Calcium-Permeable Channels in Tumor Vascularization: Peculiar Sensors of Microenvironmental Chemical and Physical Cues.

Calcium (Ca)-permeable channels are key players in different processes leading to blood vessel formation via sprouting angiogenesis, including endothelial cell (EC) proliferation and migration, as well as in controlling vascular features which are typical of the tumor vasculature.In this review we present an up-to-date and critical view on the role of Ca-permeable channels in tumor vascularization, emphasizing on the dual communication between growth factors (mainly VEGF) and Ca signals. Due to the complexity of the tumor microenvironment (TME) as a source of multiple stimuli acting on the endothelium, we aim to discuss the close interaction between chemical and physical challenges (hypoxia, oxidative stress, mechanical stress) and endothelial Ca-permeable channels, focusing on transient receptor potential (TRP), store-operated Ca channels (SOCs), and mechanosensitive Piezo channels. This approach will depict their crucial contribution in regulating key properties of tumor blood vessels, such as recruitment of endothelial progenitors cells (EPCs) in the early steps of tumor vascularization, abnormal EC migration and proliferation, and increased vascular permeability. Graphical abstract depicting the functional role of Ca-permeable TRP, SOCs and Piezo channels in the biological processes regulating tumor angiogenesis in presence of both chemical (oxidative stress and oxygen levels) and mechanical stimuli (ECM stiffness). SOCs store-operated Ca channels, TRPA transient receptor potential ankyrin, TRPV transient receptor potential vanilloid, TRPC transient receptor potential canonical, TRPM transient receptor potential melastatin, TRPM transient receptor potential vanilloid, O oxygen, ECM extracellular matrix.