Scientists have found a potential new mechanism to stimulate the body's own ability to fight cancer using Baculillus Calmette-Guerin (BCG) -- the germ commonly used to inoculate against tuberculosis (TB).
The findings are published online in the British Journal of Cancer on August 10, 2011.
The researchers, Dr Wai Liu and Professor Angus Dalgleish from St George's, University of London, say this new data suggests a mechanism by which vaccines could enhance the anti-cancer activity of currently available therapies. However, they warn that this is an early-stage study and that there is much more research to be done before patients will benefit.
In laboratory-based experiments conducted with human tumour cells outside of the body, the researchers showed that a small amount of BCG can instruct white blood cells to produce chemicals called cytokines. These make tumour cells more likely to be detected by the body's immune system.
"Cancerous cells are known to camouflage themselves as healthy cells. This means our blood cells responsible for immunity aren't able to recognise the cancerous cells as being a problem and so the disease is able to continue to spread," explains lead researcher Dr Wai Liu. "This study found that a small quantity of BCG -- similar to the amount that is administered in a TB inoculation -- can help the immune system recognise the cancer cells as 'foreign'. The immune system can then attack these cells in the same way it would any other infection."
The cytokines produced as a consequence of the BCG jab set off a chain of events that begins with the hijacking of the tumour and forcing it to switch off its camouflage. This renders it visible to the body's immune system, and so the white blood cells responsible for destroying 'foreign' cells now have targets to attack.
The researchers tested the BCG injection on human cells from lung, breast, colon, pancreatic and skin cancer. Their research showed that in three of the cancer types -- lung, breast and colon -- the restoration of their visibility to immune cells was increased. Within the limits of the laboratory-based study, those cancer cells with reduced camouflage were then successfully targeted by white cells responsible for killing cancer cells.
Scientific knowledge around using drugs to stimulate the body's natural defences against cancer is becoming more prominent. The researchers believe that these findings provide more evidence that, in the future, this treatment method may provide further options for patients that could be used in combination with existing cancer drug treatment.
"Using the body's own immune system is a relatively new way of thinking in the development of cancer treatments, and scientists are still building up a knowledge base about it. If successful, this method of treatment could be used in combination with existing cancer drugs. It could potentially see patients taking less medication, having fewer and less severe side effects and recovering quicker," says Dr Liu.
"This research is at an early stage of investigation, and so far has analysed the reaction of human blood outside of the body, so more work is needed before these findings can be used in practice. The next stage will be to develop a compound suitable for clinical trials," he concludes.
- W M Liu, D W Fowler, A M Gravett, P Smith, A G Dalgleish. Supernatants from lymphocytes stimulated with Bacillus Calmette-Guerin can modify the antigenicity of tumours and stimulate allogeneic T-cell responses. British Journal of Cancer, 2011; DOI: 10.1038/bjc.2011.306
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