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Today's CTC analysis technology

Outline of CTC analysis technology

CTCs are very rare cells as only one CTC is contained in about 1x108 or 1x109 of blood cells in cancer patient’s blood so the detection of CTCs requires a concentration step as pretreatment.

Usual method for concentration of CTC is an immunomagnetic separation system using anti-EpCAM (EpCAM; Epithelial cell adhesion molecule) monoclonal antibody. EpCAM expressed on the surface of tumor cells are trapped by the antibodies coated on the magnetic beads, and CTCs can be selectively-concentrated by magnetic attraction.

On the other hand, it is also known that the tumor cells are heterogeneous population and EpCAM is not constantly expressed on them. And it have been noted that CTM (Circulating Tumor Microemboli) or CTCs with EMT (Epithelial Mesenchymal Transition) which are attracting attention these days show no or weak expression of EpCAM, and therefore they are not detectable by the method above.

Besides the immunomagnetic separation system, there is another selective method according to the cell size. As the tumor cells are larger than the other blood cells, isolation of CTCs is possible by filtering of whole blood with a membrane filter. This method has an advantage that CTCs can be isolated as living cells without fixation. Nowadays, inexpensive and convenient devices are available but they are disadvantageous in that the blood samples have to be isolated in a short time after drawing.



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