The analysis identified different CAF subpopulations in BC tissue. CAF-S1 (CD29, FAP, α-SMA, PDGFRβ, FSP1, and CXCL12) was analyzed in detail. These cells induced an immunosuppressive TME by retaining CD4+CD25+ T cells through the signaling of OX40L, PD-L2, and JAM2, and increased CD25+FOXP3+ T lymphocytes, and B7H3, DPP4, and CD73 signaling. Here, DPP4 is linked to breast cancer.