Although you might not get them to fold in this large pot, 3-betting has the best chance of any play here of protecting your equity. Getting even the CO (who we haven't heard from yet) to fold increases your equity by a goodly percentage, which is excellent in a pot this large. Getting any player to fold in this large a pot is a huge advantage, add to that the possibility that you have the best hand (and the corresponding possibility that UTG is raising something like AK UI) and it seems like the best option to me.