Tirosh et al. identified core exhaustion signatures of T cells, including upregulation of coinhibitory (TIGIT) and costimulatory (TNFRSF9/4-1BB and CD27) receptors.172 In line with the findings for NSCLC and breast cancer,134,147 Li et al. noted that dysfunctional CD8+ T cells transitioned from early effector cells.173 Analysis of the TCR in peripheral blood mononuclear cells revealed dysfunctional processes at the tumor site. Here, CD8A is linked to breast carcinoma.