CCL2 and neuroblastoma: Supernatants derived from 1:1 co-culture of any of four neuroblastoma cell lines (SH-SY5Y, CHLA-255, NGP, SMS-KCNR) with MACS-purified monocytes contained significantly higher levels of CCL2 protein than supernatant isolated from culture of either monocytes or neuroblastoma cells alone (Fig. 3A).