Figure 1.

The workflow of plasma-based and CSF-based liquid biopsy in neuro-oncology. Tumour-derived material (cfDNA, EVs, CTCs) is released in both CSF and plasma. Samples of both fluids can be obtained in the clinic by lumbar puncture or ventricular shunts (CSF) or venous blood sampling (plasma). Fresh biological fluids should be centrifuged at different speeds according to different protocols, depending on the material, in order to separate the supernatant from the pellet and isolate the material of interest. Nucleic acids can be extracted from either EVs or CTCs and then quantified by fluorometric assay or qPCR. Once good-quality material has been obtained, a plethora of genetic analyses can be performed, from whole-genome sequencing to methylomics. cfDNA = cell-free DNA; CTCs = circulating tumour cells; EVs = extracellular vesicles; NGS = next-generation sequencing; VS = ventricular shunt; WBCs = white blood cells; WES = whole exome sequencing; WGS = whole genome sequencing. Created with Biorender.com.