RESUMO
BACKGROUND: Research in the last decade has confirmed the importance of epigenetic processes for the onset, development, and treatment of cancer. Next generation sequencing has allowed the inspection and mapping of the human epigenome and its monitoring for changes during carcinogenesis, which has revealed direct links between epigenetic abnormalities and mutations in genes that control DNA methylation and packing and those that function in chromatin dynamics and metabolism. Epigenetic changes that occur in the early stages of tumor progression thus represent promising candidates for diagnostic and prognostic markers, and epigenetic processes are suitable targets for the development of new therapeutic strategies. There are two contrasting views on how aberrant DNA methylation contributes to the development of cancer. The first view assumes that normal cells undergo transformation due to driver mutations and subsequent de novo methylation and DNA demethylation, resulting in global changes in gene expression. The second view considers changes in DNA methylation to be a consequence of cell aging, for example, and that the acquired changes increase the sensitivity of DNA to mutations and oncogenic transformation. AIMS: The aim of the review article is to briefly summarize the role of abnormal DNA methylation in the development of cancer, and to present an alternative theory that considers the role of aberrant DNA methylation patterns in cancer from a new and unconventional perspective. Key words: DNA methylation - polycomb-group proteins - CpG islands The work was supported by the project MEYS - NPS I - LO1413. The author declares she has no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Accepted: 27. 8. 2018.