Detection of rare MCF-7 breast carcinoma cells from mixtures of human peripheral leukocytes by magnetic deposition analysis

BACKGROUND: The presence of malignant breast cancer cells in bone marrow or peripheral blood is a prognostic factor. We tested the capacity of a novel magnetic cell analyzer to detect rare cancer cells in mixtures with human peripheral leukocytes. METHODS: Human peripheral leukocytes were spiked with cells of the MCF-7 line, and the cell mixture was labeled with anti-epithelial membrane antigen antibody and a magnetic colloid. The MCF-7 cells were selectively captured on a magnetic deposition substrate from the flowing leukocyte and MCF-7 cell mixture. RESULTS: The recovery of the MCF-7 cells from the original mixture ranged from 20% to 60%. The limit of detection of the MCF-7 cells was 10(-6) (n = 9). The morphology of the captured cancer cells was well preserved and comparable to that observed in cytospin smears. All deposited cells were located in a small area of 1.4 mm x 6 mm and could be quickly identified with an optical microscope following Wright's staining. CONCLUSIONS: This is a proof-of-principle study using a simplified model of rare cancer cells in a leukocyte mixture. The clinical relevance of the method will be tested in the future by extension to patient bone marrow samples and using antibody cocktails to increase specificity against the breast carcinoma cells.