<qa>  What is CEA expressed in?Since CEA is expressed in 90 of PC, it would make an attractive target for a vaccination approach. Several different vaccination approaches have been tested using CEA as a TAA. Although some investigators suggest that DC-based approaches are the most active, they are limited by the need to obtain patient-specific DCs. One attractive approach would be to add GM-CSF to the peptide to recruit endogenous DC to the site of vaccination. 