Maintenance of genomic imprinting at the IGF2 locus in hepatoblastoma.

Genomic imprinting is the parental allele specific expression of genes and has recently been shown to occur in humans. Evidence for a role for genomic imprinting in human cancer comes from the finding of preferential retention of paternal alleles in embryonal tumors undergoing loss of heterozygosity, e.g., Wilms' tumor and osteogenic sarcoma. Recent studies have demonstrated imprinting of the insulin-like growth factor II gene at 11p15 in normal individuals, with the paternally inherited allele expressed and the maternal allele silent. It has been shown that normal imprinting is relaxed, and gene expression is biallelic in a majority of Wilms' tumors which retain heterozygosity at this locus. In this study an intragenic ApaI polymorphism is used to examine imprinting of the insulin-like growth factor II gene in hepatoblastoma. Three of 5 tumors studied were heterozygous and hence informative. All cases showed monoallelic expression of the insulin-like growth factor II gene, indicating maintenance of normal imprinting at this locus.