In recent cancer vaccine trials [3,4,5], many melanoma patients who received heteroclitic peptide vaccines gp100 209–217 (210M) (IMDQVPSFV; G209–2M) and MART 26–35 (27L) (ELAGIGILTV; M26) had measurable CD8+ peptide-specific T cell responses in PBMCs detected by peptide–MHC tetramer staining. Here, CD8A is linked to cancer.