Focal Cryo-Immunotherapy with Intratumoral IL-12 Prevents Recurrence of Large Murine Tumors

Simple Summary Focal cryoablation is an FDA-approved minimally-invasive treatment for certain kidney, colon, lung, breast, and prostate cancers. However, it is difficult to ensure complete tumor destruction after ablation, and therefore, tumor recurrence rates can be as high as 80%. In order to improve primary tumor regression, we explored the addition of an immunotherapy, interleukin-12 (IL-12), delivered intratumorally, to cryoablation. We also explored the impact of this cryo-immunotherapy on systemic antitumor immunity using bilateral tumors and spontaneous metastasis models. The combination of cryoablation and IL-12 resulted in the durable regression of large (>200 mm(3)) primary tumors in multiple models and reduced lung metastasis when IL-12 was delivered as a neoadjuvant. Possible mechanisms for this anti-tumor effect were explored using whole transcriptome RNAseq. Focal ablation technologies are routinely used in the clinical management of inoperable solid tumors but they often result in incomplete ablations leading to high recurrence rates. Adjuvant therapies, capable of safely eliminating residual tumor cells, are therefore of great clinical interest. Interleukin-12 (IL-12) is a potent antitumor cytokine that can be localized intratumorally through coformulation with viscous biopolymers, including chitosan (CS) solutions. The objective of this research was to determine if localized immunotherapy with a CS/IL-12 formulation could prevent tumor recurrence after cryoablation (CA). Tumor recurrence and overall survival rates were assessed. Systemic immunity was evaluated in spontaneously metastatic and bilateral tumor models. Temporal bulk RNA sequencing was performed on tumor and draining lymph node (dLN) samples. In multiple murine tumor models, the addition of CS/IL-12 to CA reduced recurrence rates by 30-55%. Altogether, this cryo-immunotherapy induced complete durable regression of large tumors in 80-100% of treated animals. Additionally, CS/IL-12 prevented lung metastases when delivered as a neoadjuvant to CA. However, CA plus CS/IL-12 had minimal antitumor activity against established, untreated abscopal tumors. Adjuvant anti-PD-1 therapy delayed the growth of abscopal tumors. Transcriptome analyses revealed early immunological changes in the dLN, followed by a significant increase in gene expression associated with immune suppression and regulation. Cryo-immunotherapy with localized CS/IL-12 reduces recurrences and enhances the elimination of large primary tumors. This focal combination therapy also induces significant but limited systemic antitumor immunity.