Tumor Endothelium as a Modulator of Immune Responses in Cancer Metastasis

Endothelial cells not only make up the lining of blood vessels but also contribute to tissue-specific and vessel type specific niche formations required during inflammation and cancer. Importantly, endothelium activation promotes leukocyte recruitment. Accumulating evidence indicates an active involvement of endothelium in immunomodulation during tumorigenesis. We will discuss current data on a co-stimulatory immune receptor expression in tumor vasculature and its role during tumorigenesis and metastasis. Using endothelial-specific deletion, we observed not only differences in tumor angiogenesis, but also changes in the tumor microenvironment, including immune cells. Analysis of several metastatic models revealed tissue-specific modulation of tumor immune responses.