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PubMed1992

Progestin antagonism of estrogen stimulated 1,25-dihydroxyvitamin D levels.

Progestins are frequently used in combination with estrogen to prevent or treat postmenopausal osteoporosis. Progestins protect against the undesirable hyperplastic effects of estrogen on the endometrium. The possibility that progestins might antagonize the beneficial effects of estrogen on calcium homeostasis has received little attention. In this study we determined whether the addition of progestin to estrogen would alter the ability of estrogen to raise serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] levels. Women within 5 yr of menopause were treated with three cycles of oral unopposed estrogen [1 or 2 mg/day (3.67 or 7.34 mumol/day) 17 beta-estradiol (E2) for 25/30 days of each cycle] followed by three cycles of E2 plus progestin [10 mg/day (29 mumol/day) medroxyprogesterone on days 12-25]. E2 increased both total and free 1,25-(OH)2D concentrations in a dose-dependent fashion. These levels increased progressively over the three cycles of unopposed estrogen treatment. In contrast the vitamin D binding protein concentration reached maximal levels after one cycle of E2. With the addition of progestin, the levels of total and free 1,25-(OH)2D returned toward baseline although vitamin D binding protein levels remained elevated. PTH levels rose with both doses of E2 as serum calcium levels fell. Progestin did not significantly alter the effects of E2 on PTH or calcium. Our results raise the possibility that progestin may antagonize part of the salubrious effects of estrogen on calcium homeostasis.

Dihydroxycholecalciferols↗

PubMed1997

Identification of PRG1, a novel progestin-responsive gene with sequence homology to 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase.

To define early molecular targets of progestin action, the differential display technique was used to identify genes with altered levels of expression in T-47D breast cancer cells treated with the synthetic progestin ORG 2058 for 3 h. PRG1 was first isolated as a 200-bp cDNA clone and its progestin regulation confirmed by Northern analysis. Cloning of the complete coding region of PRG1 revealed that it shared a high degree of amino acid sequence identity with isoforms of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from several tissues and species. Expression of PRG1 mRNA was observed in several normal breast epithelial and breast cancer cell lines and in a variety of human tissues, with highest expression in the breast, aorta, and brain. In T-47D cells, PRG1 mRNA was rapidly and transiently induced by progestins, expression peaking between 2 and 4 h and returning to control levels by 12 h. Progestin-induced increases in PRG1 mRNA were inhibited by the progestin antagonist RU 486 and occurred via the progesterone receptor. Progestin induction of PRG1 mRNA was also inhibited by actinomycin D but not by cycloheximide. PRG1 is therefore a novel human gene that is directly regulated by progestins via the progesterone receptor.

Amino Acid Sequence↗

PubMed1999

Effect of overexpression of progesterone receptor A on endogenous progestin-sensitive endpoints in breast cancer cells.

The human progesterone receptor (PR) is expressed as two isoforms, PRA and PRB, which differ in the N-terminal region and exhibit different activities in vitro, with PRA demonstrating dominant negative inhibitory effects on the activity of PRB and other nuclear receptors. PRA and PRB are expressed in target tissues at comparable levels although cells expressing a predominance of one isoform can be identified. In breast cancers, PRA is expressed at high levels in some tumors, and this may be associated with features of poorer prognosis. To investigate the role of PRA overexpression in PR-positive target cells, the effect of PRA induction on cell proliferation and expression of endogenous progestin-sensitive genes, SOX4 and fatty acid synthetase (FAS), was examined using PR-positive T-47D cell lines, which express a predominance of PRB, in which PRA could be increased 2- to 20-fold over basal levels. No effect of PRA induction was noted on cell proliferation, but marked changes in morphology, consistent with loss of adherent properties, were observed. Increases up to 4-fold in the relative PRA levels augmented progestin induction of SOX4 mRNA expression, and RU486 treatment revealed a progestin agonist effect. There was no consistent effect of PRA induction on progestin-mediated increases in FAS mRNA levels under these conditions. Clones with PRA:PRB ratios greater than 15 were associated with diminished progestin responses on both SOX4 and FAS mRNA expression. These data show that PRA overexpression is associated with alteration in adhesive properties in breast cancer cells and effects on endogenous progestin targets that were dependent on the cellular ratio of PRA:PRB. The results of this study are consistent with the view that PRA expression can fluctuate within a broad range in target cells without influencing the nature of progestin action on downstream targets, but that overexpression of PRA, such as is seen in a proportion of breast cancers, may be associated with inhibition of progestin action and features of poor prognosis.

Breast Neoplasms↗

PubMed1984

Progestin therapy of endometrial, breast and ovarian carcinoma. A review of clinical observations.

A survey of the literature shows that in studies employing standardized criteria to define the response to progestin therapy, an objective remission is achieved in about one-third of patients with endometrial and breast cancer, and it is much less frequent in ovarian malignancy. The response is seldom complete and it is mostly of a short duration. There is a tendency towards an increased response-rate with increased dosage of progestin, in both endometrial and breast carcinoma, while the route of administration appears to be of minor importance. The clinical benefit of adjuvant progestin therapy in endometrial cancer is unproven. Simultaneous therapy with progestin and cytotoxic drugs seems not to increase the survival figures obtainable by cytotoxic therapy alone. The antiestrogen tamoxifen has an established efficacy in all these malignancies. The spectra of tumors sensitive to tamoxifen and to progestin are not completely identical. The optimal combination of these drugs awaits results from prospective studies. Selection of patients for progestin therapy with a sufficient degree of accuracy is not feasible by use of clinical or histological parameters. On the other hand, estrogen receptor determination already has an established position in the clinical evaluation of the sensitivity of breast cancer to endocrine therapy. The assay of progestin receptors from endometrial carcinoma tissue also seems to give reliable information; correct prediction was observed in 86% when the receptor data from five studies with 105 progestin therapies were correlated with the treatment results.

Aminoglutethimide↗

PubMedDate not supplied

Comparative cardiovascular effects of different progestins in menopause.

Progesterone receptors are present in the arterial wall and it is, therefore, likely that the arterial effects of progestins are mediated through progesterone receptors as well as through down-regulation of the estradiol receptor. Progestin therapy affects arterial function, as it can stabilize arteries in a state of vasomotor instability, but may also induce vasoconstriction of estrogenized vessels. Thus, the cardiovascular effects of progestins may influence the cardioprotective effect of estrogens. There has been some concern that a combined estrogen-progestogen therapy may attenuate some of estrogen's beneficial effects on cardiovascular health. This is a reflection of the past epidemiologic studies which have used primarily unopposed estrogen. The PEPI trial is the only large-scale, long-term study to compare directly the effects of different combined hormone replacement therapy regimens upon plasma lipids in healthy women. This study has shown that the adjunctive clinical impact of different progestogens on the beneficial effect of estrogen replacement therapy is trivial. It has never been proved that in normocholesterolemic women, e.g., those included in the PEPI trial, the increase in HDL reduces cardiovascular mortality or morbidity. Based on the results of PEPI, hormone replacement therapy has positive effects on key heart disease risk factors and endometrial tissue, and the magnitude of those effects does not differ significantly across the hormone replacement therapy regimens used. At present there are only few and inconclusive data available on the vascular effect of progestins in menopausal women. Some studies found that progestins reduced the beneficial effect of estrogens, while others did not. Our group has recently shown that different estrogen-progestin treatments have different effects upon vascular reactivity and that a careful selection of the progestin to be added to estrogen is of capital importance to preserve, or even enhance the positive vascular effects of estrogens. Few epidemiological studies have investigated the effect of adding a progestin to estrogen therapy upon cardiovascular mortality and morbidity, and all have suggested that hormone replacement therapy may be more effective than estrogen replacement alone in reducing cardiovascular events in primary prevention. The results of the recently published Heart and Estrogen/progestin Replacement Study (HERS) have added some critical data on the effect of hormone replacement therapy for secondary prevention in women with coronary artery disease. The study, however, is affected by several important methodological and statistical problems, which make its interpretation difficult and its conclusions useless for clinical practice. The results of the study should be evaluated with caution by physicians who give advice on hormone replacement therapy, and no woman should be taken off hormone replacement therapy because of HERS. Of importance, the results of HERS should not be used to suggest alternative forms of treatment, especially the selective estrogen receptor modulators (SERMs), for cardiovascular protection in postmenopausal women.

Adult↗

PubMed1991

Mechanisms involved in the evolution of progestin resistance in human breast cancer cells.

The emergence of resistant cells reduces the efficacy of many forms of drug therapy in human breast cancer. In order to understand some of the possible mechanisms by which hormonally dependent human breast cancers develop resistance to progestin therapy we have developed a human breast cancer cell line (5-RP) which is resistant to the growth inhibitory effects of progestins in culture. These cells routinely grow in 10 microM medroxyprogesterone acetate (MPA). The cell line was developed from T-47D-5 human breast cancer cells by stepwise selection in increasing concentrations of MPA. The progestin-resistant phenotype was relatively stable as assessed by the removal of MPA from the medium for varying periods of time. 5-RP cells passaged in the absence of MPA were still essentially insensitive to the growth inhibitory effects of MPA for at least 22 passages. Even at 53 passages out of the drug the 5-RP line was still less sensitive than the original T-47D-5 parent line. Transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) receptor mRNA were both increased in the 5-RP line compared to the T-47D-5. Consistent with increased TGF-alpha expression, the EGF receptor measured by ligand binding was decreased. When the cells were removed from MPA, TGF-alpha expression declined gradually, but EGF-receptor mRNA levels increased, as did EGF-binding activity. These cells remained estrogen and progesterone receptor positive. Although progestins did not downregulate estrogen receptor expression, they did downregulate progesterone receptor expression in the 5-RP line. The progesterone receptor level of the 5-RP line, in the absence of MPA, was approximately 58% of that found in T-47D-5 cells, even after MPA had been removed for long periods of time. This decrease in receptor level was reflected in decreased ability to respond to progestins as assessed by the decreased ability of MPA to activate expression of both an endogenous gene (EGF receptor) as well as a transiently transfected progestin-responsive gene (MMTV-TK-CAT). Progestin resistance in the 5-RP cell line appears to be multifactorial, involving both increased growth factor expression and decreased receptor levels. It is likely, however, that these two aspects do not account entirely for the progestin-resistant phenotype and as yet other unidentified mechanisms may also be involved.

Antineoplastic Agents↗

PubMed1994

Progestins and androgens.

OBJECTIVE: To consider whether the addition of a progestin or an androgen to estrogen replacement therapy (ERT) will modify the effects of the estrogen upon arterial disease risk. DESIGN: Review of selected literature. SETTING: Population studies, clinical trials, and laboratory investigations. PATIENTS: Postmenopausal women. INTERVENTIONS: Exogenous progestin or androgen in hormone replacement regimens. MAIN OUTCOME MEASURES: Lipids and lipoproteins, carbohydrate metabolism, prostaglandin and thromboxane metabolism, fibrinolysis and coagulation, fat distribution, and arterial tone. RESULTS: The favorable lipid and lipoprotein changes induced by estrogens are modified by progestin and androgen addition. Some of these modifications are potentially adverse (progestin lowering of high-density lipoprotein-2 cholesterol) but some are potentially beneficial (progestin lowering of triglycerides). Recent studies suggest that progestins may not reverse the estrogen-induced reduction in low-density lipoprotein cholesterol. The scant data upon the effects of androgens on lipid and lipoproteins suggest that the addition of T to the estrogen may block the rise in high-density lipoprotein cholesterol seen in women receiving estrogen alone. Because of a lack of appropriate data, it is this author's opinion that the clinical effects of progestin or T addition to ERT cannot be predicted at this time. Further studies are urgently needed to clarify how progestin or T addition modify estrogen effects upon carbohydrate, prostaglandin and thromboxane metabolism, upon fibrinolysis and coagulation, and upon arterial tone.

Androgens↗

PubMed2003

Influence of estrogen plus progestin on breast cancer and mammography in healthy postmenopausal women: the Women's Health Initiative Randomized Trial.

CONTEXT: The Women's Health Initiative trial of combined estrogen plus progestin was stopped early when overall health risks, including invasive breast cancer, exceeded benefits. Outstanding issues not previously addressed include characteristics of breast cancers observed among women using hormones and whether diagnosis may be influenced by hormone effects on mammography. OBJECTIVE: To determine the relationship among estrogen plus progestin use, breast cancer characteristics, and mammography recommendations. DESIGN, SETTING, AND PARTICIPANTS: Following a comprehensive breast cancer risk assessment, 16 608 postmenopausal women aged 50 to 79 years with an intact uterus were randomly assigned to receive combined conjugated equine estrogens (0.625 mg/d) plus medroxyprogesterone acetate (2.5 mg/d) or placebo from 1993 to 1998 at 40 clinical centers. Screening mammography and clinical breast examinations were performed at baseline and yearly thereafter. MAIN OUTCOME MEASURES: Breast cancer number and characteristics, and frequency of abnormal mammograms by estrogen plus progestin exposure. RESULTS: In intent-to-treat analyses, estrogen plus progestin increased total (245 vs 185 cases; hazard ratio [HR], 1.24; weighted P<.001) and invasive (199 vs 150 cases; HR, 1.24; weighted P =.003) breast cancers compared with placebo. The invasive breast cancers diagnosed in the estrogen plus progestin group were similar in histology and grade but were larger (mean [SD], 1.7 cm [1.1] vs 1.5 cm [0.9], respectively; P =.04) and were at more advanced stage (regional/metastatic 25.4% vs 16.0%, respectively; P =.04) compared with those diagnosed in the placebo group. After 1 year, the percentage of women with abnormal mammograms was substantially greater in the estrogen plus progestin group (716 [9.4%] of 7656) compared with placebo group (398 [5.4%] of 7310; P<.001), a pattern which continued for the study duration. CONCLUSIONS: Relatively short-term combined estrogen plus progestin use increases incident breast cancers, which are diagnosed at a more advanced stage compared with placebo use, and also substantially increases the percentage of women with abnormal mammograms. These results suggest estrogen plus progestin may stimulate breast cancer growth and hinder breast cancer diagnosis.

Aged↗

PubMed1984

The ontogeny of cytosol and nuclear progestin receptors in male rat brain and its male-female differences.

The fetal and postnatal development of the progestin receptor systems in the intact male rat brain was investigated by means of the in vitro cytosol binding and the nuclear exchange assay using [3H]R5020 [( 17 alpha-methyl-3H]17 alpha, 21-dimethyl-19-nor-4, 9-pregnadiene-3,20-dione). The cortical cytosol receptors, first detectable at day 0, rapidly increased at day 7, reaching a maximum at day 10, then gradually declined thereafter. The receptors in the HPOA appeared clearly at day 1, increased during the first 10 days, then remained constant at days 14-21. The postnatal developmental patterns of cytosol brain progestin receptors in males were essentially similar to those in females, but there were some differences between both sexes. The male HPOA at days 10-14 contained more receptors than the female one. Nuclear progestin binding was low in the neonatal male brain at days 1-3. Despite the low level of serum progesterone, the cortical nuclear binding suddenly increased at days 7-10, then remained high at days 14-21. A similar, though less pronounced, pattern was seen in the HPOA. The male pattern of nuclear binding, thus, essentially resembled the female one. However, lower binding in the cortex and, possibly, HPOA was found in males than in females at days 10-21. After progesterone injection postnatal male rats accumulated a lower concentration of progestin receptors in the cortex and, possibly, HPOA than similarly-treated females. It is concluded from these results that progestin receptors in male rat brain appear immediately after birth and develop differentially in the cortex and HPOA. The sudden onset of increased nuclear translocation of endogenous progestin receptor complexes may occur in the brain at around days 7-10. There is a marked sex difference in the nuclear progestin receptor system in the postnatal brain, particularly the cortex. Moreover, the postnatal male brain has lower capacities of nuclear receptor translocation than does the female one. The progestin receptor system in the cortex and, possibly, HPOA of rats in the early postnatal life might be involved with some processes in the mechanism of sexual differentiation of the brain.

Animals↗

PubMed1980

Progestins inhibit FSH-stimulated steroidogenesis in cultured rat granulosa cells.

It has been hypothesized that progesterone (P) exerts a direct inhibitory effect on ovarian follicular development, an effect which could be mediated by P receptors located in granulosa cells. We tested this hypothesis by examining the effect of several progestins on FSH-stimulated estrogen (E), P, and 20 alpha-dihydroprogesterone (DHP) production by cultured rat granulosa cells, and correlated the results with the ability of the progestins to bind to the granulosa cell P receptor. Granulosa cells from immature hypophysectomized DES-treated rat produced 9 ng/ml E, 21 ng/ml P and 29 ng/ml DHP during a 2-day incubation in McCoy's 5a medium containing 10(-7) M androstenedione and 10 ng/ml of FSH. The FSH-induced increase in E production was inhibited by 50 and 95% following concomitant treatment with 3 x 10(-6) and 10(-5) M resp. of R5020, a potent synthetic progestin. Added R5020 at these concentrations also significantly inhibited P and DHP production. R5020 had no effect on granulosa cell viability or plating efficiency, and the inhibitory action of R50920 on E production was reversible. In studies of the specificity of the progestin inhibitory action, the relative abilities of various progestins to inhibit E production were R5020 > P > DHP > 17 alpha-hydroxyprogesterone (17OHP). The relative abilities of these progestins to bind to the ovary P receptor were also: R5020 > P > DHP > 17OHP. These results indicate that exogenous progestins directly inhibit the FSH-stimulation of granulosa cell steroidogenesis in vitro and suggest that the progestin effect may be mediated by the P receptor. Such results offer a possible mechanism whereby progesterone could exert a direct but reversible inhibitory action on ovarian follicular development.

20-alpha-Dihydroprogesterone↗

PubMed1993

Insulin-like growth factor binding protein-1 inhibits the mitogenic effect of insulin-like growth factors and progestins in human endometrial stromal cells.

This study describes the effects of insulin-like growth factors (IGFs), progestins, and IGF binding protein-1 (IGF-BP1) on DNA synthesis in human endometrial stromal cells. Endometrial stromal cells treated with IGF-I or IGF-II or progestins increased their rate of DNA synthesis 3-6-fold. In a time study, IGF-I or IGF-II stimulated DNA synthesis 3-fold in 24 h. An equivalent increase by medroxyprogesterone acetate (MPA) required 48 h. Progestin-stimulated DNA synthesis was inhibited completely by an equimolar concentration of the antiprogesterone RU486. IGF-I-stimulated DNA synthesis was inhibited completely by IGF-BP1. Half-maximal inhibition of IGF-I-stimulated DNA synthesis occurred when IGF-I and IGF-BP1 were at equimolar concentrations. Non-phosphorylated and phosphorylated forms of IGF-BP1 were equipotent inhibitors of IGF-I-stimulated DNA synthesis. IGF-BP1 also inhibited progestin-stimulated DNA synthesis. Half-maximal inhibition of progestin-stimulated DNA synthesis occurred at 100 ng/ml of phosphorylated IGF-BP1. Phosphorylated IGF-BP1 was a 3-4-fold more potent inhibitor of progestin-stimulated DNA synthesis than the nonphosphorylated form. The inhibition by IGF-BP1 of progestin-stimulated DNA synthesis was reversed by an equimolar concentration of IGF-II. This study suggests that progestins regulate an autocrine growth control loop in the endometrium that involves IGFs, IGF receptors, and IGF-BPs.

Adult↗

PubMed1981

Nuclear progestin receptor-like component in human cervical tissue.

To study progestin action in human glandular cervix, we extracted the nuclear pellet with 0.5 M KCl and immediately adsorbed a progestin-binding receptor-like component to hydroxylapatite. Binding of 2 nM [3H]R5020 at 4 degrees C for 18 h, in the presence or absence of 100-fold molar excess progesterone and other steroids, was used to measure the total extractable and adsorbed progestin-binding component. With this assay, the amounts of progestin-binding component in the nuclear-rich fraction in specimens from women in the follicular and luteal phases of the ovarian cycle were 930 +/- 143 and 995 +/- 148 fmol/g wet wt (+/- SE), respectively; total cytoplasmic progestin receptor was 2,989 +/- 812 and 1,861 +/- 188 fmol/g wet wt (+/- SE) in the follicular and luteal phases, respectively. The progestin-binding component extracted from the nuclear pellet has a sedimentation velocity coefficient in the 3.5 S region when measured in high salt on 5-20% linear sucrose density gradients that contain 10% glycerol. The progestin binding measured by the hydroxylapatite-exchange assay with [3H]R5020 and radio-insert progesterone is high affinity (Kd 2.6 X 10(-10) M) and heat labile and appears specific for progestins and progesterone target tissues.

Adult↗

PubMed1991

Direct transcriptional regulation of the progesterone receptor by retinoic acid diminishes progestin responsiveness in the breast cancer cell line T-47D.

Retinoic acid (RA) treatment of T-47D human breast cancer cells results in a rapid decrease in the concentration of progesterone receptor (PR) mRNA which causes a slow loss of cellular PR protein (Clarke, C. L., Roman, S. D., Graham, J., Koga, M., Sutherland, R. L. (1990) J. Biol. Chem. 265, 12694-12700). The mechanisms involved are unknown and this study was undertaken to determine whether the decline in PR mRNA was due to transcriptional inhibition and to evaluate the functional consequences of the RA-mediated decrease in PR. The transcription rate of the PR gene was decreased by RA, and the effect was maximal 2-3 h after treatment. Cycloheximide cotreatment was unable to relieve the inhibitory effect of RA and PR transcription suggesting that the effect was not dependent on ongoing protein synthesis. There was no effect of RA on PR mRNA half-life at the times examined (0-6 h of RA treatment). To determine the functional consequence of PR down-regulation the progestin-responsive plasmid pMSG-CAT was expressed transiently in T-47D cells which were then exposed to RA for 24 h. RA-pretreated cells were then treated with the synthetic progestin ORG 2058 and the extent of progestin stimulation of chloramphenicol acetyltransferase (CAT) activity measured. ORG 2058 treatment resulted in an induction of CAT activity which was maximal at a progestin concentration of 1 nM. Interestingly, the ability of ORG 2058 to induce CAT activity was decreased in RA-pretreated cells. The diminished progestin responsiveness of RA-pretreated cells was confirmed in separate experiments which showed that the progestin inducibility of TGF-alpha mRNA was also decreased in cells treated with ORG 2058 following pretreatment with RA for 24 h. These data demonstrate that RA decreases PR mRNA concentrations by direct transcriptional inhibition, leading to decreased cellular PR concentrations. The decreased levels of PR result in impaired responsiveness to progestins and this suggests that RA derived from dietary vitamin A may have a role in modulating cellular sensitivity to progestins.

Breast Neoplasms↗

PubMed2000

Menopausal estrogen and estrogen-progestin replacement therapy and breast cancer risk.

CONTEXT: Whether menopausal hormone replacement therapy using a combined estrogen-progestin regimen increases risk of breast cancer beyond that associated with estrogen alone is unknown. OBJECTIVE: To determine whether increases in risk associated with the estrogen-progestin regimen are greater than those associated with estrogen alone. DESIGN: Cohort study of follow-up data for 1980-1995 from the Breast Cancer Detection Demonstration Project, a nationwide breast cancer screening program. SETTING: Twenty-nine screening centers throughout the United States. PARTICIPANTS: A total of 46355 postmenopausal women (mean age at start of follow-up, 58 years). MAIN OUTCOME MEASURE: Incident breast cancers by recency, duration, and type of hormone use. RESULTS: During follow-up, 2082 cases of breast cancer were identified. Increases in risk with estrogen only and estrogen-progestin only were restricted to use within the previous 4 years (relative risk [RR], 1.2 [95% confidence interval [CI], 1.0-1.4] and 1.4 [95% CI, 1.1-1.8], respectively); the relative risk increased by 0.01 (95% CI, 0.002-0.03) with each year of estrogen-only use and by 0.08 (95% CI, 0.02-0.16) with each year of estrogen-progestin-only use among recent users, after adjustment for mammographic screening, age at menopause, body mass index (BMI), education, and age. The P value associated with the test of homogeneity of these estimates was .02. Among women with a BMI of 24.4 kg/m2 or less, increases in RR with each year of estrogen-only use and estrogen-progestin-only use among recent users were 0.03 (95% CI, 0.01-0.06) and 0.12 (95% CI, 0.02-0.25), respectively. These associations were evident for the majority of invasive tumors with ductal histology and regardless of extent of invasive disease. Risk in heavier women did not increase with use of estrogen only or estrogen-progestin only. CONCLUSION: Our data suggest that the estrogen-progestin regimen increases breast cancer risk beyond that associated with estrogen alone.

Body Mass Index↗

PubMed1991

The biological effects of macrophage-colony-stimulating factor induced by progestin on growth and differentiation of endometrial adenocarcinoma cells.

Progestins have biological effects of regression and differentiation on human endometrial adenocarcinoma. We investigated the effects of progestin on the induction of macrophage-colony-stimulating factor (M-CSF) and its receptor messenger RNAs in the human endometrial adenocarcinoma cell line Ishikawa which has receptors for both estrogen and progesterone. Poly(A)+RNA extracted from Ishikawa cells cultured with or without synthetic progestin R5020 was subjected to Northern blot hybridization using M-CSF and c-fms cDNA probes. The expression of M-CSF mRNA in Ishikawa cells increased about 2.3 times following treatment with R5020 at 10(-7) M. Induction of M-CSF mRNA by R5020 was antagonized by anti-progestin RU486 in a dose-dependent manner. However, c-fms mRNA, coding the M-CSF receptor, was expressed constitutively in Ishikawa cells and its expression was not affected by hormonal treatment. We further examined the biological effects of M-CSF on endometrial cancer cells. Colony formation of Ishikawa cells in soft agar, which represents anchorage-independent cell growth, was inhibited by M-CSF treatment. On the other hand, accumulation of glycogen granules in cytoplasm detected by periodicacid-Schiff staining was observed in Ishikawa cells treated with M-CSF. These results indicate that M-CSF, whose gene expression was enhanced by progestin, suppressed growth and induced differentiation of endometrial adenocarcinoma cells. These effects of M-CSF on endometrial cancer cells are similar to those of progestins, so the effects of progestins on these cells are, at least in part, probably mediated by M-CSF in an autocrine or paracrine manner.

Adenocarcinoma↗

PubMed2000

Apoptosis may be an early event of progestin therapy for endometrial hyperplasia.

OBJECTIVE: The aim of this study was to investigate the role of apoptosis during progestin therapy for the treatment of endometrial hyperplasia. METHODS: Pre- and posttreatment paraffin-embedded endometrial tissue samples from 19 women with endometrial hyperplasia were examined for changes in glandular cellularity and apoptotic activity related to the administration of progestins. Twelve patients were successfully treated with progestin therapy and 7 patients failed treatment. Glandular cellularity was assessed based on calculating the average number of cells per gland obtained on histologic examination of hematoxylin and eosin stained tissue sections. Apoptotic activity was assessed on the same tissue sections by counting the average number of apoptotic cells per 10 high power fields (hpf) using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay. The effects of progesterone on apoptotic activity in a low-grade endometrial adenocarcinoma cell line (Ishikawa cells) was also examined using an ELISA cell death detection kit. RESULTS: Glandular cellularity significantly decreased with progestin therapy in both treatment outcome groups. The reduction in cells per gland was significantly greater in the group of successfully treated cases compared to the treatment failures (P = 0.005). However, within the successfully treated group, in situ detection of apoptotic cells using the TUNEL assay showed no statistical difference between pre- and posttreatment endometrial samples. Interestingly, a significant decrease in apoptosis was found in posttreatment samples of the group with persistent hyperplasia. The average number of apoptotic cells detected in 10 hpf was reduced from 7.9 prior to treatment to 3.1 after progestin therapy (P = 0.03). In the progesterone-treated Ishikawa cell line, an increase in apoptotic activity started at 24 h, reached a peak at 48 h, and continued up to 72 h of hormone treatment. At 48 h, apoptotic activity was 42.6% greater than in the untreated control (P = 0.04). By 72 h of progesterone treatment, apoptosis was 37.2% greater in the treated cells compared to the noninoculated cells (P = 0.04). CONCLUSIONS: Progestin-induced apoptosis may occur during the early period of treatment for endometrial hyperplasia. Compared to the fully responsive group, persistent endometrial hyperplasia may have intrinsically different molecular mechanisms in response to progestin therapy.

Adult↗

PubMed1992

Progestin regulation of insulin and insulin-like growth factor I receptors in cultured human breast cancer cells.

Recent studies indicate that the insulin receptor (IR) content is higher in breast cancer cells than in normal mammary epithelial cells. This observation has been made both in tissue specimens from patients with breast cancer, and in various human cultured breast cancer cell lines. Investigations have now been undertaken to understand the role of progestins in the regulation of the IR and the closely related insulin like growth factors-I receptor (IGF-I-R). Pretreatment of T-47D cultured human breast cancer cell lines with progestins induced a time and dose dependent increase in IR content. This increase was due primarily to an effect of progestins to increase IR mRNA levels. Other steroid hormones including glucocortocoids, estrogen, and testosterone were without effect. In contrast to their up-regulation of the IR, progestins down-regulated the IGF-I-R at the level of mRNA. An analysis of the processes involved revealed that progestins increased the biosynthesis of a ligand for IGF-I receptor, IGF-II. IGF-II in turn down-regulated the IGF-I-R. Thus these studies indicate that progestins have important effects on both the IR and the IGF-I-R. The effects of progestins on these and other growth factor receptors, therefore, may have an important role in the biology of breast cancers.

Breast Neoplasms↗

PubMed1990

Designing a schedule of progestin administration in the control of endometrial carcinoma growth in the nude mouse model.

We previously showed that combined treatment with tamoxifen and progestin was effective in arresting the growth of human endometrial carcinomas in the nude mouse model. After a 15- to 20-week tumoristatic period, the tumors began to regrow, reminiscent of the clinical situation. Lack of progestin sensitivity during the regrowth period appeared to reflect the absence of progesterone receptor. To test the prediction that intermittent progestin administration may circumvent the regrowth phenomenon, the effect of various doses of progestin on blood progestin levels, EnCa 101 tumor progesterone receptor profiles, and rate of tumor growth were examined. Whereas 1 mg progestin was ineffective in totally down-regulating tumor progesterone receptor, 2 and 5 mg doses resulted in the total disappearance of tumor progesterone receptor by 1 week followed by its reappearance at 5 to 6 weeks and 9 to 10 weeks, respectively. On the basis of these results we predict that intermittent progestin administration may result in better control of endometrial cancer growth in the nude mouse system.

Animals↗