Nobel Medicine Prize - 2009

This year’s Nobel Prize is awarded to three scientists (Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak ) who have solved one of biology’s great mysteries: How are the chromosomes that carry our genes copied in their entirety during cell division and protected against breakdown? The Nobel Laureates have shown that the answer lies in the chromosomes’ ends – the telomeres – and in the enzyme that forms them – telomerase.

Telomerase and cancer

Most normal cells seldom divide. Their chromosomes do not become too short and their telomerase does not have to be particularly active. Cancer cells, on the other hand, have an unlimited capacity to divide. But how can they retain their telomeres and escape senescence?

It has been shown that 80 to 90 percent of all cancer cells have abnormally high telomerase activity. This prevents them from losing their telomeres despite going through many cell replication cycles. Scientists believe that successive telomere shortening in normal cells can be an important protective mechanism to counteract the uncontrolled cell division that characterizes cancer.

This has aroused hope that it will be possible to treat cancer by blocking telomerase, using either substances that inhibit telomerase activity, or vaccines that cause the immune system to to attack cells with excessive telomerase activity. Several such vaccines are currently being tested in clinical trials on humans.

But many problems remain to be overcome before telomerase can be an effective target for cancer therapy. Merely reducing telomerase activity may not be enough, because some cancer cells have found alternative means of producing telomeres, independent of telomerase. There is also a risk of damage to healthy cells in which high telomerase activity is normal, particularly stem cells.

The importance of functional telomeres in the body’s stem cells is illustrated by the fact that several congenital diseases arise because of defective telomerase. These include some severe forms of inherited anemia, where inadequate replication of stem cells in bone marrow leads to a lack of red blood cells. Certain inherited diseases of the skin and lung are also related to telomerase defects.

For more details: visit Nobel Prize website