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The chronic inflammation that accompanies ulcerative colitis, a type of inflammatory bowel disease, increases the risk of developing colon cancer. New research in mice suggests a component of cannabis may prevent the development of colitis-associated colon cancer.

Cannabis, also known as marijuana, contains a family of chemicals called cannabinoids, including the psychoactive compound, tetrahydrocannabinol (THC). THC binds to cannabinoid receptors (CB), present throughout the body, altering appetite, pain, mood, and memory. CB1 receptors are more common in the brain, while CB2 receptors are mainly expressed by the immune system.

The investigators conducted a two-part study to determine the effects of THC on gut inflammation. In the first part of the experiment, they gave mice that had colitis THC by mouth (10 milligrams per kilogram body weight) or a placebo treatment twice weekly for nine weeks. They then measured inflammation and cancer development in the colonic tissue of the mice. The mice in the treatment group exhibited statistically significant decreases in tumor initiation and colitis severity. The authors of the study attributed this to decreased expression of the pro-inflammatory cytokine interleukin-22.

In the second part of the experiment, the investigators used a rodent colitis model to study the role of THC in regulating immune cells that express the CB2 receptor. Mice received the same dose of THC daily given to the mice in the first study for seven days or a placebo. Mice in the treatment group had markedly less colonic inflammation. The authors attributed this to decreased activation of the pro-inflammatory dendritic cells and macrophages and increased production of anti-inflammatory T-regulatory cells.

These findings may be important in the fight against colorectal cancer, but the results have their limitations. The dose of THC used in this study is equivalent to 680 milligrams for a 150-pound person, which is far greater than the 10 to 25-milligram range used in some clinical studies. A Cochrane review on the topic of cannabis use for ulcerative colitis concludes that there is insufficient evidence to make strong recommendations about THC safety and efficacy and that additional investigations of cannabis dosing are warranted.

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