Effect of two antiprogestins (mifepristone and onapristone) on endometrial factors of potential importance for implantation

OBJECTIVE

To investigate the effects of postovulatory administration of antiprogestins on endometrial factors that may be of importance for successful implantation.

DESIGN

Ten women were given 200 mg mifepristone and an additional 10 women 400 mg of onapristone 48 hours after the LH surge in urine (LH + 2).

MAIN OUTCOME MEASURE(S)

Biopsies were assessed for histologic dating and the immunolocalization of [1] leukemia inhibitory factor, [2] 15-hydroxyprostaglandin dehydrogenase, and [3] the cell proliferation marker Ki 67. Hormonal measurements in blood and urine were used to monitor the effects on the ovarian cycle. Glycodelin (placental protein 14) concentrations were measured in blood taken on LH + 12.

RESULT(S)

Treatment with antiprogestins retarded the development of secretory changes without affecting the length of the luteal phase. In addition, there was reduced immunostaining for 15-hydroxyprostaglandin dehydrogenase within glands and a significant reduction in serum levels of glycodelin. Reduced immunostaining for leukemia inhibitory factor also was apparent within glands in biopsies taken on LH + 6 of the treatment cycle. Increased Ki 67 immunostaining was observed on both cycle days after treatment, consistent with P antagonism.

CONCLUSION(S)

Administration of mifepristone and onapristone adversely affects uterine receptivity. This adds further evidence to support their potential as a method of postovulatory fertility control.

Estrogenic and progestagenic activities of physiologic and synthetic androgens, as measured by in vitro bioassays

Estrogenic activities of testosterone (T) and 5a-dihydrotestosterone (DHT) were detected and measured by using their specific stimulatory effects on alkaline phosphatase (AP) activity in human endometrial adenocarcinoma cells of the Ishikawa Var-1 line. These two physiologic androgens were able to induce, at microM concentrations, estrogenic effect believed to be mediated by the estrogen receptor (ER) since the antiestrogens ICI-164384 and 4-hydroxytamoxifen (OHTam), but not the antiandrogens hydroxyflutamide (OHFl) or cyproterone acetate (CPA), reversed that effect. By using another in vitro bioassay, based on the progestin-specific stimulation of AP activity in cells of the T47D human breast cancer line, progestagenic activity was detected and measured in T, DHT and three synthetic androgens: nandrolone (19-nortestosterone). 7 alpha-methyl 19-nortestosterone (MENT) and mibolerone (7 alpha, 17 alpha-dimethyl 19-nortestosterone) (DMNT). While progestagenic effects of T and DHT required relatively high concentrations (microM levels), the synthetic androgens stimulated AP activity at nM or pM levels. These effects seem to be mediated by the progesterone receptor (PR), since they are completely abolished by the antiprogestins RU-486, ZK-98299 and ZK-112993, but not by the antiandrogen OHFl. These simple in vitro bioassays, expressing biological effects of the test compounds in human cells in culture, revealed dual or multiple hormonal activities coexisting in a single compound and provide quantitative information of considerable pharmacological importance concerning the complex actions of drugs.

The antiovulatory effect of the antiprogestin onapristone could be related to down-regulation of intraovarian progesterone (receptors)

The present study was undertaken to investigate intraovarian mechanism(s) for the antiovulatory effect of Onapristone (ON), because antiprogestins possessing the same antiprogestational activity and inhibiting the preovulatory LH surge to the same extent differ in their antiovulatory potency. Ovulation was induced by treating immature female rats with pregnant mare serum gonadotropin (PMSG) for folliculogenesis and hCG for the induction of ovulation. The animals were treated twice with ON (200 mg/kg 42 h and 48 h after PMSG) and killed at different times. The ovulation rate was assessed by counting the number of ova in the fallopian tubes and uteri. Blood and ovaries were collected for radioimmunoassay (RIA) of steroid hormones and histological analysis for 3beta-hydroxysteroid dehydrogenase (3beta-HSDH), 17beta-hydroxysteroid dehydrogenase (17beta-HSDH), progesterone (PR), estrogen (ER) and androgen (AR) receptors. Treatment with ON totally blocked ovulation and the progesterone (P4) surge was significantly diminished in comparison to the control (6-8 h post-hCG), whereas androgen levels remained unaffected. The decreased P4 concentrations correlated well with a reduced staining intensity of 3beta-HSDH in granulosa cells of tertiary follicles. Moreover, we observed a down-regulation of PR in granulosa cells of tertiary follicles. Additionally, in secondary and tertiary follicles the expression of AR between 0 and 6 h after hCG was reduced. These results suggest that the antiovulatory effect of the antiprogestin ON is related to down-regulation of intraovarian progesterone, caused by attenuated 3beta-HSDH activity and PR expression. One can thus assume that intraovarian P4 is an important factor for the induction of ovulation. An effect of ON on the staining intensity of 17beta-HSDH in theca and granulosa cells could not be observed at any time. In conclusion, the inhibition of ovulation induced by the antiprogestin, ON, could be related to decreased intraovarian progesterone production through reduced 3beta-HSDH activity and the down-regulation of PR.

Influence of an antiprogestin (onapristone) on in vivo and in vitro fertilization

The effects of a progesterone antagonist (onapristone) on heat synchronization, luteinizing hormone (LH) surge, ovulation, oocyte maturation and fertilization of superovulated ewes were studied. Its effects on in vitro bovine oocyte maturation and fertilization were also studied. Estrus synchronization and superovulation treatments were applied to 39 adult ewes using an intravaginal sponge with fluorgestone acetate for 9 days with injections of prostaglandin F2 alpha and pregnant mare's serum gonadotrophin given 24 h before sponge withdrawal. The animals were randomly assigned to four different groups; T1 receiving only the synchrony treatment (n = 11); T2 ewes received two injections of onapristone (1 mg kg-1, i.v.) 12 h apart from 3 h after sponge withdrawal (n = 10); T3 ewes received two injections of progesterone 12 h apart from sponge withdrawal (n = 10); and, T4 ewes received both onapristone and progesterone as described (n = 8). Ewes were mated by a fertile male during estrus. Progesterone and LH were measured during the superovulation period in plasma samples taken every 4 h. Uterine flushings for ova recovery were performed at 5 days (n = 25), 48 h (n = 5) and 24 h (n = 5). Non-fertilized oocytes collected at 24 and 48 h were checked for meiosis resumption. The effects of two doses of onapristone (D1 and D2) on in vitro bovine oocyte maturation (control = 100, D1 = 100 and D2 = 100) and fertilization (control = 107, D1 = 40 and D2 = 75) were also studied. The percentage of animals showing heat signs was significantly lower in group T3 (50% vs. 100%). The onset of oestrus (27.6, 24.8, 68.8 and 25.5 h, respectively for T1, T2, T3 and T4) and an LH surge (32.3, 28.8, 76.5 and 30.5 h, respectively for T1, T2, T3 and T4) after sponge withdrawal were significantly delayed in group T3. There were no significant differences in the intervals between estrus and LH surge among groups (4.61 +/- 0.75 h). The response and ovulation rates until 40 h after sponge withdrawal (group T3 excluded) were similar among groups, but the fertilization rates were significantly lower in groups T2 and T4 when compared with T1 (2% and 3% vs. 41%, respectively; P < 0.001) due to sperm arrest in the cervix. Ova recovery rate decreased significantly from 24-48 h to 5 days and was not affected by treatments (76.9% vs. 37.1% respectively). Onapristone did not affect the resumption of meiosis. Fertilization of bovine oocytes in vitro decreased significantly only in group D2 when compared to control (48% vs. 62.6%, respectively). In conclusion, onapristone treatment during the preovulatory period did not interfere with normal synchronization of estrus, ovulation and oocyte maturation but severely compromised fertilization by arresting spermatozoa in the cervix.

Progesterone-independent activation of rat brain progestin receptors by reproductive stimuli

Activation of steroid hormone receptors by steroid hormones alters both the physiology and behavior of animals. Steroid hormone receptors (e.g., progestin receptors) can also be activated in the absence of steroid hormones by pharmacological treatment with neurotransmitters or neuropeptides. However, it is not known if progesterone-independent activation of brain progestin receptors occurs under natural, physiological, conditions. We report that increases in reproductive behavior and brain immediate early gene expression in female rats induced by mating stimuli can be blocked by prior treatment with progesterone antagonists in the absence of circulating progesterone. This suggests that progestin receptors are activated in a progesterone-independent manner by a physiologically relevant stimulus in female rats, thus implicating a novel pathway by which mating stimuli and other environmental influences could activate steroid receptors to influence neuronal response and behavior.

Comparative effectiveness of three antiprogestins alone and in combination with anordiol in terminating pregnancy in the rat

The effectiveness of mifepristone, onapristone, and ORG 31806 alone or in combination with anordiol to terminate pregnancy in the rat was evaluated. ORG 31806 at a dose of 2 mg/kg/day, mifepristone at 4 mg/kg/day, and onapristone at 8 mg/kg/day, terminated pregnancy in all treated animals. Anordiol, an antiestrogen, at a dose of 5 mg/kg/day, terminated pregnancy in all treated animals. Anordiol acted synergistically with all three antiprogestins terminating pregnancy in the rat. The antiprogestins at doses that were either partially effective or non-effective became 100% effective when administered with a non-effective dose of anordiol. Thus, combination of ORG 31806 (1 mg/kg/day) plus anordiol (0.31 mg/kg/ day), mifepristone (1 mg/kg/day) plus anordiol (0.62 mg/ kg/day), and onapristone (2 mg/kg/day) plus anordiol (2.5 mg/kg/day) terminated pregnancy in all treated animals. These combinations of the antiprogestins and anordiol decreased significantly the serum progesterone levels but not serum 17 beta-estradiol levels. The present results indicate that the most potent combination was ORG 31806 plus anordiol.

Antiprogestins and iatrogenic glucocorticoid resistance

The antiglucocorticoid action of the antiprogestin RU 38486 has interfered with its successful clinical application in long-term treatment. Several new antiprogestins (Org 31710, Org 31806 and ZK 98299) have recently been developed with the aim to eliminate this side-effect. We have used a human lymphocyte proliferation assay to estimate the antiglucocorticoid potency of RU 38486 and the newer antiprogestins. In this assay 100 nmol/L RU 38486 shifted the dexamethasone inhibition curve by at least one order of magnitude. The other antiprogestins showed no effect at 100 nmol/L. RU 38486 (30 nmol/L) was able to antagonize 1000 nmol/L dexamethasone. The other antiprogestins showed only slight effects even at 1000 nmol/L. We conclude that the new antiprogestins have antiglucocorticoid effects that are one to two orders of magnitude lower than that of RU 38486. This may make them more suitable than RU 38486 for application in long-term antiprogestin treatment.

Induction of connexin 32 expression by potential embryonic signals in rabbit uterine epithelium

Connexin 32 induction is found in rabbit uterine epithelium as a response to embryo recognition. Here we have chosen this connexin 32 expression as a cell biological marker to define the type of a locally acting embryonic signal. 17 beta-estradiol, onapristone, catechol estrogen (4-hydroxy-estradiol), prostaglandins E2 and F2 alpha, db-cAMP, and glass beads as mechanical stimuli were given to pseudopregnant animals on day 4, 5 or 6 posthuman chorionic gonadotropin (hCG). The induction of connexin 32 corresponded to the time of implantation at days 6-8 post-hCG by immunohistochemistry and Northern blot analysis. Untreated pseudopregnant animals started to express connexin 32 on day 8 post-hCG. In animals treated with 4-hydroxy-estradiol, 17 beta-estradiol or prostaglandins, connexin 32 expression started 1 day earlier (day 7 post-hCG) and led to an enhanced connexin 32 expression on day 8 post-hCG compared to control animals. The antigestagen, onapristone, as well as cAMP did not alter the endogenous program. Mechanical stimuli led to a high expression of connexin 32 starting at day 7 post-hCG whereas in pregnancy the blastocyst induces connexin 32 expression from day 6 postcoitum onwards. Combination of mechanical stimuli with 17 beta-estrogen advanced the induction to day 6 post-hCG. We conclude that a mechanical stimulus in combination with 17 beta-estradiol induces connexin 32 synthesis in a similar manner as compared to the blastocyst during pregnancy.

An amino-terminal truncated progesterone receptor isoform, PRc, enhances progestin-induced transcriptional activity

Previously we reported the identification of two unique progesterone receptor (PR) messenger RNA transcripts that encode a smaller PR isoform, termed the C-receptor (PRc). These two PR transcripts encode a protein that is N-terminally truncated, so that it lacks the first zinc finger of the DNA binding domain, but still contains a complete hormone binding region with sequences for dimerization and nuclear localization. We also have demonstrated the existence of a 60-kDa progestin-specific binding protein in progestin target cells using a monoclonal antibody directed to the C-terminus of PRs, suggesting that these two novel transcripts generate a truncated form of PR. In this paper, we address the hypothesis that the C-receptor arises from the initiation of translation of a methionine C-terminal to the methionine start sites that generate the larger 94-kDa A and 116-kDa B human PR isoforms. The studies shown here support the postulate that another downstream in-frame methionine within the PR-coding region can serve as a translation initiation site for the generation of a third PR protein. A partial PR complementary DNA, lacking the translation start sites for B- and A-receptors was translated in vitro. The synthetic protein product bound [3H]progestins and unlabeled progestins. The antiprogestin RU486 also competed for this binding. Transfection of this partial PR complementary DNA into PR-negative HeLa cells resulted in progestin-specific binding activity. Because the third PR isoform lacks the first zinc finger of the DNA binding domain, but contains sequences for dimerization, we reasoned that the C-receptor isoform would be transcriptionally in-active and not bind DNA directly. Surprisingly, however, in the presence of A- and/or B-receptors, we found that C-receptors can modulate the transcriptional activity of A- and/or B-receptors using a reporter gene. These studies emphasize that multiple receptor isoforms may have distinct biological properties, and that the truncated C-receptor may play a role in explaining some of the pleiotropic effects of progestins.

Induction of a novel conformation in the progesterone receptor by ZK299 involves a defined region of the carboxyl-terminal tail

Progesterone receptor antagonists are a promising class of therapeutic drugs indicated for the treatment of a variety of reproductive conditions. Understanding their mechanism of action at the molecular level is an important prerequisite for the development of future generations of these drugs. Using limited proteolytic analysis to monitor conformational changes in the progesterone receptor, we can detect three distinct classes of progestin antagonist. The effect of the first, RU486, on the conformation of the carboxyl terminus of the receptor has been previously described. The second, exemplified by RWJ 47626, a nonsteroidal compound with in vitro antiprogestin activity, induces a proteolytic fragment pattern indistinguishable from that induced by the agonist R5020. Finally, ZK299 induces a fragment pattern intermediate between that induced by R5020 and RU486. Site-directed mutagenesis of the carboxyl-terminal tail of the progesterone receptor indicates that the region containing the putative activation function AF-2 is differentially exposed to proteolytic attack depending on the nature of the antagonist bound. The differentially exposed region is most accessible when the antagonist RU486 is bound, less accessible when the antagonist ZK299 is bound, and least accessible when the antagonist RWJ47626 or agonist R5020 is bound. The results suggest that multiple types of antiprogestin can be defined in terms of their effects on the conformation of the carboxyl-terminal activation function of the progesterone receptor.

The antiovulatory activity of progesterone antagonists is not correlated to their antiprogestational potency in the rat

Progesterone antagonists often differ in regard to their potency to block ovulation in rats although they may possess similar 'antiprogestational' (abortive) activity. Therefore, the questions arose as to: (a) whether antiovulatory and antiprogestational effects (on endometrial and mammary gland parameters) of antiprogestins correlate at all; and (b) which mechanism(s) may be responsible for their ability to abolish ovulation. To answer these questions we set out to compare the influences of two progesterone antagonists, Onapristone (ON) a very potent and ZK 136798 only a weak inhibitor of ovulation, to assess changes on the one hand on typical progestational actions and on the other hand on factors known to regulate ovulation. For this purpose immature PMSG/hCG primed and adult female rats and infantile female rabbits were treated either with ON, ZK 136798 or vehicle in different treatment schedules. In these investigations ON and ZK 136798 showed similar antiprogestational activities on the progesterone-induced development of mammary glands (rats) and the secretory transformation of endometrium (rabbits). ON blocked an induced or a spontaneous ovulation, whereas ZK 136798 only revealed a very weak antiovulatory effect. Both ON and ZK 136798 stimulated basal levels of LH, estradiol, and testosterone, whereas the preovulatory LH surge was decreased to the same extent. Interestingly, in contrast to ZK 136798, ON reduced the preovulatory increase in progesterone secretion. These results clearly indicate: (a) that antiovulatory potency and antiprogestational activity may not be correlated in the rat; and (b) that decreased preovulatory levels of progesterone following treatment with ON may play an important role in intraovarian mechanism(s) contributing to a blocking of ovulation.

Synthesis and mutagenicity of some cyclopenta[c]phenanthrenes and indeno[c]phenanthrenes

An efficient two-step synthesis of 8(H)-9,10,11,12-tetra-hydrodicyclopenta[a,c]phenanthren-7-one, based on the high pressure Diels-Alder cycloaddition of 4-acetoxy-2-cyclopenten-1-one with 1-(1-naphthyl)cyclopentene and a subsequent dehydrogenation-aromatization reaction, is reported. Further, the synthesis of two cyclopenta[c]-phenanthrenes and indeno[c]phenanthrenes is described. Structural analysis of the new products by 1H and 13C NMR spectroscopy is presented. The mutagenic activity of the compounds in Salmonella typhimurium was estimated by Ames' test. Three compounds were shown to be mutagenic for the strain TA 100. The mutagenic activities exhibited by cyclopenta[c]phenanthrenes are compared with those shown by the related cyclopenta[a]phenanthrenes and then discussed with respect to the effect of the cyclopentane ring facing the bay region. Indeno[c]phenanthrenes are mostly inactive. The effect of benzoannulation on the mutagenic activities of cyclopenta[c]phenanthrenes is discussed.

Onapristone and prostaglandin E2 induction of delivery in the rat in late pregnancy: a model for the analysis of cervical softening

OBJECTIVES

Our purpose was to develop a method to induce premature delivery in rats and to use this method to identify biochemical changes that are critical to cervical dilatation by comparison to changes that occur during term delivery.

STUDY DESIGN

Rats were treated with antiprogestational agents onapristone or lilopristone in combination with prostaglandin E2 or estradiol on day 19 of pregnancy to induce delivery before term. Mechanical and biochemical changes of the isolated cervix were compared with changes found at term and in 20-day controls.

RESULTS

Rats treated with a combination of onapristone and prostaglandin E2 were consistently delivered 25 hours after treatment began. The physical characteristics of the cervix of treated rats changed to match those of term cervices. The ratio of the small sulfated proteoglycan (decorin) to collagen changed on induction to match the ratio found at term.

CONCLUSIONS

This induction protocol can be used to advance the time of delivery in rats, with the further advantage that the time of delivery can be accurately predicted. The data strengthen a proposed model in which the interaction of decorin and collagen is an important determinant of the biomechanical properties of the cervix during pregnancy.

Differential regulation of nitric oxide in the rat uterus and cervix during pregnancy and labour

The aim of this study was to determine if nitric oxide (NO) production and nitric oxide synthase (NOS) isoforms change within the uterus and cervix during pregnancy and labour either at term or preterm. NO production was compared in the rat uterus and cervix of non-pregnant and pregnant rats on days 18-22 prior to labour, day 22 during delivery, 1 day post-partum and after treatment with either 10 mg onapristone or progesterone. Uterine NO synthesis, reflected in nitrite production, increased during gestation (194.2 +/- 22.6 nmol/g on day 19) compared with the non-pregnant state (76.2 +/- 18.4 nmol/g, P < 0.05) and decreased during term labour and post-partum. Furthermore, injection of lipopolysaccharide (LPS) (100 micrograms/rat i.p.) on day 20 of gestation resulted in a significant increase in NO synthesis after 6 h. Conversely, cervical NO synthesis and nitrite production was low in the non-pregnant (65.1 +/- 9.2 nmol/g) and pregnant animals on days 18-22 of gestation (53.2 +/- 9.0 nmol/g on day 22, P > 0.05), but markedly increased during term labour (139 +/- 28.6 nmol/g, P < 0.05). Treatment with the antiprogestin onapristone suppressed uterine NO production and increased cervical production while continuous administration of progesterone from day 19 had the opposite effect. LPS produced a significant increase in cervical NO production in both the pregnant (8-fold) and non-pregnant (4-fold) states. All three known NOS isoforms (i.e., iNOS, nNOS and eNOS) were detected in the cervical samples but only two were present in the uterus (iNOs and eNOS). An increase in the presence of iNOS occurred during labour at term compared with cervices collected from day 19. This was contrary to the measurements of the isoform in the uterus. Also, there was a similar increase of nNOS in the cervix during labour. This isoform seemed absent in the uterus during gestation. No significant changes occurred in the abundance of eNOS in the cervix during labour at term compared with day 19. During preterm labour after onapristone, iNOS concentrations increased significantly in the cervix. In order to examine whether the NO pathway plays a role in cervical ripening, the effects of the nitric oxide synthesis inhibitor L-nitro-arginine methylester (L-NAME) on the duration of delivery and on cervical extensibility were also investigated. The duration of delivery was significantly prolonged in L-NAME-treated rats compared with the control group (2.4-fold). Moreover, cervical extensibility decreased significantly (1.7-fold) after in-vitro incubation with L-NAME (P < 0.005). We conclude that the NO system may have an active role in the cascade of processes involved in preparing the uterus and cervix for parturition.

Nongenomic effects of progesterone on human intestinal smooth muscle cells

Previous experiments demonstrated that progesterone affects intestinal smooth muscle cells through genomic and nongenomic pathways. We hypothesized that the nongenomic effect was mediated by changes in membrane excitability. We studied the effects of progesterone and other steroid hormones on a human intestinal smooth muscle cell line, using the whole cell patch-clamp technique. Ionic currents were elicited through steps from -70 mV to various test potentials. Progesterone dose-dependently reduced calcium currents. The decrease in inward current was partly due to a shift in the steady-state inactivation to more hyperpolarized potentials. This effect did not involve gene transcription, since it was not blocked by the progesterone antagonist ZK-98-299. The progesterone analogue 5-beta-dihydroprogesterone also decreased calcium currents, whereas its stereoisomer, 5-alpha- dihydroprogesterone, did not affect the properties of voltage-sensitive ion channels. Similarly, estradiol and dexamethasone did not alter inward currents. We conclude that progestins exert their nongenomic effects on intestinal smooth muscle cells by decreasing calcium currents. The change in the calcium signal may contribute to the reduction in muscle contraction observed after progesterone.

Non-competitive anti-oestrogenic actions of progesterone antagonists in primate endometrium: enhancement of oestrogen and progesterone receptors with blockade of post-receptor proliferative mechanisms

Previous studies have shown that the progesterone antagonists (antiprogestins) inhibit oestrogen-dependent endometrial proliferation in ovariectomized monkeys, without having affinity to the oestrogen receptor (ER). This study was designed to investigate the effect of the antiprogestins mifepristone (RU 486) and onapristone (ZK 98,299), on the concentration of ER and progesterone receptor (PR) in the endometrium of long-term ovariectomized cynomolgus monkeys (Macaca fascicularis). In untreated monkeys, tissue preparations bound in total 228 +/- 68 pmol [3H]-oestradiol/g protein (ER), and 119 +/- 42 pmol [3H]-R5020/g protein (PR). These values were not significantly different from the total binding capacities of tissues from monkeys treated with RU 486 alone or primates treated with oestradiol plus progesterone. Treatment with oestradiol alone almost doubled the ER and PR concentrations. Combined treatment with oestradiol and RU 486 enhanced the ER and PR concentrations in a dose-dependent manner: 1 mg/kg body weight (bw) RU 486/kg increased both ER and PR contents about 3-fold. The dose of 5mg/kg bw RU 486 or onapristone increased the ER and PR concentrations almost 6- and 5-fold respectively, compared with the oestradiol-treated controls. Our results demonstrate that RU 486 and onapristone increased the endometrial ER and PR concentrations far beyond the physiological level in ovariectomized, oestradiol-treated monkeys. Whether the over-expression of ER and PR in the presence of antiprogestins is causally related to the antiproliferative impact of antiprogestins in the endometrium (non-competitive anti-oestrogenic effects) or is an independent action in unknown.

Preterm birth in rats produced by the synergistic action of a nitric oxide inhibitor (NG-nitro-L-arginine methyl ester) and an antiprogestin (onapristone)

OBJECTIVE

The aim of this study was to determine whether inhibition of nitric oxide synthesis would affect the action of an antiprogesterone to provoke preterm labor.

STUDY DESIGN

Pregnant rats were continuously infused with NG-nitro-L-arginine methyl ester starting on day 16 of gestation. On day 17 of gestation groups of animals were injected subcutaneously with a single dose of either 3 or 30 mg/kg onapristone; animals were monitored for preterm labor and delivery for up to 48 hours.

RESULTS

Significant findings included the following results. (1) Combined treatment with NG-nitro-L-arginine methyl ester (50 mg per day) and low-dose onapristone (3 mg/kg) produced preterm labor, > 70% of the fetuses were delivered within 27 hours of treatment, whereas < 5% of the fetuses were delivered in the animals receiving either of these compounds alone. (2) NG-nitro-D-arginine methyl ester (50 mg per day) had no effect. (3) inhibition of nitric oxide by NG-nitro-L-arginine methyl ester also significantly increased the efficacy of high-dose onapristone (30 mg/kg) in preterm labor and delivery.

CONCLUSION

Treatment of pregnant rats with a combination of a nitric oxide inhibitor with onapristone significantly potentiated the ability of the antiprogesterone to induce preterm labor. The interaction of nitric oxide and progesterone may be required to maintain pregnancy.

Mucin (Muc-1) expression is differentially regulated in uterine luminal and glandular epithelia of the baboon (Papio anubis)

Changes in the organization and composition of apical cell surface glycoconjugates accompany the transition of luminal epithelial cells from the prereceptive state of the uterus in many species. In spite of the biological and clinical significance of this process, few molecular markers have arisen as useful predictors of uterine receptivity. Recent studies in mice demonstrate that the transmembrane mucin glycoprotein, Muc-1, is abundantly expressed at the apical surface of luminal epithelia under most conditions and is invariably reduced in receptive uteri. These and other observations have led to the suggestion that mucins serve an antiadhesive role and function to maintain a nonreceptive uterine state. A pan-species Muc-1 specific antibody recognizing a peptide motif conserved in the cytoplasmic domain of Muc-1 was used to examine the temporal and spatial expression of cell-associated Muc-1 in baboon uteri under a variety of conditions, including the pre- and perimplantation periods. Muc-1 expression was not driven by estrogen influences alone, but required progesterone action. In animals exposed to both steroids, Muc-1 was expressed at low moderate levels in epithelia of the basalis and functionalis regions. The highest expression of Muc-1 was detected in surface epithelium of the preimplantation phase, i.e., up to Day 8 (Day 0 = day of ovulation), or in ovariectomized animals receiving a steroid hormone regime that mimicked this phase (14 days of estrogen priming followed by 7 days of estrogen plus progesterone). Continued exposure to both hormones, i.e., as seen at Days 10-12 or in ovariectomized baboons given 14 days of estrogen plus progesterone treatment after estrogen priming, resulted in marked reduction of Muc-1 expression in the surface epithelium; however, staining patterns in the glandular epithelium were unchanged by this treatment. The expression of Muc-1 on the surface epithelium during the prereceptive phase was associated with the presence of both estrogen and progestin receptors in these epithelia. Muc-1 expression was reduced by neither antiestrogen treatment during the prereceptive stage nor antiprogestin treatment through to the receptive phase. Furthermore, persistent Muc-1 expression in the functionalis and basalis epithelium correlated with expression of progestin receptors. Thus, Muc-1 expression appeared to be progesterone-dependent rather than estrogen-dependent. It is concluded that Muc-1 expression in surface epithelium serves as a marker of the prereceptive phase in the baboon and that loss of Muc-1 from surface epithelium correlates with generation of a receptive uterine state.

Antiprogestins inhibit the binding of opioids to mu-opioid receptors in nervous membrane preparations

The present study showed that the glucocorticoid/progesterone antagonists, 17 beta-hydroxy-1 1 beta-(4-dimethylamino-phenyl-1)-17-(prop-1-ynyl)estra-4,9-dien+ ++-3-one (RU486) and 17 beta-hydroxy-11 beta-(4-dimethylamino-phenyl-1)-17-(propan-3-ol)estra-4,9-dien-3-o ne (ZK 98299), inhibit the binding of labeled dihydromorphine to mu-opioid receptors present on membrane preparations derived from rat and mouse brain, as well as from human neuroblastoma cells. The inhibitory effect of RU486 was dose-dependent and linked to a decrease of the affinity of labeled dihydromorphine to the mu-opioid receptors. Kinetic experiments have shown that RU486 induces a decrease of the association rate constant (k + 1) of dihydromorphine. RU486 also proved able to dissociate the dihydromorphine-mu-opioid receptor complex, although at a rate slower than that exhibited by unlabeled dihydromorphine. Finally, the addition of NaCl (100 mM) to the incubation buffer induced a 50% decrease of the inhibitory effect of RU486. A 6-day treatment of neuroblastoma cells with RU486 eliminated the inhibitory effect morphine exerts on the intracellular accumulation of cyclic AMP induced by prostaglandin E1. These results indicate that RU-486 may interact with brain mu-opioid receptors in vitro, by decreasing the affinity of opioid ligands.

Androgen-like and anti-androgen-like effects of antiprogestins in human mammary cancer cells

In addition to their antiprogestational activity, the antiprogestins RU486, ZK98.299 and ZK98.734 possess varying antiglucocorticoid as well as androgen-like or antiandrogen-like properties in human mammary cancer cells. The human mammary cancer cell line MFM-223, which contains only androgen receptors, was used as a model to investigate androgen receptor mediated effects of these antiprogestins. Proliferation of MFM-223 cells is inhibited by androgens and does not respond to oestrogens, progestins and glucocorticoids. As shown in proliferation assays, ZK98.734 was a strong inhibitor of cell proliferation. This effect was antagonised by the antiandrogen hydroxyflutamide. ZK98.734 was found to displace [3H]R1881 from the androgen receptor in MFM-223 cells, substantiating the involvement of the androgen receptor. The antiprogestin ZK98.299 failed to influence the proliferation of MFM-223 cells. ZK98.299 did not bind to the androgen receptor and was devoid of androgenic or antiandrogenic activity. RU486 bound to the androgen receptor. It was a weak inhibitor of MFM-223 cell proliferation, but the inhibition of proliferation by RU486 was not antagonised by hydroxyflutamide. This effect was probably not mediated by the androgen receptor. RU486 had antiandrogenic activity in this cell line, as it antagonised the inhibitory effect of dihydrotestosterone at a 100-molar excess. These results were confirmed by transfection experiments with an MMTV-CAT construct in the same cell line, demonstrating the biological function of the ZK98.734-androgen receptor complex. ZK98.299 and RU486 were not able to induce CAT activity. The different androgenic or antiandrogenic properties of the antiprogestins investigated should be considered when selecting antiprogestational properties of the antiprogestins investigated should be considered when selecting antiprogestational compounds for clinical applications, as a partial androgenic activity may be of benefit in breast cancer but can have undesired side-effects in other diseases.

Induction of TGF-beta by an antiprogestin in the human breast cancer cell line T-47D

BACKGROUND

Antiprogestins appear to be a new approach for the endocrine therapy of breast cancer. Most breast cancer cells are growth inhibited by TGF-beta. Any change of tumorcellular TGF-beta secretion could have some impact on tumorcellular growth. We addressed our question to whether the antiprogestin onapristone can induce TGF-beta secretion in breast cancer cells in vitro and whether a possible induction correlates with the antiproliferative effect and the receptor status of the cells.

MATERIALS AND METHODS

We examined the ER and PR positive breast cancer cell lines MCF7 and T-47D and an ER and PR negative variant T-47D/x. Hormone receptor levels were determined by EIA, total (LTGF-beta + active TGF-beta) and active TGF-beta by a radioreceptor assay. All cell biological and antiproliferative effects were measured during basal, not estrogen-stimulated growth.

RESULTS

To our knowledge, we are the first to describe, that the TGF-beta secretion of tumor cells can be increased by an antiprogestin (total: 4.8-fold, active 2.9-fold). A stimulation was found only in the markedly PR positive T-47D cells, in which onapristone proved to have strong antiproliferative potency. In the MCF7 and T-47D/x cells onapristone showed no induction of TGF-beta. Moreover, those cells were not growth inhibited. Whereas onapristone did not influence the ER-content, it dramatically downregulated the PR-content of the T-47D and MCF7 cells (93% and 65%, respectively).

CONCLUSIONS

These observations make it likely, that the antiproliferative potency of the antiprogestin onapristone is at least partly due to the ability of onapristone, to stimulate the strong growth inhibitor TGF-beta. In contrast to the antiprogestin RU 486, onapristone showed no estrogenic activity (stimulation of growth and PR), which could be a decisive advantage in the therapy of breast cancer, taking into account, that many breast carcinomas grow estrogen dependent.

Two types of anti-progestins have distinct effects on site-specific phosphorylation of human progesterone receptor

Human progesterone receptor (PR) is phosphorylated on multiple serine residues; three sites (Ser102, Ser294, and Ser345) are inducible by hormone agonist, while at least six others are basally phosphorylated and exhibit a general increase in response to hormone. In this study we have used high performance liquid chromatography phosphopeptide mapping and manual peptide sequencing to investigate how two different progestin antagonists, RU486 and ZK98299, affect site-specific phosphorylation of PR isolated from T47D breast cancer cells. As compared to the progestin agonist R5020, RU486 stimulated a similar increase in overall incorporation of [32P]phosphate per PR molecule (2.5-2.6-fold for PR-A and 2.1-fold for PR-B), and at the site-specific level, RU486 stimulated both the basal and inducible sites to the same extent as R5020. In contrast, ZK98299 produced only a minimal increase in overall phosphorylation (1.2-fold for PR-A and 1.1-fold for PR-B) which was due to a reduced stimulation of the basal sites and failure to induce any of the three hormone-dependent sites. No inappropriate phosphorylation sites were detected in response to either RU486 or ZK98299. In cotreatment studies, ZK98299 blocked the increase in overall phosphorylation of PR induced by R5020, demonstrating that the failure of this antagonist to stimulate specific phosphorylation sites is not due to an inefficient interaction with PR in the intact cell. These results indicate that the biological effects of RU486 are not mediated by an alternation in the phosphorylation state of PR, whereas failure to promote phosphorylation of certain sites may contribute to the antagonist action of ZK98299. Additionally these results support the concept of two mechanistic classes of anti-progestins that affect PR differently in vivo.

The Ernst Schering Poster Award. Intracellular traffic of steroid hormone receptors

The signal responsible for the nuclear localization of the progesterone receptor has been characterized. It is a complex signal. The study of the mechanism of this nuclear localization has revealed that the receptor continuously shuttles between nucleus and the cytoplasm. The receptor diffuses into the cytoplasm and is constantly and actively transported back into the nucleus. The same phenomenon exists for estradiol and glucocorticoid receptors. The mechanism of entry of proteins into the nucleus is well documented, whereas the mechanism of their outward movement to the cytoplasm is not understood. We have grafted different nuclear localization signals (NLSs) onto beta-galactosidase and have studied the traffic of this protein using heterokaryons and microinjection experiments. We have demonstrated that the same NLSs are involved in both the inward and the outward movement of proteins through the nuclear membrane. These results suggest that the nucleocytoplasmic shuttling may be a general phenomenon for nuclear proteins that could possibly undergo modifications in the cytoplasm and exert some biological activities there. These conclusions also imply that at least part of the cellular machinery involved in the nuclear import of proteins may function bidirectionally. Using these techniques, we have shown that the two major antiprogestins, RU486 and ZK98299, act at the same distal level of hormone action.

The effects of post-ovulatory administration of onapristone on the developmnent of a secretory endometrium

The purpose of this study was to assess the ability of the anti-progestin onapristone administered in the immediate post-ovulatory period to disrupt endometrial differentiation as a potential method of fertility control. In all, 10 healthy female volunteers were given 400 mg onapristone 2 days after the mid-cycle luteinizing hormone (LH) surge in urine (LH+2). An endometrial biopsy was taken 4 or 6 days after the LH surge (i.e. LH+4 or LH+6) in a control cycle and on the corresponding day of the treatment cycle. Biopsies were assessed for histological dating and immunolocalization of oestrogen receptors, progesterone receptors and 15-hydroxyprostaglandin dehydrogenase (PGDH). On day LH+12, blood was taken for the measurement of insulin-like growth factor binding protein-1 (IGFBP-1) and placental protein 14 (PP14). Hormonal measurements in blood and urine were used to monitor the effects on the menstrual cycle. In addition, the concentration of cortisol in plasma was measured to determine if this dose of onapristone exerted significant anti-glucocorticoid activity. Treatment with onapristone retarded the development of secretory changes within the endometrium without affecting the length of the luteal phase. Intense nuclear immunostaining of oestrogen and progesterone receptors was evident in glands and stroma after treatment, suggesting that the progesterone-dependent down-regulation of steroid receptors was inhibited by the anti-progestin. Onapristone also affected the production of luteal phase endometrial proteins, as judged by the pronounced reduction in immunostaining of PGDH within the glands and the significant reduction in plasma concentrations of PP14. However, plasma concentrations of IGFBP-1 did not differ between cycles. Onapristone did not appear to exert significant anti-glucocorticoid activity because concentrations of cortisol were unaffected. These findings suggest that onapristone could potentially be used as a method of postovulatory fertility control.

Influence of hormone antagonists on chromatin remodeling and transcription factor binding to the mouse mammary tumor virus promoter in vivo

Steroid hormones act via a group of high affinity receptors that regulate transcription by binding to hormone response elements located in the promoters of hormone-inducible genes. Our understanding of these processes has been greatly enhanced by the use of steroid hormone antagonists in both clinical and experimental procedures. However, despite their usefulness in these applications, much about their mechanisms of action remains to be elucidated. Using in vivo analysis techniques, we investigated the influence of type I (ZK98299) and type II (RU486 and ZK112993) steroid hormone antagonists on glucocorticoid-regulated transcription from the mouse mammary tumor virus promoter. Both type I and type II antagonists substantially reduced glucocorticoid-induced expression from the mouse mammary tumor virus promoter stably maintained as chromatin. Concurrent treatment with glucocorticoid and type I or type II antagonists reduced the receptor-dependent chromatin remodeling and loading of transcription factor NF1 that are signature responses of this promoter in the context of chromatin. Treatment with either type I or type II antagonists alone did not induce chromatin remodeling or transcription factor loading. Although type II antagonist-occupied receptor can bind DNA, our results show that this binding is not functionally equivalent to that of agonist-occupied receptor, as it can not interact productively with the cellular apparatus required to open a repressive chromatin structure.