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Testing breast cancer cells for how closely they resemble stem cells could identify women with the most aggressive disease, a new study suggests. Breast cancers with a pattern of gene activity similar to that of adult stem cells had a high chance of spreading to other parts of the body, according to the study in Breast Cancer Research (2015;17:31).


"Assessing a breast cancer's pattern of activity in these stem cell genes has the potential to identify women who might need intensive treatment to prevent their disease recurring or spreading," said the researchers, from the Institute of Cancer Research in London, King's College London, and Cardiff University's European Cancer Stem Cell Research Institute.


The researchers identified a set of 323 genes whose activity was turned up to high levels in normal breast stem cells in mice and, as explained in a news release, cross-referenced their panel of normal stem cell genes against the genetic profiles of tumors from 579 women with triple-negative breast cancer.


The tumor samples were divided into two categories based on their score for the activity of the stem cell genes. Women with triple-negative tumors in the highest-scoring category were much less likely to stay free of breast cancer than those with the lowest-scoring tumors. Those with tumors from the higher-scoring group had an approximately 10 percent chance of avoiding relapse after 10 years, while women from the low-scoring group had a chance of about 60 percent of avoiding relapse.


The results show that the cells of aggressive triple-negative breast cancers are particularly "stem-cell-like," taking on properties of stem cells such as self-renewal to help them grow and spread, the researcher said. The findings also suggest that some of the 323 genes could be promising targets for potential cancer drugs.


Study leader Matthew Smalley, Deputy Director of the European Cancer Stem Cell Research Institute, said: "Triple-negative breast cancer accounts for around 15 percent of breast cancers, but is more difficult to treat than other cancer types as it is not suitable for treatments such as anti-hormonal therapy. It's particularly important to understand the genetic factors that help it to spread around the body, and we were excited to find that a key factor seems to be the degree to which gene activity resembles that of stem cells.


"Although our work is not yet ready for clinical use, our next step will be to explore which of these 323 genes are the most important drivers of the disease and to use these to develop a new genetic test."


Another coauthor, Clare Isacke, Professor of Molecular Cell Biology at the Institute of Cancer Research, added in the news release: "Cancer cells can behave very much like stem cells, but stem cells gone bad. They find a way to activate genes which are usually only turned up in normal stem cells, giving them characteristics-such as self-renewal and immortality-that make them more difficult to treat.


"Our study could ultimately help lead to a genetic test assessing breast cancer cells for how closely they resemble stem cells. Picking out women with this type of aggressive disease could give us new ways of personalizing treatment."