Background Interleukin 12 (IL-12) is a highly inflammatory cytokine that has potent activity in cancer, which mediates its antitumor activity through both innate and adaptive immunity. However, finding an optimal delivery method for IL-12, giving rise to high antitumoral efficacy with minimal toxicity remains a critical challenge. Here we evaluated novel vector platforms for targeted IL-12 delivery using spontaneous canine soft-tissue sarcomas (STS) to model the human tumor microenvironment.

Methods Dogs with naturally occurring soft tissue sarcoma tumor were evaluated and enrolled in this study. Either a dendritic cell targeted lentivirus (ZVex12) or an IL-12 producing self-replicating RNA (IL12srRNA)¹ was injected intratumorally to deliver sustained IL-12 production in the tumor. Tumor biopsy tissue was analyzed through flow cytometry for dynamic changes within treated tumors.

Results Three pet dogs with sarcoma were treated with ZVex12 and one dog with IL12srRNA. All dogs receiving intratumorally cytokine therapy were found to well tolerate. Although transient tumor regression was seen in one dog, no dogs had a radiographic response by CT scan. Both ZVex12 and IL12srRNA treatment markedly increased the percentage of CD5^-NKp46⁺ and CD5^dimCD8⁺NKp46⁺ NK cell within tumor infiltrating CD45 cells compared with pre-treatment baseline (7.7 ± 5.9% vs 1.83 ± 1.4%, and 2.34 ± 0.8% vs 0.36 ± 0.3%, respectively). ZVex12 treatment reverse CD4/CD8 ratio inside tumor microenvironment (1.06 ± 10.3% vs.5.3 ± 4.42%). ZVex12 treatment induced tumor infiltrating NK and CD8 cells activation, the percentage of granzyme B expressing NK cell, CD8⁺NK and CD8 T cell increased after treatment (11.5 ± 6% vs 5.5 ± 2.5%, 35.6 ± 8.4% vs 11 ± 1.4% and 13 ± 5.6% vs 7.3 ± 3.2% respectively). ZVex12 treatment also increased MHC Class II expression on CD11b⁺ cell.

Conclusions Our results demonstrated that novel IL-12 gene delivery vehicles intratumorally therapy significantly modified TME by increasing infiltrates and activating of NK and CD8 T cells, enhanced antigen presenting cell maturation. Future studies that combining local cytokine therapy with other immunotherapy or target therapy needed to cure spontaneous tumors.

Reference

1. Leleux JA, Albershardt TC, Reeves R, et al. Intratumoral expression of IL-12 from lentiviral or RNA vectors acts synergistically with TLR4 agonist (GLA) to generate anti-tumor immunological memory. PLoS One. 2021;16(12):e0259301