People With Down Syndrome Less Likely To Have Cancer

By Margarita Nahapetyan

Individuals with Down syndrome seem to have a lower risk of developing many types of cancer and the reason is that they have extra copies of chromosome that helps to keep tumors from feeding themselves and growing, according to U.S. researchers from Boston.

Scientists at Harvard Medical School and at the Children's Hospital of Boston say that solid tumors are very rare in people with Down syndrome and explain with certainty that it happens due to 231 extra genes these individuals inherit with their extra copy of chromosome 21. To be more specific, people usually carry two copies of the 23 chromosomes that together store all their genetic data, one from each parent. Down's syndrome is a genetic disorder which occurs because of the presence of one more, a third copy of chromosome 21 - a gene called DSCR1 (Down Syndrome Candidate Region-1). It has been known for a while that individuals with Down's syndrome are less likely to develop certain types of cancer, compared to those who do not have the disorder. However, the reason why it happens so, has been unclear.

In the latest study, Sandra Ryeom, PhD, a cancer researcher with the Children's Vascular Biology Program at Children's Hospital and a cell biologist at Harvard Medical School, and her colleagues showed that a protein DSCR1, in combination with one of the genes that is also found on chromosome 21, interferes with the signals a tumor depends on in order to stimulate growth of its own blood vessels. Without these vessels feeding the tumor with its own supply of blood, it is unable to grow.

After conducting a series of experiments, the investigators found that DSCR1 protein is overproduced in people with Down syndrome, and that it is also overproduced in about the same amounts in a mouse model of Down syndrome. Tumors in mice models of Down syndrome grew fifty per cent more slowly, compared to those of healthy mice, the team revealed. Blood vessels budded in tumor-like tissues grown from stem cells engineered from one volunteer with Down syndrome but never completely formed. The difference suggests that the findings in mice might also be true in people, Dr. Ryeom noted.

Doctors already use a number of anti-angiogenic drugs for the treatment of cancer. If DSCR1 could be used for a derivation of a new drug, this new drug could also target the growth of blood vessels in cancer, the researchers said, pointing out to a new potential therapeutic pathway. Another potential drug, called endostatin, which is based on another anti-angiogenesis gene on chromosome 21, is now being tested on people. According to the U.S. National Institutes of Health, more than 80 per cent of experimental drugs never even make it to the testings in humans.

This study is based on the research of U.S. angiogenesis pioneer Dr. Judah Folkman, who passed away in 2008. Dr. Folkman hypothesized that angiogenesis inhibition might be key to preventing cancers from forming. Dr. Folkman's initial theory immersed, in part, after the observation that individuals with Down syndrome also suffered fewer angiogenesis-related diseases such as diabetic retinopathy (an eye disease related to diabetes), atherosclerosis (hardened arteries), and the eye disease macular degeneration.

The study is published in the May 20 online issue of the journal Nature.