MKI67 and neoplasm: Indeed, immunosuppressive CD4+Foxp3+ regulatory T (Treg) cells with a surface marker profile high in activation markers and proliferative indicators (e.g., high KI67 expression) tend to be the dominant Treg subset recovered from tumors and increases in the relative fraction of these activated or effector-like tumor Tregs is associated with poor outcomes in many cancers [25, 26].