This very interesting study induced telomerase in mice with modified viruses. They report a 24% increase in lifespan and no increase in cancers.
-?? I've read several times on this board that mice have super-long telomeres to begin with. -?
Rats have telomeres long enough for several lifetimes. Even when telomerase was experimentally deleted from their chromosomes, it didn't hurt them. Not right away--In humans, both in vivo and in vitro, telomere shortening appears to be a major component of cell senescence and ageing ...However, this is less apparent in mice because of the very long telomeres (30–150 kb). Telomere shortening has been extensively studied in mice, especially in telomerase-deficient knockout mice. In these mice, the critical RNA component of telomerase, mTERC, has been inactivated by homologous recombination. However, it is only after four to six generations that telomere shortening really becomes an issue.
http://www.ncbi.nlm....cles/PMC149817/
We might be overestimating the robustness of mouse telomeres. Check out this post and refs therein. Blasco's group is saying that mouse telomeres shorten at 100 times the rate of humans(!) (really?)