Delta-tetrahydrocannabinol (THC), the active ingredient in marijuana, has the potential to cut tumor growth in common lung cancer in half and significantly reduce the ability of the cancer to spread. This finding was disclosed by researchers at Harvard University who tested the chemical in both lab and mouse studies.
The compound inhibits EGF-induced growth and migration in epidermal growth factor receptor (EGFR) expressing non-small cell lung cancer cell lines. It is worthwhile to note that lung cancers, which are characterized by over-expression of EGFR, are generally highly aggressive and resistant to chemotherapy.
The active marijuana ingredient is similar in function to endocannabinoids and targets cannabinoid receptors CB1 and CB2. Endocannabinoids are naturally-producing cannabinoids in the body and activate the receptors CB1 and CB2.
It was suggested by the researchers that Delta-tetrahydrocannabinol (THC) or other designer agents that activate these receptors could be used in a targeted manner for treating lung cancer.
“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,” said Anju Preet, Ph.D., a researcher in the Division of Experimental Medicine.
Endocannabinoids (as well as THC), acting through cannabinoid receptors CB1 and CB2, are considered to play a role in variety of biological functions, such as pain control and inflammation. Even though Marinol, a medical derivative of THC, is approved for use as an appetite stimulant for cancer patients, and a small number of U.S. states allow use of medical marijuana for treating the same side effects, few studies have suggested that THC could have anti-tumor activity, according to Preet.
Researchers, in the present study, demonstrated that two different lung cancer cell lines and patient lung tumor samples express CB1 and CB2. It was also suggested that non-toxic doses of THC inhibited growth and spread in the cell lines. “When the cells are pretreated with THC, they have less EGFR stimulated invasion as measured by various in-vitro assays,” Preet said.
During the study, the researchers injected standard doses of THC into mice that had been implanted with human lung cancer cells for three weeks. They found that tumors were reduced in size and weight by about 50 percent in treated animals compared to a control group. The researchers were also able to notice a 60 percent reduction in cancer lesions on the lungs in these mice as well as a significant reduction in protein markers associated with cancer progression, Preet says.
The researchers said the substance could be activating molecules that arrest the cell cycle though they were clueless as to why THC inhibits tumor growth. It was speculated that THC may also interfere with angiogenesis and vascularization that promotes growth of cancer.
“THC offers some promise, but we have a long way to go before we know what its potential is,” Preet said. Preet also suggested that there is much work required for clarifying the pathway by which THC functions, and cautions that some animal studies have shown that THC could stimulate some cancers.
American Association for Cancer Research http://www.aacr.org/