The lack of type I interferon induces neutrophil-mediated pre-metastatic niche formation in the mouse lung.

Metastases are the major cause of death from cancer. Thus, understanding the regulation of metastatic processes is of utmost importance. Here we show that mice with impaired type I IFN signaling (Ifnar1(-/-)) develop more lung metastases in the 4T1 mammary and LLC lung carcinoma model, compared to control mice. In Ifnar1(-/-) mice, higher metastasis load is accompanied by massive neutrophil accumulation in lungs. Elevated G-CSF levels in serum and enhanced CXCR2 expression on neutrophils are most likely responsible for this phenomenon. Lung infiltrating neutrophils facilitate an improved pre-metastatic niche formation, supporting more efficient tumor cell extravasation and proliferation in this organ. This is due to the enhanced expression of pro-metastatic proteins, like Bv8, MMP9, S100A8 and S100A9. Development of pre-metastatic niche together with reduced neutrophil cytotoxicity against tumor cells results in enhanced metastatic processes in Ifnar1(-/-) mice. Overall, our findings describe a novel role for IFN during metastasis development and suggest that new treatment strategies should be considered for prevention of metastasis formation in patients.