Background: Tumor cells have been detected in mobilized peripheral blood of breast cancer patients, and they may contribute to tumor recurrence after the transplantation of peripheral blood progenitor cells. One of the most widespread technologies for tumor purging of the graft is immunomagnetic hematopoietic progenitor cell selection.
Study design and methods: The study assessed the effectiveness of a magnetic cell-separation system in selecting functional subpopulations of hematopoietic progenitors from 14 blood-derived harvests of 11 patients with high-risk breast cancer after mobilization following cytotoxic chemotherapy supported by granulocyte--colony-stimulating factor, as well as the feasibility of transplanting these selected subpopulations.
Results: CD34(+)-enriched cell fractions had a median purity of 93.0 percent (72.7-98.5%). The procedure yielded 52.6 percent of the CD34+ cell input (39.4-116.8%). Median recoveries of colony-forming units (CFUs) (36.87%) and cobblestone area-forming cells (CAFCs) (152.5%) were, respectively, 0.70 and 2.87 times those of CD34+ cells (52.6%). Moreover, CAFC efficiency in the positive cell fraction was 2.57 times that in the starting cell fraction. Peripheral blood neutrophil counts of 0.5 x 10(9) per L and platelet counts of 20 x 10(9) per L were reached after median times of 9 and 11 days, respectively. The number of transfused CAFCs per kg, CD34+ cells per kg, and postthaw CFU-granulocyte-macrophage per kg was correlated, respectively, with the speed of engraftment of neutrophils, platelets, or both. Tumor cells detected in one patient's peripheral blood were not found after CD34+ cell selection.
Conclusion: Transplantation of immunomagnetically purified peripheral blood CD34+ cells does not increase transplantation-related morbidity. It induces a selective enrichment of more immature hematopoietic progenitors, which makes it suitable for use in cell expansion and gene therapy protocols.