RB1 and retinoblastoma: In retinoblastoma, hypermethylation has been observed in the promoter regions of MSH6, CD44, PAX5, GATA5, TP53, VHL, GSTP1, MGMT, RB1, and CDKN2 genes that participate in a variety of cancer-related pathways, including DNA repair, tumor suppression, and cell-cell interactions [20].