Study sheds light on link between Down's and lower cancer risk
Tuesday 26 May 2009
US scientists have discovered that an extra copy of a particular gene may be the reason people with Down's syndrome face a lower-than-average risk of developing cancer.
It has previously been suggested that could be because of the extra copy of chromosome 21 carried by people with Down's syndrome.
Chromosome 21 is thought to carry genes that block angiogenesis, the process by which new blood vessels are created to carry nutrients to a tumour.
This theory is supported by the fact that people with Down's are also less likely to develop the eye disease macular degeneration, which also involves angiogenesis.
Publishing their results in the journal Nature, scientists at Children's Hospital Boston carried out studies on mice and human cells.
Dr Sandra Ryeom, a cancer researcher at Children's, found that mice which had a third copy of a chromosome 21 gene called Dscr1 experienced significantly less angiogenesis and tumour growth than those with the usual two copies of the gene.
The team tested tissue samples from people with Down's syndrome and confirmed that they have elevated levels of the protein made by the Dscr1 gene.
This protein suppresses the activity of another protein called vascular endothelial growth factor (VEGF), which promotes blood vessel growth.
The scientists also discovered that an extra copy of a different gene - called Dyrk1A - could also reduce blood vessel growth in mice with Down's syndrome.
The team then confirmed their findings in human cells, showing that tumours which were grown in cells derived from a person with Down's syndrome did not have properly-formed blood vessels.
Dr Ryeom revealed that the studies on human cells "helped validate and confirm that the suppression of angiogenesis that we saw in mouse models also holds true in humans".
"It suggests that these two genes might point to a viable cancer therapy."
The scientist continued: "I think there may be four or five genes on chromosome 21 that are necessary for angiogenesis suppression.
"In huge databases of cancer patients with solid tumours, there are very few with Down's syndrome. This suggests that protection from chromosome 21 genes is pretty complete."
Dr Kairbaan Hodivala-Dilke, a Cancer Research UK scientist at Queen Mary, University of London, who is also researching the link between Down's and cancer, commented: "These lab-based findings show that having three copies of the DSCR1 gene, which is found on chromosome 21, is sufficient to protect against tumour growth.
"This raises several important questions about the roles of other chromosome 21 genes that might help regulate tumour growth. The next stage is to think about how we might be able to exploit this research to improve cancer treatments in the future."
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