Ang-2 is only weakly expressed in endothelial cells under physiological conditions. However, Ang-2 expression is
dramatically increased during vascular remodeling, e.g., during tumor growth. For example, glioblastoma show increased levels of Ang-2 in their associated endothelium . Here, Ang-2 is highly expressed in necrotic and hypoxic regions. Vessels in these areas are not covered by smooth muscle cells. Only small vessels in glioblastomas express high amounts of Ang-2 but not larger ones. Overexpression of Ang-2 in a rat glioma model resulted in aberrant vessels with low SMC coverage . Ang-2 is also detectable in significant concentrations in the circulation of tumor patients, e.g., in
esophageal squamous cell cancer, hepatocellular carcinoma, and lung cancer. The expression of Ang-2 in melanomas correlates with tumor progression . Tumor cells have been shown to express Ang-2, e.g., stomach , colon , bladder carcinoma, melanoma, and non small cell lung cancer (NSCLC)