Intratumoral administration of dendritic cells overexpressing CCL21 generates systemic antitumor responses and confers tumor immunity.

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 10(6) DC-AdCCL21 intratumorally (7-10 ng/ml/10(6) 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-gamma, MIG/CXCL9, IP-10/CXCL10, and interleukin 12, but decreases in the immunosuppressive mediators transforming growth factor beta and prostaglandin E(2). DC-AdCCL21-treated tumor-bearing mice showed enhanced frequency of tumor-specific T lymphocytes secreting IFN-gamma, and tumor protective immunity was induced after DC-AdCCL21 therapy. In vivo depletion of IP-10/CXCL10, MIG/CXCL9, or IFN-gamma significantly reduced the antitumor efficacy of DC-AdCCL21. These findings provide a strong rationale for the evaluation of DC-AdCCL21 in cancer immunotherapy.