(a) MYCN enhances the expression of LIN28B via direct binding at the LIN28B promoter region. In turn, LIN28B inhibits the processing of the let-7 miRNAs, which results in loss of MYCN repression [3]. (b) MYCN indirectly represses the expression of miR-26a-5p via an unknown factor, indicated as “?”. Reduced miR-26a-5p expression levels results in increased LIN28B expression, which again, in turn, inhibits the processing of the let-7 miRNAs, resulting in loss of MYCN repression [3].