Insulin-like growth factor 1 (IGF1) binding sites were characterized in breast cancer. We demonstrate the presence of one high affinity binding site. Chemical cross-linking of 125I-IGF1 to breast cancer membranes in reducing condition and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed one band with an apparent molecular weight of 130,000. The specificity of the binding was studied. IGF2 was a good competitor whereas insulin competed with a potency lower than 1/100 that of IGF1. This IGF1 binding corresponded to the previously described type 1 IGF receptor (IGF1-R). IGF1-R was determined in 76 human breast cancer biopsies. Ninety-three % of the tumors were positive. The specific binding range was 0–16.4%; the geometric IGF1-R mean level was 3.9%. There was a relation (x2 test) between IGF1-R and progesterone receptor positivity rates (P = 0.002). The IGF1-R concentrations were correlated (Spearman test) with those of estradiol receptor (P = 0.0018) and progesterone receptor (P = 0.0011). A positive linear correlation existed between IGF1-R and estradiol receptor (P = 0.006) and between IGF1-R and progesterone receptor (P = 0.003). Our demonstration of the presence of IGF1-R in human breast cancer biopsies suggests that IGF1, acting either via the endocrine, paracrine, or autocrine pathways, could stimulate tumor growth.


This work was supported by the Association pour la Recherche sur le Cancer (Villejuif) and by the Fédération Nationale des Centres de Lutte contre le Cancer.

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