An increasingly attractive approach of active immunotherapy of cancer is to genetically engineer autologous tumor cells to secrete various cytokines. This strategy aims either to enhance the presentation of tumor-specific antigens to the immune system or to amplify the co-stimulatory signals for T-cell activation. In this project the investigator proposes to provide the local and sustained delivery of cytokines through biodegradable microspheres. The hypothesis is that synthetic controlled release microspheres containing cytokines, mixed with the irradiated tumor cells, can replace the gene-transduced tumor cells in efficiently stimulating an immune response to generate a systemic immunity. This cancer vaccine design should be less labor intensive, more reproducible, and more versatile. Initially focus will be placed on granulocyte-macrophage colony-stimulating-factor (GM-CSF), the cytokine previously demonstrated to have the most potent effect in generating systemic immunity in the B16 murine melanoma model. The GM-CSF-containing microspheres will be synthesized by the complex coacervation of gelatin and chondroitin sulfate, and characterized with respect to cytokine loading level, particle size distribution, in vitro release kinetics and bioactivity of released cytokine. To gain insight into the relationship between the cytokine level and the anti-tumor protection, the in vivo pharmacokinetics and the types of immune cells attracted to the GM-CSF controlled release microspheres implanted subcutaneously will be determined. The efficacy of this hybrid tumor vaccine will be evaluated in the poorly immunogenic B16 murine melanoma model, against different parameters of challenge schemes, rate and duration of cytokine release, and ratio of tumor antigen to cytokine. To explore the synergistic effects of GM-CSF with other cytokines, microspheres containing IL-4 and TNF-a will be individually synthesized and mixed with GM-CSF containing microspheres to be tested in the same B16 model. Other vaccine strategies will also be evaluated by co-encapsulating the cytokines with a model HPV-16E7 antigen, and this cell-free tumor vaccine will be tested in an E7 expression B16-F10 murine melanoma model.
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