CD4 and cancer: In particular, in breast cancer models, it was reported that the intra-tumoral naïve CD4+ T cells and Tregs share overlapping TCR repertoires, suggesting that the existing Tregs in the tumor microenvironment may have originated by reprograming of tumor infiltrating naïve CD4+ T cells to Tregs, and therefore blocking the recruitment of naïve CD4+ T cells might reverse immunosuppression in this cancer type [96].