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Hayflick limit

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Hayflick limit

Postby Julie5 » Tue Sep 21, 2010 8:30 am

Hi - I'm new to this board, and delighted to have found it.

I'd be grateful for any clarification on this -

Hayflick limit: Am I right in assuming that this limit applies only to non-stem-cells? (ie, not to cells that have terminally differentiated). I hope that's a sort of no-brainer assumption, ie, as part of the inherent defining characteristic of a stem cell, but I just wanted to be sure (or be corrected!)

Many thanks, Julie.
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Postby biohazard » Tue Sep 21, 2010 11:49 am

Hayflick limit does not affect cancer cells, either :)
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Re: Hayflick limit

Postby Julie5 » Thu Sep 23, 2010 7:54 am

Yes, more's the pity! :)

(although....that said ....I'm sure I've read in passing that there is a question mark still over tumours in that there is a view that says it's only the tumour stem cells that are the really dangerous ones, in that the tumour cells that show cancer-terminal-differentiation (into the caricature cellular phenotype)( I think that's the term!) may have a Hayflick limit??? (Guess it all depends on the telomeres....?)
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Postby biohazard » Fri Sep 24, 2010 6:45 am

I am not very familiar with this concept of cancer stem cells versus more terminally differentiated ones. In my experience most of the cancer cells in a given cancer are surprisingly similar to one another, although the often big mitotic activity among the cells causes always some variation.

The differentiation status of the cells in different cancers can vary considerably, though. Some cancers have highly differentiated cells that almost look what they are supposed to look as healthy cells, whereas some cancers consist only of very immature cells where you have hard time even telling which tissue they have originated from.

However, I believe that to meet the definition of cancer cell the cell must have aquired several traits, of which one is the ability to retain their telomere length. Other such traits are e.g. angiogenesis (ability to "force" body to generate blood vessels to supply the tumor) and resistance to apoptosis (the cancer cells do not die when the immune cells of the body tells them to do so). In theory, any one of these cells should be able to start a "new" cancer, which often means that it produces a metastasis. In practice, not all cancer cells are viable and they die on their own, but there is always many of those who manage to make copies of themselves and teh cancer keeps advancing.
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