C9orf50 and adenoma: They target CpG sites located in the 5′-regions of the genes C9orf50, KCNQ5, and CLIP4 (Additional file 4: Figure S4) that were found to be concurrently hypermethylated in CRC and adenoma tissues, but unmethylated in blood cells and in most other cancer types (Fig. 3, Additional file 9: Table S1).