However, none of the growth factors and cytokines involved in erythrocytes’ maturation, such as SCF, IL-3, IL-4, TPO and EPO (http://www.genome.jp/kegg/pathway.html), were under-expressed in BM resident cells from NB patients as compared to healthy children (Supplementary Table 2), suggesting that other, still unknown, factors may have a role. This evidence concerns the gene EPO and neuroblastoma.