The Study of Manuel Guzman of Madrid Spain found that cannabinoids, the active components of marijuana, inhibit tumor growth in laboratory animals. They do so by modulating key cell-signalling pathways, thereby inducing direct growth arrest and death of tumor cells, as well as by inhibiting the growth of blood vessels that supply the tumor.

The Guzman study is very important according to Dr. Ethan Russo , a neurologist and world authority on medical cannabis: "Cancer occurs because cells become immortalized; they fail to heed normal signals to turn off growth. A normal function of remodelling in the body requires that cells die on cue. This is called apoptosis, or programmed cell death. That process fails to work in tumors. THC promotes its reappearance so that gliomas, leukemias, melanomas and other cell types will in fact heed the signals, stop dividing, and die."

"But, that is not all," explains Dr. Russo: "The other way that tumors grow is by ensuring that they are nourished: they send out signals to promote angiogenesis, the growth of new blood vessels. Cannabinoids turn off these signals as well. It is truly incredible, and elegant."

In other words, this article explains several ways in which cannabinoids might be used to fight cancer, and, as the article says, "Cannabinoids are usually well tolerated, and do not produce the generalized toxic effects of conventional chemotherapies.