Indeed, hypermethylation of RB1 promoter region due to the overlapping of CpG island 106 is found to be the major epigenetic mechanism underlying decreased retinoblastoma protein expression in Rb tumors (Choy et al., 2005; Livide et al., 2012) (Ohtani-Fujita et al., 1993). This evidence concerns the gene RB1 and retinoblastoma.