Epigenomic technologies for deciphering circulating tumor DNA.

Tumor-derived DNA, found in body fluids (liquid biopsy) of cancer patients as part of cell-free DNA (cfDNA), lends itself for noninvasive cancer detection and monitoring. Advantages of cfDNA as analytical target have evoked a burst of sophisticated techniques, providing clinically relevant information. Each cell type carries a unique DNA modification profile consisting mainly of patterns of 5-methylcytosine in CpG dinucleotides, which are critical for establishing and maintaining cellular identity and which are frequently disturbed in cancer. Assessment of the tumor-derived cfDNA modifications combined with high-throughput analysis techniques holds promise for developing highly specific noninvasive diagnostic tests. This review highlights recent advances in locus-specific and whole-genome analysis of cfDNA, with a specific focus on epigenetic phenomena and their clinical value.