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Archive - May 20, 2009

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Anti-Angiogenesis Genes May Contribute to Low Cancer Rate in Down Syndrome

Researchers have provided evidence that the extra copies of two chromosome 21 genes may be responsible, at least in part, for the extremely low cancer rate in those with Down syndrome. The rate of cancer in Down syndrome individuals is lower than 10 percent of that in the general population. It had been proposed that because Down syndrome individuals have an extra copy of chromosome 21, that there may be one or more cancer-protective genes on this chromosome. The late cancer researcher Dr. Judah Folkman proposed that the extra copy of chromosome 21 may contain a gene that blocks angiogenesis, the development of blood vessels essential for cancer's growth. In the current experiments, scientists showed that a single extra copy of the chromosome 21 gene Dscr1 is sufficient to significantly suppress angiogenesis and tumor growth in mice, as well as angiogenesis in human cells. The team also found that levels of DSCR1 protein are elevated in tissues from people with Down syndrome and in a mouse model of the disease. The extra copy of another chromosome 21 gene, Dyrk1A, also appeared to decrease cells' response to an angiogenesis-promoting protein. "I think there may be four or five genes on chromosome 21 that are necessary for angiogenesis suppression," said Dr. Sandra Ryeom, the senior author of the report. "In huge databases of cancer patients with solid tumors, there are very few with Down syndrome. This suggests that protection from chromosome 21 genes is pretty complete." This research was published online on May 20 in Nature. [Press release] [Nature abstract]

Sweet Tooth May Be Achilles Heel of Salmonella

Scientists have shown that the Salmonella food poisoning bacterium requires glucose as a nutrient during infection, and that when it is unable to use this nutrient, infection is prevented. "This is the first time that anyone has identified the nutrients that sustain Salmonella while it is infecting a host's body," says Dr Arthur Thompson, the senior author of the report. Salmonella food poisoning causes infection in approximately 20 million people worldwide each year and is responsible for about 200,000 human deaths. It also infects farm animals and attaches to salad vegetables. During infection, Salmonella bacteria are engulfed by immune cells designed to kill them. Instead, however, the bacteria multiply. The scientists constructed Salmonella mutants unable to transport glucose into the immune cells they occupy and unable to use glucose as food. These mutant strains lost their ability to replicate within the immune cells, rendering them harmless. The mutant strains still stimulate the immune system, and the scientists have filed patents on these mutant strains which could be used to develop vaccines to protect people and animals against poisoning by fully virulent Salmonella. This work was published in the April 20 issue of Infection and Immunity. [Press release]