Neutrophil-macrophage crosstalk via NETs-IL-17/VEGF/S100A9 axis promotes hepatocellular carcinoma progression.

[BACKGROUND] Tumor-associated neutrophils and macrophages are key components of the hepatocellular carcinoma (HCC) microenvironment. However, the interplay between them and its contribution to HCC progression remain unclear.

[METHODS] Bioinformatic analysis of TCGA datasets and clinical HCC samples was used to evaluate neutrophil extracellular trap (NETs) levels and macrophage polarization. Co-culture of neutrophils, macrophages, and HCC cells, along with molecular analysis and in vivo mouse models, were employed to dissect the mechanisms underlying NETs-mediated macrophage reprogramming and tumor progression.

[RESULTS] NETs were significantly elevated in HCC patients, particularly in advanced and metastatic stages, which were positively correlated with intrahepatic M2 macrophage infiltration and M2d subset-associated cytokines in blood. In vitro, NETs promoted M2d polarization in the presence of HCC cells via IL-17R/NF-κB signaling activated by IL-17 carried within NETs, which subsequently enhanced angiogenesis, migration, invasion, and epithelial-mesenchymal transition; these effects were partially reversed by IL-17R inhibition. In vivo, NETs-induced M2d polarization accelerated tumor growth, angiogenesis, and metastasis, whereas IL-17R blockade attenuated these pro-tumor effects. Moreover, M2d macrophages indirectly promoted NETs formation by upregulating HCC cell-derived S100A9 through VEGF-NF-κB signaling, establishing a positive feedback loop between neutrophils and macrophages. Furthermore, IL-17 carried by NETs (NETs-IL-17) demonstrated strong predictive value for extrahepatic metastasis in HCC, with an area under the ROC curve (AUC) of 0.89.

[CONCLUSIONS] A positive feedback loop between neutrophils and macrophages via the NETs-IL-17/VEGF/S100A9 axis accelerates HCC progression and metastasis. More importantly, NETs-IL-17 exhibited potential as an alternative biomarker for predicting extrahepatic metastasis in HCC.