We have previously demonstrated that CAF‐produced SDF‐1 promotes the growth of nearby breast tumor cells in a paracrine fashion via acting through CXCR4 on these cells.10 We thus speculated that decreased levels of membrane and soluble CD26 expressions on CAFs may promote paracrine SDF‐1 signaling toward nearby carcinoma cells. This evidence concerns the gene DPP4 and carcinoma.