The CELLSEARCH® CTC Test is the first clinically validated, FDA-approved liquid biopsy blood test for CTCs. The test was developed and made commercially available by Janssen Diagnostics (formerly Veridex) in early 2000. In April 2017, Menarini-Silicon Biosystems of Bologna, Italy and San Diego, CA acquired the assets and rights to the CELLSEARCH® CTC Test system.
The system was initially approved by the FDA in 2004 for monitoring metastatic breast cancer and in 2007 for monitoring metastatic colorectal cancer. In 2008, the CELLSEARCH® CTC system was also approved for monitoring metastatic prostate cancer.
The CELLSEARCH® CTC Test uses unique immunomagnetic technology to capture, isolate, and enumerate CTCs. The steps involved in this system are summarized below:
- Magnetically separating CTCs from other cells: A 7.5 mL sample of blood is placed in a special tube and centrifuged to obtain plasma which is then placed in the magnetic separating system (CELLTRACKS® AUTOPREP® System). CTCs are magnetically separated from the bulk of the other blood cells by using ferrofluid nanoparticles with antibodies that target epithelial cell adhesion molecules.
- Differentiating CTC cells: CTCs are then stained with cytokeratin monoclonal antibodies, which are specific to epithelial cells.
- Identifying contaminating leukocytes: A monoclonal antibody stain is used to identify CD45 (a marker specific to leukocytes), which identifies any leukocytes that may have contaminated the sample.
- Highlighting cell nuclei: A DNA stain called DAPI is also added to highlight the nuclei of both CTCs and leukocytes.
- Prepping cells for analysis: Cells are then placed into a magnet cartridge that applies a magnetic force, pulling the cells to a single focal depth.
- Highlighting and enumerating CTC cells: The cartridge containing stained CTCs is placed onto the CELLTRACKS ANALYZER II® System for scanning. Once the cartridge has been scanned, the system displays tumor cell candidates that are positive for cytokeratin and DAPI. These candidate cells are then analyzed to produce a patient report.
