THC and Cancer: Antitumor Effects of THC
Delta-9-tetrahydrocannabinol (THC), the main active component of marijuana, has demonstrated antitumor properties. According to reports by Galve-Roperh, the antitumor application of THC includes neutralizing altered cells at the base level, leading to the regression of malignant tumors in rats and mice. Researchers suggest that “the results of our studies may pave the way for a new therapeutic approach in the treatment of malignant tumors. Given these findings, we believe it is necessary to consider previous research, particularly studies by the National Toxicology Program, which showed clear antitumor properties of THC. This also highlights the relevance of revisiting the discussion on the medical use of marijuana.”
The experiment involved groups of 70 male and female rats, which were administered 12.5, 25, or 50 mg of THC per 1 kg of body weight, as well as control groups that received none. Mice were fed 125, 250, or 500 mg of THC in their food, or no THC at all. The experiment lasted 104–106 weeks. During this two-year period, body weight decreased, even though all groups consumed the same amount of food. More importantly, survival rates in all THC groups were significantly higher than in the control mice and rats. Among mice, survival rates were comparable across all groups, including those receiving high doses. Cases of apathy accompanied by convulsions and seizures were observed in the THC groups, but only with high doses or immediately after injection.
In both mice and rats, the THC groups no longer showed a tendency toward tumor formation, including malignant tumors, which was attributed to the effects of THC. It was proven that, for several organ systems, the impact of tumor formation was significantly reduced. The painful effects of mammary gland fibroadenoma and cervical tumors were reduced in female rats in the THC groups, as was the development of intratissue adenoma, pancreatic adenoma, and other diseases in male rats. Regarding tissue damage without tumor involvement, increased thyroid follicular cell activity was noted in all THC groups, in which no tumors or neoplasms were found. No direct link was found between toxicity and carcinogenicity.
Regarding the carcinogenic activity of THC in mice, precursors of thyroid adenoma were observed only in groups with low doses of THC (125 mg/kg). In males, there were 6/60, 3/61, and 1/57 cases at doses of 125, 250, and 500 mg THC, respectively, compared to 0/60 in controls; in females, 9/60, 3/60, and 1/60 cases, compared to 4/60 in controls. In fact, this was not associated with THC action due to the lack of proportionality and correlation. Moreover, there was a sharp decrease in both benign and malignant tumors in both male and female subjects.
The reduction in body weight may also be explained by decreased tumor activity, which was mainly suppressed in hormone-regulated organs. After the latest studies, it became clear that the reduction in tumor numbers in six organs was linked to THC action.
Our two-year studies showed that the antitumor effects of THC are not limited to injections of the drug, and these effects influence spontaneous tumors in the bodies of mice and rats. The antitumor effects of THC are systemic and apply to various tumor types in different organs. The studies suggest that these effects are hormone-related and may explain the weight loss. There was a significant reduction in both benign and malignant tumors in all organs in both rats and mice after THC administration: in male rats, tumors were observed in 98% of controls versus 98%, 92%, and 90% in groups receiving 12.5, 25, and 50 mg/kg, respectively. In female rats: 88% in controls versus 82%, 86%, and 79% in the THC groups. The results were even more striking in male mice—73% in controls versus 30% in the THC groups. In females: 77% in controls versus 27% in the THC groups.
Interestingly, the dosage in Galve-Roperh’s studies was the same as in ours. Their results were also similar in that THC exposure did not affect blood or overall metabolic balance, nor the ability to absorb and process food and water. For example, to study the anticancer action of THC, animals were exposed to carcinogens (9,10-dimethylbenz[a]anthracene), which induced mammary tumors. The relationship between weight loss and the antitumor effect of THC also requires further study.
Genetic toxicology has proven the absence of THC mutagenicity. As a result of the research, THC did not cause any chromosomal changes, with or without the S9 catalyzing enzyme. No changes were found in erythrocytes either. At the end of all studies, it was concluded that THC does not affect the genome.
Long-term studies and bioanalyses have been and are being conducted to identify agents that directly cause cancer, as well as those that significantly increase cancer risk in people exposed to carcinogens. These studies can also help in the search for anticancer agents. Therefore, our research, in which rats and mice were exposed to THC for two years, showed weight loss, increased survival rates, and reduced tumor activity, mainly in hormone-controlled organs. All these studies on THC lead to the idea that cannabinoids may indeed be effective anticancer agents.