adamts1 crabp1 and nr3c1 identified as epigenetically deregulated genes in colorectal tumorigenesis background gene silencing through cpg island hypermethylation is a major mechanism in cancer development in the present study we aimed to identify and validate novel target genes inactivated through promoter hypermethylation in colorectal tumor developmentmethods with the use of microarrays the gene expression profiles of colon cancer cell lines before and after treatment with the demethylating agent 5aza2deoxycytidine were identified and compared the expression of the responding genes was compared with microarray expression data of primary colorectal carcinomas four of these downregulated genes were subjected to methylationspecific pcr bisulphite sequencing and quantitative gene expression analysis using tumors n198 normal tissues n44 and cell lines n30results twentyone genes with a cpg island in their promoter responded to treatment in cell lines and were simultaneously downregulated in primary colorectal carcinomas among 20 colon cancer cell lines hypermethylation was subsequently identified for three of four analyzed genes adamts1 85 crabp1 90 and nr3c1 35 for the latter two genes hypermethylation was significantly associated with absence or reduced gene expression the methylation status of adamts1 crabp1 and nr3c1 was further investigated in 116 colorectal carcinomas and adenomas twentythree of 63 37 760 12 and 263 3 adenomas as well as 3752 71 2551 49 and 1351 25 carcinomas were hypermethylated for the respective genes these genes were unmethylated in tumors n82 from three other organs prostate testis and kidney finally analysis of normal colorectal mucosa demonstrated that the observed promoter hypermethylation was cancerspecificconclusion by using a refined microarray screening approach we present three genes with cancerspecific hypermethylation in colorectal tumors adamts1 crabp1 and nr3c1