DPP4 and breast carcinoma: Similar findings were reported in breast cancer where different subsets of CAF were also identified, and where CAF-S1 enhanced Treg cell polarization through the expression of the adenosine ectonucleotidase CD73 and the inhibitory molecules B7 Homolog 3 (B7H3) and dipeptidyl peptidase-4 (DPP4) [87,88,89].