CD4 and cancer: Forkhead box P3 (Foxp3) is a member of the forkhead/winged-helix family of transcription regulators involved in regulating immune system development and function.18 This gene plays a crucial role in the generation of CD4+CD25+ Tregs, and the loss of Foxp3 function leads to a lack of Tregs, resulting in lethal autoaggressive lymphoproliferation, whereas overexpression of Foxp3 results in severe immunodeficiency.19 High levels of Tregs have been reported in the peripheral blood,20–22 lymph nodes,23,24 tumor specimens,22,25 and ascites 21 of patients with different types of cancer.