TG101209, a small molecule JAK2-selective kinase inhibitor potently inhibits myeloproliferative disorder-associated JAK2V617F and MPLW515L/K mutations

JAK2V617F and MPLW515L/K represent recently identified mutations in myeloproliferative disorders (MPD) that cause dysregulated JAK-STAT signaling, which is implicated in MPD pathogenesis. We developed TG101209, an orally bioavailable small molecule that potently inhibits JAK2 (IC(50)=6 nM), FLT3 (IC(50)=25 nM) and RET (IC(50)=17 nM) kinases, with significantly less activity against other tyrosine kinases including JAK3 (IC(50)=169 nM). TG101209 inhibited growth of Ba/F3 cells expressing JAK2V617F or MPLW515L mutations with an IC(50) of approximately 200 nM. In a human JAK2V617F-expressing acute myeloid leukemia cell line, TG101209-induced cell cycle arrest and apoptosis, and inhibited phosphorylation of JAK2V617F, STAT5 and STAT3. Therapeutic efficacy of TG101209 was demonstrated in a nude mouse model. Furthermore, TG101209 suppressed growth of hematopoietic colonies from primary progenitor cells harboring JAK2V617F or MPL515 mutations.

Regulation of estrogen receptor-alpha expression by the tumor suppressor gene p53 in MCF-7 cells

The results presented here demonstrate that p53 upregulates estrogen receptor-alpha (ER alpha) expression in the human breast cancer cell line MCF-7. Two approaches were used to alter the activity of p53 in the cells. In the first approach, stable transfectants expressing an antisense p53 were established. In the stable clones, expression of antisense p53 resulted in a decrease in the expression of ER alpha protein. In the second approach, MCF-7 cells were transiently transfected with wild-type p53. Overexpression of p53 increased the amount of ER alpha. To determine whether the effects of p53 on the expression of ER alpha were due to changes in transcription, deletion mutants of the ER alpha promoter were used. This experimental approach demonstrated that p53 up-regulates ER alpha gene expression by increasing transcription of the gene through elements located upstream of promoter A. Transfection assays using p53 mutants further demonstrated that the p53-induced increase in ER alpha gene transcription was not dependent on the ability of p53 to bind to DNA but on its ability to interact with other proteins.

Regulation of estrogen receptor-alpha expression in MCF-7 cells by taxol

Results presented in this study demonstrate that treatment of MCF-7 cells with taxol resulted in induction of estrogen receptor-alpha (ER alpha) gene transcription with a subsequent increase in ER alpha mRNA; this effect was promoter specific since taxol did not affect total transcription in MCF-7 cells and lacked an effect on transcription of the human acidic ribosomal phosphoprotein protein PO, progesterone receptor, and pS2 genes. In contrast to the increase in transcription of the ER alpha gene, taxol inhibited translation of the ER alpha mRNA. This effect is also transcript specific since taxol did not alter total protein synthesis and did not affect the concentration of progesterone receptor protein in the cell. The overall result of taxol treatment was to decrease the concentration of ER alpha protein in the MCF-7 cells. Evidence is presented that the effects of taxol on ER alpha gene transcription may be mediated through the induction of p53.

Bisphosphonates are potent inhibitors of Trypanosoma cruzi farnesyl pyrophosphate synthase

We report the cloning and sequencing of a gene encoding the farnesyl pyrophosphate synthase of Trypanosoma cruzi. The protein (T. cruzi farnesyl pyrophosphate synthase, TcFPPS) is an attractive target for drug development, since the growth of T. cruzi is inhibited by carbocation transition state/reactive intermediate analogs of its substrates, the nitrogen-containing bisphosphonates currently in use in bone resorption therapy. The protein predicted from the nucleotide sequence of the gene has 362 amino acids and a molecular mass of 41.2 kDa. Several sequence motifs found in other FPPSs are present in TcFPPS. Heterologous expression of TcFPPS in Escherichia coli produced a functional enzyme that was inhibited by the nitrogen-containing bisphosphonates alendronate, pamidronate, homorisedronate, and risedronate but was less sensitive to the non-nitrogen-containing bisphosphonate etidronate, which, unlike the nitrogen-containing bisphosphonates, does not affect parasite growth. The protein contains a unique 11-mer insertion located near the active site, together with other sequence differences that may facilitate the development of novel anti-Chagasic agents.

(31)P NMR of apicomplexans and the effects of risedronate on Cryptosporidium parvum growth

High-resolution 303.6 MHz (31)P NMR spectra have been obtained of perchloric acid extracts of Plasmodium berghei trophozoites, Toxoplasma gondii tachyzoites, and Cryptosporidium parvum oocysts. Essentially complete resonance assignments have been made based on chemical shifts and by coaddition of authentic reference compounds. Signals corresponding to inorganic pyrophosphate were detected in all three species. In T. gondii and C. parvum, additional resonances were observed corresponding to linear triphosphate as well as longer chain polyphosphates. Spectra of P. berghei and T. gondii also indicated the presence of phosphomonoesters and nucleotide phosphates. We also report that the pyrophosphate analog drug, risedronate (used in bone resorption therapy), inhibits the growth of C. parvum in a mouse xenograft model. When taken together, our results indicate that all the major disease-causing apicomplexan parasites contain extensive stores of condensed phosphates and that as with Plasmodium falciparum and T. gondii, the pyrophosphate analog drug risedronate is an inhibitor of C. parvum cell growth.

Bisphosphonates inhibit the growth of Trypanosoma brucei, Trypanosoma cruzi, Leishmania donovani, Toxoplasma gondii, and Plasmodium falciparum: a potential route to chemotherapy

We have investigated the effects in vitro of a series of bisphosphonates on the proliferation of Trypanosoma cruzi, Trypanosoma brucei rhodesiense, Leishmania donovani, Toxoplasma gondii, and Plasmodium falciparum. The results show that nitrogen-containing bisphosphonates of the type used in bone resorption therapy have significant activity against parasites, with the aromatic species having in some cases nanomolar or low-micromolar IC(50) activity values against parasite replication (e.g. o-risedronate, IC(50) = 220 nM for T. brucei rhodesiense; risedronate, IC(50) = 490 nM for T. gondii). In T. cruzi, the nitrogen-containing bisphosphonate risedronate is shown to inhibit sterol biosynthesis at a pre-squalene level, most likely by inhibiting farnesylpyrophosphate synthase. Bisphosphonates therefore appear to have potential in treating parasitic protozoan diseases.

Iron chelation therapy in sickle cell disease

Iron chelation therapy with deferoxamine enhances iron excretion and removes excessive tissue iron in regularly transfused patients with sickle cell disease. Long-term studies of deferoxamine in other hemoglobinopathies demonstrate that regular chelation therapy also reduces iron-related organ damage and mortality. Careful design of chelation regimens and attention to compliance are critical elements of successful therapy. The role of new chelators in sickle cell disease is currently under Investigation.

New image compression techniques using multiwavelets and multiwavelet packets

Advances in wavelet transforms and quantization methods have produced algorithms capable of surpassing the existing image compression standards like the Joint Photographic Experts Group (JPEG) algorithm. For best performance in image compression, wavelet transforms require filters that combine a number of desirable properties, such as orthogonality and symmetry. However, the design possibilities for wavelets are limited because they cannot simultaneously possess all of the desirable properties. The relatively new field of multiwavelets shows promise in obviating some of the limitations of wavelets. Multiwavelets offer more design options and are able to combine several desirable transform features. The few previously published results of multiwavelet-based image compression have mostly fallen short of the performance enjoyed by the current wavelet algorithms. This paper presents new multiwavelet transform and quantization methods and introduces multiwavelet packets. Extensive experimental results demonstrate that our techniques exhibit performance equal to, or in several cases superior to, the current wavelet filters.

A role for Akt in mediating the estrogenic functions of epidermal growth factor and insulin-like growth factor I

This study examines whether the serine/threonine protein kinase, Akt, is involved in the cross-talk between epidermal growth factor (EGF) and insulin-related growth factor I (IGF-I) receptors and ER-alpha. Treatment of MCF-7 cells with either EGF or IGF-I resulted in a rapid phosphorylation of Akt and a 14- to 16-fold increase in Akt activity, respectively. Akt activation was blocked by inhibitors of phosphatidylinositol 3-kinase, but not by an inhibitor of the ribosomal protein kinase p70S6K. Stable transfection of cells with a dominant negative Akt mutant blocked the effects of EGF and IGF-I on ER-alpha expression and activity, whereas stable transfection of cells with a constitutively active Akt mutant mimicked the effects of EGF and IGF-I. In the latter cells, there was a decrease in the amount of ER-alpha protein and messenger RNA (70-80%) and an increase in the amount of progesterone receptor protein, messenger RNA (4- to 9- and by 3.5- to 7-fold, respectively) and pS2 (3- to 5-fold). Coexpression of wild-type ER-alpha and the dominant negative Akt mutant in COS-1 cells also blocked the growth factor-stimulated activation of ER-alpha, but coexpression of the wild-type receptor with the constitutively active Akt mutant increased ER-alpha activity. Receptor activation was blocked by an antiestrogen. Studies using mutants of ER-alpha demonstrated that Akt increased estrogen receptor activity through the amino-terminal activation function-1 (AF-1). Serines S104 S106, S118, and S167 appear to play a role in the activation of ER-alpha by Akt.

Effects of arsenite on estrogen receptor-alpha expression and activity in MCF-7 breast cancer cells

To determine whether arsenite has estrogen-like activities, the effects of this compound on estrogen receptor-alpha (ERalpha) and other estrogen-regulated genes were measured in the human breast cancer cell line MCF-7. Treatment of cells with 1 microM arsenite resulted in a 60% decrease in the amount of ERalpha and in a parallel decrease of 40% in ERalpha messenger RNA. Progesterone receptor concentration increased 22-fold after arsenite treatment. pS2 messenger RNA also increased 2. 1-fold after treatment. The induction of progesterone receptor and pS2 was blocked by the antiestrogen ICI-182,780. In transient cotransfection experiments of wild-type ERalpha and an estrogen response element-reporter construct, arsenite stimulated chloramphenicol acetyltransferase (CAT) activity. In growth assays, arsenite significantly stimulated the proliferation of MCF-7 cells compared with cells grown in estrogen-depleted medium. Addition of an antiestrogen blocked growth stimulation by arsenite. In binding assays, arsenite blocked the binding of estradiol to ERalpha (Ki = 5 +/- 0.5 nM; n = 3), suggesting that the compound interacts with the hormone-binding domain of the receptor. To determine whether interaction of arsenite with the hormone-binding domain results in receptor activation, COS-1 cells were transiently cotransfected with the chimeric receptors GAL-ER, which contains the hormone-binding domain of ERalpha and the DNA-binding domain of the transcription factor GAL4, and a GAL4-responsive CAT reporter gene. Treatment of cells with estradiol or arsenite resulted in a 4-fold increase in CAT activity. The effects of arsenite on the chimeric receptor were blocked by the antiestrogen, suggesting that arsenite activates ERalpha through an interaction with the hormone-binding domain of the receptor. Transfection assays with ERalpha mutants identified C381, C447, H524, and N532 as interaction sites of arsenite with the hormone-binding domain.

Effects of selenite on estrogen receptor-alpha expression and activity in MCF-7 breast cancer cells

To determine whether selenite has estrogen-like activities, the effects of this compound on estrogen receptor-alpha (ER-alpha) and other estrogen-regulated genes were measured in the human breast cancer cell line MCF-7. Treatment of cells with 1 uM of sodium selenite resulted in a 40% decrease in the amount of estrogen receptor-alpha and in a parallel decrease of 40% in ER-alpha mRNA. Progesterone receptor concentration increased 2.6-fold and pS2 mRNA increased 2.4-fold after selenite treatment. The induction of progesterone receptor and pS2 was blocked by the anti-estrogen ICI-182,780. In transient co-transfection experiments of Wild-type ER-alpha and an estrogen response element-reporter construct, selenite stimulated CAT activity. In binding assays, selenite blocked the binding of estradiol to ER-alpha (K(i) = 23 +/- 17 nM, n = 3) suggesting that this compound interacts with the hormone binding domain of the receptor. To determine whether interaction of selenite with the hormone binding domain results in receptor activation, COS-1 cells were transiently co-transfected with the chimeric receptors GAL-ER, which contains the hormone binding domain of ER-alpha and the DNA binding domain of the transcription factor GAL4, and a GAL4-responsive CAT reporter gene. Treatment of cells with estradiol or selenite resulted in a three- to five-fold increase in CAT activity. The effects of selenite on the chimeric receptor were blocked by the antiestrogen, suggesting that selenite activates ER-alpha through an interaction with the hormone binding domain of the receptor. Transfection assays with ER-alpha mutants identified C381, C447, H524, and N532 as interaction sites of selenite with the hormone binding domain.

Regulation of estrogen receptor-alpha gene expression by epidermal growth factor

The role of epidermal growth factor (EGF) in the regulation of estrogen receptor-alpha (ER-alpha) gene expression in the human breast cancer cell line MCF-7 was investigated. Treatment of cells with 0.4 ng/ml EGF resulted in an approximately 60% decrease in ER-alpha protein concentration by 6 h and the amount of receptor remained suppressed for 24 h. Ligand binding assays demonstrated that the decrease in ER-alpha protein corresponded to a similar decrease (approximately 50%) in estradiol binding sites. Although EGF treatment resulted in a decrease in the number of binding sites, it had no effect on the binding affinity of ER-alpha. The dissociation constant of the estradiol-ER-alpha complex in the presence or absence of EGF was the same (K(d)=2.3x10(-)(10) M in control cells versus K(d)=1.98x10(-)(10) M in EGF-treated cells). The decrease in ER-alpha protein concentration paralleled a decrease in the steady-state amount of ER-alpha mRNA. By 9 h there was an approximately 60% decrease in ER-alpha mRNA. The amount of ER-alpha mRNA remained suppressed for 48 h. Transcription run-on experiments demonstrated that there was a decrease of approximately 70% in ER-alpha gene transcription upon EGF treatment, suggesting that the mechanism by which EGF regulates ER-alpha gene expression is transcriptional. In addition to regulating the amount of ER-alpha, EGF affected the activity of the receptor. At high concentrations, EGF induced progesterone receptor. Estradiol and high concentrations of EGF had an additive effect on progesterone receptor. In contrast to high concentrations, low concentrations of EGF had no effect on progesterone receptor and blocked estradiol induction. The effects of EGF on ER-alpha expression were inhibited by tyrophostins and wortmannin, suggesting that the effects of the growth factor are mediated by the EGF receptor and protein kinase B. When the cells were placed in serum-free medium and then treated with EGF, there was no effect on ER-alpha protein concentration or activity. However, increasing concentrations of serum restored the effects of EGF on ER-alpha, suggesting that an additional serum factor was required for the EGF-mediated effect on the decrease in ER-alpha protein concentration.

Activation of estrogen receptor-alpha by the heavy metal cadmium

Previous studies from this laboratory have shown that the heavy metal cadmium (Cd) mimics the effects of estradiol in estrogen-responsive breast cancer cell lines. To understand the mechanism by which cadmium activates estrogen receptor-alpha (ER-alpha), the ability of cadmium to bind to and activate wild-type and various mutants of ER-alpha was examined. When tested in transient cotransfection assays in COS-1 cells, cadmium concentrations as low as 10(-11) M activated ER-alpha. Scatchard analysis employing either purified human recombinant ER-alpha or extracts from ER-containing MCF-7 cells demonstrated that l09Cd binds to the ER with an equilibrium dissociation constant of approximately 4 to 5 x 10(-10) M. Cadmium also blocks the binding of estradiol to ER-alpha in a noncompetitive manner (K(i) = 2.96 x 10(-10) M), suggesting that the heavy metal interacts with the hormone-binding domain of the receptor. To study the role of the hormone-binding domain in cadmium activation, COS-1 cells were transiently cotransfected with GAL-ER, a chimeric receptor containing the DNA-binding domain of the transcription factor GAL4 and the hormone-binding domain of ER-alpha, and a GAL4-responsive reporter gene. Treatment of the transfected cells with either 10(-6) M cadmium or 10(-9) M estradiol resulted in a 4-fold increase in reporter gene activity. The effect of cadmium on the chimeric receptor was blocked by the antiestrogen, ICI-164,384, suggesting that cadmium activates ER-alpha through an interaction with the hormone-binding domain of the receptor. Transfection and binding assays with ER-alpha mutants identified C381, C447, E523, H524, and D538 as possible interaction sites of cadmium with the hormone-binding domain of ER-alpha.

Role of insulin-like growth factor-I in regulating estrogen receptor-alpha gene expression

The role of insulin-like growth factor-I (IGF-I) in regulating estrogen receptor-alpha (ER-alpha) gene expression and activity was investigated in the human breast cancer cell line MCF-7. Treatment of cells with 40 ng/ml IGF-I resulted in a 60% decrease in ER-alpha protein concentration by 3 h, and the amount of ER-alpha remained suppressed for 24 h. A multiple-dose ligand-binding assay demonstrated that the decrease in ER-alpha protein corresponded to a similar decrease of 50% in estradiol-binding sites with no effect on the binding affinity of ER-alpha. The dissociation constant of the estradiol-ER-alpha complex in the absence of IGF-I (K(d) = 3 x 10(-10) +/- 0.5 x 10(-10) M) was similar to the dissociation constant in the presence of IGF-I (K(d) = 6 x 10(-10) +/- 0.3 x 10(-10) M). The decrease in ER-alpha protein concentration was paralleled by an 80% decrease in the steady-state amount of ER-alpha mRNA by 3 h. The IGF-I induced decrease in ER-alpha mRNA was due to the inhibition of ER-alpha gene transcription. When an 128-base pair ER-alpha-promoter-CAT construct was transfected into MCF-7 cells, treatment with IGF-I resulted in a 40% decrease in CAT activity. In contrast to the effects on ER-alpha, treatment with IGF-I induced two endogenous estrogen-regulated genes, progesterone receptor and pS2, by 4- and twofold, respectively. The pure antiestrogen ICI-164, 384 blocked this induction, suggesting that ER-alpha mediates the effects of IGF-I. Transient co-transfections of wild-type ER-alpha and an estrogen response element-CAT reporter into COS-1 cells demonstrated that IGF-I increased reporter gene activity. This effect was also blocked by ICI 164,384. Protein kinase A and phosphatidylinositol 3-kinase inhibitors blocked the IGF-I effects on ER-alpha expression and activity, suggesting that these kinases may be involved in the cross-talk between the IGF-I and ER-alpha pathways.

Regulation of estrogen receptor-alpha gene expression by 1, 25-dihydroxyvitamin D in MCF-7 cells

This report describes an investigation of the role of 1, 25-dihydroxyvitamin D (VD(3)) in the regulation of estrogen receptor-alpha (ER) in the ER-positive breast cancer cell line, MCF-7. Treatment of cells with 10 nM VD(3) resulted in a 50% decline in the concentration of ER protein at 24 h. Scatchard analysis showed a corresponding decrease in the number of estradiol binding sites and no alteration in the binding affinity of estradiol for the ER (K(d) = 0.08 nM in VD(3)-treated cells compared with K(d) = 0.07 nM in control cells). Vitamin D treatment also caused a 50% decrease in the steady state amount of ER mRNA, which was maximal by 18 h. In vitro transcription run-on experiments demonstrated a decrease of approximately 60% in transcription of the estrogen receptor gene. Transient transfections using an ER promoter-CAT construct also demonstrated a 40% decrease in CAT activity after VD(3) treatment. Sequence analysis identified a potential vitamin D response element (nVDRE) within the ER promoter. When this element was mutated, the ability of VD(3) to block transcription from the ER promoter was lost. When the nVDRE was placed upstream of a heterologous promoter, nVDRE-SV40-CAT, treatment with VD(3) resulted in a 50% decrease in CAT activity. Interestingly, co-transfection of either the ER promoter-CAT or the nVDRE-SV40-CAT construct and a vitamin D receptor expression vector into COS-1 or CV-1 cells showed an approximately 4-fold increase in CAT activity after VD(3) treatment. Taken together these data suggest that VD(3) inhibition of ER gene transcription is mediated through a nVDRE in the ER promoter. Inhibition appears to be cell specific.

Nitrogen-containing bisphosphonates as carbocation transition state analogs for isoprenoid biosynthesis

Nitrogen-containing bisphosphonates are potent bone antiresorptive agents as well as having herbicidal and antiparasitic activity, and are thought to act by inhibiting enzymes of the mevalonate pathway. Using molecular modeling and ab initio quantum chemical calculations, we show that bisphosphonates can act as aza-isoprenoid transition state analogs, thereby inhibiting isoprenoid biosynthesis. The two phosphonate groups of the 1,1-bisphosphonates readily dock into the diphosphate-Mg(2+) binding site in farnesyl diphosphate synthase, while the charged ammonium (or pyridinium or imidazolium) groups act as carbocation transition state analogs, whose binding is stabilized by a cluster of oxygen atoms in the active site cleft, and an overall negative electrostatic potential in this region. Enhanced activity is shown to correlate with increasing van der Waals stabilization due to N-alkylation, or the presence of a charged, planar (sp(2)-hybridized) aromatic residue in the carbocation binding site. These results are of general interest since they suggest a rational approach to bisphosphonate drug design.

Survival of cryopreservation and thawing with all blastomeres intact identifies multicell embryos with superior frozen embryo transfer outcome

OBJECTIVE

To assess the impact of survival of cryopreservation and thawing with all blastomeres intact on the outcome of multicell frozen ET.

DESIGN

Retrospective study.

SETTING

Academic assisted reproductive technology program.

PATIENT(S)

One hundred sixteen exclusively multicell frozen ETs in 78 patients.

INTERVENTION(S)

Frozen ET.

MAIN OUTCOME MEASURE(S)

Relation of embryonic blastomere survival to the outcome of frozen ET (i.e., pregnancy).

RESULT(S)

When at least one embryo survived with all blastomeres intact, the total pregnancy rate (biochemical, clinical, or delivered) was 37.7%, the clinical pregnancy rate was 24.6%, and the delivered pregnancy rate was 18.8%. When no embryo survived with all blastomeres intact, the corresponding rates were 10.6%, 8.5%, and 6.4%. The differences in the total pregnancy rate and the clinical pregnancy rate were statistically significant. The delivered pregnancy rates approached statistical significance.

CONCLUSION(S)

Multicell embryonic survival of cryopreservation and thawing with all blastomeres intact identifies embryos with superior developmental potential.

Upregulation of estrogen receptor-alpha expression in rabbit cardiac allograft

Estrogen receptor (ER) expression has been detected in different tissues, and estradiol-17beta treatment protects against experimental transplant arteriosclerosis. In this study, ER-alpha expression in the rabbit hearts and attached aortas before and after cardiac-aorta allograft transplantation was examined. Ten male New Zealand White rabbits were transplanted with cardiac-aorta allografts from male Dutch Belted rabbits. This transplant arteriosclerosis model uses a 0.5% cholesterol diet and immunosuppression with cyclosporin A (10 mg . kg-1 . d-1) until euthanatization 42 days later. The cardiac grafts with the attached aorta were harvested. Strong staining of ER-alpha protein was shown in the coronary arteries of the cardiac allografts by immunohistochemistry with the use of a mouse anti-human ER-alpha monoclonal antibody (ID5). In contrast, both the nongrafted hearts of the recipients and donor hearts expressed only weak staining. RNase protection assay with the use of a 32P-labeled ER-alpha antisense riboprobe (pOR 300) proved that the basal expression of ER-alpha mRNA is similar in the nongrafted aorta of both recipients and donors. A marked increase of ER-alpha mRNA was observed in the allograft aorta compared with the nongrafted aorta (289+/-69%, P<0. 02) by reverse transcription and polymerase chain reaction. The DNA sequence analysis confirmed that the polymerase chain reaction-amplified fragment corresponded to ER-alpha. This is the first observation of ER-alpha upregulation in the allograft vasculature and may relate to the allograft cardiovascular protective effects of estrogen.

Estradiol regulates estrogen receptor mRNA stability

Previous studies suggest that post-transcriptional events play an important role in estrogen-induced loss of estrogen receptor expression. The present study shows that treatment of MCF-7 cells with estradiol resulted in a six-fold decrease in estrogen receptor mRNA half-life from 4 h in control cells to 40 min in estradiol treated cells. To determine the role of protein synthesis in the regulation of estrogen receptor mRNA stability, several translational inhibitors were utilized. Pactamycin and puromycin, which prevent ribosome association with mRNA, inhibited the effect of estradiol on receptor mRNA stability, whereas cycloheximide, which has no effect on ribosome association with mRNA, had no effect on estradiol regulation of estrogen receptor mRNA stability. In control cells, the total cellular content of estrogen receptor mRNA was associated with high molecular weight polyribosomes. Treatment with estradiol resulted in a 70% decrease in estrogen receptor mRNA associated with polyribosomes but had no effect on the polyribosome distribution of estrogen receptor mRNA. In an in vitro degradation assay, polyribosomes isolated from estradiol-treated cells degraded ER mRNA faster than polyribosomes isolated from control cells. The nuclease activity associated with the polysome fraction appeared to be Mg2+ independent and inhibited by RNasin. Freeze-thawing and heating at 90 degrees C for 10 min resulted in the loss of nuclease activity. These studies suggest that an estrogen-regulated nuclease activity associated with ribosomes alters the stability of estrogen receptor mRNA.

Consumption of a high-fat diet alters estrogen receptor content, protein kinase C activity, and mammary gland morphology in virgin and pregnant mice and female offspring

Previous studies have shown that a diet high in polyunsaturated fatty acids increases mammary tumor incidence in adult and pregnant mice and rats and in the female offspring. The present study investigated whether a high-fat diet alters the number of estrogen receptor (ER) binding sites and protein kinase C (PKC) activity in the mammary gland of these animals. In the female offspring, the effects of maternal exposure to a high-fat diet during pregnancy on development of the mammary epithelial tree were studied also. BALB/c mice were kept on a diet containing either 43% (high-fat) or 16% (low-fat) calories from corn oil, which consists mostly of n-6 polyunsaturated fatty acids, for 1 month. In adult female mice, a 6-fold increase in the number of ER binding sites and 2-fold increase in PKC activity were found in the mammary glands of the high-fat mice when compared with the low-fat mice. In pregnant mice, a high-fat diet increased ER binding sites by 61% and PKC activity by 51%. In contrast to adult and pregnant mice, females exposed to a high-fat diet only in utero through their pregnant mother exhibited a significantly reduced number of mammary ER binding sites by age 45 days (78% decrease) and a reduction in PKC activity by ages 30 and 100 days (44 and 20% decrease, respectively). The mammary epithelial tree of the high-fat offspring contained more terminal end buds and was less differentiated than that of the low-fat offspring. These findings show that consumption of a high-fat diet increases ER and PKC in the adult and pregnant mouse mammary gland, perhaps contributing to the fat-induced promotion of mammary tumorigenesis. In contrast, reduced ER and PKC following a high-fat exposure in utero may be associated with increased susceptibility to carcinogenesis, possibly due to an increased number of terminal end buds that are the sites of neoplastic transformation in the mammary gland.

Structure-activity relationships of N-hydroxyurea 5-lipoxygenase inhibitors

The discovery of second generation N-hydroxyurea 5-lipoxygenase inhibitors was accomplished through the development of a broad structure-activity relationship (SAR) study. This study identified requirements for improving potency and also extending duration by limiting metabolism. Potency could be maintained by the incorporation of heterocyclic templates substituted with selected lipophilic substituents. Duration of inhibition after oral administration was optimized by identification of structural features in the proximity of the N-hydroxyurea which correlated to low in vitro glucuronidation rates. Furthermore, the rate of in vitro glucuronidation was shown to be stereoselective for certain analogs. (R)-N-[3-[5-(4-Fluorophenoxy)-2-furyl]-1-methyl-2-propynyl]-N-hydroxyure a (17c) was identified and selected for clinical development.

The role of transforming growth factor-beta in the regulation of estrogen receptor expression in the MCF-7 breast cancer cell line

The role of transforming growth factor-beta1 (TGFbeta1) in the regulation of estrogen receptor (ER) expression in MCF-7 cells was investigated. After treatment of the cells with 100 pM TGFbeta1, ER protein declined by about 30% at 6 h from a concentration of 413.5 fmol/mg protein in control cells to 289.5 fmol/mg protein in treated cells. The concentration of receptor remained suppressed for 24 h. Scatchard analysis demonstrated that the decrease in ER protein corresponded to a decrease in estradiol-binding sites, with no effect on the binding affinity of the ER. The dissociation constant of the estradiol-ER complex was 0.117 nM in TGFbeta1-treated cells compared to 0.155 nM in control cells. Treatment with TGFbeta1 did not influence the half-life of the ER. In TGFbeta1-treated cells, as well as in control cells, the half-life of the receptor was approximately 4 h. In contrast to the effect on ER concentration, TGFbeta1 treatment resulted in a greater decrease in the steady state level of ER messenger RNA (approximately 75%) at 6 h. By 24 h, a small recovery in the amount of messenger RNA was observed. Transcription run-on experiments demonstrated a decrease of approximately 70% in the level of ER gene transcription at 3 h. Transient transfections using an ER promoter-chloramphenicol acetyltransferase construct demonstrated that after TGFbeta1 treatment, chloramphenicol acetyltransferase activity decreased by 50%, suggesting that TGFbeta1 inhibition of the ER gene transcription is mediated through the ER promoter. Although treatment with TGFbeta1 decreased the ER concentration, the growth factor had no effect on the activity of ER, as measured by its effects on estradiol induction of progesterone receptor and pS2, suggesting that TGFbeta1 does not inhibit proliferation of MCF-7 cells by blocking ER activity.

Regulation of estrogen receptor concentration and activity by an erbB/HER ligand in breast carcinoma cell lines

Expression of the erbB-2 oncogene in breast cancer patients correlates with poor prognosis and failure of hormonal therapy. In this study, the effects of a putative erbB/HER ligand, gp30, on estrogen receptor (ER) concentration and activity was investigated in the estrogen receptor positive human breast cancer cells, BT474 and MCF-7, which express either high or low levels of erbB-2 and erbB-4, respectively. Treatment of cells with gp30 resulted in a decrease in the steady-state level of estrogen receptor protein by approximately 70-80%. The effect of gp30 on the concentration of ER was independent of serum in the media and was not inhibited by an epidermal growth factor receptor blocking antibody. In addition to the effect on ER protein, gp30 decreased the steady-state level of ER messenger RNA. Transcription run on experiments demonstrated that the decrease in ER expression was mediated by a decrease in ER gene transcription. The effect of gp30 on estrogen receptor activity was also investigated in this study. Treatment of cells with gp30 blocked estradiol induction of progesterone receptor. Inhibition was observed at the level of progesterone receptor protein, messenger RNA, and gene transcription. gp30 also blocked estradiol induction of pS2 gene transcription. In addition to its effects on progesterone receptor and pS2, gp30 blocked activation of an estrogen response element in a transient transfection assay and inhibited ER binding to its response element in a DNA mobility shift assay, suggesting a direct effect on the estrogen receptor. The effects of gp30 on estrogen receptor concentration and activity were independent of the level of erbB-2 and erbB-4 in the cell. These data show that gp30 regulates the concentration of ER and modulates ER activity.

Expression of an estrogen receptor by human coronary artery and umbilical vein endothelial cells

BACKGROUND

Premenopausal women have much lower susceptibility to coronary artery disease than do men or postmenopausal women. It has been proposed that estrogen plays a role in cardioprotection, but little information is available regarding the mechanism by which estrogen may help to protect the vasculature. Here, we describe an estrogen receptor (ER) in human coronary artery and umbilical vein endothelial cells.

METHODS AND RESULTS

Human umbilical vein endothelial cells and human coronary artery endothelial cells were cultured in hormone-free medium for 48 hours before experiments. Estradiol (3.7 nmol/L) added to cultures promoted proliferation by a mechanism that is inhibited by the specific ER antagonist ICI182,780. Estradiol-treated cells incorporated twice the [3H]thymidine of hormone-free cells; this increase was prevented by ICI182,780. Endothelial cells from both sources stained in a nuclear pattern with an ER-specific antibody. Ribonuclease protection assay detected mRNA for the ER. Ligand-binding studies estimated 2 x 10(4) to 8 x 10(4) receptors per cell and a Kd of approximately 5 nmol/L. Interaction of ERs with a consensus estrogen response element was shown by an electrophoretic mobility shift assay. In addition, an antibody against the ER supershifted the protein-DNA complex.

CONCLUSIONS

These studies define the presence of an ER in human coronary artery and umbilical vein endothelial cells. They support the hypothesis that cardioprotective effects of estrogen are mediated, at least in part, through a classic steroid hormone receptor mechanism.