Rapid detection of gene expression

Conventional methods of in situ hybridization are not only complex, laborious and lengthy, tending to produce poor cellular resolution but are also inherently hazardous. We report a new method that overcomes many of these difficulties. Denovo attachment of a non-isotopic ligand, viz. 5-bromo-2'-deoxyuridine (BrdU) to oligonucleotide probes guaranteed the production of labelled probes of 100% specific activity that gave consistent, reproducible results, within hours, in a rapid in situ hybridization (ISH) technique. The method is demonstrated by localization of insulin-like growth factor II (IGF-II) mRNA in human intracranial tumours and foetal brain. Five of 10 meningiomas expressed IGF-II mRNA to an extent of 1% of their tumour cells and two of three pituitary adenomas exhibited a less than 0.2% IGF-II mRNA-positive cell population. IGF-II may be important in the progression and/or maintenance of these tumours. Foetal brain showed no hybridization. The method's simplicity, rapidity and reliability commends its use in a variety of research and diagnostic applications and the BrdU-labelled probes can be used in any hybridization technique.