Figure 1

Enrichment of CTCs from peripheral blood of cancer patients by physical or biological properties. A: Transition of CTC from primary lesion to metastasis lesion. B: Physical properties include density (Ficoll centrifugation) - CTCscope. C: Biological properties are based on the following: the expression of cell surface markers, including an epithelial cell adhesion molecule (EpCAM) for positive selection – CellSearch/AdnaTest; anti-EpCAM antibodies conjugated with magnetic beads, for enriching CTCs in a magnetic field – MagSweeper; anti-EpCAM antibodies on microposts or columns of nanobeads – ELISPOT/Ephesia; anti-EpCAM antibodies conjugated to 3-μm beads to increase the size of CTCs before filtration - Cytometry. D: Schematic of the RNAscope assay procedure - CTCscope. In step 1, cells are fixed and permeabilized to allow for target probe access. In step 2, target RNA-specific oligonucleotide probes (Z) are hybridized in pairs (ZZ) to multiple RNA targets. In step 3, multiple signal amplification molecules are hybridized, each recognizing a specific target probe, and each unique label probe is conjugated to a different fluorophore or enzyme. In step 4, signals are detected using an epifluorescent microscope (for fluorescent label) (CTCscope image are reproduced from Payne et al. [4]) PBMC: peripheral blood mononuclear cells; CTC: circulating tumor cells; RBC: red blood cell.