Telomere Research Provides New Perspective for Treating Cancer

Author:  Falishia Sloan
Institution:  Eastern Virginia Medical School
Date:  November 2007

Researchers at the Swiss Institute for Experimental Cancer Research (ISREC) and at the University of Pavia have found that RNA is present in the components of chromosomes called telomeres. This discovery about telomeres, whose DNA has long been thought to not transcribe into RNA as the rest of the DNA present on a chromosome does, could provide scientists with a novel way of halting the replenishment of telomeres in cancer cells.

DNA held in chromosomes is transcribed into RNA in the nucleus of their respective cells, and are transported out of the nucleus to carry out a variety of functions, including protein synthesis. While the chromosomal DNA is transcribed into RNA, the DNA present on telomeres, which span the end of the chromosomes, has long been thought not to be involved in this transcription process. The scientists of this study, published online October 4th in Science Express, have found that this previous belief is not true, and that telomeres do, in fact, contain RNA that has been transcribed from DNA.

Cellular division includes the replication by division of chromosomes, the structures that hold the DNA information needed to carry genetic information from cell to new cell. To complete their role of protecting the ends of chromosomes from fusion or destruction, telomeres present on the ends of chromosomes contain a ribonucleoprotein enzyme called telomerase that protects the telomeres from destruction. It is a normal occurrence for telomerase to gradually dwindle and telomeres to subsequently shorten with each cellular replication (in fact, telomerase is often absent in the body cells of humans), and this leads to the gradual and eventual inactivity of the cell. After a certain number of replications, the telomeres of a chromosome activate a sort of stop signal to prevent further replication. The dysfunction of the telomeres in providing this stop signal can lead to continuously dividing or damaged chromosomes, in turn leading to cancer or other diseases.

It has been found, however, that in about 90% of human cancers, telomere maintenance occurs, where telomerase continues to regenerate the telomeres long after they, and the cancer cells they are in, should have died. This continuing regeneration of the telomeres leads to a continuing maintenance and lifespan of cancer cells.

While the mechanism behind the maintenance of the telomeres is not well understood, the scientists in this new study have found that a protein in the telomerase enzyme also regulates the RNA present in telomeres. This discovery provides additional clues to telomere function, and perhaps also to additional ways of combating cancer cells.

Senior scientist and an Associate Professor at the EPFL (Ecole Polytechnique Fédérale de Lausanne), Lingner Joachim, PhD, states that the RNA present in the telomeres may be able to serve as a sort of target that can be used to attack the telomere function of the chromosomes and, therefore, disenable cancer cells from growing.

"It's too early to give.a definitive answer," Joachim said. "But the experiments published in the paper suggest that telomeric RNA may provide a new target to attack telomere function in cancer cells to stop their growth."

Written by Falishia Sloan

Reviewed by Emma Wear

Published by Pooja Ghatalia