Abstract 2266: Tumor associated neutrophils (TAN) may produce neutrophil extracellular traps (NETs) which can suppress the infiltration of activated T cells in tumor tissue
Authors: Tamura Kohei , Miyato Hideyo , Matsumiya Misaki , Takahashi Rei , Kaneko Yuki , Futoh Yurie , Takahashi Kazuya , Kimura Yuki , Saito Akira , Ohzawa Hideyuki , Saga Yasushi , Takei Yuji , Fujiwara Hiroyuki , Kitayama Joji 
Published: April 2023

Abstract
Objective: High density of tumor-infiltrating lymphocytes (TIL) in the tumor is associated with favorable prognosis of cancer patients. It has been reported that many neutrophils also infiltrate in various tumor tissues as tumor-associated neutrophils (TAN) which produce considerable amounts of neutrophil extracellular traps (NETs). However, the crosstalk between TAN and TIL and its impact on tumor behavior have not been fully examined.
Methods: Neutrophils and mononuclear cells (PBMC) were collected from the blood of healthy donor. Neutrophils were stimulated with PMA or LPS for 15 min, washed extensively, and incubated for another 4 hours to produce NETs. PBMC were cultured on anti-CD3 mAb-coated plate with recombinant-IL-2 for 7-14days. The migration of activated T cells through 3μm pore to CXCL-11 was examined in vitro. The localization and densities of TAN and TIL were immunohistochemically evaluated in 38 human serous ovarian cancer tissue. NETs were quantified with the density of CD66b(+) and Citrullinated Histon H3(+) cells.
Results: Chemotactic migration of T cells to CXCL-11 was inhibited by 99%±1.6% (p&lt;0.001) in the presence of PMA-activated neutrophils in lower chamber. The inhibition was similarly detected when NET components were removed by ultracentrifugation. Timelapse analysis also showed the NETs-depleted supernatant inhibited random migration, which was totally canceled by the pretreatment with catalase. When neutrophils were activated by LPS, T cell migration was also inhibited by 49%±19.9% (p&lt;0.01), but not by NETs-depleted supernatant. In western blotting, CXCL11 was totally degraded by LPS-stimulated neutrophils, which was greatly reduced by the depletion of NET component and restored by DNase I as well as phenylmethylsulfonyl fluoride (PMSF) or Neutrophil elastase inhibitor (NEI). The reduced migration induced by LPS-stimulated neutrophils was also restored with these reagents. In ovarian cancer tissues, density of TIL was greater in tumors with diameter ≥10cm than that of tumors &lt;10cm (p=0.04). However, the densities of TIL and NETs were irrelevant with age, tumor stage and neutrophil-to-lymphocyte ratio (NLR) in peripheral blood. Multicolor immunohistochemistry showed that TAN and TIL tended to be reciprocally distributed in tumor stroma in most of the ovarian cancer tissues. Cit-H3 was positively detected in 2.1%~75% of CD66b(+) TANs, and the proportion of NET in TAN greatly varied among tumors. In all cases, the densities of CD4(+) and CD8(+) T cells inversely correlated with that of NETs (r = -0.5182, p = 0.0012; r = -0.5684, p = 0.0003, respectively).
Conclusion: Activated neutrophils negatively regulate T cell migration partially through NET formation. TAN may suppress T cell traffic into tumor tissue, which may attenuate cell-mediated immunity in tumor microenvironment and promote tumor progression.
Citation Format: Kohei Tamura, Hideyo Miyato, Misaki Matsumiya, Rei Takahashi, Yuki Kaneko, Yurie Futoh, Kazuya Takahashi, Yuki Kimura, Akira Saito, Hideyuki Ohzawa, Yasushi Saga, Yuji Takei, Hiroyuki Fujiwara, Joji Kitayama. Tumor associated neutrophils (TAN) may produce neutrophil extracellular traps (NETs) which can suppress the infiltration of activated T cells in tumor tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2266.