OX40+ regulatory T cells suppress neoadjuvant chemotherapy response in NSCLC and reversed by combination of PD-1 blockade therapy.

BACKGROUND: OX40+ regulatory T cells mediate tumor immune escape and correlate with clinical response to neoadjuvant therapy in NSCLC, but the underlying mechanisms remain incompletely understood.

METHODS: We collected formalin-fixed paraffin-embedded (FFPE) tumor sections from 30 NSCLC patients receiving neoadjuvant chemotherapy (NAC) and 28 patients receiving neoadjuvant PD-1 blockade and chemotherapy (NAPC), and explored the effect of OX40+ Tregs on the efficacy of neoadjuvant therapy and the level of immune cell infiltration by multiplex immunofluorescence staining (mIHC).

RESULTS: Our results showed that the proportion of OX40+ Tregs was significantly increased after NAC. NAPC led to elevated infiltration of Th17 cells and Tregs within tumors, while OX40+ Tregs were markedly reduced. In patients achieving major pathological response (MPR) following NAPC, total Treg levels remained unchanged, but OX40+ Tregs decreased significantly and showed a strong negative correlation with tumor necrosis rate. Spatial analysis revealed that after NAPC, Tregs and OX40+ Tregs tended to decrease in proximity to CD8+ T cells, whereas Th17 cells increased significantly. Tumor cells were surrounded by higher densities of CD4+ T cells, Th17 cells, and CD8+ T cells. Furthermore, patients with MPR after NAPC exhibited fewer Tregs and OX40+ Tregs adjacent to CD8+ T cells and more CD8+ T cells encircling tumor cells.

CONCLUSIONS: Our study reveals the critical role of Treg/Th17 balance in tumor immunotherapy and demonstrates that OX40+ Tregs inhibit the neoadjuvant chemotherapy response in NSCLC, which can be reversed by combining with PD-1 blockade via boosting Th17 cells, providing new insights to improve the efficiency of chemoimmunotherapy for NSCLC.