It has become increasingly evident over the years that certain compounds present in cannabis may have antitumor properties against certain types of cancer - at least in in vitro models. However, little was known about the cellular signaling systems involved in mediating these apparent effects. In a recently published mouse study, researchers from the University of East Anglia have identified previously unknown signaling platforms that mediate the anticancer effects of THC, the main psychoactive ingredient of cannabis. The study has been published in The Journal of Biological Chemistry.
The use of cannabis extracts for medicinal purposes is well documented throughout history. Some of the earliest known records come from the third millennium BC where ancient Chinese texts have been found describing its usefulness in pain relief. In recent years, interest in the medicinal properties of marijuana has been sparked as our understanding of the endogenous cannabinoid, or endocannabinoid, system has increased.
The endocannabinoid system refers to the collection of molecules and receptors that are involved in a diverse range of physiological processes such as appetite and pain. It also mediates the psychoactive effects of marijuana. It is known that THC, one of the substances found in cannabis, exerts various effects by interacting with certain cannabinoid receptors found throughout the body, but scientists weren’t sure which receptors were responsible for the apparent antitumor effects observed in animal or lab-based studies.
To find out more, researchers first induced tumors in mice using human cancer cells and then administered different doses of THC. They found that interactions with two cannabinoid receptors, CB2 and GPR55, which are overexpressed in tumor cells facilitate some of the antitumor effects of THC. They found that these receptors form a complex with unique signaling properties that are crucial to the response of tumor cells to THC in vitro (in the lab) and in vivo (in whole organisms). The researchers suggest that direct targeting of these two particular receptors may be an effective method to reduce tumor growth.
“Our findings help explain some of the well-known but still poorly understood effects of THC at low and high doses on tumor growth,” Dr Peter McCormick said in a news-release. However, he made it abundantly clear to the Huffington Post that correct dosage is critical as lab studies have shown that the wrong dose can actually promote cancer growth. He therefore stresses the importance of not taking these results to mean that cancer patients should start self-medicating.
It is also important to note that while various lab or animal studies have highlighted the potential antitumor effects of cannabis compounds such as THC or CBD, no human trials have yet been published, so at this stage we cannot say whether these compounds or synthetic derivatives will live up to expectations. Cancers of all types are notoriously difficult to treat, and treatments that seem revolutionary in models often display completely different effects in human trials. However, the findings presented here are certainly promising and may lead to the development of drugs that can take advantage of the cellular interactions identified in this study.
[Header image, "LEGAL Colorado Marijuana Grow," by Brett Levin, via Flickr, used in accordance with CC BY 2.0]
