To investigate whether the bone marrow derived factors play a role in the organ specific metastasis of neuroblastoma cells to the bone marrow, neuroblastoma cells were pre-treated with mRPMI for 12 hours, and then assayed for CXCR4 expression levels, secreted MMP-9 levels, integrin expression levels and invasion indices. This evidence concerns the gene MMP9 and neuroblastoma.