Figure 3.

Tumor angiogenesis and metastasis. Tumor cells proliferate rapidly and have a high metabolic demand. To fulfill their energy requirements, tumor cells and other stromal cells produce different angiogenic factors including VEGF, which activates the endothelial cells and stimulate proliferation. Tumor stroma also produce a host of proteases and MMPs which helps basement membrane remodeling. Following the breakdown of basement membrane, proliferating endothelial cells lead to uncontrolled neovascularization. These newly formed vessels are irregular and leaky, through which tumor cells escape and metastasize to distant organs.