The formation of new blood vessels or angiogenesis is a normal process required for growth and wound healing. Unfortunately, it also plays a critically enabling role in the growth, proliferation, invasion and metastasis of cancers since tumors cannot grow beyond a certain size without a blood supply. The resulting new blood vessels feed the growing tumors with necessary oxygen and nutrients, allowing the cancer cells to invade nearby tissue, and gain access to immature blood vessels to metastasize throughout the body. Platelet Derived Growth Factor (PDGF), which is secreted by carcinoma cells, is the most important signaling molecule to stimulate and proliferate stromal cells. Myofibroblasts, transdifferentiated from stromal fibroblasts by PDGF, secretes chemokines that recruit endothelial precursor cells (EPC) in to the stroma. Myofibroblasts also secrete vascular endothelial growth factor (VEGF), which induces the differentiation of EPCs into endothelial cells, subsequently forming the neo-vasculature. Continue reading →