Fig. 1.

Liquid biopsy markers. Biomarkers that are currently used as liquid biopsy include cell free nucleotides, circulating tumor cells (CTCs), tumor educated platelets (TEPs), and disseminated tumor cells (DTCs). Cell free nucleotides are released into the blood circulating by apoptotic or necrotic cells, or by active secretion of exosomes containing a cell's genetic material. Cell free DNA (cfDNA) is highly fragmented but is still wrapped around nucleosomes providing its typical length of 166 or 320 bp. cfDNA may be used to study a tumor's methylation patterns, chromosomal aberrations, or other mutations.