Epigenetics and DNA methylation in cancer

Figure 3 Model of loss of imprinting of insuline-like growth factor 2, H19 and methylation of the H19 promoter in Wilms’ tumor. In normal cells, the paternal IGF2 and maternal H19 genes are expressed (shown large). Several sites upstream of H19 are methylated on the paternal allele (filled circles) and unmethylated on the maternal allele (open circles). In tumors with LOI, the maternal chromosome reverses to a paternal epigenotype, with a paternal pattern of methylation of the H19 promoter, IGF2 turned on, and H19 turned off, causing increased cell growth. LOI of H19 on the maternal chromosome, when it occurs, could occur independently or could be influenced by events in the paternal chromosome. Adapted by Steenman et al[9], 1994. LOI: Loss of imprinting; IGF2: Insuline-like growth factor 2.