DNMT3B and cancer: We then determined the number of methylated CpG sites in patient-derived cancer line HCT116 (WT) versus HCT116 cells with a double knock-out for DNA-methyltransferases (DNMTs) DNMT1 and DNMT3b. As shown in Figure 2A (middle panel), in two independent studies [27,28], the number of methylated cytosines decreases in the MAGBE2 promoter region when DNA-methyltransferases (DNMT1 and DNMT3b) are depleted.