MYCN and neuroblastoma: Several studies to date including our own have observed an inverse relationship between DKK3 expression and MYCN amplification and/or expression in both cell lines and primary tumors, thereby suggesting that downregulation of DKK3 is necessary for progression of MYCN amplified neuroblastoma (Table 3; Bell et al., 2007a; Koppen et al., 2008; Chen et al., 2010; Haug et al., 2011; De Brouwer et al., 2012; Figure 4).