Active Ingredient in Marijuana Kills Brain Cancer Cells

April 1 (HealthDay News) -- New research out of Spain suggests that THC -- the active ingredient in marijuana -- appears to prompt the death of brain cancer cells.

The finding is based on work with mice designed to carry human cancer tumors, as well as from an analysis of THC's impact on tumor cells extracted from two patients coping with a highly aggressive form of brain cancer.

Explaining that the introduction of THC into the brain triggers a cellular self-digestion process known as "autophagy," study co-author Guillermo Velasco said his team has isolated the specific pathway by which this process unfolds, and noted that it appears "to kill cancer cells, while it does not affect normal cells."

Velasco is with the department of biochemistry and molecular biology in the School of Biology at Complutense University in Madrid. The findings were published in the April issue of The Journal of Clinical Investigation.

The Spanish researchers focused on two patients suffering from "recurrent glioblastoma multiforme," a fast-moving form of brain cancer. Both patients had been enrolled in a clinical trial designed to test THC's potential as a cancer therapy.

Using electron microscopes to analyze brain tissue taken both before and after a 26- to 30-day THC treatment regimen, the researchers found that THC eliminated cancer cells while it left healthy cells intact.

The team also was able, in what it described as a "novel" discovery, to track the signaling route by which this process was activated.

These findings were replicated in work with mice, which had been "engineered" to carry three different types of human cancer tumor grafts.

"These results may help to design new cancer therapies based on the use of medicines containing the active principle of marijuana and/or in the activation of autophagy," Velasco said.

Outside experts suggested that more research is needed before advocating marijuana as a medicinal intervention for brain cancer.

Dr. John S. Yu, co-director of the Comprehensive Brain Tumor Program in the Maxine Dunitz Neurosurgical Institute at Cedars-Sinai Medical Center in Los Angeles, said the findings were "not surprising."

"There have been previous reports to this effect as well," he said. "So this is yet another indication that THC has an anti-cancer effect, which means it's certainly worth further study. But it does not suggest that one should jump at marijuana for a potential cure for cancer, and one should not urge anyone to start smoking pot right away as a means of curing their own cancer."

But that's exactly what many brain cancer patients have been doing, said Dr. Paul Graham Fisher, the Beirne Family director of Neuro-Oncology at Stanford University.

"In fact, 40 percent of brain tumor patients in the U.S. are already using alternative treatments, ranging from herbals to vitamins to marijuana," he said. "But that actually points out a cautionary tale here, which is that many brain cancer patients are already rolling a joint to treat themselves, but we're not really seeing brain tumors suddenly going away as a result, which we clearly would've noticed if it had that effect. So we need to be open-minded. But this suggests that the promise of THC might be a little over-hoped, and certainly requires further investigation before telling people to go out and roll a joint."

SOURCES: Guillermo Velasco, Ph.D., department of biochemistry and molecular biology, School of Biology, Complutense University, Madrid; John S. Yu, M.D., co-director, Comprehensive Brain Tumor Program, Maxine Dunitz Neurosurgical Institute, Cedars-Sinai Medical Center, Los Angeles; Paul Graham Fisher, M.D., associate professor, neurology, pediatrics, and neurosurgery and human biology and the Beirne Family Director of Neuro-Oncology, Stanford University; April 2009, The Journal of Clinical Investigation