A new study in mice has suggested that tetrahydrocannabinol (THC), which is the psychoactive compound in cannabis, can help prevent colon cancer associated with ulcerative colitis.
Rates of IBD increased drastically in the latter half of the 20th century, and they continue to rise in certain countries. Indeed, in the United States, around 3 million adults received an IBD diagnosis in 2015.
The recent surge in the prevalence of these conditions suggests that something in the way we live may precipitate onset. For example, researchers have suggested that increased meat consumption may be a factor.
Increasing diagnoses are a particular concern, as people with IBD have a higher risk of developing colon cancer, a condition with an average 5-year survival rate of 63%. Colon cancer is also becoming increasingly common among young people.
In a new study that appears in the journal iScience, researchers from the University of South Carolina (USC) in Columbia trialed a novel approach to preventing colon cancer.
They treated mice with the cannabis compound THC, which effectively prevented inflammation and stopped the development of colon cancer.
The scientists based the study on mouse models of colitis-associated colon cancer. They treated some of the mice with THC, while the mice in the control group received only a vehicle, which is similar to a placebo.
At the end of the study, the mice who received THC showed no tumors, unlike the control group. The mice in the THC group also had significantly less colonic inflammation, which is a symptom of IBD.
“The fact that we were able to show that treatment with THC prevents inflammation in the colon and at the same time inhibits the development of colon cancer supports the notion that inflammation and colon cancer are closely linked,” explains senior study author Dr. Prakash Nagarkatti.
The researchers went on to explore how THC may be having this effect. They found that the compound binds to cannabinoid receptor type 2 (CB2), which is expressed on immune cells and throughout the gastrointestinal system.
“Thus, in [people] who are at a higher risk of developing colon cancer, THC or other anti-inflammatory agents may be beneficial,” adds Dr. Nagarkatti.
CB2 receptors modulate inflammation in the intestine, and scientists have previously identified them as a potential therapeutic target for IBD. This study provides valuable proof of concept for this idea.
“[C]ompounds that activate CB2 and cause no psychoactive effects may be beneficial to prevent IBD and colon cancer.”
– Study co-author Dr. Mitzi Nagarkatti, chair of the Center for Cancer Drug Discovery at USC
Future efforts will focus on developing non-psychoactive compounds that target the CB2 receptor to elicit similar effects.
The study also provides extensive mechanistic detail on how the pathway works, showing that the action of THC binding to the CB2 receptor triggers an anti-inflammatory process.
As a result, cells in the intestine are less likely to secrete pro-inflammatory molecules and instead secrete anti-inflammatory molecules. These molecules recruit regulatory T cells, which are a type of immune cell that can help resolve inflammation and protect against cancer.
These findings advance the biological understanding of IBD and will be beneficial for future drug development efforts.
It is important to note that this study demonstrates a preventive, but not a curative, effect. This means that there is no evidence to suggest that THC or other CB2 agonists could treat IBD or colon cancer.
This study is also not recommending the use of cannabis to prevent colon cancer. It merely indicates that the development of non-psychoactive compounds targeting the CB2 receptor may be beneficial in people with IBD.