Marijuana — from issues of legalization to the massively disproportionate arrests of minority youth for its possession — is frequently in the news. However, rarely does the coverage involve a premier Ivy League research institution. A new study published by researchers at Harvard University suggests that the active ingredient in marijuana cuts tumor growth in by 50 percent in common lung cancer and significantly reduces the ability of the cancer to spread. The findings were presented at the annual meeting of the American Association for Cancer Research.
The scientists, who tested the chemical in both lab and mouse studies, say that this is the first set of experiments to show that the compound, Delta-tetrahydrocannabinol (THC), inhibits EGF-induced growth and migration in the epidermal growth factor receptor (EGFR) expressing non-small cell lung cancer cell lines. The reason marijuana is effective is because that lung cancers that over-express EGFR are usually highly aggressive and resistant to chemotherapy. Since cannabinoid receptors are part of the endogenous cannabinoid system and are found throughout the entire body, they can both regulate and repair damage as well as created an atmosphere that makes it hard for tumors to develop and grow.
According to scientists, THC that targets cannabinoid receptors CB1 and CB2 is similar in function to end cannabinoids, which are cannabinoids that are naturally produced in the body and activate these receptors. Thus, THC agents that activate these receptors may be used in a targeted fashion to treat lung cancer. Anju Preet, Ph.D., a researcher in the Division of Experimental Medicine states that “The beauty of this study is that we are showing that a substance of abuse, if used prudently, may offer a new road to therapy against lung cancer.” Dr. Preet believes that via cannabinoid receptors CB1 and CB2, THC is thought to play a role in variety of biological functions, including pain and anxiety control, and inflammation.
Although a medical derivative of THC, known as Marinol, has been approved for use as an appetite stimulant for cancer patients, and a small number of U.S. states allow use of medical marijuana to treat the same side effect, few studies have shown that THC might have anti-tumor activity. Moreover, the only clinical trial testing THC as a treatment against cancer growth was a recently completed British pilot study in human glioblastoma.
In the present study, the researchers first demonstrated that two different lung cancer cell lines as well as patient lung tumor samples express CB1 and CB2, and that non-toxic doses of THC inhibited growth and spread in the cell lines. Next, for three weeks in a row, researchers injected standard doses of THC into mice that had been implanted with human lung cancer cells, and found that tumors were reduced in size and weight by about 50 percent in treated animals compared to a control group and near a60 percent reduction in cancer lesions on the lungs in these mice as well as a significant reduction in protein markers associated with cancer progression.
Although the study demonstrates the effectiveness of marijuana in reducing lung cancer tumors, the researchers do not know why THC inhibits tumor growth, and suggest that the substance could be activating molecules that arrest the cell cycle, may also interfere with angiogenesis and vascularization, which promotes cancer growth.