Beziaud et al. set to investigate whether peptide-based therapeutic vaccination would influence cancer stemness and metastatic disease dissemination in a mouse model of breast cancer expressing hormone receptors (HRs), at least at during early oncogenesis and tumor progression, as well as erb-b2 receptor tyrosine kinase 2 (ERBB2, best known as HER2). Here, ERBB2 is linked to breast carcinoma.