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Science : Hidden damage triggers cancer

发布时间:2019-02-27 10:14:06来源:未知点击:

By Ben Crystall SOME women with breast cancer may be at risk of recurring disease because their tumour is surrounded by tissue that looks healthy but is genetically abnormal, say researchers in the US. The scientists have found specific genetic changes in tissue surrounding tumours which, they believe, make the cells more likely to turn cancerous than normal cells. The discovery could affect the way breast cancer is treated. A team from the California Pacific Medical Center and the University of California, San Francisco, and Northwestern University School of Medicine, Evanston, examined the “normal” cells around breast tumours for hidden genetic damage. They dissected human breast tumours and isolated DNA from both the malignant areas and from the adjacent tissue. Surprisingly, in eight out of the 30 cases studied, the supposedly normal tissue from around the tumour actually showed genetic damage (Science, vol 274, p 2057). Normal cells contain two copies of each chromosome, one from each of the parents. But in the breast cells the researchers examined, segments of genetic material were missing from one copy of certain chromosome pairs—a condition known as a “loss of heterozygosity”. In most cells, the missing genetic material was from the short arm of chromosome 3, says Helene Smith, who led the team. This is the site of a gene that is already known to act as a so-called “tumour suppressor”. Tumour suppressor genes prevent some of the changes that make a cell cancerous. If a person has one mutated form of the gene and then loses the healthy copy in some cells, the cells can divide unchecked. Most cells pass through a series of distinct stages as they turn cancerous. But researchers have noticed that some breast cancers appear to develop directly from normal cells, bypassing these intermediate forms. Smith believes that some breast tumours may arise from the genetically damaged tissue. Such tissue could be present in the breast even before puberty, she says. Girls with this type of tissue may be more vulnerable to certain risk factors for cancer, such as radiation. The results may also affect treatment. If surgeons simply remove the tumour and no surrounding tissue,