Hypermethylation of the transporter 1 ATP-binding cassette subfamily B member (TAP1) has been shown to suppress TAP1 expression in immunoreactive cancer stem cells (CSCs) within murine models of breast carcinoma, these CSCs manifest a downregulation in the expression of transporter associated with antigen processing genes and co-stimulatory molecules, thereby reducing their sensitivity to T-cell-mediated immune surveillance and potentially culminating in immunotherapy resistance.624,625 Additionally, the methylation of chemokines can also lead to resistance to immunotherapy. The gene discussed is TAP1; the disease is breast carcinoma.