100 Evidence for intrinsic control of ligand binding by the cytoplasmic estrogen receptor

34s

100

EVIDENCE FOR INTRINSIC CONTROL OF LIGAND BINDING BY THE CYTOPLASMIC ESTROGEN RECEPTOR. Anthony L. Rosner, Department of Pathology, Beth Israel Hospital, Boston, MA; Arnold M. Schwartz, George Washington University Medical Center, Washington, DC; and Nelson A. Burstein, Department of Pathology, St. Elizabeth's Hospital, Boston, MA. USA. We have extended our earlier studies (Arch. Biochem. and Biophys. 198: 153 (1979)), which demonstrated hat immature rat uterinemasfi estrogen receptor dissociates more rapidly from ( 5 H)-estradiol-17/? at higher degrees of saturation by ligand (LAD = accelerated dissociation in the presence of additional ligand). Insignificant variations of such dissociation rates were observed in the presence of 0,5,10 and 20 mM sodium molybdate, diminishing the possibility that the in vitro activation of receptors .-produced LAD in our investigations. Association studies of cytoplasmic estrogen receptor and ligand showed no significant alterations of initial association rate constants (k ) at the varying concentrations of ligand (0.1-0.5 nM) known to alter the dissociati8n rate constants (kd). These differences of k are therefore directly reflected by inversely proportional changes of equilibrium as g ociation constants, consistent with a model of negative cooperativity of binding of ligand. LAD was absent in 6 of 12 cytoplasmic extracts derived from dif rent specimens of human breast carcinomas under conditions of insignificant (
101

Peanut

lectin Binding sites in N-Ntrosomethylurea induced rat mammary carcinomas: Their relationship to hormone dependence. M. Vierbuchen, P.J. Klein, S. Rbsel, J. Fischer, H. Wiirz, and G. Uhlenbruck, Institute of Pathology, University of Cologne, J. Stelzmann Str.9, Cologne,FRG.

The occurrence, amount,and distribution of binding sites for the lectin from Arachis hypogaea (peanut agglutinin, PNA) which are represented by the disaccharide sequence O-D-Gal(l-3)NAcGal was histochemically analyzed in N-‘?itrosomethylurea induced rat mammary carcinomas with regard to hormonal influences and tumor growth. Administration of 17R-estradiol innduced binding sites for PNA and Progesterone in hormone dependent tumors whereas ovariectomy reduced the progesterone receptor content and the amount of PNA binding sites in tumor tissue. From these observations one can conclude that PNA binding sites which were associated with secretory activities of the neoplastic tissue represent a useful histochemiaal parameter to analyze the hormonal regulation in this model for human breast studies (tamoxifen, ovariectomy) on these cancer. Endocrine therapeutic tumors (n = 91) revealed a correlation between tumor response and the amount of secretory activity with positive staining for PNA binding sites, i.e. the amount of secretion associated PNA binding sites was significantly lower in hormone independent than in hormone dependent tumors.

_~._~__ .-

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Cytochemical End

of

a

Analysis

of

Human

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B.Manz,W.BBcker*,H.-J.Grill,O.Belovsky

Cytochemical

steroids

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found

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even or

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activity using

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K.Pollow.

Sex-Steroid

but

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oxygen

20-01

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,

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Experimentelle Hamburg,

cancer

serum one

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the

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visualized

biochemically.

they

as

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specimen.

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the

dependi

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dye

our

results

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conjugates, are

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steroid-BSA-dye sites

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TMRITC)

human

undistinguishably of

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Universitat

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dexamethasone

respective In

binding sections

16-CMO-estradiol-,

dexamethasone. and

and Patholog.Institut*,

tetramethylrhodamin

were

estradiol-, one

with

Legend?

Mainz, nologie, _~__ ______Universitat___--.--

in

________-____.

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Cancer

on

the

cytochemical class to

compo-

estrogen of do

or labe-

hormone.

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: