Surgery-induced Neutrophil Extracellular Traps lead to tumor metastasis by reprogramming cancer cell lipid metabolism

Although surgery is a crucial intervention to treat patients with solid tumors, the accompanying immune response, including the release of Neutrophil Extracellular Traps (NETs), may enhance tumor metastasis. In this study, we explored the effects of systemic surgical NETs in reprogramming cancer metabolism and thereby fostering metastatic tumor growth. To model the effect of surgery on tumor progression, C57BL/6 mice inoculated with subcutaneous MC-38 or subcutaneous LLC-1 cells underwent a midline laparotomy with mesenteric exploration for 30 mins. Mice subjected to surgery showed accelerated primary subcutaneous and lung metastatic tumor growth. Perioperative NETs inhibition utilizing DNAse, GSK484, or PAD4-KO mice prevented the surgically-induced tumor growth. Pre-treating cancer cells with NETs in vitro before inoculation also increased tumor burden. Transcriptomic analysis of MC-38 cancer cells exposed to surgical stress in vivo or treated with NETs in vitro showed activation of the MYC oncogenic pathway. This was associated with upregulation of fatty acid oxidation (FAO), shown with METAFlux analysis and Acetyl-CoA quantification. Blocking FAO with etomoxir (CPT1α inhibitor) prevented the cancer proliferation and metastatic tumor growth induced by surgical NETs. NETs also stimulated uptake of long-chain fatty acids (LCFA) and expression of CD36, the main LCFA transporter. FA metabolism was crucial for cancer cells under anoikis stress, allowing survival of circulating cancer cells exposed to NETs. These findings were corroborated in human tumors analyzed from the TCGA database. In conclusion, the immune response to surgery promotes tumor metastasis through NETs activating cancer cell lipid metabolism. Inhibiting this metabolic reprogramming offers a potential strategy to modulate the protumorigenic effects of surgical stress. To elucidate the transcriptomic changes in MC-38 cancer cells exposed to surgically-induced NETs, we performed bulk RNA-sequencing on MC-38 cancer cells cultured in vitro alone or with NET-chromatin collected fro neutrophils in vitro. Bulk RNA seq was also performed on MC-38 cancer cells expressing GFP isolated by flow sorting at day 30 from in vivo tumors in WT mice, WT mice exposed to laparotomy on days 0 and 10, PAD-4 KO mice or PAD-4 KO mice exposed to laparotomy on days 0 and 10.