More information: The transduced sequences include GFP and antibiotic resistance. Or, can I simply subject the cells to a period of antibiotic selection and then harvest them right away for xenograft implantation?
Don't forget to demonstrate the expression of the transduced gene at protein level in the xenograft as cells may delete the ectopically expressed gene when it may negatively affect their growth! When not selecting cells, you potentially have a very heterogenous population of cells. Always compare the gene/protein expression pattern in your xenograft swith that of the cells that you have injected.
Hi, as in any experiment of that kind, depends on the objective. For anti-tumour responses, there will be selection in vivo of non-expressing cells, for example. If you have a toxic gene, there will also be a strong in vivo selection. The immune system can also "see" your expressed gene as foreign, and kill transduced cells with time. Be careful. If your lenti/retrovector has antibiotic resistance, select the cells. It shouldn't take long and in my experience, it will not be a loss of time...
David makes a very good point- a high transfection efficiency is great for a transient transfection, but if you monitor expression of you target gene over time you will find that they will drop. This is mostly because the transfected DNA will not all integrate into the host genome, but be maintained ectopically, and these copies will be lost with time. I suspect that if you are going to use your transfectanted cells as a xenograft then by the end point of your experiment they may not express your target gene. I would select them and then measure target gene expression in my selected clones. This will also give the possible benefit of a series of clones with different levels of target gene expression which can be used to make a couple of different xenografts each with different levels of expression as well.
Selection is well worth it- if the xenograft experiments do not work with a pool of cells, you will have lost a fair amount of time.
Good Luck
Just a remind, if your gene induces cell death or cell cycle arrest, the antibiotic pressure may select the cells that are resistants to your gene. So I think the best solution is to make a antibiotic selection if you have a responsive promoter regulating your gene. Then, your gene won't be expressed during antibiotic selection.
I would suggest to clone the cells, there is always a selection when you injected cells in vivo and you cannot know what will you end up with.
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