Endothelial cells as targets of immune checkpoint blockade

The tumor vasculature acts as the gatekeeper to the tumor microenvironment, thus regulating the ability of immune cells to roll, anchor, and cross the endothelium from blood to tissue. While the role of endothelial cells (EC) in T Cell migration and extravasation has been extensively studied, the ability of ECs to control T Cell function is less well appreciated. Several well-characterized regulators of T Cell function are expressed by ECs, while others are induced by soluble factors required for EC development and differentiation. Targeting the molecules expressed by immunomodulatory ECs may provide approaches to improve tumor immunotherapy.