May 18, 2012
LONDON, May 18 — Scientists have mapped the complete genetic
codes of 21 breast cancers and created a catalogue of the mutations that
accumulate in breast cells, raising hopes that the disease may be able
to be spotted earlier and treated more effectively in future.
The research, the first of its kind, untangles the genetic history of
how cancer evolves, allowing scientists to identify mutational patterns
that fuel the growth of breast tumours, and start to work out the
processes behind them.
“These
findings have implications for our understanding of how breast cancers
develop over the decades before diagnosis in adults and might help to
find possible targets for improved diagnosis or therapeutic intervention
in the future,” said Mike Stratton, who led the research team.
“This is the first time we’ve been able to delve fully into breast
cancer genomes in such a thorough way,” said Peter Campbell, head of
cancer genetics and genomics at the Wellcome Trust Sanger Institute in
Cambridge, where the studies were led.
The work had given scientists “a full panoramic view of the cancer
genome” and helped them identify “mutational patterns rather than
individual mutations in specific genes”, he added.
“We’ve known for many years now that all cancers are due to
abnormalities of DNA... that occur in every single cell of the body over
the course of a lifetime,” said Stratton.
“But although we’ve known that, it’s remarkable how rudimentary our
knowledge is about what the processes are that cause these
abnormalities, these mutations in our DNA.”
Stratton’s team sequenced the genomes of the 21 breast cancers and
catalogued all the mutations. They found five major processes that cause
one letter of code to be changed to another letter. Genetic code comes
in four DNA letters, A, C, G and T.
Stratton said one of the most exciting findings was that one of these
processes is characterised by small pockets of massively mutated
regions of the genome. This sudden “storm” of mutations is often seen in breast cancers, he explained in an audio briefing. While his team don’t fully understand the process behind these
storms, they think it may be down to components of the cell whose normal
function is to edit, or mutate, DNA.
“What we believe... is that sometimes in normal cells... this stops
functioning properly and over-functions. It causes too many mutations
and the accumulation of those mutations pushes the cell along the line
to become cancer.”
The team found that these and other mutations accumulate in breast
cells over many years, initially slowly, but picking up greater momentum
as genetic damage builds up. By the time the breast cancers are large enough to be diagnosed, they
are made up of a number of genetically related families of cells, with
one family dominating the cancer, Stratton explained.
Mark Walport, director of the Wellcome Trust which helped fund the
work, said the results showed how scientists are starting to see the
landscape of mutations in breast cancer “in something approaching its
full complexity”.
“As this work continues, we can hope to understand how breast cancer
develops and thus how it might be treated more effectively,” he said in a
statement. — Reuters
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