In murine tumor models, histone deacetylase is enrich CD8+ T cell subsets expressing high levels of effector molecules (Prf1, Ifng, Gzmk, Gzmb) while also upregulating exhaustion-associated molecules (Tox, Pdcd1, Lag3, Havcr2), shaping a tumor microenvironment dominated by immunosuppressive myeloid cells. This evidence concerns the gene PDCD1 and neoplasm.