Dendritic cells (DC) loaded with apoptotic, allogeneic melanoma cells reduce tumor progression and improve survival in a murine immunotherapy model

Abstract

Introduction: DC loaded with apoptotic, syngeneic melanoma cells slow tumor growth and improve survival in a murine immunotherapy model. The use of allogeneic cells as a source of tumor antigen could increase the clinical applicability of this therapy, so we investigated the efficacy of DC loaded with apoptotic, allogeneic cells in this model. Methods: DC were cultured from bone marrow from C-57/BL-6 mice with GMCSF (10 ng/ml), IL-4 (5 ng/ml). Syngeneic B-16 or allogeneic K-1735 melanoma cells were irradiated (20 Gy) to induce apoptosis and cultured with DC at a 1:1 ratio for 48 hr to make DC/Apo vaccine. C-57/BL-6 mice (n = 6) were injected with 2.5 x 105 B-16 SQ and treated with 1 x 106 DC/Apo vaccine cells SQ or saline control weekly x4 starting 5 days after tumor implantation. In other experiments, splenocytes were harvested from control and immunized tumor-bearing animals at day 30 and stimulated weekly x2 with IFN-gamma treated, irradiated B-16 cells. Cytotoxic T lymphocyte (CTL) assays were performed with B-16 targets for 48 hr and % specific lysis calculated. Results: Summarized in table 1. TABLE—ABSTRACT 35Tumor sizeMedian survival60d survivalSpecific lysis#Control11 ± 6 mm31 days0%9 ± 12%DC/ApoB-163 ± 3 mm∗>60 days∗67%∗63 ± 20%∗DC/ApoK-17354 ± 3 mm∗45 days∗33%∗51 ± 21%∗∗P < 0.05 vs control.#At E:T ratio of 100:1.Conclusions: Mice treated with DC loaded with apoptotic, syngeneic melanoma cells (DC/ApoB-16) or apoptotic, allogeneic melanoma cells (DC/ApoK-1735) had delayed tumor progression and improved survival compared to controls. CTL responses to B-16 cells were seen in both treatment groups, and there was no difference in tumor size, survival, or CTL responses among the treatment groups. We conclude that DC loaded with apoptotic allogeneic melanoma cells may be a practical and effective approach to polyvalent immunotherapy of melanoma. We are currently designing a clinical trial to evaluate the efficacy of this treatment in patients with high-risk disease.