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Biomedical subjects

V C Jordan

Publications and source records attributed to V C Jordan.

At least 307 records · Page 17Linked to original sources
PubMed1983

Reliability of steroid hormone receptor assays: an international study.

The reproducibility of oestrogen and progestin receptor assays performed by laboratories participating in an international breast cancer treatment trial has been assessed. Three tissue reference powders containing low, medium and high oestrogen receptor levels (22 +/- 4, 88 +/- 7, 227 +/- 13 fmol/mg cytosol protein respectively) were prepared in Louisville, KY, U.S.A., assayed repeatedly and multiple samples of each shipped on solid CO2 to the coordination-distribution centre in Berne, Switzerland. Samples were dispatched from Berne to Cantons within Switzerland, to Yugoslavia, South Africa, Australia, New Zealand and also back to the United States for oestrogen and progestin receptor assays. Results were returned to Berne, Switzerland. There was a decrease in the levels of oestrogen and progestin receptors during the time of storage and transit. However, the ability to assign a powder to either the low, medium or high level of oestrogen receptor was not affected. Laboratories also determined progestin receptor. All laboratories clearly identified the powder containing the low level of progestin receptor, but there was poor quantitation with the other two assay standards. It is recommended that clinical hormone receptor laboratories, especially those participating in clinical trials, establish regular quality control procedures for both daily evaluation internally and periodic outside monitoring of interlaboratory variation.

Animals↗
PubMed1983

A comparative study of electrophoretic mobilities of [3H]-estradiol and monohydroxytamoxifen binding components in the cytosols of human breast carcinomas and sera of healthy adult females.

Cytosols from human breast carcinomas rich in estrogen receptors (ER) were examined for the presence of [3H]-estradiol (E2) and [3H]-monohydroxytamoxifen (OH-TX) binding components. Polyacrylamide gel electrophoresis was used to examine the comparative anodal mobilities of ER-[3H]-E2 and ER-[3H]-OH-TX complexes, and also to identify any cytosol or serum component that may exhibit preferential high affinity to OH-TX. We have demonstrated that [3H]-OH-TX binds ER with high affinity and the anodal mobility of ER-[3H]-OH-TX complexes is identical to that of ER-[3H]-E2 complexes. We were unable to identify an antiestrogen-specific component in ER-positive or ER-negative cytosols or in sera of healthy adult females. A serum component exhibiting a higher affinity to [3H]-OH-TX and [3H]-DES than to [3H]-E2 has been identified in all the female sera examined, but this binding is of high capacity and is unsaturable by a 1000-fold molar excess of unlabeled E2 or antiestrogens. The electrophoretic mobility of this component is comparable to that of serum albumin.

Adult↗
PubMed1983

Binding of [3H] monohydroxytamoxifen in ovarian carcinoma.

A monoclonal antibody (D-547) against human breast cancer oestrogen receptor was used to demonstrate that the oestrogen receptor in ovarian epithelial carcinomata binds [3H]monohydroxytamoxifen. This binding was observed in sedimentation velocity analyses of both cytosol and nuclear compartments. Binding of [3H]monohydroxytamoxifen to the antibody-recognized moiety could be inhibited by diethylstilboestrol or oestradiol, but not by androgen, progestin or corticoid, indicating oestrogen specificity for the binding site. The sedimentation coefficient of the antibody-recognized [3H]monohydroxytamoxifen binding moiety was similar to that when 16 alpha-[125I]iodo-oestradiol was used as the ligand.

Antibodies, Monoclonal↗
PubMed1983

Inhibition of the uterotropic activity of estrogens and antiestrogens by the short acting antiestrogen LY117018.

The aim of the study was to determine whether the dihydroxylated antiestrogen LY117018, with a high affinity for the estrogen receptor and low intrinsic estrogenic activity, could inhibit the uterotropic actions of steroidal [estradiol-17 beta (E2)] and nonsteroidal [ICI 3188 and trianisylchloroethylene (TACE)] estrogens in immature rats and also the uterotropic actions of tamoxifen and monohydroxytamoxifen in the ovariectomized mouse and immature rat. In the first series of experiments, LY117018 was compared with monohydroxytamoxifen. Both antiestrogens inhibited the uterotropic actions of E2 (0.32 micrograms daily), ICI 3188 (5 micrograms daily), and TACE (40 and 160 micrograms daily) in a dose-related manner (0.32-82 micrograms daily). The potency of the antiestrogens against E2 and ICI 3188 was similar, however, at higher doses (20.48 and 82 micrograms daily) LY117018 reduced uterine weights to below the lowest level achieved by monohydroxytamoxifen. In contrast, LY117018 was less effective against the long acting estrogen TACE. The competitive interaction of LY117018 with tamoxifen and monohydroxytamoxifen was compared in 3-day ovariectomized mouse and immature rat uterine weight tests. Tamoxifen and monohydroxytamoxifen were fully estrogenic in the mouse (5 micrograms daily) and partially estrogenic in the rat (1.5-20 micrograms daily). LY117018 was a partial estrogen in the mouse and a weekly active partial estrogen in the rat (2.5-120 micrograms daily). LY117018 produced dose-related decreases in the uterine weight increases induced by tamoxifen and monohydroxytamoxifen in both species. However, in the rat, LY117018 was more effective against the less potent compound tamoxifen, at a 6:1 dosage ratio compared with a 24:1 dosage ratio required for the potent compound monohydroxytamoxifen. LY117018 had a short duration of action as an antiestrogen when compared with monohydroxytamoxifen. LY117018 (120 micrograms) was only completely effective as an antiestrogen if administered repeatedly with E2 whereas a single injection of monohydroxytamoxifen (120 micrograms) was sufficient to inhibit fully E2 action in the uterus for up to 4 days. Because LY117018 has a shorter duration of action than monohydroxytamoxifen, a high dosage ratio of LY117018 over monohydroxytamoxifen is required to maintain effective competitive antagonism in the uterus. Overall, these findings suggest that monohydroxytamoxifen and LY117018 probably act through the same mechanism of action via the estrogen receptor.

Animals↗
PubMed1983

Determination and pharmacology of a new hydroxylated metabolite of tamoxifen observed in patient sera during therapy for advanced breast cancer.

A new hydroxylated metabolite of tamoxifen, Metabolite Y [trans-1-(p-beta-hydroxyethoxyphenyl)-1,2-diphenylbut-1-ene] was characterized and subsequently measured by high-performance liquid chromatography in serum from patients receiving normal (10 mg twice daily) and high dose (greater than or equal to 150 mg twice daily) tamoxifen therapy for treatment of advanced breast cancer. In normal-dose patients, the serum level of Metabolite Y ranged between 6 and 60 ng/ml. This contrasted with serum levels of 80 to 180 ng/ml for tamoxifen and 200 to 300 ng/ml for N-desmethyltamoxifen, the major metabolite of tamoxifen. Serum levels of all three components were unchanged in one patient during the 24 hr after the cessation of tamoxifen therapy. Maximum serum levels of Metabolite Y were 800 ng/ml with concentrations of 1 micrograms/ml for tamoxifen and 2 micrograms/ml for N-desmethyltamoxifen in a patient on a 2-year course of high-dose therapy. Metabolite Y inhibited the binding of 17 beta-[3H]-estradiol to rat uterine and human breast carcinoma estrogen receptor. However, this metabolite was only weakly active: monohydroxytamoxifen [relative binding affinity (RBA) = 280]; tamoxifen (RBA = 6); Metabolite E (RBA = 3); N-desmethyltamoxifen (RBA = 4); Metabolite Y (RBA = 0.5). In 3-day immature rat uterine weight tests, Metabolite Y was a partial agonist with weak antiestrogenic activity. Although Metabolite Y has only weak activity, this compound would be expected to contribute to the overall antiestrogenic and antitumor properties of tamoxifen during therapy.

Animals↗
PubMed1982

High affinity binding of anti-oestrogen to the chick liver nuclear oestrogen receptor.

Tamoxifen is a potent inhibitor of specific oestrogen-induced yolk protein synthesis by chicken liver. The oestradiol receptor in salt extracts of liver nuclei from oestrogen-treated chicks has a K(d) for oestradiol of 0.7+/-0.2nm. Tamoxifen and its metabolite, monohydroxytamoxifen, compete for binding to the salt-soluble nuclear receptor with K(i) values of 2.6 and 0.1nm respectively. The anti-oestrogens show much less inhibition of [(3)H]oestradiol binding when assays are carried out using intact nuclei. The competition by unlabelled oestradiol for [(3)H]oestradiol binding to receptor is identical in both salt extracts and intact nuclei. This suggests that intact nuclei contain components which bind anti-oestrogens, but not oestradiol. While tamoxifen and desmethyltamoxifen will readily dissociate from the salt-soluble nuclear oestrogen receptor, monohydroxytamoxifen does not dissociate under the conditions generally used for exchange assays. A modified assay was developed in which 60-70% of monohydroxytamoxifen-bound sites were shown to be exchangeable for [(3)H]oestradiol. Soluble receptor preparations were first incubated in a 1.7% charcoal suspension at 37 degrees C for 15min before assay of specific oestradiol binding. This technique was used in examining the effects of tamoxifen and monohydroxytamoxifen given in vivo on the nuclear oestrogen receptor concentration. Despite their 30-fold difference in binding affinity for the receptor, both anti-oestrogens increase nuclear receptor levels to about the same degree. When given with oestradiol, both compounds have the same apparent partial inhibitory effect on the oestrogen-induced increase in nuclear receptor. These data are consistent with the metabolic hydroxylation of tamoxifen before binding to the hepatic oestrogen receptor.

Animals↗
PubMed1982

Metabolites of tamoxifen in animals and man: identification, pharmacology, and significance.

Over the past decade, the non-steroidal antiestrogen tamoxifen has gained general acceptance for the palliative treatment of breast cancer. Although there has been much interest in the pharmacology of tamoxifen, our knowledge of its metabolism in laboratory animals and patients is incomplete and the precise mechanism of action within target tissue and breast tumor cells is unknown. This review briefly describes the pharmacology of tamoxifen in various laboratory species and patients. Several metabolites of tamoxifen are known and their relative potencies as estrogens and antiestrogens are compared with the parent compound. Apart from monohydroxytamoxifen, none of tamoxifen's metabolites are more potent antiestrogens, but a metabolite in the dog, Metabolite E, is fully estrogenic. Routine assays (tlc, HPLC, glc/ms) are available to detect tamoxifen, N-desmethyltamoxifen, monohydroxytamoxifen, and a newly identified metabolite, designated Metabolite Y, in biological fluids. Continuous therapy with tamoxifen (10 mg bid) produces steady-state levels (100-200 ng/ml serum) within 4 weeks. Levels of N-desmethyltamoxifen are often up to twice the levels achieved with tamoxifen, while levels of monohydroxytamoxifen and Metabolite Y are below 10 ng/ml. Although monohydroxytamoxifen has a high binding affinity for the estrogen receptor, the metabolic activation of tamoxifen is an advantage rather than a requirement for antiestrogenic activity. The action of tamoxifen in vivo is the net result of the individual actions of the parent compound and its metabolites competing for the occupation of receptors within target tissues and tumors.

Breast Neoplasms↗
PubMed1981

Geometric isomers of substituted triphenylethylenes and antiestrogen action.

The estrogenic and antiestrogenic activities of tamoxifen ICI 47,699, enclomiphene, zuclomiphene, and the geometric isomers of monohydroxytamoxifen and CI628 were determined in the 3-day immature rat uterine weight test. Tamoxifen, enclomiphene, and the releated geometric isomers of monohydroxytamoxifen and CI628 were partially estrogenic with antiestrogenic properties. ICI 47,699 and zuclomiphene were predominantly estrogenic; however, an antiestrogen effect for zuclomiphene (100 micrograms daily) was demonstrable and large doses of ICI 47,699 (1 or 10 mg daily) inhibited full estrogen action. In contrast, the geometric isomers of monohydroxytamoxifen and CI628 related to ICI 47,699 and zuclomiphene were partially estrogenic with antiestrogenic properties. The estrogenic properties of ICI 47,699 were classified in three ways: elevation of uterine wet weight, increase in whole uterine DNA, and increase in the mitotic activity of luminal epithelial cells. In general, ICI 47,699 was able to initiate estrogenic responses of DNA synthesis or mitosis by translocation of fewer cytoplasmic estrogen receptors to the nuclear compartment than tamoxifen. A model is proposed to explain antiestrogen action in terms of the geometric requirements for receptor binding. It is suggested that the position in space of the alkylaminoethoxyside chain is of fundamental importance. Overall, these data lend support to the view that a structurally specific ligand-estrogen receptor complex can influence the future events within a target tissue to produce either an agonist or an antagonist response.

Animals↗
PubMed1980

Evidence for the metabolic activation of non-steroidal antioestrogens: a study of structure-activity relationships.

1 The oestrogenic and antioestrogenic activities of tamoxifen and monohydroxytamoxifen have been compared with those of para-methoxy, -methyl, -fluoro, and -chloro tamoxifen in the 3 day immature rat uterine weight test.2 The oestrogenic activity of mestranol, a steroid with low oestrogen receptor binding affinity which is believed to be demethylated to ethinyl oestradiol before exerting its effects, was less potent than ethinyl oestradiol when assayed in the 3 day immature rat uterine weight test. Similarly, para-methoxytamoxifen was less active than monohydroxytamoxifen in oestrogenic and antioestrogenic tests.3 The introduction of a para-methoxy group into tamoxifen did not affect oestrogenic or antioestrogenic activity.4 All the derivatives of tamoxifen were partial oestrogen agonists when compared with oestradiol benzoate in the 3 d immature rat uterine weight test. All test compounds inhibited the uterotrophic activity of oestradiol benzoate (0.16 mug daily) in a dose-related manner. The order of potency was: monohydroxytamoxifen > tamoxifen identical with methoxytamoxifen > p-fluoro identical with p-chloro identical with p-methyltamoxifen.5 Tamoxifen was approximately equiactive with its p-methyl, p-fluoro and p-chloro derivatives in the ability to inhibit [(3)H]-oestradiol binding to rat uterine oestrogen receptors in vitro.6 Tamoxifen was approximately equiactive with its p-methyl and p-fluoro derivatives in the ability to inhibit vaginal cornification of ovariectomized rats upon intravaginal administration with oestradiol (3.2 ng total dose).7 Since tamoxifen in vivo was more active as a partial oestrogen agonist and antagonist than the para substituted fluoro, chloro and methyl derivatives that cannot undergo metabolic hydroxylation to monohydroxytamoxifen, whereas the antioestrogenic activity of the compounds upon local application in the vaginal cornification test was equivalent as was their ability to inhibit [(3)H]-oestradiol-17beta binding to the oestrogen receptor in vitro, it is suggested that at low doses; i.e. over the range of the partial agonist dose-response curve, the biological activity of tamoxifen is the net result of the activities of the parent compound and its metabolites.8 The results demonstrate that metabolic activation of non-steroidal antioestrogens is only an advantage and not a requirement for antioestrogenic activity.

Animals↗