The effort to create cancer vaccines using allogeneic cell lines, differentiation antigens (such as gp100 and MART1), cancer testes (CT) antigens (such as MAGE, NY-ESO-1) or other common molecules (such as carcinoembryonic antigen, mucins, prostate-specific antigen, and prostatic acid phosphatase) represent this approach. Within this approach lie several subthemes. Thus, CT antigens, which are not expressed on normal somatic tissues but only on cancers or gonads, might be a better target for breaking tolerance than are differentiation antigens expressed on somatic tissues. Another subtheme is the idea that artificially mutated differentiation or CT antigens as vaccines might be better at breaking tolerance than their wild-type counterparts. Finally, there is a multiplicity of choices of delivery agents for these antigens – whole proteins, peptides, RNA, DNA, viral vectors, DCs and so on.