To ascertain any functional differences between the different isoforms of CXCR4 in neuroblastoma cell lines, CXCR4 immunoprecipitates from 3 highly invasive cell lines NB 19, MNB-OZ and SK-N-SH and 3 less invasive cell lines, NB Mass, SJ-N-KP and IMR 32, were subjected to far western blot analysis with CXCL12. The gene discussed is CXCL12; the disease is neuroblastoma.