Circulating tumor cells (CTCs) are cancer cells that migrate out from tumor masses, and enter the blood stream. Once in the circulation, they have the potential to engraft in distant tissues to develop into new tumors (metastases). It is this tumor spread that is responsible for most cancer deaths. Since, all distant tumors were derived from CTCs, CTCs hold clues to the biology of metastatic cancer.
The number of CTCs in circulation have been demonstrated to be prognostic of recurrence and treatment outcome in many types of cancer. Finding CTCs is difficult, however, because they are rare (typically one CTC per ml of blood) and require discovery methods that are sensitive and specific.
RareCyte's AccuCyte® - CyteFinder® system uses the characteristic density and protein expression of CTCs to identify them in the blood. It consistently finds over 90 percent of model CTCs when spiked into blood, and can detect a single CTC in a tube of whole blood (see Campton, et al., BMC Cancer. 2015 May 6; 15:360).
The technology is flexible – it allows the user to incorporate stains for research biomarkers of interest in addition to traditional epithelial markers used for identification of CTCs. This includes markers of specific cell lineage – such as breast or prostate cancer or melanoma markers – and of physiology – such as proliferation or mesenchymal transition. The drug target Her2 and proliferation marker Ki-67, are pictured in the figures below. It is also possible to investigate variability in expression of biomarkers in CTCs in a single patient. For example, in the cluster of breast cancer CTCs pictured below, it was observed that some of the identified CTCs express Her2, while others demonstrate very low expression.
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