Type I interferons induced upon respiratory viral infection impair lung metastatic initiation

Invasive breast cancer accounts for 7% of all cancer-related deaths, with the lungs being a common site of metastases. At the same time, lower respiratory tract infections are a common cause of morbidity and mortality worldwide. Acute viral respiratory infections induce transitional changes in the lung; however, the impact of these changes on metastasis initiation and cancer progression remains unclear. Using primary murine MMTV-PyMT breast cancer cells in an experimental lung metastasis model, we show that changes induced by respiratory syncytial virus (RSV) infection impair tumor cell seeding and early establishment in the lung, resulting in lower number of metastatic nodules. Furthermore, we demonstrate that this reduction of metastases is due to alterations in the lung environment mediated by type I interferons (IFNs) that are produced in response to RSV infection. Consistent with that notion, intranasal administration of recombinant IFN- recapitulates the anti-tumor effect of RSV infection. Type I IFNs change the lung cellular composition and induce an Interferon Stimulated Gene (ISG) driven response, creating an alveolar environment that is less supportive of tumor cell growth. Indeed, epithelial cells from mice infected with RSV or intranasally exposed to IFN-, are less supportive of tumor cell growth ex vivo. Altogether, our results suggest that type I IFNs induced by infection with some respiratory viruses perturb the lungs and consequently interfere with the ability of tumor cells to successfully initiate metastatic colonization. SignificanceWomen diagnosed with metastatic breast cancer have a low survival rate. The lungs are a common metastatic site and are constantly exposed to viral pathogens, such as coronavirus, RSV and influenza virus. Thus, breast cancer and respiratory virus infection are likely to co-occur, but their interplay remains unclear. We show that type I interferons (IFNs), induced upon viral infection impair metastatic cancer cell seeding of mouse lungs. This is potentially via an effect of IFNs on lung epithelial cells, which become less supportive of early tumor cell proliferation. These findings indicate that viral infections and type I IFNs can alter the lung environment and impair implantation of metastatic cells, which could be explored to improve future cancer treatments.