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.