If you stop a tumour feeding itself then you have stopped the tumour. Such is the simple logic behind a major goal in cancer research - finding a way to prevent the growth of blood vessels around the tumour.
The body can grow the blood vessels it needs through a process called angiogenesis. It has been known for many years that tumours release substances that cause a rapid proliferation of extra blood vessels, which connect nearby arteries and veins to the tumour site, feeding its abnormal energy demands.
Biochemists are looking for substances that can prevent the extra blood vessel growth, cutting off the cancer's energy supply and inhibiting its development. Thalidomide, the drug which caused so much anguish by being responsible for limb malformation in newborns, holds out promise as a block against angiogenesis.
"The reason it caused the trouble with children's limbs is because it inhibited blood flow and the limbs didn't form properly," explained Dr John Nelson of the School of Biology and Biochemistry at Queen's University, Belfast, and director of the Action Cancer Research Unit attached to the department.
Cells can break away from a cancer site and migrate around the body, eventually lodging and causing secondary cancers in other tissues, he said. These tumours become dormant if their blood supply can be cut off.
There was an element of luck in the Queen's discovery, Dr Nelson explained. "We were looking at something completely different." He and colleagues were studying a number of the growth factors released by a tumour, hoping to find a way to block one or more of these factors and so slow a cancer's development.
"We were looking at one of these factors and fragments of it. One bit did not behave like a growth factor, but it did prevent angiogenesis." In particular, the substance seemed to prevent the attachment of new blood vessel cells to the surfaces of other tissues.
When blood vessels grow they need to be able to pass through and around other tissues and to stick themselves to surfaces. These "endothelial" cells must be able to migrate to the positions where they are needed to deliver a future blood supply. The new substance seems to inhibit both cell migration through tissues and also their attachment to surfaces.
"It seems to be an essential part of endothelial cell growth into a tumour. These substances block this system up," Dr Nelson said.
Substances known to inhibit angiogenesis tend to be very large and complex molecules which can be difficult to produce. The growth factor fragment identified by the Queen's group is very much smaller - only 10 amino acids assembled in a chain - "which does more or less the same thing" as the complex compounds, Dr Nelson explained.
The work is at a very early stage so it will be some time before it could have any impact on cancer treatment. "We are still at the stage of laboratory work," Dr Nelson said, and a patent on the substance was being sought. It was known as an "analogue" or "lead compound", but held much promise because of its actions, because it was based on a compound native to the body and because it was easy to synthesise as a pharmaceutical.
"I think there should be less of an effect" on the patient when giving such a substance compared with the current generation of chemotherapy drugs, Dr Nelson stated.