A team of Spanish researchers has discovered that cannabinoids, the active ingredients in marijuana, make brain tumors shrink by halting the growth of blood vessels that feed the tumors, reports New Scientist. The researchers have successfully tested the effect of this cannabis extract on thirty mice which were given a cancer similar to the human brain cancer (glioblastoma multiforme). More importantly, they also successfully tested the procedure on two human patients who had glioblastoma multiforme and had not responded to chemotherapy, radiotherapy or surgery. Of course, these results are encouraging, even if larger studies need to be done to be sure that these cannabinoids are really effective on human brain cancers, and possibly other forms of cancers. Read more...

Here is the introduction of the New Scientist article.

Cannabis extracts may shrink brain tumours and other cancers by blocking the growth of the blood vessels which feed them, suggests a new study.

An active component of the street drug has previously been shown to improve brain tumours in rats. But now Manuel Guzmán at Complutense University, Spain, and colleagues have demonstrated how the cannabis extracts block a key chemical needed for tumours to sprout blood vessels -- a process called angiogenesis.

Will this turn on a new weapon against cancer?

Cristina Blázquez at Complutense University, and one of the team, stresses the results are preliminary. "But it’s a good point to start and continue."

"The cannabinoid inhibits the angiogenesis response - if a tumour doesn’t do angiogenesis, it doesn’t grow," she explains. "So if you can improve angiogenesis on one side and kill the tumour cells on the other side, you can try for a therapy for cancer."

What kind of tests were done?

The team tested the effects of delta-9-tetrahydrocannabinol in 30 mice. They found the marijuana extract inhibited the expression of several genes related to the production of a chemical called vascular endothelial growth factor (VEGF).

VEGF is critical for angiogenesis, which allows tumours to grow a network of blood vessels to supply their growth. The cannabinoid significantly lowered the activity of VEGF in the mice and two human brain cancer patients, the study showed.

In "Cannabis extract makes brain tumors shrink, halts growth of blood vessels," Medical News Today gives other details about the tests done on human patients.

[The researchers] selected two patients who had glioblastoma multiforme and had not responded to chemotherapy, radiotherapy or surgery. The scientists took samples from them before and after treating them with a cannabinoids solution -- this was administered directly into the tumor.

Amazingly, both patients experienced reduced VEGF levels in the tumor as a result of treatment with cannabinoids.

The researchers said that the results were encouraging. In order to be sure about their findings they need to carry out a larger study, they said.

Here you can see the effect of the treatment on the two patients with brain cancers. VEGFR-2 activation is shown in green and its expression in red. Cell nuclei are stained in blue. Relative values of activated-VEGFR-2 pixels are displayed in parentheses and total-VEGFR-2 pixels in square brackets are given for the two patients per cell nucleus. (Credit: Cancer Research).

For more information, you also can read this news release from the American Association for Cancer Research, "Marijuana ingredient inhibits VEGF pathway required for brain tumor blood vessels."

The research work has been published by the Cancer Research journal under the title "Cannabinoids Inhibit the Vascular Endothelial Growth Factor Pathway in Gliomas." Here are two links to the abstract and to the full paper (PDF format, 7 pages, 732 KB). The above illustration comes from this paper.

Sources: Shaoni Bhattacharya, New Scientist, August 15, 2004; Medical News Today, August 15, 2004; American Association for Cancer Research news release, via EurekAlert!, August 15, 2004; Cancer Research, Vol. 64, Num. 16, Pages 5617-5623, August 15, 2004