MYCN and neuroblastoma: Therefore, when MYCN is amplified/overexpressed, LIN28B expression also increases and blocks let-7 biogenesis, with consequent let-7 dependent de-repression of MYCN, thus establishing a direct MYCN/LIN28B/let-7 regulatory axis and activated feedback loops that greatly contribute to NB tumorigenesis [18,19,20,21] (Figure 4).