Abstract 4747: Neutrophils in gastric cancer tissue inhibit the proliferation of CD4+T cells and contribute to immunosuppression

Abstract

Abstract [Background] Neutrophils are essential effector cells in the host's defence against invasive pathogens, On the other hand, neutrophils in the tumor-microenvironment are known to have potential to induce angiogenesis, lymphangiogenesis, and be an important factor in tumor progression. We have reported that neutrophils infiltrating in gastric cancer tissue (Tumor-Associated Neutrophil: TAN) correlated with lymph node metastasis, systemic inflammatory response and be a poor prognostic factor. So we hypothesized that neutrophils in gastric cancer tissue suppressed anti-tumor immune response, but their details are still unclear. [Aim] The aim of this study was to investigate the immunosuppressive ability of neutrophils in gastric cancer tissue and to explore the influence of neutrophils on the proliferation of CD4 (+) T cells. [Materials and Methods] We isolated neutrophils from blood samples taken from healthy donors and added tumor tissue culture supernatants (TTCS) purified from human scirrhous gastric cancer cell line (OCUM12) or purified supernatants from patients who underwent gastrectomy at our department. Then, we examined the expression of apoptotic cells, PDL-1, and HLA-DR on neutrophils with TTCS. We also observed the expression of PD-1, CD25 on T cells co-cultured with neutrophils added TTCS. Furthermore, CD4 T cell labeled Carboxyfluorescein diacetate succinimidyl ester (CFSE) were co-cultured with allogenic dendritic cells and neutrophils with TTCS, and the proliferation of CD4 (+) T cells were examined by flow cytometry. We also performed immunohistochemistry (IHC) staining using anti CD15 and anti PD-1 antibodies for 117 patients who underwent gastrectomy in our department from 2007 to 2013 to explore the positional relationship. [Results] Neutrophils with TTCS were upregulated the expression of PDL-1 than those without TTCS. We also found that the apoptotic cell ratio and the expression of HLA-DR on neutrophils with TTCS was decreasing. CD4 (+) T cells co-cultured with neutrophils added TTCS were suppressed their proliferation, and upregulated the expression of PD-1 and downregulated the expression of CD25. IHC showed that PD-1 positive cells formed clusters and TAN was infiltrating around the clusters. And a positive correlation was found between the number of TAN and PD-1 positive cells in the scatter plot. [Conclusion] Our findings suggested that neutrophils in gastric cancer tissue inhibited the proliferation of CD4 T cells and formed a local immunosuppressive environment through the PD1-PDL1 pathway. Citation Format: Soichiro Hiramatsu, Hiroaki Tanaka, Yoshihito Yamakoshi, Junya Nishimura, Tatsuro Tamura, Takahiro Toyokawa, Kazuya Muguruma, Masaichi Ohira. Neutrophils in gastric cancer tissue inhibit the proliferation of CD4+T cells and contribute to immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4747.