It should be noted that the authors used mouse-derived stromal cells to influence CXCR4 expression on human neuroblastoma cells, however in the context of our findings the possible contributory effects from other stromal-derived cytokines such as IFN-γ and IL-5γ on the expression and function of CXCR4 in our system warrant investigation. This evidence concerns the gene CXCR4 and neuroblastoma.