Potent induction of antitumor immunity by combining cryo-thermal ablation with immune checkpoint inhibitors in hepatocellular carcinoma.

ABSTRACT

BACKGROUND: The low response rate of immune checkpoint inhibitors (ICIs) prompts the exploration of novel combination therapies for patients with hepatocellular carcinoma (HCC). Here, we aimed to examine the efficiency and potential mechanism of cryo-thermal ablation (Cryo-A) combined with anti-programmed death protein 1 (αPD1) and/or cytotoxic T-lymphocyte antigen 4 (αCTLA4) inhibitors in a murine hepatoma model. METHOD: Immunocompetent C57BL/6 mice inoculated with unilateral or bilateral H22 hepatic tumour cells were treated with Cryo-A and/or ICIs (αPD1 and/or αCTLA4). Flow cytometry, immunohistochemistry, ELISpot assay, time-of-flight cytometry, tumour rechallenging, and T-cell depletion assay were used to assess the dynamic changes of immune cell subsets following therapy. RESULTS: We found Cryo-A resulted in immunogenic cell death of tumour cells, activation of dendritic cells, and enhancement of antitumor immunity. Cryo-A alone was insufficient to extend survival, combining Cryo-A with αPD1 and αCTLA4 further modulated the tumour microenvironment, inducing a durable antitumor immune response by tumour-reactive CD8+ T cells and significantly prolonged survival. Time-of-flight cytometry (CyTOF) data revealed that combination therapies reshaped the tumour microenvironment by the increase of intratumoral CD8+ T cells expressed higher levels of cytotoxic markers and immune checkpoint molecules, and by downregulation of intratumoral granulocytes. The combination also resulted in the eradication of remote unablated tumours (abscopal effect). CONCLUSIONS: These findings suggested that Cryo-A turned HCC from "cold" tumours to "hot" tumours and the combination of Cryo-A with αPD1 and αCTLA4 may be a promising approach to improve the prognosis of HCC.