CD4 and breast carcinoma: Additionally, FAP + PDGFRβ + CAFs in breast cancer, also termed CAF-S1 cells (introduced earlier in the review), were proven to not only enhance the migration of CD4 + CD25 + T cells by releasing CXCL12 but also express CD73, dipeptidyl peptidase IV (DPP4) and B7H3, enabling them to transform CD4 + T cells into Foxp3 + Treg cells [96].