LONDON -- Scientists believe they may have found the secret of "switching off" the ability of cancers to spread and grow.

The molecule found in the kidney, can starve tumors by blocking their ability to supply themselves with blood by growing new vessels.

Researchers believe it could be effective against a wide range of cancers, as well as other conditions such as artery disease and diabetes.

The molecule is a special form of a protein called VEGF - vascular endothelial growth factor, reports the BBC news On-Line quoted by IRNA.

Normally, VEGF encourages angiogenesis, the growth of new blood vessels.

This is vital to the survival and spread of a tumor - without extra blood supplies, such rapid growth would be impossible.

Usually VEGF is only seen in diseased tissue. But it also occurs in normal, healthy kidneys, where it does not seem to generate tumors.

Scientists led by Dr. Dave Bates and Dr. Steve Harper at the University of Bristol investigated this apparent paradox.

They found that the version of VEGF in the kidney was different -- and had precisely the reverse effect on the growth of blood vessels.

Dr. Bates, whose work is published in the journal **** Cancer Research ****, said: "We are very excited about this. Theoretically it could apply to any cancer. Every cancer known uses VEGF to make new blood vessels."

The researchers are quoted by IRNA as saying that in the kidney, something appeared to convert VEGF from one form to another.

When it switched from the 165B form to the dangerous type of VEGF, this provided the right environment for cancer to develop.

Learning what caused the switch could lead to the design of new drugs, said Dr. Bates.

"If you can find a drug that can switch it back, you'll stop blood vessel growth," he said.