Presence and characterization of insulin-like growth factor 1 receptors in human benign breast disease.

Insulin-like growth factor 1 binding sites were characterized in human benign breast disease. We demonstrated the presence of one high affinity binding site. Chemical cross-linking of [125I]IGF1 to benign breast disease membranes in reducing condition and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed one band with an apparent Mr of 130,000. The specificity of the binding was studied: IGF 2 was a good competitor whereas insulin competed for binding with a potency lower than 1/100 that of IGF1. This IGF1 binding corresponded to the previously described type I IGF receptor (IGF1-R). IGF1-R was assayed in 35 cases of benign breast disease and two samples of normal breast tissue. Forty-three per cent of the lesions were IGF1-R positive. The mean geometric level of specific binding was 1.98% in the whole population, it was significantly lower in adenofibromas (1.55%) than in epithelial hyperplasia (2.5%); it was 2% in dystrophic disease. IGF1-R was undetectable in normal tissue. Considering our previous results showing that almost all the breast cancers contained IGF1-R, these data suggest that the increase in IGF1-R could be a marker of malignant tumor development.