Cryotherapy with Concurrent CpG Oligonucleotide Treatment Controls Local Tumor Recurrence and Modulates HER2/neu Immunity

Abstract

Percutaneous cryoablation is a minimally invasive procedure for tumor destruction, which can potentially initiate or amplify antitumor immunity through the release of tumor-associated antigens. However, clinically efficacious immunity is lacking and regional recurrences are a limiting factor relative to surgical excision. To understand the mechanism of immune activation by cryoablation, comprehensive analyses of innate immunity and Her2/neu humoral and cellular immunity following cryoablation with or without peritumoral CpG injection was conducted using two Her2/neu+ tumor systems in wild type, neu-tolerant, and SCID mice. Cryoablation of neu+ TUBO tumor in BALB/c mice resulted in systemic immune priming, but not in neu-tolerant BALB NeuT mice. Cryoablation of human Her2+ D2F2/E2 tumor enabled the functionality of tumor-induced immunity but secondary tumors were refractory to anti-tumor immunity if rechallenge occurred during the resolution phase of the cryoablated tumor. A step-wise increase in local recurrence was observed in wild type, neu-tolerant, and SCID mice indicating a role of adaptive immunity in controlling residual tumor foci. Importantly, local recurrences were eliminated or greatly reduced in wild type, neu tolerant and SCID mice when CpG was incorporated in the cryoablation regimen, showing significant local control by innate immunity. For long-term protection, however, adaptive immunity was required because most SCID mice eventually succumbed to local tumor recurrence even with combined cryoablation and CpG treatment. This improved understanding of the mechanisms by which cryoablation affects innate and adaptive immunity will help guide appropriate combination of therapeutic interventions to improve treatment outcomes.

Evolution of animal models in cancer vaccine development

“…In addition to tumor debulking, the necrotic tissue becomes a rich reservoir of TAA that are cleared by antigen presenting cells, creating a unique opportunity to prime or boost antitumor immune responses [89]. Using wild type mice bearing TUBO tumors [26], cryoablation alone resulted in systemic immune priming and partial protection upon tumor rechallenge, while little impact was seen in tolerant NeuT mice [26]. Peritumoral injection of the TLR9 agonist CpG following cryoablation significantly eliminated, reduced or delayed local tumor recurrences in WT, NeuT and SCID mice, respectively.…”

“…Tools for distinguishing tumor cells and host infiltrates in live animals will be essential. As an example, in pIL-1β-DsRed Tg mice, increased DsRed intensity, marking IL-1 production, is sustained for 2–3 weeks in cryoablated tumor tissue, displaying sustained inflammation after cryoablation [26]. …”

Effect of vaccine administration modality on immunogenicity and efficacy

“…The immune modulation effect is through activation of TLR-9[44, 45]. It has been used as a stand-alone agent to combat cancer, including lymphocytic leukemia[46] and glioblastoma[47], or in combination with other agents or therapies[48]. It has also been used successfully to enhance the efficacy of many vaccines for infectious diseases[49].…”

Effective Combination of Innate and Adaptive Immunotherapeutic Approaches in a Mouse Melanoma Model

“…Instead of injecting CpG i.p., as in our previous studies (10), we gave it here i.t. because it was shown that local treatment with CpG can induce both innate and adaptive immunity (28, 40). Similar to our previous studies (10), the antitumor effect of anti-CD40 given i.p.…”