Prolonged nephrogenesis was observed also in mice with overexpression of Lin28, Lin28b or inactivated Let-7 (Let-7a1; Let-7d; Let-7f1) (Urbach et al., 2014; Yermalovich et al., 2019), which also either show direct tumorigenesis or activation of the Igf2 or H19h loci associated with pediatric kidney cancer Wilms' tumor (Chen et al., 2018; Ogawa et al., 1993). Here, IGF2 is linked to childhood malignant kidney neoplasm.