CXCL12 and nasopharyngeal carcinoma: Taking into consideration both our data and literature reports, it appears that CXCL12 may have a dual impact in HIV infection, namely, stimulation of NPC proliferation through the CXCR4/FOXO3 signaling pathway, and induction of neuronal cell death after being cleaved by MMP2 and binding to CXCR3.