Snake Venom May Slow
Cancer Growth, Studies Hint
Jennifer
Hile
June
1, 2004
Preliminary research shows a natural compound
in some snake venoms may prevent the growth of cancerous tumors, potentially
transforming one of nature's deadliest toxins into a curative agent.
"Snakes use venom to alter biological
functions, and that's what medicine does too," explained John Perez,
director of the Natural Toxins Research Center at Texas A&M
University-Kingsville. "This is why venoms have always been of interest to
medical researchers."
Today roughly a dozen diagnostic tests and
drugs are derived from snake venom, according to Zoltan Takacs, a toxinologist
(natural-toxins scientist) and herpetologist based at the Yale University
School of Medicine in New Haven, Connecticut.
ACE inhibitors, a class of drugs used to
treat high blood pressure and other cardiovascular disorders, were developed
from the venom of a Brazilian snake. Scientists anticipate that this is just
the beginning.
Of the nearly 3,000 species of snakes in the
world, about 650 are venomous. Ten of the most deadly live in Australia, making
it a logical base for new experiments.
"We knew Australia could be a rich
source of drugs because there are so many venomous creatures here," said
Tony Woods, a biologist at the University of South Australia in Adelaide. Woods
is co-leader of a project to investigate whether the toxins in venom can be
used to destroy blood vessels that feed cancerous tumors.
The Power of Nature's Toxins
Venoms are exquisitely complex, composed of
as many as a hundred different peptides, enzymes, and toxins. Not only are the
venoms of every snake species different, there are also subtle variations
within each species. "There are differences between [venoms of] juveniles
and adults, and even among different geographic regions," Takacs said.
"These differences may be due to different evolutionary pressures, like
different ancestry, prey, and environments."
The variations between venom types and the
number of venomous snakes worldwide create a rich molecular hunting ground for
researchers, like Woods, seeking to design new drugs.
"A tumor is made of tissue," Woods
said. "Like tissue in any part of the body, if you can prevent it from
developing a blood supply, or interfere with that supply, then you will have an
effect on the growth of that tissue."
Woods is working with Michael Venning, a
pharmacologist at the University of South Australia, and graduate student Emma
Bateman. Peter Mirtschin, a toxinologist at Venom Supplies in Tanunda, South
Australia, is providing the venom directly from the snakes.
Woods's group has found a compound in snake
venom that disrupts endothelial cells, which line the inner surface of blood
vessels. "It causes the cells to separate from one another, which kills
them," Woods said. "When that happens, the function of the blood
vessel is inhibited, preventing or at least interfering with blood flow to the
tumor [effectively starving it of nutrients]."
Woods will not specify which snake venoms his
team is studying, because the compounds have not yet been patented.
The Cure That Doesn't Kill
The advantage of these venom-derived toxins
is that they seem to act only on certain types of cells.
Chemotherapy
and many other drug treatments do not distinguish between tumor cells and other
healthy cells, causing debilitating side effects. But natural toxins have
evolved to impact very specific targets.
"We believe the cells that line blood
vessels in tumors are different in subtle ways from similar cells elsewhere in
the body, because they are exposed to different stimulation and
chemicals," Woods said. That means toxins inhibiting tumor blood vessels
may not effect surrounding healthy cells, which would theoretically leave
patients using these toxins feeling better than those who go through
chemotherapy.
Woods anticipates that he will begin testing
the venom-derived toxin in animals within the year. Those results will reveal
whether the drug is suitable for human clinical trials.
"I don't actually like snakes, they
scare me to death, but I'm fascinated by their venom," Woods said.
"So long as it's provided to me in nice plastic tubes, I'm very
comfortable with handling it."
Tiada ulasan:
Catat Ulasan
Nota: Hanya ahli blog ini sahaja yang boleh mencatat ulasan.