Methylation status of the PXR promoter and exon 3 regions, as detected by the COBRA assay. Unmethylated and methylated DNAs are shown as U and M, respectively. PCR products that were not cut by the restriction enzymes are shown as UC. (a) PXR promoter methylation was examined in the 6 cell lines after treatment with 5-aza-2'-deoxycytidine (0, 0.5 or 5 μM). (b) Methylation status of the CpG island of the PXR exon 3 region in 6 of the 18 primary colorectal cancers (numbers are those for particular cases). DNA samples from normal and cancerous tissue are shown as N and C, respectively. Note that a high degree of methylation was detected in cancerous, but not normal, tissue. (c) Methylation status of the CpG-rich sequence of the PXR promoter region in 8 primary colorectal cancers. Note that a lower degree of methylation was detected in cancerous tissue compared to normal tissue.