Promoter methylation of specific genes is associated with the phenotype and progression of colorectal adenocarcinomas.

BACKGROUND: Promoter methylation of colorectal cancer-related genes were examined with respect to phenotype and tumor progression.
MATERIALS AND METHODS: We assayed promoter methylation of 11 genes including established CpG island methylator phenotype (CIMP) markers (MLH1, MINT1, MINT2, MINT31, p16 ( INK4a ), p14 ( ARF ), and CACNA1G) and four genes (COX2, DAPK, MGMT, and APC) frequently methylated in colorectal cancer in 285 patients with sporadic colorectal cancer.
RESULTS: CIMP+ tumors were more than two times more frequent among high-frequency microsatellite instability tumors (MSI-H) than in tumors without MSI (P < or = .0001-.002). COX2 and DAPK methylation were significantly associated with CIMP+ and MSI. KRAS showed tendency toward more frequent codon 12-13 mutations identified in tumors with APC and p16 ( INK4a ) methylation than in those with unmethylation (P = .033 and .05, respectively). Additionally, tumors with synchronous adenoma were associated with p16 ( INK4a ) methylation (P = .004). The p16 ( INK4a ) methylation was significantly associated with poor overall and disease-free survival in 131 rectal cancer patients who underwent curative operation, according to multivariate analyses (relative risk [RR] = 0.317 and 0.349; P = .033 and .024, respectively). Specifically, in 175 stage II and III patients receiving adjuvant-based fluoropyrimidine chemotherapy, p16 ( INK4a ) methylation and MINT31 unmethylation showed a significant or tendency toward an association with recurrence and DFS (P = .007-.032).
CONCLUSIONS: The study suggests that specific CIMP markers, such as p16 ( INK4a ) and MINT31, should be further verified as potential epigenetic targets for the design of efficient chemotherapy regimens. We also identified a subset of colorectal cancer, possibly comprising APC methylation-KRAS mutation-p16 ( INK4a ) methylation.