Particle-mediated cytokine gene therapy leads to antitumor and antimetastatic effects in mouse carcinoma models

IL-12 based gene therapy in veterinary medicine

The use of large animals as an experimental model for novel treatment techniques has many advantages over the use of laboratory animals, so veterinary medicine is becoming an increasingly important translational bridge between preclinical studies and human medicine. The results of preclinical studies show that gene therapy with therapeutic gene encoding interleukin-12 (IL-12) displays pronounced antitumor effects in various tumor models. A number of different studies employing this therapeutic plasmid, delivered by either viral or non-viral methods, have also been undertaken in veterinary oncology. In cats, adenoviral delivery into soft tissue sarcomas has been employed. In horses, naked plasmid DNA has been delivered by direct intratumoral injection into nodules of metastatic melanoma. In dogs, various types of tumors have been treated with either local or systemic IL-12 electrogene therapy. The results of these studies show that IL-12 based gene therapy elicits a good antitumor effect on spontaneously occurring tumors in large animals, while being safe and well tolerated by the animals. Hopefully, such results will lead to further investigation of this therapy in veterinary medicine and successful translation into human clinical trials.

A Kunjin replicon vector encoding granulocyte macrophage colony-stimulating factor for intra-tumoral gene therapy

We have recently developed a non-cytopathic RNA replicon-based viral vector system based on the flavivirus Kunjin. Here, we illustrate the utility of the Kunjin replicon system for gene therapy. Intra-tumoral injections of Kunjin replicon virus-like particles encoding granulocyte colony-stimulating factor were able to cure >50% of established subcutaneous CT26 colon carcinoma and B16-OVA melanomas. Regression of CT26 tumours correlated with the induction of anti-cancer CD8 T cells, and treatment of subcutaneous CT26 tumours also resulted in the regression of CT26 lung metastases. Only a few immune-based strategies are able to cure these aggressive tumours once they are of a reasonable size, illustrating the potential of this vector system for intra-tumoral gene therapy applications.

Inhibition of Lewis lung carcinoma growth by Toxoplasma gondii through induction of Th1 immune responses and inhibition of angiogenesis

Toxoplasma gondii is an obligate intracellular protozoan parasite that induces antitumor activity against certain types of cancers. However, little information is available regarding the immunologic mechanisms that regulate these effects. For this purpose, C57BL/6 mice were administered either the T. gondii Me49 strain orally or Lewis lung carcinoma (LLC) cells intramuscularly. Survival rates, tumor size, histopathology, and immune responses were determined for each group, and angiogenesis was evaluated by in vivo Matrigel plug assay. Toxoplasma-infected (TG-injected) mice survived the entire experimental period, whereas cancer cell-bearing (LLC-injected) mice died within six weeks. Mice injected with both T. gondii and cancer cells (TG/LLC-injected group) showed significantly increased survival rates, CD8+ T-cell percentages, IFN-gamma mRNA expression levels, serum IgG2a titers, and CTL responses as compared to the LLC-injected mice. In addition, angiogenesis in the TG/LLC-injected mice was notably inhibited. These effects in TG/LCC-injected mice were similar or were increased by the addition of an adjuvant, Quil-A. However, TG/LLC-injected mice showed decreased percentages of CD4+ and CD8+ T cells, IFN-gamma mRNA expression levels, and serum IgG1 and IgG2a titers as compared to TG-injected mice. Taken together, our results demonstrate that T. gondii infection inhibits tumor growth in the Lewis lung carcinoma mouse model through the induction of Th1 immune responses and antiangiogenic activity.