User-defined protein marker assay development for characterization of circulating tumor cells using the CellSearch system

The purpose of the flow cytometry experiments in this study was to assess expression/presence of circulating tumor cell (CTC)-associated markers/characteristics in immortalized human cancer cell lines and normal human blood (i.e. percentage of cell population expressing the marker/characteristic of interest). Conclusion: Flow cytometry analysis is a useful way of validating the percentage of cells within a given cell population that are positive for CTC-associated markers/characteristics of interest. This analysis provides a valuable starting point for optimization of user-defined markers for CTC characterization using the CellSearch® system (Veridex) For marker expression analysis, FMO or appropriate IgG isotype controls were used. For experiments involving assessment of apoptosis, untreated cells were used as a negative control.