CellTracks cytometer for detection of circulating tumor cells

Introduction: In patients with carcinomas, tumor cells are shed into the circulation. The number of the circulating tumor cells is low and technology is needed that has sufficient sensitivity and specificity to enumerate and characterize these cells. The CellTracks system was developed to provide an immunophenotype, fluorescence wave forms as well as images of immuno-magnetically enriched tumor cells with an occurrence frequency <1 per ml whole blood. Methods: 7.5 ml of whole blood of patients having known breast (n=13) or colorectal (n=12) cancers was immunomagnetically enriched for EpCam positive (epithelial) cells reducing the volume to 320 μl. Fluorescent labels against Cytokeratin and DNA were added. As a negative control a CD45 labelled fluorescent probe against white blood cells was used. This sample was transferred to a measuring chamber, which was inserted in a specially designed strong magnetic field. The magnetic force aligns the cells on a glass slide. These cells were scanned one by one by a multi-laser scanning system and their fluorescence intensities were measured. As a control samples of healthy volunteers were measured in duplicate. To test the immuno-magnetic collection efficiency a known number of fixed SKBR-3 cells were spiked into blood samples. Results: In all patients samples tumor cells were detected. The number of tumor cells found ranged from 1-120 per 7.5 ml of whole blood. For the control samples 0-1 positive cells per 7.5 ml have been detected. The overall immuno-magnetic selection and detection efficiency for SKBR-3 cells was > 70 %. Conclusions: We showed that the novel CellTracks technology has a very high sensitivity and specificity, which is sufficient for the detection of tumor, cells in peripheral blood.