Consistent with that function, we observed by immunohistochemistry increased Ki-67+ (proliferating) epithelial cells in BPH hub epithelium adjacent to inner IGF1+CXCL13+ stroma, in comparison with the outer IGF1–CXCL13– stroma (Figure 5, G and H, and Supplemental Figure 3) (P = 0.04, paired 2-sided Student’s t test). Here, CXCL13 is linked to benign prostatic hyperplasia.