Cristina Sanchez, a young biologist at Complutense University in Madrid, was studying cell metabolism when she noticed something peculiar. She had been screening brain cancer cells because they grow faster than normal cell lines and thus are useful for research purposes. But the cancer cells died each time they were exposed to tetrahydrocannabinol (THC), the principal psychoactive ingredient of marijuana. In 1998, she reported in a European biochemistry journal that THC “induces apoptosis [cell death] in C6 glioma cells,” an aggressive form of brain cancer.
A team of Spanish scientists led by Manuel Guzman conducted the first clinical trial assessing the antitumoral action of THC on human beings. Guzman administered pure THC via a catheter into the tumors of nine hospitalized patients with glioblastoma, who had failed to respond to standard brain-cancer therapies. The results were published in 2006 in the British Journal of Pharmacology: THC treatment was associated with significantly reduced tumor cell proliferation in every test subject.
Around the same time, Harvard University scientists reported that THC slows tumor growth in common lung cancer and “significantly reduces the ability of the cancer to spread.” What’s more, like a heat-seeking missile, THC selectively targets and destroys tumor cells while leaving healthy cells unscathed. Conventional chemotherapy drugs, by contrast, are highly toxic; they indiscriminately damage the brain and body.
Dr. Sean McAllister, a scientist at the Pacific Medical Center in San Francisco, has been studying cannabinoid compounds for 10 years in a quest to develop new therapeutic interventions for various cancers. Backed by grants from the National Institute of Health (and with a license from the DEA), McAllister discovered that cannabidiol (CBD), a nonpsychoactive component of the marijuana plant, is a potent inhibitor of breast cancer cell proliferation, metastasis, and tumor growth.
In 2007, McAllister published a detailed account of how cannabidiol kills breast cancer cells and destroys malignant tumors by switching off expression of the ID-1 gene, a protein that appears to play a major role as a cancer cell conductor.
“Cannabidiol offers hope of a non-toxic therapy that could treat aggressive forms of cancer without any of the painful side effects of chemotherapy,” says McAllister, who is seeking support to conduct clinical trials with the marijuana compound on breast cancer patients.