Kaempferol (kaem) is a dietary flavonoid found in a variety of fruits and vegetables. The inhibitory effects of kaem on primary tumour growth have been extensively investigated; however, its effects on tumour metastasis are largely unknown. In the present study, we found that kaem significantly suppresses both primary tumour growth and lung metastasis in mouse breast tumour model. Furthermore, decreased expression of citrullinated histone H3 (H3‐cit), a biomarker of neutrophil extracellular traps (NETs), had been founded in metastatic lung upon treated with kaem. The reduction of H3‐cit is not, however, due to the cytotoxicity of kaem on neutrophils since the frequency of CD11b⁺Ly6G⁺ neutrophils did not change in lung, tumour or blood in the presence of kaem. We then confirm the anti‐NETs effects of kaem in vitro by co‐culturing mouse neutrophils and kaem. Supplementing the neutrophils with GSK484, a potent NET inhibitor, totally abrogated the inhibitory effects of kaem on tumour metastasis while having little or no impact on primary tumour growth, indicating the specificity of kaem acting on NET formation and tumour metastasis. We also found that kaem suppressed ROS production in mouse bone‐marrow derived neutrophils. Supplementing with the ROS scavenger DPI abrogated kaem's effects on NET formation, suggesting the involvement of kaempferol in NADPH/ROS‐NETs signalling. Finally, we applied the kaem on NET‐deficient PAD4^‐/‐ mice and found decreased primary tumour volume and weight but similar lung metastatic tumour with kaempferol treatment. Therefore, our findings reveal a novel mechanism of kaem in breast cancer development by targeting NETs induced tumour metastasis.

中文翻译：

---

山emp酚可通过抑制ROS-PAD4途径来阻断嗜中性白细胞胞外陷阱的形成并减少肿瘤转移。

山茱fer醇（kaem）是一种饮食类黄酮，存在于多种水果和蔬菜中。已经广泛研究了kaem对原发性肿瘤生长的抑制作用。然而，其对肿瘤转移的作用尚不清楚。在本研究中，我们发现kaem可以显着抑制小鼠乳腺肿瘤模型中的原发性肿瘤生长和肺转移。此外，经kaem处理后，已经在转移性肺中发现了瓜氨酸化组蛋白H3（H3-cit）（中性粒细胞胞外陷阱（NETs）的生物标志物）的表达降低。但是，H3-cit的降低不是由于kaem对中性粒细胞的细胞毒性，因为CD11b ⁺ Ly6G ⁺在有kaem的情况下，中性粒细胞在肺，肿瘤或血液中没有变化。然后，我们通过共同培养小鼠嗜中性粒细胞和kaem来确认kaem的抗NETs效应。向中性粒细胞补充有效的NET抑制剂GSK484，完全废除了kaem对肿瘤转移的抑制作用，而对原发性肿瘤的生长几乎没有影响，这表明kaem对NET形成和肿瘤转移的特异性。我们还发现kaem抑制了小鼠骨髓来源的中性粒细胞中ROS的产生。补充ROS清除剂DPI消除了kaem对NET形成的影响，这表明山fer酚参与了NADPH / ROS-NETs信号传导。最后，我们将kaem应用到NET缺乏的PAD4上^。小鼠，发现原发性肿瘤的体积和重量减少，但使用山emp酚治疗的肺转移性肿瘤相似。因此，我们的发现通过靶向NETs诱导的肿瘤转移揭示了kaem在乳腺癌发展中的新机制。