A tandem approach to shrinking brain tumors with two of marijuana’s key ingredients — tetrahydrocannabinol and cannabidiol —  has proven successful, according to the result of a newly published study.

Cannabis has enjoyed a meteoric rise in the United States as of late. Recreational use was recently approved in Oregon and Washington, D.C., and many more states are currently onboard for its letting people use it as medicine. This boom coincides with greater research into the ways in which cannabis acts on the brain’s cannabinoid receptors, alleviating pain, restoring appetite, and, now, shrinking tumors.

Senior author of the new study, Dr. Wai Liu, of the University of London, says the one-two punch of THC and CBD is really what makes cannabis yield such impressive effects.

“We think this is due to the different pathways that these cannabinoids hit,” Liu told Medical Daily in an email. “Specifically, THC works via receptors, whilst CBD may not need them; consequently, using them together results in a ‘priming’ effect in tumour cells, making them more sensitive to the ‘cell killing’ effects of  irradiation.”

Liu’s study  in mice models found THC and CBD, when used together, helped shrink the tumors to a far greater extent than radiation and just one of the compounds or radiation alone, which actually yielded a negligible effect on tumor growth. What’s more, the team needed a smaller dosage of each substance when they were used together in order to kill 50 percent of the cancer cells. They needed 14 millimolar (a unit of concentration) of CBD and 19 millimolar of THC. Using both, they needed only seven millimolars each.

This finding is especially important because it means patients won’t need as much THC, the main psychoactive ingredient in cannabis that may be unpleasant for people receiving treatment. When a psychoactive compound binds to the cannabinoid receptor inside a brain cell, it can trigger the traditional “high” effects of recreational use. But in small enough doses, the compound can retain its anti-cancer properties without any side effects. The trick is to find the balance, Liu says.

So what’s actually going on that allows cannabis to be so effective? Liu suspects the answer has to do with how the substances interact with the receptors and the radiation treatment.

“We think that the cannabinoids are hitting a number of cell signaling pathways, which primes them to the effects of irradiation,” he said. “Pre-treatment with the cannabinoids seems to interfere with the ability of the tumour cell to repair the DNA-damaging effects of irradiation.” Thus, the tumor cells get wiped out.

There are more than 85 cannabinoids in total, which bind to different receptors in cells and receive outside chemical signals. The brain houses many of these receptors, and prior evidence has already shown cannabis to destroy certain cancer cells, giving the researchers a natural starting point to see how THC and CBD work together. Their targets — glioma cells — are notoriously hard to kill with standard methods. Fewer than five percent of people who survive glioblastoma, a form of glioma, live past three years.

Killing these cancer cells has never been more crucial, as medical science continues to peel back the layers of cannabis’s medicinal benefits. We may have a simple, effective, and safe treatment to help cancer patients, but without a social or legal framework in place to allow the method’s use, it becomes worthless. Though, people like Liu remain hopeful.  

“The results are promising,” he wrote recently. “There may be other applications, but for now it could provide a way of breaking through glioma and saving more lives.”

Source: Scott K, Dalgleish A, Liu W. The Combination of Cannabidiol and Δ9-Tetrahydrocannabinol Enhances the Anticancer Effects of Radiation in an Orthotopic Murine Glioma Model. Molecular Cancer Therapeutics. 2014.