Are MGMT promoter methylation and EGFR mutations early markers of tumor progression in colorectal cancer

3584 Background: The colorectal adenoma-carcinoma sequence summarizes the epigenetic and genetic modifications arising during cancer progression. These modifications notably affect the methylation status of different gene's promoters and mutation in the K-ras gene. In the present study, in order to determine if MGMT (O6-methylguanine-DNA methyltransferase) promoter methylation and EGFR mutation may be an early event in the progression of colorectal cancer, we determine the methylation status of H-cadherin and E-cadherin promoters as early and late markers of the disease in more than 200 patients. Methods: Tumour samples were obtained from CRC patients at the adenocarcinoma stage. After resection, they were rapidly frozen in liquid nitrogen and stored at -80°C. Methylation statuses were analyzed by methylation-specific PCR (MSP) and mutation determined by direct sequencing. Results: We screened 236 clinical tumours to detect mutations in the EGFR gene exons 18 to 21, mainly covering the EGFR TK catalytic d...