A negative selection system PowerMag for effective leukocyte depletion and enhanced detection of EpCAM positive and negative circulating tumor cells

Background: Circulating tumor cells (CTCs) can be enriched from peripheral blood by leukocyte depletion. In this study, a PowerMag system was designed to enhance leukocyte depletion and CTC detection. Methods: The efficiency of PowerMag in leukocyte depletion and recovery of CTCs was evaluated. The cell populations in leukocyte-depleted cell filtrate were characterized by immunofluorescence staining using anti-EpCAM and anti-CD45 antibodies. The suitability of PowerMag in monitoring cancer patient CTCs was assessed by analyzing blood samples collected at baseline and 2. weeks after baseline from the patients with colorectal cancer (CRC, n = 24) and head and neck squamous cell carcinoma (HNSCC, n = 28). Results: Only few contaminated CD45⁺-leukocytes were retained in the leukocyte-depleted cell filtrate. The enriched CTCs were viable with a recovery rate of 46-62%. Immunofluorescence staining of the nucleated cells enriched by PowerMag revealed 2 major cell populations EpCAM⁺CD45^- and EpCAM^-CD45^-. The number for both cell types was significantly increased in cancer patients when compared to healthy control. After chemotherapy, the number of EpCAM⁺CD45^- and EpCAM^-CD45^- cells was decreased more prominently for CRC and HNSCC patients, respectively. Conclusions: PowerMag holds great promise as a platform for leukocyte depletion and CTC detection in a clinical setting.