Intratumoral Administration of Dendritic Cells Overexpressing CCL21 Generates Systemic Antitumor Responses and Confers Tumor Immunity

Abstract

To achieve in situ tumor antigen uptake and presentation, intratumoral administration of ex vivo-generated, gene-modified murine bone marrow-derived dendritic cells (DC) was used in a murine lung cancer model. To attract mature host DC and activated T cells at the tumor site, the DC were transduced with an adenoviral vector expressing secondary lymphoid tissue chemokine (CCL21/SLC). Sixty percent of the mice treated with 10⁶ DC-AdCCL21 intratumorally (7–10 ng/ml/10⁶ cells/24 h of CCL21) at weekly intervals for 3 weeks showed complete tumor eradication, whereas only 25% of mice had complete resolution of tumors when mice were treated with fibroblasts expressing CCL21. In contrast only 12% of the mice treated with unmodified or control vector modified DC (DC-AdCV) showed complete tumor eradication. DC-AdCCL21 administration led to increases in the CD4⁺, CD8⁺, and CD3⁺CXCR3⁺ T cells, as well as DC expressing CD11c⁺ DEC205⁺. CD4⁺CD25⁺ T-regulatory cells infiltrating the tumors were markedly reduced after DC-AdCCL21 therapy. The tumor site cellular infiltrates were accompanied by the enhanced elaboration of granulocyte macrophage colony-stimulating factor, IFN-γ, MIG/CXCL9, IP-10/CXCL10, and interleukin 12, but decreases in the immunosuppressive mediators transforming growth factor β and prostaglandin E₂. DC-AdCCL21-treated tumor-bearing mice showed enhanced frequency of tumor-specific T lymphocytes secreting IFN-γ, and tumor protective immunity was induced after DC-AdCCL21 therapy. In vivo depletion of IP-10/CXCL10, MIG/CXCL9, or IFN-γ significantly reduced the antitumor efficacy of DC-AdCCL21. These findings provide a strong rationale for the evaluation of DC-AdCCL21 in cancer immunotherapy.