Introduction: Under surgical trauma, the pathological amplification and activation of neutrophils with potent immunosuppressive functions, also known as polymorphonuclear myeloid-derived suppressive cells (PMN-MDSCs), can promote metastasis by forming neutrophil extracellular traps (NETs) that are web-like structures consisting of nuclear DNA, histones, and granule proteins. Preoperative exercise (PEx) reduces postoperative complications with improved clinical outcomes in cancer patients undergoing surgeries. are. Our preliminary data show that PEx suppresses liver ischemia/reperfusion (I/R)-induced colorectal cancer (CRC) liver metastasis. Our recent studies have shown I/R-induced NETs promote liver CRC metastasis by capturing tumor cells and preventing infiltration and cytotoxicity of CD8+ T cells in tumor microenvironment (TME). We hypothesize that PEx remodels the TME by suppressing PMN-MDSCs formation of NETs.

Methods: Male mice were subjected to exercise for 4 weeks, before MC38 colorectal cancer cells were injected through portal vein, and then subjected to 70% partial liver warm I/R as surgical stress. The single-cell RNA sequencing (scRNA-seq) was performed on CD45+leukocytes from TME 3 weeks after surgery. Immunofluorescence staining and Western Blot were used to determine NETs formation in the TME. Flow cytometry was used to determine the infiltration of PMN-MDSCs and CD8+ T lymphocytes in the tumors.

Results: Our scRNA-seq data reveal that PEx leads to a remarkable transcriptomic shift in most immune cells types, such as PMN-MDSCs, M-MDSCs, T cells, Kupffer cells, B cells, NK and NKT cells, in the TME. PEx decreases the percentages of PMN-MDSCs in the TME and inhibits theNETs formation by PMN-MDSCs. scRNA-seq shows a significant increase of the chemokines CXCL10 in PEx-trained PMN-MDSCs obtained 3 weeks after I/R-induced hepatic metastasis, compared with sedentary controls. In addition, PEx increases the number of CD8+ T lymphocytes infiltrating the TME.

Summary: Our study shows that PEx downregulates NETs formation and increases the CXCL10 expression in PMN-MDSCs, thus promoting the recruitment more cytotoxic CD8 T lymphocytes to suppress tumor metastasis.

Citation Format: Xiang Cheng, Hongji Zhang, Allan Tsung, Hai Huang. Preoperative exercise inhibits hepatic metastasis by suppressing PMN-MDSC formation of NETs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2544.