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.
Keywords: interferon; metastasis; neutrophils; premetastatic niche.
© 2015 UICC.