Our laboratory investigates the interactions between myeloid-lineage hematopoietic cells and the vascular system in tumors. By using targeted gene transfer vectors and conditional cell elimination strategies, we demonstrated that myeloid-lineage cells play an important role during tumor vascularization. In particular, we showed that tumor angiogenesis and growth are dependent on a distinct subset of circulating and tumor-infiltrating monocytes/macrophages. We are currently investigating how monocyte and macrophage heterogeneity in the tumor microenvironment influences angiogenesis and tumor responses to anti-angiogenic therapies. Furthermore, our studies will be applied to the screening and validation of candidate therapeutic targets and the development of novel cancer gene therapy strategies.