Despite the frequency of lung metastasis and its associated mortality, the mechanisms behind metastatic tumor cell survival and colonization in the lungs remain elusive. Here, we show that tumor cell-released microparticles (T-MPs) from the primary tumor site play a critical role in the metastatic process. The T-MPs remodeled the lung parenchyma via a macrophage-dependent pathway to create an altered inflammatory and mechanical response to tumor cell invasion. Mechanistically, we show that circulating T-MPs readily enter the lung parenchyma where they are taken up by local macrophages and induce CCL2 production. CCL2 recruits CD11b+Ly6Chigh inflammatory monocytes to the lungs where they mature into F4/80+CD11b+Ly6C- macrophages that not only produce IL6 but also trigger fibrin deposition. IL6 and the deposited fibrin facilitate the survival and growth of tumor-repopulating cells in the lungs by providing chemical and mechanical signals, respectively, thus setting the stage for lung metastasis. These data illustrate that T-MPs reprogram the lung microenvironment promoting metastasis. Cancer Immunol Res; 6(9); 1046-56. ©2018 AACR.
©2018 American Association for Cancer Research.