Immunotherapies are revolutionizing oncology allowing many cancer patients with aggressive disease to
enjoy durable remissions with excellent quality of life. However, these therapies are generally not effective for
patients with "cold" solid tumors that have few infiltrating T cells and low levels of antigen presentation. IL-12 is
a highly inflammatory cytokine with the potential to transform cancer immunotherapy. It can make "cold"
tumors "hot", drive elimination of tumors as a single agent and synergize with checkpoint inhibitors and
adoptive cellular therapy in multiple experimental models. Despite multiple clinical trials of IL-12, using direct
intravenous administration or a variety of formulations and vehicles, finding an optimal delivery method
remains a critical barrier to its widespread clinical use. Several intra-tumor (IT) IL-12 gene delivery vehicles are
currently being tested clinically; however each of these has major drawbacks that could prevent general
implementation. Our group has been collaborating with the Seattle-based biotechnology company, Immune
Design, to test two separate, novel and highly promising IL-12-producing vectors for gene delivery. One uses a
potent self-replicating RNA delivery system to delivery high levels of IL-12 production through out the tumor.
The other uses a lentivirus with an envelope that specifically targets dendritic cells.
While both experimental vectors can eliminate tumors and prevent re-challenge in murine models, the
significant investment required for clinical-grade virus production has impaired their swift movement into the
clinic. Using a large animal model to demonstrate anti-tumor efficacy in a spontaneous cancer will catalyze the
production of a clinical-grade product, thus in this proposal we will test both these vectors in spontaneous high
grade soft tissue sarcomas in companion animals. If both vector approaches are efficacious, the analysis
described here will help identify which vector should move towards testing in humans (using a human IL-12-
containing construct). Furthermore, our comparison of these two agents will answer a fundamental question in
cancer immunology; i.e., can precise delivery of IL-12 to DCs achieve superior anti-tumor immunity despite
fewer transduced cells and a lower overall level of IL-12 production?