Marijuana Cuts Lung Cancer Tumor Growth In Half, Study Shows

ScienceDaily (Apr. 17, 2007) - 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.

Acting through cannabinoid receptors CB1 and CB2, endocannabinoids (as
well as THC) are 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, Preet says. 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. "When the cells are pretreated with THC,
they have less EGFR stimulated invasion as measured by various in-vitro
assays," Preet said.

Then, for three weeks, 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. There was also about 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.

Although the researchers do not know why THC inhibits tumor growth,
they say the substance could be activating molecules that arrest the
cell cycle. They speculate that THC may also interfere with angiogenesis
and vascularization, which promotes cancer growth.

Preet says much work is needed to clarify the pathway by which THC
functions, and cautions that some animal studies have shown that THC can
stimulate some cancers. "THC offers some promise, but we have a long way
to go before we know what its potential is," she said.
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