New evidence that TB vaccine can stimulate body to fight cancer
16 August 2011
Researchers at St George’s University of London have found a
potential new mechanism to stimulate the body’s own ability to fight
cancer using Baculillus Calmette-Guerin (BCG), the bacteria commonly
used to inoculate against tuberculosis (TB). The findings were published
online in the British Journal of Cancer.
The researchers, Dr Wai
Liu and Professor Angus Dalgleish 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.
Reference
W M Liu, D W Fowler, A M Gravett, P Smith and 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
advance online publication 9 August 2011; doi: 10.1038/bjc.2011.306,
www.nature.com/bjc/journal/vaop/ncurrent/abs/bjc2011306a.html