|
News Clippings
By Roger Highfield (Daily Telegraph)
Snake's venom may help treat breast
cancer
A PROTEIN found in copperhead snake venom dramatically
retards the growth of breast tumours, scientists reported
last week.
Preliminary studies by a research team from the
University of Southern California, led by Professor
Francis Markland, have shown that it can also inhibit
growth of other cancers.
In studies with mice implanted with human breast cancer
cells, a 60 to 70 per cent reduction in the growth rate
of the breast tumours and a 90 per cent reduction of
tumours that spread to the lungs was found in rodents
treated with the protein. However, it will take at least
18 months before the venom protein will be ready to test
on patients.
"We have a long way to go from mice to the female of
the human species," Prof Markland told colleagues in
Boston, at the national meeting of the American Chemical
Society, the world's largest scientific society. He said:
"We are in the process of genetically engineering
the venom. We would have to milk every snake in the world
to get the venom we would need for a trial."
Earlier this year there was great excitement about the
efforts to block a process called angiogenesis, the
development of new blood vessels, which is exploited by a
tumour to obtain a supply of nutrients and growth
factors, a disposal route for its wastes, and a route for
cancerous cells to spread.
The copperhead protein acts by inhibiting the development
of new blood vessels to nourish the tumours and by
putting tumour cells into a "suspended state of
animation". Prof Markland said the dual action
helped prevent the spread of cancer, a process called
metastasis.
When first diagnosed with breast cancer, many women
already have metastatic disease, which means that the
cancer has spread to another site such as the lymph
nodes, brain or bone.
Called contortrostatin, CN, the protein is purified from
the venom of the southern copperhead and is one of a
cocktail used by the snake to immobilise prey, keeping
blood fluid so that other damaging proteins can spread
through the body. Prof Markland said: "Snake venoms
in general are loaded with proteins, many of which lead
to tissue destruction at the site of the bite." The
mice trials had not revealed any side-effects other than
local bleeding.
CN belongs to a class of proteins known as disintegrins,
so named because they disrupt the function of certain
other proteins, called integrins, on the surface of cells
that enable them to stick together.
CN is effective in retarding the spread of tumour cells
because it inhibits their adhesion to and invasion of
normal cells. CN would need to be administered
periodically over time in the hope of shrinking the
tumour to a size where treatment could be scaled back or
stopped.
Dr Lesley Walker, head of scientific information at the
Cancer Research Campaign, said: "It's the spread of
cancer which in the majority of cases is so devastating.
This work is interesting because it is highly targeted to
tumour cell behaviour . . . it's an intelligent way of
dealing with cancer and has therapeutic potential."
It is not the first time that snake venom has been the
basis of medical treatment. Venom from the Brazilian
arrowhead viper is used to help reduce blood pressure.
|
