In recent years, researchers working on forms of telomerase gene therapy have produced evidence to show that increased levels and activity of telomerase does not raise cancer risk in mice. The open access paper and publicity materials noted below report the latest example. Extra telomerase increases the sort of activities that are beneficial in the context of improved regenerative capacity, but might be thought to raise the risk of cancer when they take place in the damaged environment of old tissue. This means more stem cell activity, more cellular replication, and so forth.
Somatic cells are limited in the degree to which they can replicate by the length of their telomeres, repeated DNA sequences at the ends of chromosomes. A little of that length is dropped with each cell replication, and a cell with short telomeres will become senescent or self-destruct, and in either case cease replicating. The primary function of telomerase is to extend telomeres, so the operation of telomerase in somatic cells will act to push them past their evolved limits to replication. Stem cells, on the other hand, naturally deploy telomerase to bypass the telomere countdown and retain the