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Apoptosis detection using PI on FACS

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#1 pjgenomics



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Posted 13 March 2005 - 10:44 AM

Hi all,

I have been trying for weeks to observe a sub G1 peak that corresponds to apoptotic cells after treatment with TRAIL. So far I have seen nothing but normal profiles (G1, S, G2). I have been fixing using the method below:

1.Fix in cold 70% ethanol. Add dropwise to the cell pellet while vortexing. This should ensure fixation of all cells and minimise clumping.

2.Fix for at least 30 minutes at 4C. Specimens can be left at this stage for several weeks.

3.Wash x2 in Phosphate-citrate buffer. Spin at 2000rpm and be careful to avoid cell loss when discarding supernatant especially after spinning out of ethanol.

4.To ensure that only DNA is stained, treat cells with Ribonuclease. Add 50 l of 100 g/ml RNase.

5.Add 200 l propidium iodide (50 g/ml).

6.Analyse by flow cytometry.

Can anyone explain why I am not seeing this peak in HCT116 cells treated with TRAIL (10ngml) over a time course of days ?

Thanks on advance

#2 badcell



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Posted 14 March 2005 - 03:42 AM

I used this technique some time ago, and the only difference I see with yours is that I fixed the cells in ethanol for 5 min @ -20C. Also, I always processed the cells inmediately, even thought the protocol says that you can stop at that step.
I guess you're recovering all the floating cells and that you're seeing apoptosis by other independent method. I don't know what to suggest, as this is quite a straightforward method. Maybe you could use a higher number of cells for your assays?
Sorry I could not be of more help. Good luck!
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