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in Study of MiceAngela Zimm
April 17, 2007
Bloomberg News
April 17 (Bloomberg) -- Giving marijuana to mice with cancer shrank their lung tumors by half and slowed spread of the disease, findings that may one day expand legal use of the substance as a treatment, researchers said.
The research is the first to show that marijuana's active ingredient, tetrahydrocannabol, or THC, blocks a known cancer-related protein that's already the target of drugs such as ImClone System Inc.'s Erbitux and Amgen Inc.'s Vectibix.
The findings, presented today at the American Association for Cancer Research meeting in Los Angeles, add to evidence that marijuana may have anti-tumor properties and its potential should be probed further, researchers said. Scientists speculate THC may activate biological pathways that halt cancer cell division or block development of blood vessels that feed tumors.
"THC can have a potential therapeutic role," said Anju Preet, the study's lead author and a researcher at Harvard University's division of experimental medicine. "Maybe THC is killing cells. The preliminary studies are promising."
Tumor cells dosed with THC also showed a reduction in epidermal growth factor receptor, or EGFR, which means the substance may be acting in ways similar to Erbitux and Vectibix, which block the protein, Preet said.
The group includes Erbitux, which treats colon and head and neck cancers, Vectibix, which treats colon cancer, Genentech Inc.'s Tarceva, approved for lung and pancreatic cancer, and AstraZeneca Plc's Iressa, which treats lung cancer.
Lung cancer cells with high levels of EGFR are generally very aggressive and treatment resistant, researchers said.
Receptors
THC activates "cannabinoid receptors," which are proteins found in the brain and other parts of the body that are involved in a number of biological functions, including inflammation and pain. Researchers set out to see if they could inhibit tumor growth by targeting these receptors in both human lung tumor samples and in mice.
In addition to reducing tumor size by half, THC was also associated with a 60 percent reduction in cancer lesions in the lungs of mice.
More work needs to be done to understand how THC prevents tumor growth and to find the right dose before starting clinical trials, Preet said. Previous research has shown that too much THC can stimulate cancer growth, she said.
"Before jumping into clinical study we need to understand how it works, which can help us design a better therapeutic," Preet said.
In the U.S., 11 states have enacted laws the allow patients to use marijuana for medical purposes. The states are Alaska, California, Colorado, Maine, Montana, Nevada, Oregon, Washington, Hawaii, Vermont and Rhode Island, according to the Marijuana Policy Project, a marijuana policy reform organization based in Washington D.C. Last month, Bill Richardson, the governor of New Mexico, signed a bill that would make his state the 12th to legalize marijuana for medical use.
Only one THC drug, called Marinol, is approved in the U.S. The treatment, made by Solvay Pharmaceuticals, is used as an appetite stimulant for cancer patients.
