Analysis of the methylation status of the TSC2 promoter by COBRA and bisulfite sequencing. a) Bisulfite treated DNA samples from 16 oral tumors, three normal oral tissues, peripheral blood samples from two normal individuals and two cell lines were analyzed by COBRA. Normal and tumor samples are marked as N and T, respectively. Numbers correspond to patient numbers. Note, the undigested 571 bp fragment and a major digested fragment of ~175 bp in all tumors and cell lines. CB DNA1 and CB DNA 2 are peripheral blood DNA samples from two unrelated normal individuals. b) Representative bisulfite sequencing chromatograms of the promoter region from normal and tumor samples. The underlined region denotes the Aci I site which is lost in the normal tissue from patient 55 and retained in the tumor from patient 59 because of methylation at the C residue at this site.