The active ingredient in marijuana cuts tumor growth in common lung cancer in half and significantly reduces the ability of the cancer to spread, say researchers at Harvard University who tested the chemical in both lab and mouse studies.

They say this is the first set of experiments to show that the compound, Delta-tetrahydrocannabinol (THC), inhibits EGF-induced growth and migration in epidermal growth factor receptor (EGFR) expressing non-small cell lung cancer cell lines. Lung cancers that over-express EGFR are usually highly aggressive and resistant to chemotherapy.

THC that targets cannabinoid receptors CB1 and CB2 is similar in function to endocannabinoids, which are cannabinoids that are naturally produced in the body and activate these receptors. The researchers suggest that THC or other designer agents that activate these receptors might be used in a targeted fashion to treat 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.