Hypoxia within a tumor acts as a strong selective pressure that promotes angiogenesis, invasion, and metastatic spread. In this study, we used immune competent bone marrow chimeric mice and syngeneic orthotopic mammary cancer models to show that hypoxia in the primary tumor promotes premetastatic niche formation in secondary organs. Injection of mice with cell-free conditioned medium derived from hypoxic mammary tumor cells resulted in increased bone marrow-derived cell infiltration into the lung in the absence of a primary tumor and led to increased metastatic burden in mammary and melanoma experimental metastasis models. By characterizing the composition of infiltrating bone marrow-derived cells, we identified CD11b

Summary Accumulation of CD103 + CD8 + resident memory T (T RM ) cells in human lung tumors has been associated with a favorable prognosis. However, the contribution of T RM to anti-tumor immunity and to the response to immune checkpoint blockade has not been clearly established. Using quantitative multiplex immunofluorescence on cohorts of non-small cell lung cancer patients treated with anti-PD-(L)1, we show that an increased density of CD103 + CD8 + lymphocytes in immunotherapy-naive tumors is associated with greatly improved outcomes. The density of CD103 + CD8 + cells increases during immunotherapy in most responder, but not in non-responder, patients. CD103 + CD8 + cells co-express CD49a and CD69 and display a molecular profile characterized by the expression of PD-1 and CD39. CD103 + CD8 + tumor T RM , but not CD103 − CD8 + tumor-infiltrating counterparts, express Aiolos, phosphorylated STAT-3, and IL-17; demonstrate enhanced proliferation and cytotoxicity toward autologous cancer cells; and frequently display oligoclonal expansion of TCR-β clonotypes. These results explain why CD103 + CD8 + T RM are associated with better outcomes in anti-PD-(L)1-treated patients.