Explaining angiogenesis
Over at the blog Respectful Insolance, the author Orac gives a primer on angiogensis
preexisting blood vessels. It is a normal physiological process that
occurs during wound healing, the changes in the lining of the uterous
during the menstrual cycle, embryonic and fetal development, and
inflammation. Tumors hijack this process in order to feed their need
for oxygen and nutrients. They have to; the diffusion of nutrients and
oxygen is limited to only around 1 mm in aqueous solution. Without
angiogenesis, tumors can only grow to a diameter of less than 2 mm.
Tumors induce angiogenesis by a variety of strategies, but most
commonly they secrete large amounts of factors, usually small proteins,
that stimulate the endothelial cells (cells that line blood vessels) to
invade the basement membrane upon which they sit, migrate towards the
stimulus, form tubes, and finally form functional blood vessels. The
most common and studied of these factors belong to the vascular
endothelial growth factor (VEGF) family. Usually, tumor vessels tend to
be tortuous and “leaky,” and indeed the original name for VEGF was
vascular permeability factor, because of its ability to increase the
leakiness of blood vessels.
A good succinct explanation. He says he got interested in the field in the late 1990s when there was a lot of stuff in the popular press about inhibiting angiogensis as a means of controlling cancer. That hype faded when miracles did not transpire, but the basic idea is still intriguing, and cancer research continues.
