摘要AIM:To isolate and analyze the DNA sequences which are methylated differentially between gastric cancer and normal gastric mucosa.METHODS:The differentially methylated DNA sequences between gastric cancer and normal gastric mucosa were isolated by methylation-sensitive representational difference analysis (MS-RDA).Similarities between the separated fragments and the human genomic DNA were analyzed with Basic Local Alignment Search Tool (BLAST).RESULTS:Three differentially methylated DNA sequences were obtained,two of which have been accepted by GenBank.The accession numbers are AY887106 and AY887107.AY887107 was highly similar to the 11th exon of LOC440683 (98%),3'end of LOC440887 (99%),and promoter and exon regions of DRD5 (94%).AY887106 was consistent (98%) with a CpG island in ribosomal RNA isolated from colorectal cancer by Minoru Toyota in 1999.CONCLUSION:The methylation degree is different between gastric cancer and normal gastric mucosa.The differentially methylated DNA sequences can be isolated effectively by MS-RDA.