Gastric cancer cells alter the immunosuppressive function of neutrophils

Abstract

Tumor-associated neutrophils (TANs) have an immunosuppressive function and play an important role in tumor progression. However, the detailed mechanism is largely unknown. The present study investigated the immunosuppressive ability of TANs in gastric cancer. Tumor tissue culture supernatant (TTCS) and non-tumor tissue culture supernatant (NTCS) were purified and added to neutrophils. Expression of programmed cell death ligand-1 (PDL-1), 7-amino-actinomycin D and human leukocyte antigen-DR (HLA-DR), and the levels of hydrogen peroxide (H2O2) were determined. Levels of programmed cell death-1 (PD-1) and CD25 were assessed in T cells co-cultured with neutrophils. Furthermore, CD4+ T cells were co-cultured with dendritic cells and neutrophils to examine their proliferation. CD15 and PD-1 immunohistochemical staining was also performed to explore the positional relationship. The results revealed that the neutrophils incubated with TTCS showed upregulation of PDL-1 expression, as well as a decreases in the ratio of apoptotic cells, expression of HLA-DR, and levels of H2O2. CD4+ T cells co-cultured with neutrophils conditioned with TTCS showed a decrease in proliferation, upregulation of PD-1 expression, and downregulation of CD25 expression. IHC showed that PD-1+ T cells formed clusters and TANs infiltrated around the clusters. In conclusion, neutrophils in gastric cancer tissue inhibit the proliferation of CD4+ T cells and may form a local immunosuppressive environment through the PD-1/PDL-1 pathway.