Preclinical study of TLR stimulation combined PD-1 antibody enhance the therapeutic effect of microwave ablation on NSCLC.

Purpose: The purpose of this study was to investigate the therapeutic efficacy of the combination of microwave ablation (MWA) with immune checkpoints blockade and TLR9 stimulation in the treatment of non-small cell lung cancer (NSCLC) using the C57BL/6 tumor-bearing mice model.

Materials and methods: Tumor-bearing mice were treated with MWA, programmed cell death protein1 blockade (PD-1) plus MWA (MWA + P), TLR9 agonist CpG ODNs and MWA (MWA + C), PD-1 blockade and CpG ODNs (P + C), MWA plus PD-1 blockade and CpG ODNs (MWA + P + C), or untreated. Survival time was evaluated with the Kaplan-Meyer method comparing survival curves by log-rank test. On day 15 after MWA, ten mice from the combination therapy group received tumor rechallenge with LLC cells and the volumes of rechallenge tumor were calculated every 5 days. Immune cells were identified by immunohistochemistry and flow cytometry, and the concentrations of IFN-γ、TNF-α and TGF-β were identified by enzyme-linked immunosorbent assay (ELISA).

Results: The MWA + P + C combination therapy significantly prolonged tumor-bearing mice survival and reduced tumor size compared to untreated group, MWA group, MWA + P group, M + C group, P + C group. The combination therapy also protected most surviving mice from LLC tumor rechallenge. CD8 + T-cell in tumor and spleen were remarkably induced by MWA + P + C and Treg cell further diminished by combination therapy. Both tumor necrosis factor-alpha (TNF-α) and interferon-gama (IFN-γ) concentrations in plasma were significantly elevated in the combination therapy group compared to other groups, while transforming growth factor Beta (TGF-β) was reduced.

Conclusion: MWA combined with immune checkpoints blockade and TLR stimulation could significantly enhance antitumor efficacy with augmented specific immune responses, and the combination therapy is a promising approach to treat non-small cell lung cancer (NSCLC).