Ex-vivo expansion of bone marrow progenitor cells for hematopoietic reconstitution following high-dose chemotherapy for breast cancer

The use of hematopoietic growth factors, stromal monolayers, and frequent medium exchange allows the expansion of hematopoietic progenitors ex-vivo. We evaluated the use of ex-vivo expanded progenitor cells for hematopoietic reconstitution following high dose chemotherapy (HDC) in breast cancer patients. Patients with high-risk Stage II or metastatic breast carcinoma underwent bone marrow aspirations using general anesthesia. A total of 675–1125 × 106 mononuclear cells (MNC) were seeded for ex-vivo expansion for 12 days in controlled perfusion bioreactors (Aastrom Biosciences, Inc.). The bone marrow cultures, which included the stromal cells collected with the aspirate, were supplemented with erythropoietin, granulocyte-macrophage-colony stimulating factor (GM-CSF)/IL-3 fusion protein (PIXY 321), and flt3 ligand. Stem cell transplant was performed with expanded cells after HDC. A median bone marrow volume of 52.9 mL (range 42–187 mL) was needed to inoculate the bioreactors. Median fold expansion of nucleated cells (NC) and colony forming unit granulocyte-macrophage (CFU-GM) was 4.9 and 9.5, respectively. The median fold expansion of CD34+lin−and long-term culture–initiating culture (LTC-IC) was 0.42 and 0.32, respectively. Five patients were transplanted with ex-vivo expanded NC. Median days to an absolute neutrophil count > 500/μL was 18 (range 15–22). Median days to a platelet count > 20,000/μl was 23 (range 19–39). All patients had sustained engraftment of both neutrophils and platelets. Immune reconstitution was similar to that seen after HDC and conventional stem cell transplantation. We conclude that ex-vivo expansion of progenitor cells from perfusion cultures of small volume bone marrow aspirates, allows hematopoietic reconstitution after HDC.