A. E. Wakeling

Biology and mode of action of pure antioestrogens

The properties of ICI 164,384, a 7 alpha-alkyl amide analogue of 17 beta-oestradiol, are described and contrasted with those of tamoxifen. These studies demonstrate that ICI 164,384 has many of the characteristics of a pure antioestrogen.

Type I IGF receptor and acquired tamoxifen resistance in oestrogen-responsive human breast cancer cells

Tamoxifen inhibited the oestrogen-stimulated proliferation of MCF-7 cells but had little effect on the oestrogen-stimulated proliferation of two tamoxifen-resistant variants (RL-3 and AL-1). The lack of oestrogen antagonist activity in the resistant cells was largely a result of an increased oestrogen agonist activity of tamoxifen on cell proliferation. Proliferation of the tamoxifen-resistant cells was also stimulated by 4-hydroxytamoxifen but not by ICI 164,384, a structurally distinct pure anti-oestrogen. Tamoxifen does not have increased oestrogen agonist activity for the induction of a series of oestrogen-regulated RNAs, and this suggests that the increased agonist activity may be restricted to key components involved in the proliferative response. Tamoxifen-stimulated cell proliferation was dependent on insulin-like growth factor I (IGF-1) in the resistant cells, suggesting that tamoxifen stimulates cell proliferation by sensitising cells to the proliferative effects of IGF-1. This may involve induction of the type-I IGF receptor.

Receptor binding and biological activity of steroidal and nonsteroidal antiandrogens

Abstract The competition of a series of steroidal androgens and steroidal and non-steroidal antiandrogens, with [3H]-methyltrienolone, for androgen receptor binding sites of the rat prostate, has been studied under conditions designed to distinguish between agonists and antagonists. The antiandrogenic activity of these compounds was determined in both castrate and intact male rats. Androgenic activity was monitored by measurements of prostate growth in castrate rats and also by induction of prostatic S-adenosyl- l -methionine decarboxylase. We report for the first time the existence of partial agonist (androgenic) activity in a number of novel antiandrogens. In these studies no correlation was established between biological potency and relative receptor binding affinity. We were also unable to distinguish unequivocally between agonists and antagonists on the basis of receptor binding behaviour.

Responses to Pure Antiestrogens (ICI 164384, ICI182780) in Estrogen-Sensitive and-Resistant Experimental and Clinical Breast Cancer

The last ten years has seen the emergence of a new class of pharmacological agents termed pure antiestrogens (reviewed in Refs. 1, 2). These compounds, which were originally discovered by ICI Pharmaceuticals Division (now Zeneca Pharmaceuticals) in the UK, have the unique property of binding to the estrogen receptor (ER),3 producing a receptor complex which lacks estrogenic a~tivity.4.~ They are of use in two important areas of breast cancer research. Firstly, as clinical agents, where it is hoped that their ability to induce total estrogen deprivation will improve the effectiveness of endocrine therapy. Secondly, as pharmacological probes to investigate the cellular and molecular actions of estrogens and tamoxifen. Inherent in each of these areas of research are questions associated with the impact pure antiestrogens may have on the therapy of endocrine-resistant states and whether resistance develops as a consequence of incomplete estrogen withdrawal; with tumor cells more efficiently utilizing either a reduced estrogenic pool or the agonistic activity of an antiestrogen,

Interaction of the antioestrogen ICI 164,384 with the oestrogen receptor

The use of partially purified preparations of the human uterine oestrogen receptor has enabled, for the first time, a study of the binding of the steroidal, pure antioestrogen ICI 164,384 [N-n-butyl-11-(3,17 beta-dihydroxy-oestra-1,3,5(10)-trien-7 alpha-yl)N-methyl-undecamide] to the oestrogen receptor. Scatchard analyses of the binding of [3H]oestradiol and [3H]ICI 164,384 to the receptor show that the equilibrium dissociation constants for the interactions of these ligands with the receptor at 0 degrees C are 0.44 and 0.69 nM respectively. The concentration of receptor binding sites for the agonist was 1986 fmol/mg protein whilst that for the antagonist was 1400 fmol/mg protein. The affinity of the antioestrogen-receptor complex for DNA-cellulose does not increase following exposure to conditions that transform the oestrogen-receptor complex.

Short-term effects of pure anti-oestrogen ICI 182780 treatment on oestrogen receptor, epidermal growth factor receptor and transforming growth factor-alpha protein expression in human breast cancer

Expression of oestrogen receptor (ER), epidermal growth factor receptor (EGFR) and transforming growth factor-alpha (TGF alpha) proteins was assessed by immunocytochemistry on primary breast cancer specimens obtained before and following short-term (7-day) presurgical exposure to pure anti-oestrogen (7 alpha- [9- (4,4,5,5,5-pentafluoropentylsulphinyl) nonyl] estra-1,3,5, (10)-triene-3,17 beta-diol, ICI 182780) treatment and compared with no-treatment controls. Paired needle-core and mastectomy samples were obtained from 21 patients. Effects of ICI 182780 (10(-7)M) on MCF7 breast cancer cell ER, EGFR and TGF alpha expression were also examined over 14 days. ER protein was significantly suppressed by ICI 182780 in vivo (P = 0.009) and comparative analysis of short term ICI 182780 effects in vitro, using ER-positive MCF7 cells, gave largely equivalent results. EGFR and TGF alpha protein levels were unaltered by treatment. ICI 182780 suppresses ER without a concomitant rise in either EGFR or TGF alpha.

A comparative study of the interaction of oestradiol and the steroidal pure antioestrogen, ICI 164,384, with the molybdate-stabilized oestrogen receptor

The kinetics of binding of oestradiol and the steroidal pure antioestrogen ICI 164,384 to the molybdate-stabilized oestrogen receptor, partially purified from pig and human uterine tissue, were determined. ICI 164,384 bound directly to the oestrogen receptor protein and the kinetic parameters of this interaction were, in general, similar to those for the binding of oestradiol, regardless of the source of the receptor protein. However, the rate of association of oestradiol, regardless of the source of the receptor protein. However, the rate of association of the antagonist with the receptor protein was slower when compared to that of oestradiol. Furthermore, the concentration of binding sites for the two ligands was of the same order. The binding of oestradiol resulted in a steroid-receptor complex which could be transformed in vitro, to a form with increased affinity for DNA-cellulose. However, the complex formed between ICI 164,384 and the receptor protein did not show increased affinity for DNA-cellulose when exposed to conditions that transformed agonist-receptor complexes. Therefore, the binding of ICI 164,384 to the oestrogen receptor protein results in a suppression of the transformation process. A similar suppression in vivo may account for the pure antagonist properties of ICI 164,384.

Effects of the antioestrogen, ICI 164,384, on oestrogen induced RNAs in MCF-7 cells

The effects of ICI 164,384 on the expression of six oestrogen-regulated RNAs (pNR-1, pNR-2, pNR-13, pNR-17, pNR-25 and pNR-100) and the 46 kDa secreted protein were measured in MCF-7 cells. In marked contrast to tamoxifen, an antioestrogen commonly used in the treatment of breast cancer, ICI 164,384 administered alone had little or no effect on the RNAs or protein. ICI 164,384 completely inhibited the induction of the RNAs and 46 kDa protein by oestradiol. Although ICI 164,384 has an affinity for the human oestrogen receptor only slightly less than that of oestradiol, half maximal inhibition of oestradiol action was attained with between a 50 and 150-fold molar excess of ICI 164,384. The pNR-1 RNA is induced by tamoxifen but this induction was abolished by ICI 164,384. Thus, ICI 164,384 acts as a potent antioestrogen for the regulation of the expression of specific oestrogen-responsive genes in human breast cancer cells.

Loss of estrogen receptor (ER) expression in MCF-7 cells following long-term exposure to fulvestrant [Abstract]

Forest decline has been going on for last decades i n Europe, North America and in the Russian Far East. This process gives rise to n egative ecological and economic problems. In many countries the monitoring activiti es have been undertaken, including surveys at national and sub-national leve l. A considerable number of the hypotheses have been proposed as the forest decline reasons, but neither has gained universal recognition. At first time for a main rea son of the decline was taken industrial pollution of the environment, at present , however, majority of researchers are inclined to the opinion that both natural and i ustrial causes are to be blamed for forest decline. Large-scale forest decline of natural Picea jezoens is and Abies nephrolepis forests in the Russian Far East has happened repeatedly and spread all over vast areas. The first reliable information about it is related to 1 920s. In succeeding years forest decline was recorded in 1930s – 1940s in Primorye a nd in 1950s in Priamurye. Once again forest decline spread all over enormous areas of fir-spruce forests in the Sikhote-Alin during 1970s – 1980s. The large-scale fir and spruce forest decline typic al for Primorye and Priamurye was not observed in Sakhalin and Kamchatka, as well as in spruce formation in the northern areas of the Amur Region. In this work the investigation materials of declini ng plots of fir-spruce forests in Primorye Territory and the main results of monitori ng of fir-spruce forest decline in the basins of the rivers Svetlaya, Bol’shaya Peya a nd Edinka are presented. In the light of global dark-conifer forest deterioration t he critical review of the previous investigation is considered. Picea jezoensis is the principal forest-forming spe cies of fir-spruce forests in the Russian Far East; high hydrophily and low tolerance to drought conditions characterise it; horizontal root system makes spruc e strongly depending upon temperature and moisture of the soil surface layers . Fir-spruce forest decline has occurred on various e lem nts of relief (mountain slopes of different aspects and steepness, plateau’ s surfaces, over-flood plain and transitional terraces in rivers valleys) placed on the different altitude heights (from sea