strong attaching epithelial cells - molecular explanations? (Apr/28/2007 )

we isolated some transfectants which show unusual high attachment to cell culture dishes so that our routine protocol for detaching with TrypLE fails;

now we are interested in the molecular reasons for strong attachment - are there any hard molecular markers for attachment I should look at first?

f.i. phosphorylation of FAK? or number of focal adhesion sites?

any suggestions are highly appreciated!