Figure 2.

Common epigenetic alterations in cancer. Epigenetic changes are observed in many cancer types. Hypermethylation of gene promoters decreases the expression of proteins or non‐coding RNAs that have antiproliferative or proapoptotic effects, or mediate DNA repair, or inhibit invasion or angiogenesis. In some cases, hypomethylation of the promoters of proto‐oncogenes was demonstrated (not depicted). In certain cancers, for example, colorectal carcinomas, differential methylation was found mainly in so‐called CpG island shores that reside upstream of promoter‐associated CpG islands. As an example, CpG island shore hypermethylation is depicted resulting in reduced transcription. Hypomethylation of the gene body may unblock alternative transcription start sites. Moreover, hypomethylation of repetitive sequences is associated with genomic instability. The cancer‐associated changes in DNA methylation pattern are accompanied by further “epimutations”, such as histone modifications that alter the chromatin structure (not depicted). Methyl groups are symbolized by black circles; green and red crosses symbolize the block of gene expression or transposition; TSS: transcriptional start site.