An ingredient in marijuana may be useful for treating brain cancers, say Spanish researchers from Madrid.
An extract of cannabis was used in the study
Chemicals called cannabinoids could starve tumours to death by halting the growth of blood vessels that feed it, the Complutense University team hope.
By studying mice, the team has shown for the first time how these chemicals block vessel growth.
Their study, published in Cancer Research, also shows the treatment appears to work in humans.
Glioblastoma multiforme is the most common brain cancer and is notoriously difficult to treat.
It can evade destruction by radiotherapy, chemotherapy and surgery.
Dr Manuel Guzmán and colleagues set out to determine whether they could prevent the cancer from growing by destroying its blood supply.
Previous research has shown cannabinoids block the growth of blood vessels in mice, but little is known about how these chemicals do this and whether they might do the same in human tumours.
The researchers first gave mice cancer resembling the human form of brain cancer they wanted to study.
They then treated the mice with cannabinoid and examined the genes of the mice.
The activity of genes associated with blood vessel growth in tumours through the production of a substance called vascular endothelial growth factor (VEGF) was reduced.
Cannabinoids appeared to stifle VEGF production by increasing the activity of a substance that controls cell death, called ceramide.
Lead researcher Dr Guzmán said: "As far as we know, this is the first report showing that ceramide depresses VEGF pathway by interfering with VEGF production."
Their next challenge was to see if cannabinoids had the same effect in humans.
They took samples from two patients with glioblastoma multiforme who had not responded to surgery, chemotherapy and radiotherapy treatment.
Treatment for humans
Samples were taken before and after the patients were treated with cannabinoid solution infused directly into the tumour.
In both patients, VEGF levels in the tumour were reduced following treatment with cannabinoids.
Although they only looked at two patients, the researchers hope their findings could lead to new treatments.
"The present findings provide a novel pharmacological target for cannabinoid-based therapies," said Dr
Dr Richard Sullivan, Head of Clinical Programmes at Cancer Research UK, said: "This research provides an important new lead compound for anti-cancer drugs targeting cancer's blood supply.
"Although this work is at an early stage of development, other research has already demonstrated that VEGF is an important drug target for a range of cancers.
"The key now will be to show further activity in pre-clinical cancer models, find out in which combinations cannabinoids show greatest activity and formulate a product that can be tested in man.
"It is important to note that cannabinoids would need to generate very strong data in the future as there are already a number of VEGF inhibitors in clinical development," he said.