ECRG4 promoter methylation and expression in different cancer cell lines. a) Schematic representation of the 5'-CpG island located in the ECRG4 promoter region and covering exon 1 as well as parts of intron 1. Primer binding sites are indicated by arrows and labeled with numbers. The transcription start site is marked with +1; the first exon is represented by the grey box. b) COBRA analysis of ECRG4 promoter methylation in various cancer cell lines. The arrow indicates the fragments corresponding to the methylated sequence. c) Re-expression of ECRG4 in SW480 and HCT116 cells following treatment with AZA at different concentrations, either alone or in combination with TSA as indicated in the figure.