Genomic imprinting is defined as a differential expression of genes depending on their parental origin. IGF2 gene on chromosome 11p, which is maternally imprinted in normal human development, has been demonstrated to be activated by loss of imprinting (LOI) during tumorigenesis of Wilms tumor or other kidney neoplasms in childhood. Although the molecular mechanism of genomic imprinting is not clarified yet, it is certain that disruption of the imprinting mechanism has a causative role in some human cancers.