Two arms to embrace the oncopeptidome. The oncopeptidome can be determined by definition of mutations in the genome followed by peptide prediction and validation (right arm). A complementary arm (left) defines the oncopeptidome directly by analyzing MHC class I–associated peptides by mass spectrometry and then validation. These are mainly nonmutated peptides. Integration of the 2 arms will further expand the oncopeptidome associated with clinical responses and ultimately be applied in personalized tumor vaccination programs. Professional illustration by Patrick Lane, ScEYEnce Studios.