Oestrogen-Binding Components in Human Renal Cell Carcinoma

Abstract

Bojar, Dreyfürsl, Balzer, Staib and Wittliff: Oestrogen-binding components in human renal cell carcinoma 521 Summary: Specific binding-of [ 3 H]oestradiol-17j3 by the cytosol fraction of human renal cell carcinoma was studied. The binding reaction displayed marked ligand specificity and high affinity of binding. Unlabelled oestradiol, oestriol and oestrone inhibited the binding of [ 3 H]oestradiol-17|3 to the cytosol binding sites, whereas all other steroids tested turned out to be only weak or insignificant competitors for the oestrogen binding sites. Scatcliard analyses suggested the existence of a single class of binding sites. The dissociation constant of the oestradiol-binder complex was found to be 2.51 ± 0.75 10" 9 mol/1. The number of binding sites was limited (17.5 ± 3.8 fmoles per mg of cytosol protein). Sucrose gradient centrifugation revealed these binding components to be macromolecules, either displaying a complex sedimentation pattern (peaks at 3.5S, 4S, 5.7S and, in addition, high molecular weight aggregates) or sedimenting in the 4 S region alone. By agar gel electrophoresis it could be demonstrated that the oestradiol-binding components migrated into the receptor region of the gel. Binding of [ 3 H]oestradiol-17j3 to these entities was markedly reduced, when the cytosol was heated (60 min at 45°C) prior to the reaction with the labelled hormone. Since the specific binding components exhibit properties of oestradiol receptors in target tissues, a direct effect of oestradiol on human renal cell carcinoma is suggested. Ostrogefcbindende Komponenten in hypernephroiden Karzinomen des MenschenZusammenfassung: Die spezifische Bändung von [ 3 H]Östradiol-17)3 durch die Cytosolfraktion hypernephroider Nierenkarzinome des Menschen wurde untersucht. Die Bindungsreaktion zeigte eine ausgeprägte Spezifität und hohe Affinität. Unmarkiertes Östradiol, Östriol und Östron hemmten die Bindung von [ 3 H]Östradiol-17|8, während alle übrigen getesteten Steroide sich nur als schwache bzw. nicht signifikante Kompetitoren erwiesen. Scatchard-Analysen deuten auf nur eine Klasse von Bindungsstellen hin. Die Dissoziationskonstante des Östradiol-Binderkomplexes betrug 2,51 ± 0,75 nmol/1. Die Zahl der Btadungsstellen war limitiert (17,5 ± 3,8 fmol/mg Cytosolprotein). Saccharosegradientenzentrifugation zeigte, daß diese Bindungskomponenten Makromoleküle waren. Das Sedimentationsprofil war entweder komplex (Maxima bei 3,5S, 4S, 5,7S und zusätzlich hochmolekulare Aggregate) oder zeigte nur ein Maximum in der 4 S=Region. Durch Agarelektrophorese konnte demonstriert werden, daß die östradiolbindenden Komponenten in die Rezeptorregion des Gels wanderten. Die Bindung des tritiierten Hormons an diese Moleküle nahm erheblich ab, wenn das Cytosol vor der Reaktion mit dem radioaktiv markierten Östradiol erhitzt wurde (60 min bei 45°C). Da die spezifischen Bindungskomponenten Eigenschaften von Östradiolrezeptoren in Zielorganen haben, wird eme direkte Wirkung von Östradiol auf hypernephioide Karzinome des Menschen erwartet.

Distribution of Oestradiol Receptor Molecules in Human Kidney

“…Based on our previous observations of a considerable variability in the oestradiol-binding capacity of cytosols prepared from different kidney specimens, we speculated that the binding sites were not evenly distributed among medulla and cortex (1). The results presented here strongly confirm this idea.…”

“…Specific oestrogen-binding components were recently demonstrated in the cytosol of normal human kidney (1) as well as human kidney carcinoma (2). On the basis of the observed variability in the binding capacity and sucrose gradient sedimentation patterns of oestrogen binding components, prepared from tissue samples of different kidneys, it was assumed that inter-organ and/or intra-organ variations may exist.…”

Identification and Partial Characterization of Specific Oestrogen-Binding Components in Human Kidney

“…One of the reasons for the paucity of information on the oestrogen responsiveness of kidney is the former paradoxical failure to demonstrate oestrogen receptors in normal hamster kidney (3). However, there are some indications of oestradiol binding to cytosol macromolecules and the nuclear fraction of rat kidney (4,5). Moreover, oestrogens have been shown to decrease renal sodium excretion in adrenalectomized rats (4), dogs (6), and normal humans (7).…”

Usefulness and Limitation of Estrogen Receptor Protein (ERP) Assay in Human Renal Cell Carcinomas

“…Recently the discovery of estrogen receptors in human renal carcinoma has represented a valid confirmation of the possibility that this tumor may be a target tissue for estrogen and therefore sensi tive to antiestrogen treatment (5,7,9).…”