Multimodal tumor thermal therapy enhances antitumor immunity by expanding tumor-reactive CX3CR1⁺GPR56⁺ T cells in hepatocellular carcinoma.

[RATIONALE] Tumor local ablation could facilitate the release of tumor antigens, thereby activating systemic antitumor immunity. Nevertheless, clinical observations have indicated that the systemic response induced by conventional local ablation methods is rather transient, weak, and insufficient to induce protective immunity. Multimodal tumor thermal therapy (MTT), a novel local ablation technology that involves liquid nitrogen freezing followed by radiofrequency heating, has been suggested to stimulate robust and sustained antitumor immunity. However, in patients with hepatocellular carcinoma (HCC), how MTT promotes the patients' antitumor immunity remains unknown.

[METHODS] In this study, we enrolled four patients to receive MTT and three patients to receive radiofrequency ablation (RFA), aiming to explore the mechanism by which MTT promotes antitumor immunity.

[RESULTS] We found that MTT significantly prolonged the patients' PFS compared with RFA and identified a novel T cell subset characterized by CX3CR1 and GPR56 that specifically correlated with the efficacy of MTT. MTT elicited a significant increase in CX3CR1GPR56 T cells and a concomitant decrease in regulatory T cells in PBMCs compared with the samples obtained from patients following RFA. CX3CR1GPR56 T cells express high levels of cytotoxic molecules and share TCR sequences with tumor-reactive-like T cells in tumors, and the degree of increase in the proportion of these cells is positively correlated with the PFS of patients. Compared to RFA, MTT significantly induced release of damage-associated molecular patterns (including extracellular DNA and heat shock protein 70), more effectively promoted dendritic cell maturation, and strengthened their interaction with CX3CR1GPR56 effector T cells via MHC I-TCR. Meanwhile, MTT diminished the interactions between DCs and Tregs through LGALS9-CD45 axis, leading to a reduction in peripheral Tregs.

[CONCLUSIONS] These findings reveal the mechanism by which MTT promotes antitumor immunity in patients with HCC and warrant further investigation in large-scale clinical studies.