IGF2 but not H19 shows loss of imprinting in human glioma.

Genomic imprinting is a gamete-specific modification resulting in the allele-specific expression of genes in somatic cells. A loss of imprinting (LOI) has been found in many embryonal and adult tumors, suggesting that it plays a role in tumor development. The incidence of LOI, however, does not seem to be ubiquitous among tumors because neuroblastoma and colorectal cancer revealed no LOI. We examined the involvement of LOI of IGF2 and H19 genes in human gliomas. The two genes were imprinted in normal brain subcortex tissues. In glioma, 8 of 14 informative cases (57%) revealed LOI in IGF2. The frequency did not depend on the tumor grade. For H19, in contrast, all 13 informative cases maintained imprinting. These results suggest that LOI of IGF2 but not H19 plays a role in the development of human glioma.