Epidermal growth factor binding sites in human pituitary macroadenomas M L Jaffrain-Rea 1 , E Petrangeli 2 , C Lubrano 3 , G Minniti 3 , D Di Stefano 4 , F Sciarra 3 , L Frati 4,6 , G Tamburrano 3 , G Cantore 5,6 and A Gulino 1 1 Department of Experimental Medicine, University of L’Aquila, Italy, 2 TBM Institute, CNR, Rome, Italy, Departments of 3 Endocrinology, 4 Experimental Medicine and Pathology and 5 Neurosurgery, University of Rome, La Sapienza, Italy and 6 Neuromed Institute, Pozzili, Italy (Requests for offprints should be addressed to M L Jaffrain-Rea, Dipartimento di Medicina Sperimentale, Universita` degli studi di L’Aquila, Via Vetoio-Coppito 2, 67 100 L’Aquila, Italy) Abstract The number of epidermal growth factor (EGF) binding sites was determined by competitive binding assays in a series of 46 pituitary macroadenomas. A single concen- tration of 125 I-EGF (1 nM) was used for all experiments. In four cases, a displacement curve was obtained by adding increasing concentrations of cold EGF, and Scatchard analysis showed the presence of two classes of EGF binding sites, with K d1 =0·62 0·23 nM and K d2 =53·8 8·2 nM for the high- and low-affinity binding sites respectively. The distribution of EGF binding sites was studied in 42 cases by a single-point assay, in the presence and in the absence of a 100-fold cold EGF excess. A non-parametric distribution of EGF binding sites was observed (median 10·2 fmol/mg membrane protein, range 0·0–332·0). EGF-receptor positivity, defined as EGF binding 10·0 fmol/mg protein, was observed in 23 samples (54·8%), especially in prolactinomas (76·5%, P<0·05 vs other tumors taken together) and in gonadotrope adeno- mas (62·5%). EGF binding was higher in invasive than in non-invasive adenomas (median: 12·8 vs 0·0 fmol/mg membrane protein, P=0·047), and especially in adenomas invading the sphenoid sinus (median 26·7 fmol/mg mem- brane protein, P=0·008 vs other adenomas). EGF binding also tended to increase with the grade of supra/extrasellar extension according to Wilson (P=0·15). Sex steroid receptors (SSRs) were simultaneously determined in both cytosolic and nuclear fractions of 31 pituitary adenomas. Estrogen and progesterone receptors were determined by an enzyme-linked immunoassay and androgen receptors by a competitive binding assay with [ 3 H]methyltrienolone. No correlation could be found between EGF binding and either the gender and gonadal status of the patients, or the expression of SSRs by the adenomas. We conclude that the EGF family of growth factors may play a role in the evolution of a significant subset of human pituitary adeno- mas, especially in their invasiveness, and that a high EGF binding capacity may represent an additional marker of aggressiveness for these tumors. Sex steroids do not appear to have a significant role in the regulation of EGF binding in vivo in these tumors. Journal of Endocrinology (1998) 158, 425–433 Introduction Pituitary tumors are frequent benign neoplasia, accounting for about 10% of symptomatic endocranial neoplasms. In addition, autoptic studies indicate that silent pituitary adenomas – mostly microadenomas – are present in up to 10–20% of the general population (Molitch & Russell 1990). Therefore, attempts to identify factors which can promote or inhibit the clinical expression of these tumors – i.e. the ability to produce pituitary hormones in excess, leading to a specific syndrome of hormone hypersecretion, and the increase in proliferation rate and invasiveness, leading to neurological manifestations – are of special importance for the understanding of the pathogenesis of these tumors, and for the development of new thera- peutic strategies (von Mehren & Weiner 1996, Huang & Heimbrook 1997). Pituitary tumors are mostly monoclonal in origin (Herman et al. 1990), indicating that primary genetic alterations can determine the clonal expansion of abnormal cells. However, few such abnormalities have been identified in these tumors (for review see Shimon & Melmed 1997). On the other hand, pituitary tumor cell function and/or proliferation can be modulated by a variety of extracellular factors, including steroid hormones ( Jaffrain-Rea et al. 1996), cytokines and growth factors (for review see Shimon & Melmed 1997). The epidermal growth factor (EGF) family of growth factors is able to modulate the proliferation, secretion and differentiation of most endocrine glands (for review see Fisher & Lakshman 1990). EGF is normally present in the 425 Journal of Endocrinology (1998) 158, 425–433  1998 Society for Endocrinology Printed in Great Britain 0022–0795/98/0158–0425 $08.00/0 Downloaded from Bioscientifica.com at 06/19/2022 02:36:24AM via free access