Immunomagnetic Tumor Cell Enrichment Is Promising in Detecting Circulating Breast Cancer Cells

Objective: Magnetic-activated cell separation (MACS) for the enrichment of tumor cells was evaluated with immunocytochemistry (ICC) and flow cytometry (FCM). Methods: Blood (20 ml) was sampled in 36 affected patients before surgery. Nucleated blood cells were obtained with the removal of red blood cells in the buffy coat. Nucleated blood cells (2 × 10 6 ) from breast cancer patients were aliquoted before enrichment for direct immunostaining (ICC group), while all remaining cells were enriched and then immunostained (MACS/ICC group). Breast cancer cell lines were spiked serially in normal nucleated blood cells for FCM evaluation of the enrichment efficiency of MACS. Results: The enrichment rate of spiked tumor cells was 37- to 2,300-fold and was negatively correlated with the ratio of tumor cells to normal nucleated cells (p < 0.05). The positive rate was only 5.6% (2/36) in the ICC group and was as high as 38.9% (14/36) in the MACS/ICC group (p < 0.001). The positivity in the enriched fraction was 0% (0/4), 33.3% (8/24), 60% (3/5) and 100% (3/3) for tumors at stages I, II, III and IV, respectively (p < 0.05). Conclusion: MACS can enrich circulating tumor cells, and the presence of circulating breast cancer cells correlates with clinical staging.