Sunday, February 26, 2006

Nonrandom chromatid distribution in embryonic stem cells

As we suspected, the asymetric division of a stem cell makes sure the older chromatid is retained to minimise accumulation of errors. This reminded me of some work not that long ago about aging in bacteria, and in yeast. Does asymmetric division underly culture immortality ? If so, the stem cell hypothesis of cancer has to be true. With more and more labs looking for those stem cells it has become evident that they exist in certain cases, but I am unconvinced for the majority of cancers. Am I the only one who can grow cells to confluence starting from just one? High error rates and rampant replication give more variation for natural selection to work on and this is the very essence of cancer. If there is only a small pool of cancer stem cell to begin, then variation is severly limited. And in a solid tumour, shouldn't those cells get stuck in the middle, where necrosis gradualy takes over? I just don't buy it.


Bayman said...

Can you grow out your cell lines in culture from a single cell? Have you tried? I haven't but that would be a good experiment...plate out your cells at one cell per well in a 96-well plate and count the number of wells that fill up with cells.

Secondly, even if you can grow out a culture from one cell in a dish it says nothing about the role of stem cells in cancer. Cells growing in a dish don't have much to do with real tumors in a real person.

Although a tumor relying on a stem cell population for its survival could indeed be a evolutionary disadvantage, it may also be a necessity for tumorigenesis in vivo. For example these may be the only cells with the capacity for self-renewal and immortality in the context of a tumor. It may well be that in the environment of our bodies, our cells are hard-wired in such a way that maintaining stem cell pools is the only way to continually renew tissues, whether they be normal or malignant.

Anonymous Coward said...

I'll quote the Great One: "Well it's not a question of wether my shit is better than your shit, it's a queation of putting it together and see if it smells better"

Yeah I get your point and tumours are turning out to be a lot more like normal organs than we originaly thought. But if the cell has the plasticity to be dedifferentiated into a stem cells why not only have those? Why limit yourself to mortality if you can easily overcome it. What is putting selective pressure for this trait?