MLH1 and colorectal cancer: To test this, we analysed the methylation status of all CpG sites of the MLH1 5′ end (C region containing promoter, exon 1 and majority of intron 1) (Fig. 1) in colorectal cancer cells and tissues, gastric cancer tissues and normal tissues using bisulfite genomic sequencing, and found that Alu elements in the intron 1 of MLH1 are hypomethylated, and the promoters and the regions between MLH1 promoters and Alu elements are hypermethylated in cancers.