The potential medical properties of marijuana are interesting to researchers because of the drug’s pain and nausea-relieving effects in patients with cancer, HIV and multiple sclerosis. Now, scientists at Complutense University, Spain, have discovered that compounds acting at cannabinoid receptors eradicate brain tumors in one third of rats and mice treated, and prolong the survival of another third.
Dr. Manuel Guzman and colleagues studied mice and rats with a brain tumor called malignant glioma and treated them with THC or a man-made chemical with similar properties. The substances eradicated the tumor in almost a third of the animals. THC is the active ingredient in marijuana.
Although rare, malignant glioma is always fatal. Even after treatment with surgery, chemotherapy and radiation, the average survival time is less than a year.
The findings suggest that these substances, known as cannabinoids, hold promise as a therapy for the cancer, which often fails to respond to conventional treatment, the authors explain. Dr. Guzman says cannabinoids like THC appear to extend survival time and even cure the disease, in rats at least. According to Dr. Guzman, the next step is to try to gain a better understanding of how the substances attack the cancer and to see if they will work in people. In the study, Guzman and colleagues pumped THC or a synthetic cannabinoid directly into brain tumors in rats and mice. Overall, animals that received the treatment fared better than those that did not. Of the 30 rats treated with either THC or the synthetic compound, 13 survived longer than untreated rats, according to the report. And in 8 of the animals, the treatment completely destroyed the tumor. However, 9 of the rats that received the treatment did not live any longer than untreated animals. The technique may represent a promising new approach for a particularly deadly form of cancer, Guzman and his colleagues conclude. Synthetic cannabinoids may turn out to be particularly useful, since the one used in the study provided better results at about 10% of the dose of THC, according to the report. In an editorial that accompanies the study, Dr. Daniele Piomelli, of the University of California at Irvine, points out that the new research suggests that there may be a way to develop cannabinoid medications that block the growth of the brain tumor, without producing other effects, such as the "high" associated with smoking marijuana. However, she notes that the potential benefits of the treatment may outweigh the risks of these other effects, given that the prognosis for people with malignant glioma is so bleak.
Both the article and the accompanying comment appear in the March 1, 2000 issue of the journal Nature Medicine.
SOURCE: Nature Medicine, March 1, 2000; 6:255-256, 313-319 AND Reuters Health, Feb. 28, 2000.