PD-1 Blockade Enhances the Anti-Tumor Immune Response Induced by Cryoablation in A Murine Model of Lung Cancer

Purpose To investigate the efficacy of cryoblation plus PD-1 inhibitor in the treatment of mouse lung cancer, and its possible mechanism on regulating cellular immune function. Materials and Methods Murine lung cancer xenograft model was constructed. Mice were randomly divided into Control, Cryo + IgG, Anti-PD-1, and Cryo + Anti-PD-1 group, and given corresponding treatment. Tumor growth (n = 10) and survival of (n = 10) were observed. Flow cytometry was used to detect the proportion of CD4 + T cells, CD8 + T cells, and regulatory T (Treg) cells. Results Tumor volume of the three treatment groups were significantly smaller than that of the Control group ( P <0.01), those of Anti-PD-1 or Cryo + Anti-PD-1group were much smaller than that of the Cryo + IgG group ( P <0.05). The medium survival time of the three treatment groups were significantly longer than that of the Control group ( P <0.01). The proportions of CD4 + T cells in the peripheral blood, spleen and tumor of the three treatment groups were significantly lower than that of the Control group ( P <0.05), while the CD8 + T cells were markedly higher than that of the Control group ( P <0.05). The proportions of Treg cells in the spleen of the three treatment groups were notably lower than that of the Control group ( P <0.05). mRNA level of IFN-γ was increased while IL-10 was decreased in the three treatment groups ( P <0.01). Conclusion Either cryoblation or PD-1 inhibitor treatment alone enhances the anti-cancer effect of the body immune system by down-regulating the proportion of CD4 + T cells and Treg cells, while up-regulating the proportion of CD8 + T cells. Notably, the combination of cryoblation and PD-1 inhibitor get better effect on lung cancer treatment.