MYCN and Nephroblastoma: Given the tissue specific nature of miRNA function, it is not excluded that these miRNAs regulate MYCN in an other cellular context, such as that of normal brain development [34] and a number of childhood malignancies with demonstrated involvement of MYCN: medulloblastoma [31,35], retinoblastoma [35,36], Wilms' tumor [36,37], rhabdomyoscaroma [37,38] and T-cell acute lymphoblastic leukemia [38].