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.”
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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.
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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.”