Activated dendritic cells from bone marrow cells of mice receiving cytokine-expressing tumor cells are associated with the enhanced survival of mice bearing syngeneic tumors.

Dendritic cells (DCs), which phagocytose antigens and subsequently proliferate and migrate, may be the most powerful antigen-presenting cells that activate naive T cells. To determine their role in the immune response to tumors, we used WEHI-3B murine leukemia cells transduced with adenovirus vectors expressing cytokines. We found that mixtures of irradiated cells expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) plus those expressing interleukin-4 (IL-4) or tumor necrosis factor alpha (TNFalpha) protected mice against WEHI-3B-induced leukemias. When bone marrow mononuclear cells (BMMNCs) obtained from mice that had been injected with irradiated, cytokine-expressing tumor cells were injected into tumor-bearing mice, the survival of the latter was significantly prolonged; the longest survival was observed in mice receiving BMMNCs containing an increased number of DCs from animals injected with a mixture of tumor cells expressing GM-CSF with those expressing IL-4. Assay for antileukemic effects in spleen of the latter animals showed specific antitumor cytotoxicity against WEHI-3B, suggesting that DCs from donor mice activate specific T cells in the tumor-bearing recipients. These results suggest that the infusion of syngeneic BMMNCs stimulated with cytokine-expressing tumor cells may be effective in treating certain types of tumors.