Many biomedical terms have a familiar ring, but unless you've been schooled in Latin or Greek -- or fancy yourself a crossword master -- puzzling out their meaning without a dictionary can confound. "Angiogenesis" cloaks itself in such welcoming warmth. Too bad it can sometimes kill.

In its most direct definition, angiogenesis simply means the formation of blood vessels from existing blood vessels. Think of it as a branching out, an extension, a vascularization, if you will. Which, if you do, soon brings you to the term vasculogenesis, the term used to describe the formation of the blood vessel, or vascular, system -- consisting of all those special transport tubes we refer to as arteries, arterioles, capillaries and veins. Since both terms include the root word genesis, it's clear that both refer to a production process. Angio comes from the Greek word angeion, which means "vessel," while vasculo comes from the Latin word vasculum, which means small vessel. Despite the fact that the Greeks preceded the Romans, the order is reversed when it comes to explaining blood vessels. In short, you can't angio before you vasculo as any developing embryo could tell you if it could talk.

Moreover, healthy adults don't angio at all, except when a cut is healing or a bone is mending. Healing and mending are considered good things, of course. So why is it that angiogenesis, when you hear the word at all, casts a shadow on the rest of the sentence? The answer: because most people learn about the word only in relation to a cancer diagnosis. Sadly, angiogenesis is a fundamental step in the transition of tumors from a dormant state to a malignant state.

Think of it this way. Cancers that do not grow do not usually kill. Indeed, without a supply of oxygen and other nutrients, cancerous tumors stay small, usually no larger than 2 millimeters, or about the size of an eraser atop a pencil. But tumors are clever mutants. They know how to trick the nearby blood vessels into branching out (as they would do to help heal an open wound, for example) by secreting what are known as growth factors. These sirens of death lure new capillaries into the tumor, providing it with a blood supply and nutrients it needs to grow. Worse, once vascularized, the tumor can shed its malignant cells into these capillaries, which provide a ready transit route to other parts of the body. Once relocated, these cells then spread the disease, a process called metastasis.

Given these facts, it is no wonder that many cancer researchers at UCSF are concentrating on anti-angiogenesis therapies, since depriving a tumor of its blood supply would keep it small and localized. Nuanced approaches abound but in short, all the anti-angiogenesis research divides into methods for negating the growth factors or enhancing the inhibitors (these exist to shut down angiogenesis when its job is done, for example, after a wound heals). No wonder then that as this research becomes more common, so does the term itself. The British National Corpus, which keeps track of word usage, reports that angiogenesis is used about 18 times out of a sample 100 million words spoken or written in English. That may not seem like much, but consider this: There are 700,000 words used in the English language and angiogenesis ranks 82,615. One can hope than in the end, anti-angiogenesis will rank even higher.

See also:

UCSF Comprehensive Cancer Center