furthermore, markers of the oxidative and inflammatory status (MDA, TAS, SOD, and CRP) were evaluated. The p66Shc methylation status was determined using the methylation-specific PCR. Results Our results showed that levels of blood glucose, urea, creatinine, uric acid, ChT, TG, albuminuria, CRP and MDA were significantly elevated in CRF patients compared to controls. Furthermore, p66Shc promoter region was highly demethylated in CRF patients compared to healthy controls (84% vs 4%). Our data showed a positive correlation between p66Shc hypomethylation and levels of MDA (r = 0.93; p<0, 05) and CRP (r = 0.89; P <0, 05), as well as a significant negative correlation between p66Shc hypomethylation, TAS (r = -0.76; P <0, 05) and SOD (r = -0.77; p<0, 05) levels. Similarly, there was a positive correlation between p66Shc hypomethylation and the disease stages. Importantly, multiple regression analysis showed that p66shc DNA hypomethylation remains strongly correlated with MDA, CRP and stages of CRF. Conclusion This study indicates that the DNA hypomethylation of p66shc promoter was correlated with oxidative and inflammatory stress and the disease stages in CRF patients.