Since mesothionin polypeptides provided by MUC16 and its ligand MHC were exclusively presented at MHC class II antigens, while human leukocyte antigen (HLA) ligands derived from MUC16 are overexpressed on cancer cells, more than 85% of HLA ligands derived from MUC16 are immunogenic and capable of activating T cells in healthy individuals. This evidence concerns the gene MUC16 and cancer.