Learned Helplessness About Immortality (fwd)

Don Ashley dashley at TENET.EDU
Sat Mar 2 06:03:57 EST 1996



---------- 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.






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