To examine whether this region-specific effect in cell lines also applies to primary tumours and gain a better understanding of the mechanism of the inactivation of MMR genes in sporadic colorectal cancer, we first evaluated a method, called ‘COBRA’ (Xiong and Laird, 1997), by comparing the methylation status of hMLH1 promoter in cell lines determined using COBRA with the NaHSO3-sequencing method. This evidence concerns the gene MRC1 and neoplasm.