Cancer researchers may have found the Achilles heel of malignant tumours - a treatment that kills cells by blocking their blood supply but without triggering resistance to the drug involved.

Traditional chemotherapy often fails because cancers are either intrinsically resistant to drugs or become resistant after a period of treatment.

But drug resistance is not a problem for a new approach that targets the Achilles heel of tumours - their reliance on a blood supply for growth,researchers in Boston, Massachusetts, are demonstrating.

Their discovery that mice respond well to anti-angiogenic therapy that knocks out resistant tumours by targeting blood cells could herald a new era of cancer treatment.

Successive cycles of treatment with the drug, endostatin, are given and gradually the tumours diminish until they disappear.

No return

Unlike treatment with standard chemotherapy, successive cycles produce no resistance. And the researchers are discovering that, after a certain number of cycles, the tumours do not return even when treatment is stopped.

The findings, from a team led by Dr Judah Folkman from the Dana Farber Cancer Center, are published in the science journal Nature.

"It is the first time one has been able to repeatedly treat tumours in animals and not have the tumours develop resistance against the drugs," said Dr Folkman.

So far the treatment has only been tested on mice and human trials are still some time away but eventually anti-angiogenic treatment could be used alongside chemotherapy and may offer new hope to patients with persistent tumours that do not respond to standard therapy.

In a commentary accompanying the Nature article, leading expert Robert Kerbel, from the University of Toronto, Ontario, Canada, says : "Perhaps the most significant finding was that all treated tumours eventually became indefinitely dormant even when endostatin treatment was halted.

"This startling event, the basis of which is unknown, occurred after a variable number of cycles (two to six), the number of which depended on the particular tumour being treated."

He adds: "The results ... are unprecedented and could herald a new era of cancer treatment."

British at work

The Boston team are not alone in looking at tackling cancer by cutting off its blood supply. In Britain, the Cancer Research Campaign is carrying out encouraging tests on a different drug, derived from the African Bush Willow, which works by stopping the blood capillaries from elongating.

The drug has been shown to kill 95% of tumours in the laboratory and the first patient trials are expected to start next year.

Dr Lesley Walker, head of science information at the charity, says: "The importance of blood supply for tumours is a completely novel target and common right across the board for most cancers.

"Everyone had assumed you wouldn't have this problem of acquired drug resistance and it's nice that it has now been formally shown."
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