People who have Down syndrome hardly ever get tumors, an observation that has long puzzled scientists. They suspected that patients might be getting a bonus dose of cancer-protective genes, because the disorder is caused by an extra copy of a chromosome—specifically, chromosome 21. Researchers at Children’s Hospital Boston and their colleagues found that an added copy of DSCR1, one of the 231 genes on chromosome 21, could inhibit the spread of mouse and human tumors. The gene suppresses the growth of new blood vessels that cancers need by blocking the activity of the protein calcineurin, suggesting a new target for future cancer drugs. The investigators, whose findings were posted online May 20 by Nature (Scientific American is part of the Nature Publishing Group), add that chromosome 21 might possess four or five antiangiogenesis genes.
The extra chromosome arises as a mistake in cell division during embryonic development. Researchers at Tufts Medical Center and their colleagues discovered that the amniotic fluid surrounding Down syndrome fetuses shows evidence of oxidative stress that could harm cells, particularly neural and cardiac tissue. The signs, unfortunately, appear in the second trimester, too late for antioxidants to treat the hallmarks of Down syndrome that arise in the first trimester, such as mental impairment. Still, the team suggests in the June 9 Proceedings of the National Academy of Sciences USA that second-trimester antioxidants might fend off aspects of the syndrome that are yet to be discovered.