Molecular pathways: the complexity of the epigenome in cancer and recent clinical advances.

Human cancer is causally linked to genomic and epigenomic deregulations. Epigenetic abnormalities occurring within signaling pathways regulating proliferation, migration, growth, differentiation, transcription, and death signals may be critical in the progression of malignancies. Consequently, identification of epigenetic marks and their bioimplications in tumors represents a crucial step toward defining new therapeutic strategies both in cancer treatment and prevention. Alterations of writers, readers, and erasers in cancer may affect, for example, the methylation and acetylation state of huge areas of chromatin, suggesting that epi-based treatments may require "distinct" therapeutic strategies compared with "canonical" targeted treatments. Whereas anticancer treatments targeting histone deacetylase and DNA methylation have entered the clinic, additional chromatin modification enzymes have not yet been pharmacologically targeted for clinical use in patients. Thus, a greater insight into alterations occurring on chromatin modifiers and their impact in tumorigenesis represents a crucial advancement in exploiting epigenetic targeting in cancer prevention and treatment. Here, the interplay of the best known epi-mutations and how their targeting might be optimized are addressed.