stable cell line, but quenched GFP? - (Apr/02/2008 )

hello everybody
I have selected stable cell lines transfected with VHH-GFP ( camel antibody-GFP ), RT-PCR result shows that the selected cells express both VHH and GFP after 60 days, but I can't see any fluorescence under microscope.
could anybody give any hints?
tnx

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Have you confirmed GFP expression by western?

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tnx for replying
I dont have any anti-GFP to detect on western blot,
but I observed bands in RT-PCR.
the point is that I can detect GFP until 2 weeks after transfection but since then it becomes weak and dispersed.

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