CXCR4 and cancer: Boesch et al. published a study in 2017 where IL-7-expressing cancer-associated fibroblasts promoted breast tumor growth and provided critical niches for the maintenance of breast cancer stemness while CXCL12 was identified as an important niche factor in Il7-expressing cancer-associated fibroblasts (CAFs), indicating that the stromal cell-derived factor 1/cluster of differentiation 184 CXCL12/CXCR4 pathway may serve as a therapeutic anti-cancer stem cell (anti-CSC) target [26].