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Wednesday, August 26, 1998 Published at 20:11 GMT 21:11 UK


Scientists target breast cancer with snake venom

A poisonous American snake could provide a new weapon to fight breast cancer, according to new research.

The protein extracted from the venom of the Southern Copperhead viper slowed the growth of tumours in mice implanted with human breast cancer cells by up to 70%.

The protein, contortrostatin (CN), had an even bigger impact on metastasis - the spread of a malignant tumour from its original site. CN reduced tumour spread to the lungs in the mice by 90%.

Clinical trials using CN to treat breast cancer in women could start in "the not too far distant future," said Dr Francis Markland, a professor of biochemistry at the University of Southern California School of Medicine.

Suspended animation

CN is cytostatic rather than cytotoxic. This means it does not kill tumour cells but "freezes" them in a long lasting state of "suspended animation". The cancer cells are prevented from adhering to and invading normal surrounding cells.

The protein also inhibits new blood vessel development. Tumors need blood vessels to deliver nutrients necessary for their continued growth, said Dr Markland

Because the protein does not kill cells directly it has none of the side effects of powerful chemotherapy drugs, such as severe nausea.

Dr Markland, who has presented his research to the national meeting of the American Chemical Society, believes CN would need to be administered over a period of time in the hope of shrinking a tumour to a size where treatment could be scaled back or stopped.

Therapeutic potential

The Cancer Research Campaign in the UK welcomed the research.

"It's the spread of cancer which in the majority of cases is so devastating," a spokeswoman said. "This work is interesting because it's highly targeted to tumour cell behaviour. Although it's early days its an intelligent way of dealing with cancer and clearly has therapeutic potential.

"Inhibiting metastatic spread of cancer and tumour blood vessel development are two of the key approaches under investigation at the moment."

New drugs

The Copperhead, Agkistrodon contortrix, grows to about three feet long and has a distinctive copper head and reddish brown bands. Although poisonous, its bite is rarely fatal.

The US Food and Drug Administration (FDA) has already approved one drug this year derived from snake venom.

Integrilin, found in the venom of a rattlesnake, can be used to treat people suffering from chest pains, or unstable angina, and from "small" heart attacks.

In a study of 10,948 patients in 27 countries, the drug was found to cut the risk of heart attacks or death by 1.5% worldwide.

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