The disclosure relates to polypeptides and pharmaceutical compositions comprising polypeptides that find use in the prevention or treatment of cancer, in particular breast cancer, ovarian cancer and colorectal cancer. The disclosure also relates to methods of inducing a cytotoxic T cell response in a subject or treating cancer by administering pharmaceutical compositions comprising the peptides, and companion diagnostic methods of identifying subjects for treatment. The peptides comprise T cell epitopes that are immunogenic in a high percentage of patients.