While Yin Yang-1 (YY1) transcription factor recruits EZH2 histone methyltransferase to the IL-2 locus and inhibits the production of the pivotal cytokine in an in vitro exhaustion model created by persistent antigen and co-stimulatory signal stimulation, whether YY1 regulates T cell exhaustion in vivo in a similar way remains to be investigated.328 Inhibitory receptors and their ligands are ectopically upregulated in tumor-infiltrating CD8+ T cells and tumor cells respectively, marking T cell exhaustion and immunosuppression. Here, PRDM9 is linked to neoplasm.