LONDON (Reuters) - The active ingredient in marijuana appears to reduce tumor growth, according to a Spanish study published on Wednesday.
The researchers showed giving THC to mice with cancer decreased tumor growth and killed cells off in a process called autophagy.
"Our findings support that safe, therapeutically efficacious doses of THC may be reached in cancer patients," Guillermo Velasco of Complutense University in Madrid and colleagues reported in the Journal of Clinical Investigation.
Autophagy can promote cell survival or cell death, but the molecular basis underlying its dual role in cancer remains obscure. Here we demonstrate that Δ9-tetrahydrocannabinol (THC), the main active component of marijuana, induces human glioma cell death through stimulation of autophagy. Our data indicate that THC induced ceramide accumulation and eukaryotic translation initiation factor 2α (eIF2α) phosphorylation and thereby activated an ER stress response that promoted autophagy via tribbles homolog 3-dependent (TRB3-dependent) inhibition of the Akt/mammalian target of rapamycin complex 1 (mTORC1) axis. We also showed that autophagy is upstream of apoptosis in cannabinoid-induced human and mouse cancer cell death and that activation of this pathway was necessary for the antitumor action of cannabinoids in vivo. These findings describe a mechanism by which THC can promote the autophagic death of human and mouse cancer cells and provide evidence that cannabinoid administration may be an effective therapeutic strategy for targeting human cancers.
The findings add to mixed evidence about the effects of marijuana on human health. Studies have suggested the drug can raise a person's risk of heart attack or stroke and cause cancer.
Other research has shown benefits, such as staving off Alzheimer's, and many doctors view THC as a valuable way to treat weight loss associated with AIDS, and nausea and vomiting associated with chemotherapy in cancer patients.
Velasco and his team's study included an analysis of two tumors from two people with a highly aggressive brain cancer which showed signs of autophagy after receiving THC.
The researchers said the findings could pave the way for cannabinoid-based drugs to treat cancer, although that approach has so proved unsuccessful when it comes to obesity.
Sanofi-Aventis SA in November terminated further development of its cannabinoid drug Acomplia, and Pfizer Inc, Merck & Co Inc and Belgium's Solvay have also scrapped similar products recently over health fears.
The drugs, which work by blocking the same receptors in the brain that make people hungry after smoking marijuana, have also been linked to psychiatric side effects, such as depression and suicidal thoughts.
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