Study finds compound in the plant can help shrink aggressive brain tumours
Cannabis can have a dramatic effect on aggressive forms of brain cancer, a new study shows.
The new research, conducted by specialists at St George’s, University of London, studied the treatment of brain tumours in the laboratory.
It found the most effective treatment was to combine active chemical components of the cannabis plant, which are known as cannabinoids.
Two of these – called tetrahydrocannabinol (THC) and cannabidiol (CBD) – were tested as part of the research into brain cancer.
This is particularly difficult to treat and claims the lives of about 5,200 patients each year.
It also has a particularly poor prognosis as the rate of survival after five years of patients’ diagnosis is around 10 per cent, the new research is the first to show a drastic effect when combining THC and CBD with radiation.
Dr Wai Liu, Senior Research Fellow and lead researcher on the project, said: ‘The results are extremely exciting.
‘The tumours were treated in a variety of ways – either with no treatment, the cannabinoids alone, and radiation alone.
‘Or, with both the cannabinoids and radiation at the same time.
‘Those treated with both radiation and the cannabinoids saw the most beneficial results and a drastic reduction in size.
In some cases, the tumours effectively disappeared in the animals.
‘The benefits of the cannabis plant elements were known before.
‘But the drastic reduction of brain cancers – if used with radiation – is something new and may well prove promising for patients who are in gravely serious situations with such cancers in the future.’
Here, writing in The Conversation, Dr Lui describes his work in detail…
Widely proscribed around the world for its recreational uses, cannabis is being used in a number of different therapeutic ways to bring relief for severe medical conditions.
Products using cannabinoids, the active components of the cannabis plant, have been licensed for medical use.
Sativex, for example, which contains an equal mixture of the cannabinoids tetrahydrocannabinol (THC) and cannabidiol (CBD), is already licenced as a mouth spray for multiple sclerosis.
In the US, dronabinol and nabilone are commercially available for treating cancer-related side effects.
Now, in a study published in the journal Molecular Cancer Therapeutics, we’ve also shown that cannabinoids could play a role in treating one of the most aggressive cancers in adults.
There are more than 85 cannabinoids, which are known to bind to unique receptors in cells and which receive outside chemical signals.
These receptors feed into signalling pathways, telling cells what to do. Recent studies have shown that some cannabinoids have potent anti-cancer action.
For example, both THC and CBD have been shown in a number of laboratory studies to effectively induce cell death in tumour cells by modifying the faulty signalling pathways inside these cells.
Depending on the cell type this can disrupt tumour growth or start to kill it.
The psychoactivity associated with some cannabinoids, principally THC (which gives people a cannabis high), is also mediated via the same receptors.
Because these receptors are found in the highest abundances in brain cells, it follows that brain tumours also rich in these receptors may respond best to cannabinoids.
We wanted to investigate the anti-cancer effects of Sativex in glioma cells.
High-grade glioma is an aggressive cancer, with very low long-term survival rates.
Statistics show that just over a third (36 per cent) of adult patients in the UK with glioma live for at least a year, while the five-year survival rate is 10 per cent.
Depending on the individual, treatment can consist of surgery, radiotherapy, and/or chemotherapy with the drug temozolomide.
However, due primarily to the intricate localisation of the tumour in the brain and its invasive behaviour, these treatments remain largely unsuccessful.
However, as our study showed, combining radiotherapy with cannabinoid treatment had a big effect.
FINDING THE RIGHT DOSE
We first had to perform lab tests on cells to optimise the doses of the cannabinoids, and showed that CBD and THC combined favourably.
We found that to achieve a 50% kill rate of glioma cells, a dose of 14mM (millimolar – a measure of amount-of-substance concentration) of CBD or 19mM of THC would be needed if each was used singularly.
However, when used in combination, the concentrations required to achieve the same magnitude of cell kill is significantly reduced to just 7mM for each.
This apparent reduction in the doses of the cannabinoids, in particular THC, without a loss of overall anti-cancer action is particularly attractive as unwanted side effects are also reduced.
Once we had these results, we then tested the impact of combining the cannabinoids with radiation in mice with glioma.
The efficacy of this treatment was tracked using sophisticated MRI technology – and we determined the effects on tumour growth of either CBD and THC together, radiation, or the combination of both.
The drugs were used at suboptimal doses to allow us to see if there was any improvement in the therapy from combining them.
BALANCING ANTI-CANCER WITH PSYCHOACTIVE
In principle, patients treated with THC could experience some psychoactive activity.
But the secret to successfully exploiting cannabinoids as a treatment for cancer is to balance the desired anti-cancer effects with the less desirable psychoactive effects.
This is possible, as some cannabinoids seem to function independently of the receptors and so do not engage the adverse effects. CBD is one such cannabinoid.
The doses of THC we selected were below the psychoactive level, but together with CBD it partnered well to give the best overall anti-cancer effect.
Our results showed that the dose of radiation we used had no dramatic effect on tumour growth, whereas CBD and THC administered together marginally reduced tumour progression.
However, combining the cannabinoids with radiation further impeded the rate at which tumour growth progressed and was virtually stagnant throughout the course of the treatment.
Correspondingly, tumour sizes on the final day of the study were significantly smaller in these subjects compared with any of the others.
The results are promising. There may be other applications but for now it could provide a way of breaking through glioma and saving more lives.
Written by Wai Liu for the Daily Mail, November 26, 2014.
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