CD4 and neoplasm: MicroRNA‐155 (miR‐155) is another factor that upregulates IFNγ expression in the tumor microenvironments and slows tumor growth.10, 11 Huffaker et al reported a defect in the accumulation of IFNγ‐expressing CD4+ and CD8+ T cells in the tumors from miR‐155 knockout mice, indicating miR‐155 has tumor regression activity.