HOUSTON CHRONICLE (Texas) 23 January 08 Cancer fight turns to toxic toad venom - Local experts study Chinese remedy (Todd Ackerman)
Photo: Bufo gargarizans, the Asiatic toad, sickens attackers with its toxic venom. (Wikimedia Commons)
A Houston hospital known for seeking the most advanced cancer therapies that modern science can develop is turning its attention to a centuries-old Chinese treatment: toad venom.
Scientists from the University of Texas M.D. Anderson Cancer Center are investigating whether the stuff that some types of toads use to sicken their natural predators can also be a healer, as doctors of traditional Chinese medicine have long believed.
"Without hesitation, toad venom was the No. 1 drug (Chinese) doctors mentioned when we asked them to suggest the best natural cancer medicines to test," Lorenzo Cohen, director of M.D. Anderson's integrative medicine program, said from China. "It may sound wild to Americans, but it's accepted as a standard of care here."
It also appears to hold promise. In clinical trials Cohen is leading in Shanghai, the venom secreted by the Asiatic toad has shown some benefit and no apparent side effects in patients with advanced liver, pancreatic and lung cancer — which are not easy cancers to fight.
Cohen said he hopes to bring the drug to Houston to test on M.D. Anderson patients in a couple of years. It already has been tested successfully in laboratory and mouse studies at the cancer center.
The research, funded by the National Cancer Institute, is part of an M.D. Anderson program to determine whether alternative therapies can be integrated with accepted Western practices. In his work in the program, Cohen makes frequent trips to China.
One expert said he was impressed that M.D. Anderson would take up the research of toad venom, or ChanSu, as it's known in China.
"In terms of clinical research, we're in the infancy of testing herbs, much less animal products," said Ted Kaptchuk, a Harvard professor of medicine and author of The Web That Has No Weaver: Understanding Chinese Medicine.
"Animal products tend to make scientists queasy," he said, "to be seen as possibly culturally influenced, as if they're hocus-pocus."
Kaptchuk said it makes sense to investigate toad venom because it's much-discussed in cancer alternative treatment circles. He was hard-pressed to think of other animal products used in traditional Asian medicine that have been exposed to clinical trials.
The remedy is thought to date at least to the Song dynasty (960-1279) and has been used to treat many ailments, including cancer and heart problems. Although it now is injected in patients in China in conjunction with chemotherapy or other treatment, it also is still given in some parts of the country as a broth of dried toad skin, herbs or other animal products.
Cohen hopes to come up with a pill form of the venom to use in the U.S. In China, the injections are given daily for 14 consecutive days, or five days a week for three weeks. That would be too costly at U.S. hospitals.
M.D. Anderson researchers believe the toad venom works because of a compound called cardiac glycosides. The substance can be toxic in overdoses, but from other sources is already used in the treatment of congestive heart failure.
''It appears to inhibit proteins promoting cancer cell growth, and then cause cancer cell death," said Peiying Yang, an assistant professor of experimental therapeutics at M.D. Anderson.
''A lot of people think it's unwise to use," said Yang, "but in Chinese medicine, one philosophy is: To cure a toxic disease, you may have to use a toxic substance. The dose just needs to be low enough to not cause side effects."
Yang said that, in the mouse studies, pancreatic tumors shrank in as many as 60 percent of the subjects. That result is slightly better than the performance of the standard chemotherapy drug gemcitabine.
In the clinical trial at Fudan University Cancer Hospital in Shanghai, the extract stopped tumor growth in six of 14 patients with advanced lung, liver or pancreatic cancer, Cohen said.
Of course, in some respects, the success of natural remedies comes as no surprise. Cohen and Kaptchuk note that more than 60 percent of cancer drugs are derived from plants.
But Cohen said he isn't yet looking down the road at commercialization.
"Right now, I'm just looking for evidence for further exploration," he said. "But it's not that easy to isolate a single biologically active ingredient from Chinese medicine remedies."
Cancer fight turns to toxic toad venom

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