Angiogenesis is a term used to refer to “formation of new blood vessels”. Endothelial cells play a key function in maintaining homeostasis and formation of new blood vessels. “Angiogenesis involves the migration, growth, and differentiation of endothelial cells, which line the inside wall of blood vessels.” 1
Angiogenesis has been found to have key applications in cancer research. Tumor is supported by formation of new blood vessels that provides oxygen nutrients for cancer cells to grow and invade other tissue. Current research is focused on understanding how natural and/or synthetic angiogenesis inhibitors, also known as antiangiogenic agents, can have implications on stopping or lessening tumor growth. The key role of angiogenesis in tumor development and cancer metastasis makes inhibition of angiogenesis an attractive strategy to target a number of cancer types (Timar et. al., 2001).
Human umbilical vein endothelial cells (HUVEC) are commonly used primary endothelial cell types for studying angiogenesis in vitro. VEGF (or VEGF-A “vascular endothelial growth factor”) and VEGFR-2 are key cytokines involved in stimulating angiogenesis. One of the easiest screening and target validation strategies for anti-angiogenic target identification involves knocking down targets in HUVECs and assessing subsequent effects on tube formation. The usage of small interfering RNA (siRNA) is one of the strategies to knock-down RNA, and thereby protein expression within cells. siRNA can be delivered within cells using either chemical transfection or electroporation-based strategies such as the one offered by the Lonza NucleofectorTM Technology.