αPD-1 immunotherapy promotes IL-17A production and promotes the formation of acute radiation-induced lung injury.

BACKGROUND

Radiotherapy (RT) is essential in the treatment of thoracic neoplasms. Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) have significantly improved the clinical management of non-small cell lung carcinoma (NSCLC).

OBJECTIVE

This study aimed to investigate the impact of combining anti-PD-1 (αPD-1) immunotherapy with radiotherapy on lung injury. Additionally, it investigates the role and mechanism of interleukin (IL)-17A, a pro-inflammatory cytokine involved in immune regulation, in lung injury arising from this combination treatment.

METHODS

Experiments were conducted using a PD-1 deficient mouse model to simulate acute radiation-induced lung injury. Inbred female BALB/c wild-type (WT) mice and PD-1 mice were divided into six groups: WT group, PD-1 group, WT_LIR + IgG group, PD-1_LIR + IgG group, WT_LIR + αIL-17A group, and PD-1_LIR + αIL-17A group. The mice were subjected to 8 Gy × 3 irradiation in both lungs. Various methods including histological scoring, immunofluorescence, qPCR, and flow cytometry were employed to analyze the role of IL-17A in lung injury and the effect of PD-1 gene deletion on the severity of radiation-induced lung injury.

RESULTS

The PD-1_LIR mice exhibited evident radiation-induced lung injury after receiving 8 Gy × 3 doses in both lungs. The expression level of IL-17A peaked at 2 weeks. Lung injury-related factors IFN-γ, TNF-α, IL-6, and RORγt in the PD-1_LIR groups increased 2 weeks after irradiation. The CD4 and CD8 T cells in lung tissue of the PD-1_LIR mice significantly increased. Post αIL-17A administration, the incidence of alveolitis in the treatment group decreased, the expression levels of lung injury-related factors IFN-γ, TNF-α, IL-6, RORγt, TGF-β1, and IL-17A decreased, and the CD4 and CD8 T cells in lung tissue significantly declined. Throughout the observation period, the survival rate of the mice in the treatment group was significantly higher than that of the isotype control group (60% vs 0%, P = 0.011).

CONCLUSION

Combining αPD-1 immunotherapy with radiotherapy in mice can induce radiation-induced lung injury, with IL-17A playing a critical role in this process. αIL-17A administration significantly mitigated radiation-induced lung injury caused by the combination of αPD-1 immunotherapy and radiotherapy, improving mouse survival. This finding offers a promising treatment target for lung injury resulting from the combination of αPD-1 immunotherapy and radiotherapy.