Shift of tumor-infiltrating immune cells after adding immune checkpoint inhibitors to neoadjuvant chemotherapy against NSCLC.

e21002 Background: Immunotherapy, represented by immune checkpoint inhibitors (ICIs), has revolutionized the treatment strategies in multiple cancer types, including NSCLC. Anti-PD1 combined with chemotherapy was superior to chemotherapy alone, but the fundamental mechanisms underlying their synergic effect remain incompletely understood. Here, we investigated the different effects induced by neoadjuvant pembrolizumab combined with chemotherapy (NAPC) and neoadjuvant chemotherapy (NAC) on tumor immune microenvironment in patients with NSCLC. Methods: We performed single-cell RNA-sequencing (scRNA-seq) to characterize the immune cells composition in seven patients with NSCLC received NAPC or NAC and validated these findings in a large population cohort (n = 58) utilized multiplex fluorescent immunohistochemistry (mIHC). Results: The results of scRNA-seq revealed that patients with NSCLC received NAPC or NAC displayed distinct immune cell composition, with myeloid cells being the predominant cells in NAC patients, whereas T cells, B cells and NK cells were more abundant in NAPC patients. Consistent with these results, mIHC confirmed that compared to NAC, NAPC was associated with increased infiltration of CD8 + T cells, CD8 + KLRG1 + effector cells, CD8 + CD127 + memory cells, CD4 + CD127 + memory cells, CD20 + B cells, accompanied by reduced CD66b + neutrophils but had no effect on other immune subsets examined, including CD68 + macrophage, CD68 + CD163 + M2 and mast cells. Survival analysis showed that, for both NAPC and NAC patients, CD8 + T cells, CD8 + KLRG1 + effector cells, CD8 + CD127 + memory cells were associated with favorable overall survival (OS), while CD66b + neutrophils was related to inferior OS. Moreover, CD20 + B cells appear to have a more pronounced effect than CD8 + T cells on the efficacy of NAPC, but not for NAC. Conclusions: Compared to neoadjuvant chemotherapy, the addition of pembrolizumab induced a shift in tumor-infiltrating immune cells toward enhanced antitumor immunity and reduced immunosuppressive cells. In additional, post-treatment tumor-infiltrating immune cells were able to provide prognostic value.