CD4 and cancer: In 2003, studies reported that the transcription factor FoxP3 was critical for Treg development (15–17), Subsequently, Curiel et al. (18) examined CD4+CD25+FoxP3+ cells and found that increased infiltration of Treg cells correlated with disease progression in ovarian carcinoma, and infiltration of these cells in each stage of cancer served as a good metric for survival prediction.