Genetics and Epigenetics in Tumorigenesis: Acting Separately or Linked?

Tumorigenesis represents both genetic and epigenetic alterations. Genetic changes are defined as genomic DNA sequence changes, including point mutation, single nucleotide polymorphism (SNP) or copy number variability (CNV), including loss of heterozygozity (LOH), gain copy number or deletion. On the other hand, epigenetic modification is responsible for regulation of gene expression without changing the underlying DNA sequence. Such mechanisms include DNA methylation, post-translational modifications of the histone proteins, and micro RNA, resulting in selective gene activation and/or in activation. As opposed to solely isolated genetic and epigenetic components acting in tumorigenesis, the complex nature of cancer seems to stem from the interaction of these mechanisms.