Dendritic cells generated from naïve and tumor-bearing mice uniquely restores different leukocyte subpopulations in chemotherapy-treated tumor-bearing mice

Background: Dendritic cell (DC)-based vaccination has shown promising application in tumor immunotherapy. However, it is not clear whether the presence of tumor impacts the efficacy of generation and functionality of DCs. Aim: To compare the phenotype of DCs generated from naïve or tumor bearing mice and their capability to restore leukopenia-associated chemotherapy. Materials and Methods: DCs were generated from bone marrow (BM) of naïve or Ehrlich ascites carcinoma (EAC) bearing mice. EAC is an undifferentiated breast cancer cell line with the high transplantable capability and rapid proliferation. BM cells were cultured in vitro for 7 days with granulocyte macrophage colony-stimulating factor and interleukin-4 (20 ng/ml each), loaded with different concentrations of EAC cell lysate (0.5, 1, 3 and 5 mg/10⁶) DCs followed by activation with the toll-like receptor 3 ligand poly(I:C). For DC-based vaccination, CD1 mice (n = 5/group) were inoculated with an intraperitoneal (i.p.) injection of 0.25 × 10⁶ EAC cells to form ascites, treated on day 14 with an i.p. injection of cyclophosphamide (4 mg/mouse) and on day 15 with subcutaneous injection of 2 × 10⁶ DCs from control or EAC bearing mice. Injected DCs were loaded with or without EAC lysate followed by i.p. injection of 50 μg/mouse poly(I:C). On day 21, mice were bled and sacrificed for peripheral blood count and spleen and BM cellularity. Results: Yield of DCs generated from naÏve or EAC bearing mice, as well as their phenotype (CD11c⁺ CD11b⁺) and activation (CD40 and CD80) with poly(I:C) were similar. Loading DCs with 1 mg EAC lysate induced better viability and activation phenotype as compared with the other concentrations. Regardless the source of DCs, DCs vaccination restored the total numbers of leukocytes in blood but not in the spleen and BM. The effect on peripheral blood leukocytes was coincided with the restoration of the relative numbers of lymphocytes, monocytes, and granulocytes. Conclusion: These data support the use of allogenic DCs from healthy donors in anticancer DC-based vaccination.