Further studies also found that in the region where PIN occurs, PIN cells can recruit macrophages to gather by secreting ICAM-1 and CCL2, while recruited macrophages can activate ERK and JNK signals in PIN cells by secreting C5a, CXCL1, and CCL2 to promote the proliferation of PIN cells (90). Here, CCL2 is linked to prostate intraepithelial neoplasia.