Transient high-level DNA release mediated by cryo-thermal therapy promoted myeloid cell hyperactivation to induce CD4+ Th1 cell-dominant antitumor immunity

Tumor patients often exhibit limited responses to immunotherapy owing to the low immunogenicity and immunosuppressive environment of tumors. Our previous studies revealed that cryo-thermal therapy caused tumor cell rupture due to mechanical compression, notably causing the release of a substantial amount of DAMPs (danger-associated molecular patterns), such as heat shock protein 70, calreticulin and high-mobility group box protein 1; the release of these DAMPs increased myeloid cell maturation, thereby reshaping the systemic immune environment and ultimately inducing durable CD4⁺ T helper type 1 (Th1) cell-dominated antitumor immunity. In fact, under conditions of mechanical stress and rapid temperature changes, the disruption of tumor cells caused by cryo-thermal therapy results in extensive deoxyribonucleic acid (DNA) damage and the rapid release of substantial amounts of DNA. Consequently, tumor-derived DNA, which potently activates innate immunity by engaging multiple DNA sensors, plays a pivotal role in orchestrating antitumor immunity. We hypothesized that cryo-thermal therapy induces the transient release of high levels of DNA, which modulates CD11b⁺ myeloid cell function, subsequently influencing CD4⁺ Th1-cell dominated antitumor immune responses. In this study, a B16F10 melanoma model was established, and DNA concentrations were measured at different time points after cryo-thermal therapy. Deoxyribonuclease I (DNase I) was subsequently administered immediately following cryo-thermal therapy to deplete extracellular DNA, allowing an investigation of the role of DNA in regulating CD11b⁺ myeloid cell function and CD4⁺ T cell differentiation. The phenotype and function of CD11b⁺ myeloid cells and CD4⁺ T cells were assessed by flow cytometry, RNA sequencing, and cell culture in vitro. Our studies confirmed that cryo-thermal therapy triggered a transient release of high levels of DNA, which was internalized by CD11b⁺ myeloid cells via C-type lectin receptors and subsequently sensed by inflammasomes. Then, the intracellular sensing of DNA induced the production of the mature form of interleukin (IL)-18, ultimately promoting the Th1 differentiation of CD4⁺ T cells. This study highlights the pivotal role of DNA release after cryo-thermal therapy in driving CD4⁺ Th1 cell-dominant antitumor immunity.