Mobilization of dendritic cells from patients with breast cancer into peripheral blood stem cell leukapheresis samples using Flt-3-Ligand and G-CSF or GM-CSF

Abstract

Treatment with myeloablative chemotherapy and autologous peripheral blood stem cell (PBSC) transplantation followed by vaccination with autologous dendritic cells (DCs) treated with tumor antigens is a promising therapeutic strategy for several types of cancer. Obtaining sufficient numbers of both PBSCs and DCs is central to this approach. Previously, it has been shown that administration of Flt-3-Ligand (FL) combined with either G-CSF or GM-CSF mobilizes large numbers of PBSCs in patients with cancer. In the current study, we sought to determine whether these same cytokines could simultaneously mobilize DCs into the PBSC leukapheresis collection. DCs were analysed in PBSC leukapheresis samples obtained from five patients with high-risk breast cancer who received G-CSF alone as priming prior to leukapheresis, four patients who received FL+G-CSF and five patients who received FL+GM-CSF. DCs were defined as cells with a lin(dim/-) HLA-DR+ CD11c+ phenotype. The proportions of DCs in the FL+G-CSF and FL+GM-CSF samples were significantly higher than in pre-mobilization peripheral blood and G-CSF leukapheresis samples. The mean yield of DCs/kg in the FL+GM-CSF samples was also significantly higher than the mean yield of DCs in the G-CSF samples. The FL+G-CSF and FL+GM-CSF mobilized DCs were immature by morphologic and phenotypic criteria but stimulated allogeneic T-cells at levels similar to DCs generated in culture from PBMCs. Overnight culture?of the immature DCs obtained from patients receiving either FL+G-CSF or FL+GM-CSF in TNF-alpha?resulted in the generation of mature DCs. In summary, administration of FL in combination with GM-CSF and G-CSF to patients with breast cancer can mobilize large numbers of immature DCs into PBSC leukapheresis collections.