Currently, it remains unknown how RB cells show this unexpected difference in DNA methylation regulation, but the canonical function of DNMT1 in maintenance methylation appears to be preserved in RB cells as treatment of 5‐azacytidine (DNMT inhibitor) was shown to induce global hypomethylation and re‐expression of EPCAM gene by promoter demethylation in Y79 cells (Kan et al., 2017). This evidence concerns the gene DNMT1 and retinoblastoma.