The roles of telomeres and telomerase in cellular immortalization and the development of cancer.

Normal human cells have a limited lifespan in culture called the Hayflick limit. Recent studies have indicated that telomere shortening is one of the important meters utilized by cells to determine the Hayflick limit, and that activation of a mechanism to maintain telomere length is essential for cells to become immortal. It is generally believed that cells must have a means to maintain telomeres in order to progress to malignancy. Most cancers do this by activating an enzyme called telomerase which adds telomeric repeats to the telomere ends. Recently, expression of this enzyme has been shown to extend the lifespan of cells. This review discusses the research that led to the discovery of telomerase, the characteristics of telomerase complex, and how recent and future advances in the telomerase field may lead to better diagnostic and treatment protocols for many different cancer types.