While leukemia treatment is largely successful, some patients cannot be treated with conventional therapy; 25 percent of children fail treatment, leaving them with a poor-prognosis outcome. Scientists have previously reported that Δ9-THC has anti-cancer properties, so its use as an anti-leukemia drug may be promising, however, the psychoactive side effects, as well as its current legal status, complicate its use in cancer chemotherapy. Researchers are now trying to identify the molecular pathways targeted by Δ9-THC in order to develop new drugs that combat the same disease-pathway without the unwanted side effects.
In a study published in the February 2005 issue of Blood, Dr. Wai Man Liu and colleagues at St. Bartholomew's Hospital in London reported that Δ9-THC induced cell death in a panel of leukemia cells, including two AML cell lines. Surprisingly, Dr. Lui's group found that neither CB1 or CB2—the two receptors thought to mediate Δ9-THC effects—were involved in the leukemia cell death. Activation of the CB1 receptor in the brain produces the psychoactive effects associated with marijuana use. The CB2 receptor is usually found in cells of the immune system and may regulate immune function. Moreover, the anti-leukemia properties of Δ9-THC did not involve the p53 protein, which is often involved in cancer cell death; thus Δ9-THC did not appear to function through known pathways.