Epigenetic
alterations are related to inherited but reversible changes in modifications
that regulate gene activity beyond the DNA sequence. DNA methylation is the
best characterized epigenetic modification, controlling DNA stability, DNA structure,
transcription, and regulation, contributing to normal development and differentiation.
In this section, we first discuss the cellular functions of DNA methylation and
focus on how this fundamental biological process is impaired in cancer. Changes
in DNA methylation status in cancer have been heralded as promising targets for
the development of diagnostic, prognostic, and predictive biomarkers due to their
noninvasive accessibility in bodily fluids (such as blood, urine, stool), reversibility,
stability, and frequency. The absence of markers for definitive diagnosis of
most types of cancer and, in some cases, DNA methylation biomarkers being more specific
and sensitive than commonly used protein biomarkers indicate a strong need for
continued research to expand DNA methylation markers. Although the information on
changes in DNA methylation status in cancer and research on its clinical
relevance is rapidly increasing, the number of DNA methylation biomarkers
currently available as commercial tests is very small. Here, we focus on the
importance of DNA methylation location and target genes likely to be developed
in the future for the development of biomarkers in addition to existing
commercial tests. Following a detailed study of possible target genes, we
summarize the current clinical application status of the most studied and
validated DNA methylation biomarkers, including SEPT9, SDC2, BMP3, NDRG4, SFRP2, TFPI2, VIM and MGMT.
Keywords: Biomarkers, Cancer, Carcinogenesis, CpG islands, DNA Damage, DNA Methylation, Genes, Gene Expression, Gene Silencing, Hypomethylation, Hypermethylation, Methyltransferases, Neoplasms, Oncogenes, Tumor, Tumor Suppressor.
