More evidence that breast cancer is not just one disease

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Breast cancer cells have genomes that are chopped up and reassembled far more extensively than scientists previously knew -- and in widely varying ways, researchers from the Wellcome Trust Sanger Institute in the UK said Wednesday in the journal Nature. The finding adds even more weight to the idea that breast cancer is not one disease, but many.

In the study, researchers scanned the genomes of 24 different breast cancer tumors and found 2,166 rearrangements — deletions and duplications in chunks of the genome caused by pieces breaking then sticking back together. Analyzing more closely, the team found that many of these rearrangements were due to tandem duplication, which is when a small segment of DNA gets copied and repeated again and again.

“Despite being the commonest class of rearrangement in breast cancer, tandem duplications have previously been overlooked,” the study’s authors wrote in their paper. That’s because older genetic tools were only sensitive enough to detect larger changes.

The scientists spotted many differences between the 24 cancer cell lines, highlighting the fact that breast cancer can arise from a variety of genetic mistakes. One cancer line displayed just a single rearrangement in its chromosomes. Others had many more, and one line had at least 238. The high number of anomalies in that line could point to a “defect in the machinery that maintains and repairs DNA,” Andy Futreal, one of the study’s authors, said in a statement from the Sanger Institute.
If that’s the case, it is possible that new and more effective cancer-fighting therapies could be designed specifically for those cancers with defective DNA repair machinery, the scientists said.

-- Amina Khan