---------- Forwarded message ----------
Date: Fri, 01 Mar 1996 14:48:16 +0000
From: David Kipling <davidk at hgu.mrc.ac.uk>
To: ageing at net.bio.net
Subject: Re: Learned Helplessness About Immortality (fwd)
> Consider the discovery of telomerase, the 'immortality' enzyme in cancer
> cells. If telomerase is manipulated into healthy cells, we may literally
> be able to stop aging.
Hi
There is a big leap of faith here. Telomerase may ne necessary for tumor
cells to continue growing but that does *not* mean that the reason normal,
somatic cells stop growing normally has anything to do with telomeres and
telomerase. To put it bluntly, in vivo many cells cease growth before the
equivalent # of generations that they would undergo in vitro (Hayflick
limit). This is terminal differentiation.
Good examples of this comes from the behaviour of cells in multistage
carcinogenesis systems. The first oncogenic transformation overcomes the
differentiation/arrest signal and allows the cells to continue growing -
without telomerase activation. Later on, as even more divisions are
required, telomerase is sometimes seen to be up-regulated. The point is
that the cells stopped dividing in the first place not because of a lack of
telomerase, but because of normal cellular differentiation.
If this is true, then ageing problems will come down more to questions of
cellular regeneration (getting out of my field here).
David Kipling
Edinburgh
##########################################
Quick plug for a couple of reviews:
Kipling, D (1995) Telomerase: immortality enzyme or oncogene? Nature
Genetics 9:104
Kipling, D (1995) The Telomere. Oxford University Press.
