IRF4 and neoplasm: When isolated tumor-infiltrating macrophages from 4T1 tumors were analyzed, reduced expression of interferon regulatory factor 4 (IRF4), which plays a significant role in macrophage M2 activation, and relatively increased H3K27M3 (Histone 3 Lysine 27 Tri-methylation) levels and increased T cell activation were found in breast tumors.