Consistent with prior studies in which AMD3100 and a second specific CXCR4 antagonist AMD3465 only blocked CXCL12-induced U87 cell growth [14], [31], AMD3100 only inhibited primary GBM cell growth when the GBM cells were co-cultured with HBMECs, but not when they were in mono-culture. The gene discussed is CXCL12; the disease is glioblastoma.