J. Buechner, J. R et al. reported that knocking down MYCN in SK-N-BE cells led to the downregulation of 12 miRNAs (including mir-21), but artificial regulation of mir-21 levels (overexpression or inhibition) did not significantly affect the differentiation or proliferation of neuroblastoma cells with high MYCN levels (Buechner et al., 2011). The gene discussed is MYCN; the disease is neuroblastoma.