As CD26 expression was attenuated on stromal myofibroblasts in human breast carcinomas, we investigated whether CD26 expression is also downregulated in primary cultured CAFs extracted from human breast carcinomas, compared to the corresponding control fibroblasts isolated from the adjacent noncancerous tissues in same patients using public gene expression data.25 A significantly lower level of CD26 mRNA expression was detected in myofibroblastic CAFs that presumably acquired TGF‐β and SDF‐1 autocrine signaling, as exemplified by increased TGF‐β2 and SDF‐1 mRNA expression9, 26 (Figure 2A). Here, DPP4 is linked to breast carcinoma.