Fig. 1

Circulating molecules in liquid biopsy. There are a number of molecules that can be measured in body fluids including cell-free DNA, circulating tumor cells (CTCs), different circulating RNA classes (miRNAs, lncRNAs, mRNAs), cell-free proteins and exosomes. Cell-free DNA escapes into circulation from the primary tumor or metastatic loci through necrosis or apoptosis of tumor cells. Circulating cell-free DNA can then be used as a liquid biopsy to measure DNA levels, integrity, methylation, mutational status and copy number aberration