Why does introduction of telomerase not lead to cancer?
Previously, we found that the enzyme, telomerase was present in specialized reproductive cells and most cancer cells that appear to divide indefinitely. Even though telomerase is present in some stem cells of renewal tissues, the levels are generally much lower and these tissues show continuing telomere shortening throughout life. Telomerase works by adding back telomeric DNA to the ends of chromosomes, thus compensating for the losses that normally occur. Most normal cells do not have this enzyme and thus they lose telomeres with each division. A potential paradox was to explain why introduction of telomerase did not result in cancer progression. To understand this, it is important remember that cancer is caused by the accumulation of several alterations that occur over a lifetime, and which affect processes controlling cellular growth rates, responses to growth factors and the ability to invade and undergo metastasis. Telomerase only affects the counting of the number of times a cell
