Background: For the relatively nonimmunogenic B16-F10 murine melanoma, it has been found that genetically engineered expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) but not interleukin (IL)-2, IL-4, or interferon-gamma (IFN-gamma) resulted in a vaccine that could induce resistance to rechallenge. Because T cells from lymph nodes draining the sites of some progressive tumors can mediate tumor regression after in vitro activation, it seemed possible that even apparently nonimmunogenic melanoma cells might induce similar preeffector cells in the vaccine-draining lymph nodes (DLNs).
Methods: C57BL/6 mice were vaccinated with B16-F10 cells that were either unmodified or genetically modified to produce IL-2, IL-4, GM-CSF, or IFN-gamma. DLNs were harvested 10 days after vaccination for adoptive immunotherapy (AIT). The DLN cells were activated with bryostatin 1 and ionomycin (B/I), expanded for 10 days in culture, and transferred to mice with 3-day pulmonary metastases. Pulmonary nodules were counted 14 days after AIT.
Results: Adoptive transfer of expanded DLN lymphocytes sensitized by inoculation of WT B16-F10, or IL-4, GM-CSF, or IFN-gamma expressing cells significantly reduced pulmonary metastases. Despite the spontaneous regression of IL-2-transduced B16-F10 tumors, DLN from mice inoculated with IL-2 producing B16 cells had little or no antitumor activity.
Conclusions: B16-F10 vaccination strategies that apparently do not induce systemic immunity can effectively sensitize DLN preeffector cells.