Tumor endothelial cells are targets for selective therapies: in vitro and in vivo models to evaluate antiangiogenic strategies.

Angiogenesis is a complicated process, essential for tumor progression and metastasis. Extensive work has been done to understand the mechanisms of tumor angiogenesis and identify angiogenesis inhibitors. It is now recognised that tumor endothelial cells present different functional and phenotypic characteristics than normal resting endothelial cells. These differences and advances in molecular biology have allowed the development of selective agents targeting tumor endothelial cells as therapeutic approaches for cancer. These new targeted strategies need to be evaluated in relevant models before being transferred from the laboratory bench to the clinic. In vivo tumor models remain a good way to evaluate the effect of these agents on tumor growth and metastasis. Nevertheless, in parallel to the development of tumor angiogenesis inhibitors, in vitro models have been designed to mimic angiogenesis steps and enable the evaluation of these new drugs. In this paper, after reviewing the phenotypic characteristics of tumor endothelial cells that make them easy to target for antiangiogenic therapy, some of the most commonly used in vitro and in vivo models, which enable the evaluation of antiangiogenic agents, are presented and discussed.