Our laboratory studies the interactions between tumor cells and blood and lymphatic vessels during tumor progression and metastasis, as it relates to the growth of blood vessels in tumors. Angiogenesis, the sprouting of new blood vessels from existing vessels, is an oncofetal process that occurs physiologically during development and postnatal growth, but in adults is mostly restricted to pathological processes, which makes it an attractive target. Angiogenesis is characterized by molecular and cellular events which enable cells of the vessel wall (endothelial cells) to sprout from a pre-existing capillary to form new capillaries, which could then form a vascular network that matures over time with the recruitment of perivascular mural cells (smooth muscle cells, pericytes). We study the essential role of Angiopoietin/Tie signaling in blood and lymphatic vessels and analyze the molecular and functional properties of endothelial cells and pericytes during physiological and pathological angiogenesis and vessel remodeling. Given the critical roles of blood and lymphatic dysfunction for numerous oncological and non-oncological diseases, this work is aimed at better understanding the complexity of vessel functions to pave the way for rational therapeutic exploitation.