Detection of anti-sense transcripts of the insulin-like growth factor-2 gene in Wilms' tumor

The expression of the insulin-like growth factor-2 (IGF-2) gene was studied by means of both in situ hybridization and immunohistochemistry in eight cases of Wilms' tumor with different histological features. An anti- sense cRNA IGF-2 probe revealed the presence of abundant IGF-2 mRNAs in all eight tumors examined, localized in the most undifferentiated tumoral cells (blastemal cells): none of the tumors showed immunoreactivity for the anti- IGF-2 antibody. Using a sense cRNA IGF-2 probe, we also detected anti-sense transcripts of the IGF-2 gene in five of eight tumors. These transcripts were exclusively localized in the cells expressing the IGF-2 mRNAs. Although the function of these anti-sense transcripts is unknown, we think that their presence could explain the lack of IGF-2 peptides in Wilms' tumors despite increased expression of IGF-2 mRNAs.