Cryo-thermal therapy reprograms myeloid cells into CCL5+ mature phenotype to increase T cell infiltration and potentiates anti-PD-1 therapy

Although immune checkpoint blockade (ICB) represented by anti-PD-1 therapy has demonstrated significant clinical benefits, its efficacy remains limited by the immunosuppressive tumour microenvironment (TME). Cryo-thermal therapy (CTT) not only completely ablates local solid tumours by pre-freezing before radiofrequency heating, but also reverses immunosuppression and triggers strong systemic anti-tumour immunity to inhibit tumour recurrence and metastasis. Our present study reveals that combining CTT with anti-PD-1 treatment potently enhances myeloid cell maturation and simultaneously promotes the infiltration and functional activation of T cells in distal tumours, resulting in superior suppression of distal tumour growth compared to either cryoablation or radiofrequency ablation combined with anti-PD-1. Mechanistically, CTT specifically induces TNF-a production in mature myeloid cells, triggering autocrine CCL5 secretion that recruits peripheral IFN-?+ T cells induced by CTT in distal tumours, creating a cytokine loop where IFN-? derived from T cells and TNF-a derived from myeloid cells collectively promote CCL5 secretion in myeloid cells to enhance effector T cell recruitment in distal tumours. Subsequently, after CTT, anti-PD-1 treatment amplifies this cascade by enhancing TNF-a production in T cells, and high levels of IFN-? and TNF-a in distal tumours promotes higher secretion of CCL5 in myeloid cells, resulting in robust infiltration of T cells. The parallel activation of STAT1 by IFN-? and NF-?B by TNF-a in myeloid cells converges to drive IRF7-dependent CCL5 upregulation to create a local immune enhancing environment via CCL5-mediated recruitment of T cells. Our study demonstrates that CTT establishes an immunologically favorable TME by reprogramming immunosuppressive myeloid cells into mature myeloid cells with high CCL5 production, thereby facilitating effector T cell recruitment, providing an efficient therapeutic strategy to promote the response to anti-PD-1 therapy. Overall design: RNA-seq profiling of untreated side tumours from mice after cryoablation, combined cryoablation and anti-PD-1 therapy, radiofrequency ablation, combined radiofrequency ablationand anti-PD-1 therapy, cryo-thermal therapy, combined cryo-thermal or anti-PD-1 therapy