The treatment loses effectiveness for a significant number of patients with
secondary cancers.
Writing in Nature Medicine, US experts said chemo causes wound-healing cells
around tumours to make a protein that helps the cancer resist treatment.
A UK expert said the next step would be to find a way to block this
effect.
Around 90% of patients with solid cancers, such as breast, prostate, lung and
colon
that spread - metastatic disease - develop resistance to chemotherapy.
Treatment is usually given at intervals, so that the body is not overwhelmed
by its toxicity.
But that allows time for tumour cells to recover
and develop resistance.
In this study, by researchers at the Fred Hutchinson Cancer
Research Center in Seattle looked at fibroblast cells, which normally play a
critical role in wound healing and the production of collagen, the main
component of connective tissue such as tendons.
But chemotherapy causes DNA damage that causes the fibroblasts to produce up
to 30 times more of a protein called WNT16B than they should.
The protein fuels cancer cells to grow and invade surrounding tissue - and to
resist chemotherapy.
Success v failure
It was already known that the protein was involved in the development of
cancers - but not in treatment resistance.
The researchers hope their findings will help find a way to stop this
response, and improve the effectiveness of therapy.
Peter Nelson, who led the research, said: "Cancer therapies are increasingly
evolving to be very specific, targeting key molecular engines that drive the
cancer rather than more generic vulnerabilities, such as damaging DNA.
"Our findings indicate that the tumour microenvironment also can influence
the success or failure of these more precise therapies."
Prof Fran Balkwill, a Cancer Research UK expert on the microenvironment
around tumours, said: "This work fits with other research showing that cancer
treatments don't just affect cancer cells, but can also target cells in and
around tumours.
"Sometimes this can be good - for instance, chemotherapy can stimulate
surrounding healthy immune cells to attack tumours.
"But this work confirms that healthy cells surrounding the tumour can also
help the tumour to become resistant to treatment.
"The next step is to find ways to target these resistance mechanisms to help
make chemotherapy more effective."
read more :
http://www.bbc.co.uk/health/physical_health
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