In research on mice, active ingredient in pot shrank growths by half, reduced cancer lesions
By Angela Zimm
Bloomberg News
Giving marijuana to mice with cancer shrank their lung tumors by half and slowed the spread of the disease, findings that may one day expand legal use of the drug as a treatment, researchers said.
The research is the first to show that marijuana's active ingredient, tetrahydrocannabinol, or THC, blocks a known cancer-related protein that's already the target of drugs such as ImClone System's Erbitux and Amgen's Vectibix.
The findings, presented this past week 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's Tarceva, approved for lung and pancreatic cancer; and AstraZeneca's Iressa, which treats lung cancer.
Lung cancer cells with high levels of EGFR are generally very aggressive and treatment resistant, researchers said.
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 human lung tumor samples and in mice.
In addition to reducing tumor size by half, THC was associated with a 60 percent reduction in cancer lesions in the lungs of mice.
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