Transactivation of large ribozymes

The domains of large ribozymes are composed of secondary structural elements that fold independently in solution. Interactions between these structures contribute to the overall structure of the ribozyme. These elements can also be deleted, reducing catalytic activity, and their structure-function relationships determined by assaying the ability of variant elements to activate the deleted ribozyme in trans. This is illustrated for an unusual loop structure from Bacillus subtilis Ribonuclease P RNA.

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.

Frequency of RNA-RNA interaction in a model of the RNA World

The RNA World model for prebiotic evolution posits the selection of catalytic/template RNAs from random populations. The mechanisms by which these random populations could be generated de novo are unclear. Non-enzymatic and RNA-catalyzed nucleic acid polymerizations are poorly processive, which means that the resulting short-chain RNA population could contain only limited diversity. Nonreciprocal recombination of smaller RNAs provides an alternative mechanism for the assembly of larger species with concomitantly greater structural diversity; however, the frequency of any specific recombination event in a random RNA population is limited by the low probability of an encounter between any two given molecules. This low probability could be overcome if the molecules capable of productive recombination were redundant, with many nonhomologous but functionally equivalent RNAs being present in a random population. Here we report fluctuation experiments to estimate the redundancy of the set of RNAs in a population of random sequences that are capable of non-Watson-Crick interaction with another RNA. Parallel SELEX experiments showed that at least one in 10(6) random 20-mers binds to the P5.1 stem-loop of Bacillus subtilis RNase P RNA with affinities equal to that of its naturally occurring partner. This high frequency predicts that a single RNA in an RNA World would encounter multiple interacting RNAs within its lifetime, supporting recombination as a plausible mechanism for prebiotic RNA evolution. The large number of equivalent species implies that the selection of any single interacting species in the RNA World would be a contingent event, i.e., one resulting from historical accident.

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.

Structure of the UGAGAU hexaloop that braces Bacillus RNase P for action

Long-range interactions involving the P5.1 hairpin of Bacillus RNase P RNA are thought to form a structural truss to support RNA folding and activity. We determined the structure of this element by NMR and refined the structure using residual dipolar couplings from a sample weakly oriented in a dilute liquid crystalline mixture of polyethylene glycol and hexanol. Dipolar coupling refinement improved the global precision of the structure from 1.5 to 1.2 A (to the mean), revised the bend angle between segments of the P5.1 stem and corroborated the structure of the loop region. The UGAGAU hexaloop of P5.1 contains two stacks of bases on opposite sides of the loop, distinguishing it from GNRA tetraloops. The unusual conformation of the juxtaposed uracil residues within the hexaloop may explain their requirement in transactivation assays.

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.

Effect of divergent self-monitoring strategies on motor performance and emotion as a function of alternating task complexity

The aim of this study was to determine the effectiveness of implementing different self-monitoring (SM) strategies as a function of varying task complexity on a computer game, 'Shufflepuck'. Self-monitoring theory suggests that positive self-monitoring (PSM) results in better performance for difficult tasks, whereas negative self-monitoring (NSM) is preferable for easy tasks. When SM was tested under easy and complex task conditions, it was found that performance effectiveness was a function of matching appropriate task difficulty with the SM strategy. Unpaired t-tests compared the first set of 100 trials (pre-task) with the second set of 100 trials (post-task) on a computer skills game requiring hand-eye coordination. The results showed that subjects who changed from the difficult task/PSM condition to the easy task/PSM condition (different task, same SM strategy) performed significantly poorer (P < 0.001) than subjects who changed from the difficult task/PSM condition to the easy task/NSM condition (different task, different SM strategy). A second unpaired t-test comparing the two sets of difference performance scores indicated that performance was significantly superior for subjects using the PSM than the NSM strategy while performing the difficult task (P < 0.05). That is, changing from the easy task/NSM condition to the difficult task/NSM condition produced poorer performance than changing from the easy task/NSM to the difficult task/PSM condition. In terms of subjects' emotions, the use of NSM and PSM when performing easy and difficult tasks, respectively, resulted in markedly less negative affect (P < 0.01), but did not influence positive affect, on pre- and post-task comparisons. Finally, correlations between affect and performance, based on pre- and post-performance and affect scores, were moderate to high. Implications of the present results for slumps in sport performance are offered.

Regulation of retinoblastoma gene expression in hormone-dependent breast cancer

Studies have shown an increased risk for breast cancer in the mothers of children suffering from retinoblastoma and osteosarcoma, suggesting a role for the retinoblastoma susceptibility (Rb) gene product in breast cancer. We now show that estradiol decreases the expression of Rb at the level of protein and messenger RNA (mRNA) in estrogen-dependent breast cancer cell lines. Treatment of MCF-7 cells with 10(-9) M estradiol for 48 h resulted in a 70% decrease in the level of Rb protein. Ribonuclease protection assays showed a 50% decrease in the steady state levels of Rb mRNA by 12 h and a 70% decrease in Rb mRNA by 24 h. Treatment with estradiol had no effect on the rate of Rb gene transcription or on Rb mRNA stability, but resulted in an increase in the steady state level of Rb mRNA in the nucleus. The effect of estradiol was inhibited by 10(-7) M 4-hydroxytamoxifen. In the absence of estradiol, the antiestrogens 4-hydroxytamoxifen and ICI 164,384 increased Rb mRNA by 50% over that in estrogen-depleted conditions. Estradiol regulation of Rb mRNA also occurred in other estrogen-dependent breast cancer cell lines. Insulin-like growth factor I, insulin, progestins, and epidermal growth factor had no effect on Rb expression. In summary, these results show that estradiol specifically regulates the expression of the Rb susceptibility gene product in hormone-dependent breast cancer by a posttranscriptional mechanism that occurs in the nucleus. The results from this study suggest that the negative regulation of Rb expression by estradiol, rather than Rb loss or mutation, may play an important role in breast carcinogenesis.

Bidirectional interactions between the estrogen receptor and the cerbB-2 signaling pathways: heregulin inhibits estrogenic effects in breast cancer cells

The responsiveness of estrogen receptor (ER)-positive breast cancer to endocrine therapy is frequently reduced in cells over-expressing c-erbB-2. Stimulation of ER suppresses c-erbB-2, indicating that estrogen controls the activity of c-erbB-2. Heregulin (HRG) has been described to bind to c-erbB-3/c-erbB-4 and to stimulate c-erbB-2. Here we describe the effects of HRG on cell growth and on ER and c-erbB-2 expression in breast cancer cell lines containing distinct levels of c-erbB-2 and ER (BT-474: c-erbB-2 , ER+; MDA-MB-361: c-erbB-2++, ER++; MCF-7: c-erbB-2+, ER ). Proliferation of estrogen-stimulated, c-erbB-2 and ER-positive cells is inhibited by HRG in a dose-dependent manner. In addition, HRG dose-dependently inhibits ER expression. Estrogen, however, inhibits c-erbB-2. Estrogen-mediated down-regulation of c-erbB-2 is most pronounced in MCF-7 but weaker in BT-474. In the latter cells HRG efficiently blocks the estrogenic effect on c-erbB-2. In MCF-7 cells, however, the inhibition of c-erbB-2 cannot be completely reverted by HRG. This modulation occurs in all 3 cell lines at protein, RNA and transcriptional levels, suggesting that the activity of the c-erbB-2 promoter, which contains an estrogen-responsive region, is affected by HRG. The intensity of the mutual inhibition between the HRG/c-erbB-2 and the estrogen/ER system depends on the relative levels of ER and c-erbB-2 expression in the respective cell lines.

Effects of 12-O-tetradecanoylphorbol-13-acetate on estrogen receptor activity in MCF-7 cells

The effects of long term treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) on estrogen receptor (ER) expression in the human breast cancer cell line, MCF-7, were studied. This study demonstrates that treatment of cells with the phorbol ester blocked estrogen receptor activity. Treatment of cells with 100 nM TPA resulted in an 80% decrease in the level of ER protein and a parallel decrease in ER mRNA and binding capacity. Following removal of TPA from the medium, the level of ER protein and mRNA returned to control values; however, the receptor failed to bind estradiol. These cells also failed to induce progesterone receptor in response to estradiol. In addition, TPA treatment blocked transcription from an estrogen response element in transient transfection assays and inhibited ER binding to its response element in a DNA mobility shift assay. The estrogen receptor in treated cells was recognized by two monoclonal anti-ER antibodies and was not quantitatively different from ER in control cells. RNase protection analysis failed to detect any qualitative changes in the ER mRNA transcript. Mixing experiments suggest that TPA induces/activates a factor which interacts with the ER to block binding of estradiol. The effects of TPA on ER levels and binding capacity were concentration-dependent. Low concentrations of TPA inhibited estradiol binding without a decrease in the level of protein, whereas higher concentrations were required to decrease the level of ER protein. The effects of TPA appear to be mediated by activation of protein kinase C since the protein kinase C inhibitors, H-7 and bryostatin, block the effects of TPA on estradiol induction of progesterone receptor. TPA treatment had no effect on the level or binding capacity of the glucocorticoid receptor, indicating that the effects are not universal for steroid receptors. These data demonstrate that activation of the protein kinase C signal transduction pathway modulates the estrogen receptor pathway. The long term effect of protein kinase C activation is to inhibit estrogen receptor function through induction/activation of a factor which interacts with the receptor.

Genetic alterations of microsatellites on chromosome 18 in human breast carcinoma

Allelic alterations of chromosome 18 microsatellites were determined using normal and tumor DNA pairs from 29 patients with infiltrating ductal carcinoma of the breast. Loss of heterozygosity was detected in 62% (18 of 29 patients) of the tumors at one or more of these microsatellites. Eight of the 18 patients exhibited deletions in the region at 18q21.1. This chromosomal band is known to contain a tumor suppressor gene (DCC) whose expression is frequently inactivated in several types of cancer. Ten other patients had deletions in regions not included in the DCC locus. Five of these patients revealed a common deletion at the D18S50 locus (18q23), and the other five patients had deletions in various other regions of the chromosome. No apparent correlation between loss of heterozygosity of chromosome 18 microsatellites and the clinical stage was found in this series. The results indicate that, in addition to the DCC locus, the 18q23 region is likely to contain a second tumor suppressor gene relevant to breast carcinogenesis. Four percent of all microsatellites tested in these patients showed allelic differences in the sizes of repeat units between tumor and the corresponding constitutional DNAs. The pattern of allele instability observed in breast carcinoma differed from that originally reported in a hereditary type of colorectal carcinoma. The observation suggests that this phenomenon is not a mechanism specific to neoplastic processes in breast carcinoma.

Familial translocation t(10;14) (q26.1;q32.3): report of three offspring with 10q deletion and 14q duplication

We describe two brothers and a cousin with common clinical features, including mild mental retardation, motor delays, hypotonia with truncal ataxia, esotropia, and mild facial and hand dysmorphia. The initial routine chromosome study failed to detect any abnormality in the proband. Based on a high index of clinical suspicion, high-resolution chromosome studies were performed on the proband's parents. A small reciprocal translocation t(10;14) (q26.1;q32.3) was detected in the father. The breakpoint on the derivative chromosome 14 was further placed telomeric to the immunoglobulin heavy-chain gene cluster at the band q32.33 by fluorescence in situ hybridization. Studies of the proband and two affected paternal cousins revealed that each had inherited the same derivative chromosome 10 from their carrier parents. This unbalanced karyotype resulted from an adjacent-1 segregation of the 10;14 translocation.

Effect of cadmium on estrogen receptor levels and estrogen-induced responses in human breast cancer cells

The effects of cadmium on estrogen receptor and other estrogen-regulated genes in the human breast cancer cell line MCF-7 were studied. Treatment of MCF-7 cells with 1 microM cadmium decreased the level of estrogen receptor 58%. Cadmium induced a parallel decrease in estrogen receptor mRNA (62%). Progesterone receptor levels increased 3.2-fold after cadmium treatment. This induction was blocked by the anti-estrogen ICI-164,384. Progesterone receptor mRNA was also increased by cadmium, as well as cathepsin D mRNA. An in vitro nuclear transcription run-on assay showed that cadmium increased the transcription of the progesterone receptor and pS2 genes and decreased transcription of the estrogen receptor gene. These are not general effects of heavy metals, as zinc, 25 and 100 microM, did not affect progesterone receptor protein and mRNA levels. Cadmium stimulated pS2 and progesterone receptor mRNAs in a clone of MDA-MB-231 cells transfected with the human estrogen receptor, but had no effect in MDA-MB-231 cells transfected with antisense estrogen receptor. Cadmium also stimulated an estrogen response element in transient transfection experiments. These data suggest that the effects of cadmium are mediated by the estrogen receptor independent of estradiol. In addition to its effect on gene expression, cadmium induced the growth of MCF-7 cells 5.6-fold.

Erythrocytapheresis therapy to reduce iron overload in chronically transfused patients with sickle cell disease

Chelation therapy with deferoxamine is effective in preventing the risk of transfusional iron overload, but treatment failure is common because of noncompliance. To reduce the transfusional iron load, we have evaluated longterm erythrocytapheresis in 14 subjects with sickle cell disease and stroke (11) or other complications (3) as an alternative to simple transfusion. Subjects were treated with erythrocytapheresis using the Haemonetics V50 (Haemonetics Corp, Braintree, MA) to maintain the target pretransfusion hemoglobin S (Hb S) level less than 50% for 6 to 71 months. The transfusional iron load and the donor blood usage were analyzed for a 6- to 36-month study period and were compared with similar data from a subset of 7 subjects previously treated with conventional (target Hb S < 30%) and modified (target Hb S < 50%) simple transfusion protocols. The effect of erythrocytapheresis on iron accumulation was determined by assessment of serum ferritin levels in the absence of iron chelation. The mean transfusional iron load and donor blood usage with erythrocytapheresis were 19 +/- 14 mg iron/kg/yr (range, 6 to 50) and 188.4 +/- 55.2 mL packed-red blood cells (RBC)/kg/yr (range, 107 to 281), respectively. Of 6 subjects receiving no iron chelation therapy, 5 maintained normal or nearly normal serum ferritin levels during 11 to 36 months of erythrocytapheresis. In comparison with conventional simple transfusion and modified simple transfusion, erythrocytapheresis reduced iron loading by 87% (P < .01) and 82% (P < .01), respectively, but increased donor blood usage by 23% and 73%, respectively. Subjects with pre-erythrocytapheresis Hb levels > or = 8.0 g/dL had lower iron accumulation (P < .001) and less donor blood usage (P < .005) than subjects with Hb levels < or = 8.0 g/dL. Although donor blood usage is increased in comparison with simple transfusion, long-term erythrocytapheresis markedly reduces or prevents iron accumulation. This form of transfusion therapy allows the cessation of iron chelation in well-chelated subjects and, if used as the initial form of transfusion therapy, may prevent long-term complications of sickle cell disease without risk of iron overload and the need for chelation therapy.

Loss of heterozygosity detected in formalin-fixed, paraffin-embedded tissue of colorectal carcinoma using a microsatellite located within the deleted in colorectal carcinoma gene

We determined loss of heterozygosity from formalin-fixed, paraffin-embedded tissue of colorectal carcinoma using microsatellite polymorphism. The polymorphism was assayed based on DNA amplification by the polymerase chain reaction (PCR). The PCR-analyzed microsatellite method was applied to assay degraded DNA extracted from paraffin-embedded blocks with adenocarcinoma of colon. The DNA from 26 tumors as well as their corresponding normal tissue samples were successfully amplified using a dinucleotide microsatellite located within an intron of the deleted in colorectal carcinoma gene. Allele losses on this marker were detected in 33% of informative colorectal carcinomas. This study demonstrates that microsatellites provide a powerful set of DNA markers for loss of heterozygosity on archival specimens.

Increased epidermal growth factor receptor in an estrogen-responsive, adriamycin-resistant MCF-7 cell line

We examined the expression of the estrogen and epidermal growth factor (EGF) receptors in a drug-resistant subline of MCF-7 cells in order to study potential alterations in hormone dependence or in the growth factor pathway that could be related to the development of drug resistance in human breast cancer. The drug-resistant subline was derived from MCF-7 cells by selection with Adriamycin in the presence of the P-glycoprotein antagonist, verapamil, to prevent acquisition of the classical multidrug resistance phenotype. The Adriamycin-resistant cells retain estrogen-binding, estrogen-responsive monolayer growth, and estrogen-dependent tumorigenesis. Estrogen-binding studies demonstrate 1.4 x 10(6) sites per cell with unaltered affinity when compared to parental MCF-7 cells, which have 2.7 x 10(5) sites per cell. An increase in expression of EGF receptor, eight to 12-fold, occurred early in the selection for drug resistance, and appears to be unrelated to verapamil exposure, since cells maintained in Adriamycin without verapamil also have increased EGF receptor expression. Partially drug-sensitive revertants carried a verapamil, but out of Adriamycin, demonstrate a decline in EGF receptor expression. We postulate that activation of growth factor pathways in drug-resistant cells may enhance mechanisms of drug resistance, or provide mitogenic stimuli for cells to recover after damage by drug exposure.

Expression of transforming growth factor alpha antisense mRNA inhibits the estrogen-induced production of TGF alpha and estrogen-induced proliferation of estrogen-responsive human breast cancer cells

To ascertain if 17 beta-estradiol (E2)-induced proliferation could be attenuated by blocking the expression of endogenous transforming growth factor alpha (TGF alpha), estrogen receptor (ER)-positive, estrogen-responsive MCF-7 or ZR-75-1 cells and ER-negative, estrogen-nonresponsive MDA-MB-468 or HS-578T cells were infected with a recombinant amphotropic, replication-defective retroviral expression vector containing a 435 base pair (bp) Apa1-Eco R1 coding fragment of the human TGF alpha cDNA oriented in the 3' to 5' direction and under the transcriptional control of an internal heavy metal-inducible mouse metallothionein (MT-1) promoter and containing the neomycin (neo) resistance gene. E2-stimulated expression of endogenous TGF alpha mRNA was inhibited by 4-5-fold, and the production of TGF alpha protein was inhibited by 50-80% when M-1 mass-infected MCF-7 or MZ-1 mass-infected ZR-75-1 cells were treated with 0.75-1 microM CdCl2, whereas in comparably treated parental MCF-7 or ZR-75-1 cells there was no significant effect upon these parameters. E2-stimulated anchorage-dependent growth (ADG) and anchorage-independent growth (AIG) of the M-1 or MZ-1 cells was inhibited by 60-90% following CdCl2 treatment. In contrast, neither the ADG nor AIG of the parental noninfected MCF-7 or ZR-75-1 cells that were maintained in the absence or presence of E2 was affected by comparable concentrations of CdCl2. The ADG and AIG of TGF alpha antisense MD-1 mass-infected MDA-MB-468 cells that express high levels of endogenous TGF alpha mRNA were also inhibited by 1 microM CdCl2, whereas the ADG and AIG of MH-1 mass-infected HS-578T cells, a TGF alpha-negative cell line, were unaffected by CdCl2 treatment. These results suggest that TGF alpha may be one important autocrine intermediary in regulating estrogen-induced cell proliferation.

Understanding the basics of beta thalassemia major

beta thalassemia major, a severe genetic disorder of the red blood cell, affects about 1,400 people in the United States, including children. Clinical management of this disorder has improved significantly in recent years, and ongoing research will lead to an even brighter outlook in the future.

Regulation of estrogen receptor expression in breast cancer

One of the most prevalent of cancers, breast cancer, is characterized by hormonal control of its growth. Expression of the estrogen receptor (ER) in MCF-7 breast cancer cells appears to be a complex process involving multiple steps subject to hormonal regulation by estrogen. Treatment of MCF-7 cells with estradiol results in the suppression of estrogen receptor protein. By 6 hours, the receptor protein declined by about 60% from a level of approximately 3.6 to 1.2 fmol/micrograms DNA and remained suppressed for 24-48 hours. Similar results were obtained with an estrogen receptor binding assay. Estrogen treatment also resulted in a decrease of receptor mRNA to approximately 10% of control values by 6 hours. Estrogen receptor remained at the suppressed level for up to 48 hours. Transcription run-on experiments demonstrated a transient decrease of about 90% in receptor gene transcription after 1 hour. By 3-6 hours transcription increased approximately 2-fold and remained elevated for at least 48 hours. These data suggest that estrogen suppresses ER mRNA by inhibition of ER gene transcription at early times and by a post-transcriptional effect on receptor mRNA at later times. To determine whether post-transcriptional regulation of ER gene expression is mediated by an ER-dependent mechanism independent of protein synthesis, we used the competitive estrogen antagonist, 4-hydroxytamoxifen, and the inhibitor of protein synthesis, cycloheximide, to study the regulation of ER mRNA by estradiol. 4-Hydroxytamoxifen had no effect on the steady-state level of receptor mRNA and effectively blocked the suppression of ER mRNA by estradiol. The metabolic inhibitor, cycloheximide, was unable to prevent the estrogen induced decrease in ER mRNA. These data provide evidence that the post-transcriptional suppression of ER expression through estradiol is mediated through the ER independent of protein synthesis.

Hepatic iron stores and plasma ferritin concentration in patients with sickle cell anemia and thalassemia major

To examine the relationship between hepatic iron stores and plasma ferritin concentration in individuals treated with red cell transfusion and iron chelation therapy, 37 patients with sickle cell anemia and 74 patients with thalassemia major were studied. In each patient, hepatic iron stores were measured by an independently validated noninvasive magnetic method, and plasma ferritin was determined by immunoassay. The correlation between hepatic iron and plasma ferritin was significant both in patients with sickle cell anemia (R = 0.75, P < 0.0001) and in those with thalassemia major (R = 0.76, P < 0.0001). Regression analysis showed no significant difference between the two groups in the linear relationships between hepatic iron stores and plasma ferritin. Considering all 111 transfused patients as a group, the coefficient of correlation between hepatic iron stores and plasma ferritin was highly significant (R = 0.76, P < 0.0001). Regression analysis found that variation in body iron stores, as assessed by magnetic determinations of hepatic iron, accounted for only approximately 57% of the variation in plasma ferritin, suggesting that the remainder was the result of other factors, such as hemolysis, ineffective erythropoiesis, ascorbate deficiency, inflammation, and liver disease. The 95% prediction intervals for hepatic iron concentration, given the plasma ferritin, were so broad as to make a single determination of plasma ferritin an unreliable predictor of body iron stores. Variability resulting from factors other than iron status limits the clinical usefulness of the plasma ferritin concentration as a predictor of body iron stores.

A modified transfusion program for prevention of stroke in sickle cell disease

Regular red blood cell transfusions reduce the rate of recurrent cerebral infarction in sickle cell disease but lead to accumulation of excessive iron. We studied the effect on the prevention of recurrent stroke and the volume of blood transfused of a modified transfusion program in which the pretransfusion percentage of hemoglobin S (HbS) was maintained at 50%, rather than the conventional 30%. Fifteen patients with sickle cell disease and cerebral infarction who had been free of recurrent stroke for at least 4 years during which the pretransfusion HbS was maintained below 30% were assigned to a transfusion program in which the HbS was allowed to increase to 50%. Transfusion regimens included simple transfusion and manual and automated partial exchange transfusion. The duration of follow-up was 14 to 130 months with a median duration of 84 months. None of the 15 patients had a recurrent cerebral infarction during 1,023 patient-months in which the target pretransfusion HbS was 50%. Analysis of this finding, using a binomial distribution, indicates that there is less than a 5% chance that the risk per patient of recurrent stroke in the first year of the modified transfusion program is greater than 18%. One 23-year-old patient had a fatal intraventricular hemorrhage when the HbS was 30% and a 21-year-old patient had a fatal subarachnoid hemorrhage in the 40th week of pregnancy when the HbS was 29%. Blood requirements with simple transfusions decreased by 17% to 48% (mean 31%) when the target pretransfusion HbS level was increased from 30% to 50% (P less than .001). Manual or automated partial exchange transfusions and a target HbS level of 50% in eight patients reduced blood requirements by 33% to 99% (mean 67%) in comparison with simple transfusion and a target HbS level of 30% (P less than .001). This study offers evidence that a target pretransfusion HbS level of 50% affords a continuing high rate of protection against recurrent cerebral infarction in sickle cell disease after 4 years of a conventional transfusion program. Increasing the target HbS level from 30% to 50% provides a major reduction in blood requirements and lowers the rate of iron accumulation.

Post-transcriptional destabilization of estrogen receptor mRNA in MCF-7 cells by 12-O-tetradecanoylphorbol-13-acetate

The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the regulation of the estrogen receptor (ER) was investigated in this study. After treatment with 100 nM TPA the concentration of receptor protein was measured using an enzyme immunoassay. By 24 h the receptor protein declined by about 80% from a level of approximately 236 fmol of ER/mg of protein in control cells to 50 fmol of ER/mg of protein in cells treated with TPA. Similar results were obtained with an estrogen receptor ligand binding assay. After removal of TPA, the level of ER returned to control values. 4-alpha-Phorbol, a compound related to TPA, had no effect on ER. The effects of TPA on ER expression appear to be mediated by activation of protein kinase C as H-7, an inhibitor of protein kinase C, blocks these effects. In addition to the effect on ER protein, TPA treatment also resulted in a decrease in the steady-state level of ER mRNA as determined by a RNase protection assay. The metabolic inhibitor cycloheximide was unable to prevent the TPA-induced decrease in ER mRNA. Transcription run-off experiments demonstrated that TPA had no effect on ER gene transcription. A half-life study demonstrated that TPA decreased ER mRNA half-life by a factor of 6 from approximately 4 h in control cells to 40 min in TPA-treated cells. These data suggest that the decline in ER expression is mediated by post-transcriptional destabilization of ER mRNA.

Role of an estrogen receptor-dependent mechanism in the regulation of estrogen receptor mRNA in MCF-7 cells

We have previously demonstrated that regulation of estrogen receptor (ER) expression in MCF-7 breast cancer cells is a complex process involving transcriptional and posttranscriptional regulation by estradiol. Treatment of MCF-7 cells with estradiol results in the down-regulation of receptor expression; posttranscriptional suppression of receptor mRNA appears to be the predominant mechanism. To determine whether posttranscriptional regulation of ER gene expression is mediated by an ER-dependent mechanism independent of protein synthesis, we have used the competitive estrogen antagonist, 4-hydroxytamoxifen, and the inhibitor of protein synthesis, cycloheximide, to study regulation of ER mRNA by estradiol. 4-Hydroxytamoxifen had no effect on the steady-state level of receptor mRNA and effectively blocked the suppression of ER mRNA by estradiol. The metabolic inhibitor, cycloheximide, was unable to prevent the estrogen induced decrease in ER mRNA. These data provide evidence that the posttranscriptional suppression of ER expression through estradiol is mediated through the ER independent of protein synthesis. A study of the effects of estradiol on the steady-state levels of nuclear and cytoplasmic receptor mRNA suggest that posttranscriptional suppression is a nuclear event.