Intratumoral Myeloid Cells Regulate Responsiveness and Resistance to Antiangiogenic Therapy

• Sensitivity to VEGF/VEGFR inhibition is driven by myeloid-cell-derived CXCL14
• Myeloid PI3K activation overrides sensitivity and promotes angiogenic relapse
• Myeloid-cell oscillation in tumors maintains resistance to antiangiogenic therapy
• Inhibition of myeloid PI3K activity overcomes resistance to antiangiogenic therapy

SummaryAntiangiogenic therapy is commonly used in the clinic, but its beneficial effects are short-lived, leading to tumor relapse within months. Here, we found that the efficacy of angiogenic inhibitors targeting the VEGF/VEGFR pathway was dependent on induction of the angiostatic and immune-stimulatory chemokine CXCL14 in mouse models of pancreatic neuroendocrine and mammary tumors. In response, tumors reinitiated angiogenesis and immune suppression by activating PI3K signaling in all CD11b+ cells, rendering tumors nonresponsive to VEGF/VEGFR inhibition. Adaptive resistance was also associated with an increase in Gr1+CD11b+ cells, but targeting Gr1+ cells was not sufficient to further sensitize angiogenic blockade because tumor-associated macrophages (TAMs) would compensate for the lack of such cells and vice versa, leading to an oscillating pattern of distinct immune-cell populations. However, PI3K inhibition in CD11b+ myeloid cells generated an enduring angiostatic and immune-stimulatory environment in which antiangiogenic therapy remained efficient.

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