Glutamine synthetase induction by glucocorticoids in the glucocorticoid-sensitive human leukemic cell line CEM-C7

Cortisol affects macrophage polarization by inducing miR-143/145 cluster to reprogram glucose metabolism and by promoting TCA cycle anaplerosis

Chronic stress can have adverse consequences on human health by disrupting the hormonal balance in our body. Earlier, we observed elevated levels of cortisol, a primary stress hormone, and some exosomal microRNAs in the serum of patients with breast cancer. Here, we investigated the role of cortisol in microRNA induction and its functional consequences. We found that cortisol induced the expression of miR-143/145 cluster in human monocyte (THP1 and U937)-derived macrophages but not in breast cancer cells. In silico analysis identified glucocorticoid-response element in the upstream CARMN promoter utilized by the miR-143/145 cluster. Enhanced binding of glucocorticoid-receptor (GR) upon cortisol exposure and its regulatory significance was confirmed by chromatin-immunoprecipitation and promoter-reporter assays. Further, cortisol inhibited IFNγ-induced M1 polarization and promoted M2 polarization, and these effects were suppressed by miR-143-3p and miR-145-5p inhibitors pretreatment. Cortisol-treated macrophages exhibited increased oxygen-consumption rate (OCR) to extracellular-acidification rate (ECAR) ratio, and this change was neutralized by functional inhibition of miR-143-3p and miR-145-5p. HK2 and ADPGK were confirmed as the direct targets of miR-143-3p and miR-145-5p, respectively. Interestingly, silencing of HK2 and ADPGK inhibited IFNγ-induced M1 polarization but failed to induce M2 polarization, since it suppressed both ECAR and OCR, while OCR was largely sustained in cortisol-treated M2-polarized macrophages. We found that cortisol treatment sustained OCR by enhancing fatty acid and glutamine metabolism through upregulation of CPT2 and GLS, respectively, to support M2 polarization. Thus, our findings unfold a novel mechanism of immune suppression by cortisol and open avenues for preventive and therapeutic interventions.

Corticosterone induces obesity partly via promoting intestinal cell proliferation and survival

INTRODUCTION

A vicious cycle ensues whereby prolonged exposure to social stress causes increased production of glucocorticoids (GCs), leading to obesity even further. Understanding the role of GCs, the key element in the vicious circle, might be helpful to break the vicious circle. However, the mechanism by which GCs induce obesity remains elusive.

METHODS

Corticosterone (CORT) was administered to mice for 8 weeks. Food and water intake were recorded; obesity was analyzed by body-weight evaluation and magnetic resonance imaging (MRI); intestinal proliferation and survival were evaluated by H&E staining, EdU-progression test, TUNEL assay and immunofluorescence staining of Ki67 and CC3; RNA-seq was performed to analyze transcriptional alterations in small intestines and livers.

RESULTS

Chronic CORT treatment induced obesity, longer small intestines, hepatic steatosis and elevated levels of serum insulin and leptin in mice; CORT-treated mice showed increased cell proliferation and decreased apoptosis of small intestines; RNA-seq results indicate that differentially expressed genes (DEGs) were enriched in several cell growth/death-associated signaling pathways.

DISCUSSION

Herein we find that administration of CORT to mice promotes the proliferation and survival of intestinal cells, which might contribute to the longer small intestines and the elongated intestinal villi, thus leading to increased nutrient absorption and obesity in mice. Understanding CORT-induced alterations in intestines and associated signaling pathways might provide novel therapeutic clues for GCs or stress-associated obesity.

Metabolic reprogramming of acute lymphoblastic leukemia cells in response to glucocorticoid treatment

Glucocorticoids (GCs) are metabolic hormones with immunosuppressive effects that have proven effective drugs against childhood acute lymphoblastic leukemia (ALL). Yet, the role of metabolic reprogramming in GC-induced ALL cell death is poorly understood. GCs efficiently block glucose uptake and metabolism in ALL cells, but this does not fully explain the observed induction of autophagy and cell death. Here, we have performed parallel time-course proteomics, metabolomics, and isotope-tracing studies to examine in detail the metabolic effects of GCs on ALL cells. We observed metabolic events associated with growth arrest, autophagy, and catabolism prior to onset of apoptosis: nucleotide de novo synthesis was reduced, while certain nucleobases accumulated; polyamine synthesis was inhibited; and phosphatidylcholine synthesis was induced. GCs suppressed not only glycolysis but also entry of both glucose and glutamine into the TCA cycle. In contrast, expression of glutamine-ammonia ligase (GLUL) and cellular glutamine content was robustly increased by GC treatment, suggesting induction of glutamine synthesis, similar to nutrient-starved muscle. Modulating medium glutamine and dimethyl-α-ketoglutarate (dm-αkg) to favor glutamine synthesis reduced autophagosome content of ALL cells, and dm-αkg also rescued cell viability. These data suggest that glutamine synthesis affects autophagy and possibly onset of cell death in response to GCs, which should be further explored to understand mechanism of action and possible sources of resistance.

Expression and Regulation of 11- β Hydroxysteroid Dehydrogenase Type 2 Enzyme Activity in the Glucocorticoid-Sensitive CEM-C7 Human Leukemic Cell Line

Glucocorticoids are commonly used in the first-line treatment of hematological malignancies, such as acute lymphoblastic leukemia, due to the ability of these steroids to activate pro-apoptotic pathways in human lymphocytes. The goal of the current study was to examine the gene expression and enzyme activity of the microsomal enzyme, 11-β hydroxysteroid dehydrogenase type 2 (HSD11B2, HSD2), which is responsible for the oxidation of bioactive glucocorticoids to their inert metabolites. Using the glucocorticoid-sensitive human leukemic cell line, CEM-C7, we were able to detect the expression of HSD2 at the level of mRNA (via RT-PCR), protein (via immunohistochemistry and immunoblotting), and enzyme activity (via conversion of tritiated cortisol to cortisone). Furthermore, we observed that HSD2 enzyme activity is down regulated in CEM-C7 cells that were pretreated with the synthetic glucocorticoid, dexamethasone (100 nM, <15 hours), and that this down regulation of enzyme activity is blocked by the administration of the glucocorticoid receptor antagonist, RU-486. Taken collectively, these data raise the possibility that the effectiveness of glucocorticoids in the treatment of human leukemias may be influenced by: (1) the ability of these neoplastic cells to metabolize glucocorticoids via HSD2 and (2) the ability of these steroids to regulate the expression of this key enzyme.

Glucocorticoid resistance in T-lineage acute lymphoblastic leukaemia is associated with a proliferative metabolism

Glucocorticoids (GCs) are among the most important drugs for acute lymphoblastic leukaemia (ALL), yet despite their clinical importance, the exact mechanisms involved in GC cytotoxicity and the development of resistance remain uncertain. We examined the baseline profile of a panel of T-ALL cell lines to determine factors that contribute to GC resistance without prior drug selection. Transcriptional profiling indicated GC resistance in T-ALL is associated with a proliferative phenotype involving upregulation of glycolysis, oxidative phosphorylation, cholesterol biosynthesis and glutamate metabolism, increased growth rates and activation of PI3K/AKT/mTOR and MYC signalling pathways. Importantly, the presence of these transcriptional signatures in primary ALL specimens significantly predicted patient outcome. We conclude that in lymphocytes the activation of bioenergetic pathways required for proliferation may suppress the apoptotic potential and offset the metabolic crisis initiated by GC signalling. It is likely that the link between GC resistance and proliferation in T-ALL has not been fully appreciated to date because such effects would be masked in the context of current multiagent therapies. The data also provide the first evidence that altered expression of wild-type MLL may contribute to GC-resistant phenotypes. Our findings warrant the continued development of selective metabolic inhibitors for the treatment of ALL.

Prediction of relapse in paediatric pre-B acute lymphoblastic leukaemia using a three-gene risk index

Despite high cure rates 25% of children with acute lymphoblastic leukaemia (ALL) relapse and have dismal outcome. Crucially, many are currently stratified as standard risk (SR) and additional markers to improve patient stratification are required. Here we have used diagnostic bone marrow specimens from 101 children with pre-B ALL to examine the use of gene expression profiles (GEP) as predictors of long-term clinical outcome. Patients were divided into two cohorts for model development and validation based on availability of specimen material. Initially, GEP from 55 patients with sufficient material were analysed using HG-U133A microarrays, identifying an 18-gene classifier (GC) that was more predictive of outcome than conventional prognostic parameters. After feature selection and validation of expression levels by quantitative reverse transcription polymerase chain reaction (qRT-PCR), a three-gene qRT-PCR risk index [glutamine synthetase (GLUL), ornithine decarboxylase antizyme inhibitor (AZIN), immunoglobulin J chain (IGJ)] was developed that predicted outcome with an accuracy of 89% in the array cohort and 87% in the independent validation cohort. The data demonstrate the feasibility of using GEP to improve risk stratification in childhood ALL. This is particularly important for the identification of patients destined to relapse despite their current stratification as SR, as more intensive front-line treatment options for these individuals are already available.

Overexpression of catalase or Bcl-2 alters glucose and energy metabolism concomitant with dexamethasone resistance

Glucocorticoids induce apoptosis in lymphocytes by causing the release of cytochrome c into the cytosol; however, the events in the signaling phase between translocation of the steroid-receptor complex to the nucleus and the release of cytochrome c have not been elucidated. Previously, we found that, in response to steroid treatment, WEHI7.2 mouse thymic lymphoma cells overexpressing catalase (CAT38) show delayed apoptosis (delayed cytochrome c release) compared to the parental cells, while Bcl-2 overexpressing cells (Hb12) are protected from steroid-induced apoptosis. In lymphocytes, glucocorticoid treatment decreases glucose uptake. Both glucose deprivation and the attendant ATP drop are known inducers of apoptosis. Therefore, we used (31)P and (1)H NMR spectroscopy to compare metabolic profiles of WEHI7.2, CAT38 and Hb12 cells in the presence and absence of dexamethasone to determine: (1) whether glucocorticoid effects on glucose metabolism contribute to the mechanism of steroid-induced apoptosis; and (2) whether catalase or Bcl-2 overexpression altered metabolism thereby providing a mechanism of steroid resistance. Loss of mitochondrial hexokinase activity was correlated to the induction of apoptosis in WEHI7.2 and CAT38 cells. CAT38 and Hb12 cells have an altered basal metabolism which includes increases in hexokinase activity, lactate production when subcultured into new medium, use of mitochondria for ATP production and potentially increased glutaminolysis. These data suggest that: (1) glucocorticoid effects on glucose metabolism may contribute to the mechanism of steroid-induced lymphocyte apoptosis; and (2) the altered metabolism seen in catalase and Bcl-2 overexpressing cells may contribute to both the steroid resistance and increased tumorigenicity of these variants.

Glucocorticoids induce glutamine synthetase expression in human osteoblastic cells: a novel observation in bone

Glucocorticoids have marked effects on bone metabolism, and continued exposure of skeletal tissue to excessive amounts of these steroids results in osteoporosis. Therefore, in the present proteomic study, we characterized the potential effects of glucocorticoids on protein expression in human osteoblastic cells. Using two-dimensional gel electrophoresis and mass spectrometry, we identified an increased expression of glutamine synthetase (GS) in dexamethasone (Dex)-treated human MG-63 osteosarcoma cells. GS is an enzyme catalyzing the conversion of glutamate and ammonia to glutamine. Intracellular and extracellular glutamate levels may be important in cell signalling mediated by glutamate transporters and receptors which have recently been found in bone cells. The induction of GS protein by Dex was accompanied by an increase in mRNA level and enzyme activity. Dex induction of GS was also mediated by glucocorticoid receptors (GRs) because it was blocked by the GR antagonist RU-38486. In addition, Dex induction of GS expression was partially blocked by cyclohexamide indicating that it at least partly required new protein synthesis. GS induction by Dex was not associated with apoptosis as determined by Bax/Bcl-2 ratio and DNA staining. In addition to MG-63 cells, Dex induction of GS was also observed in human G-292 osteosarcoma cells as well as conditionally immortalized human preosteoblastic (HOB-03-C5) and mature osteoblastic (HOB-03-CE6) cells. However, in two other human osteosarcoma cell lines, SaOS-2 and U2-OS, GS expression was not affected by Dex. This observation may be explained by the lower levels of GR protein in these cells. In summary, this is the first report of the regulation of GS expression by glucocorticoids in bone cells. The role of GS in bone cell metabolism and glucocorticoid action on the skeleton is not yet known, but as a modulator of intracellular glutamate and glutamine levels, it may have an important role in these processes.

Regulation of the spatiotemporal pattern of expression of the glutamine synthetase gene

Glutamine synthetase, the enzyme that catalyzes the ATP-dependent conversion of glutamate and ammonia into glutamine, is expressed in a tissue-specific and developmentally controlled manner. The first part of this review focuses on its spatiotemporal pattern of expression, the factors that regulate its levels under (patho)physiological conditions, and its role in glutamine, glutamate, and ammonia metabolism in mammals. Glutamine synthetase protein stability is more than 10-fold reduced by its product glutamine and by covalent modifications. During late fetal development, translational efficiency increases more than 10-fold. Glutamine synthetase mRNA stability is negatively affected by cAMP, whereas glucocorticoids, growth hormone, insulin (all positive), and cAMP (negative) regulate its rate of transcription. The signal transduction pathways by which these factors may regulate the expression of glutamine synthetase are briefly discussed. The second part of the review focuses on the evolution, structure, and transcriptional regulation of the glutamine synthetase gene in rat and chicken. Two enhancers (at -6.5 and -2.5 kb) were identified in the upstream region and two enhancers (between +156 and +857 bp) in the first intron of the rat glutamine synthetase gene. In addition, sequence analysis suggests a regulatory role for regions in the 3' untranslated region of the gene. The immediate-upstream region of the chicken glutamine synthetase gene is responsible for its cell-specific expression, whereas the glucocorticoid-induced developmental appearance in the neural retina is governed by its far-upstream region.

Glucocorticoid antagonist RU 486 reverses agonist-induced apoptosis and c-myc repression in human leukemic CEM-C7 cells

A synthetic glucocorticoid dexamethasone (DEX) inhibits proliferation and induces apoptosis of clone CEM-C7 cells, but not in clone CEM-C1 cells, even though they contain glucocorticoid receptors (GR). We previously showed that suppression of c-myc is a critical step in glucocorticoid-induced cell lysis of C7 cells. It is not reduced in C1 cells. In this study we review the basis for this conclusion and present evidence that the glucocorticoid antagonist RU 486 rescues DEX-treated C7 cells from cell death. An increase in DEX-repressed c-myc mRNA levels precedes the recovery of cell growth. A threshold level of Myc expression appears to be required to maintain growth and viability of C7 cells. Although C1 cells are highly resistant to lysis by glucocorticoids, addition of forskolin, an inducer of protein kinase A, synergizes to evoke complete apoptosis. This synergistic effect is prevented by RU 486, indicating direct involvement of the GR.

Glucocorticoid receptors in leukemias, lymphomas and myelomas of young and old

In this paper we have briefly reviewed the nature of leukemias and lymphomas in the old and the young. We surveyed in general the ways in which lymphoid cells and other hematologic elements respond to glucocorticoids, mentioning that there may be direct or indirect effects on their growth by these ligands. We have reviewed the current general model for the action of glucocorticoids in all cells, namely the fact that the actions of these steroids are mediated to a large extent through binding with ligand-activated transcription factors, their receptors. The growing wealth of detail about the nature of the interaction of these receptors with regulatory sites in the genome is discussed. Finally, we have described our results with lines of tissue culture cells representing clones from a typical leukemia of the young, and of myeloma, a typical hematologic malignancy of the elderly. Several features of the effects of glucocorticoids on these cells point up areas that would be pertinent to explore in aging and in the relationship of hematologic diseases to survival and response to therapy in the older versus the younger patient.

Glucocorticoid receptors in human malignancies: a review

The present knowledge of the human glucocorticoid receptor (hGCR) in primary malignancies is reviewed. It is concluded that hGCR is present in a large number of these tissues; in all tissue specimens of lymphoid malignancies and in varying fractions of the different solid tumors. The hGCR functions as a hormone dependent, specific enhancer interacting protein in mediating the considerable effects of glucocorticoids on growth regulation, both through stimulation and inhibition of expression of the target genes, including other transcription regulation systems. The processes of receptor activation and regulation, as well as the effects of glucocorticoids, are tissue-specific. Subjects for future research are proposed: Establishment of more cell lines and animal models to extend investigation beyond the present concentration on only a few cell lines, especially CEM-C7, application of 'dynamic' assays to cells obtained from patients, in an attempt to predict development of glucocorticoid resistance, and further investigation of the relationships among GCR and growth factors and oncogenes.

Isolation of a cDNA clone, encoding a human beta-galactoside binding protein, overexpressed during glucocorticoid-induced cell death

In this report we describe the isolation and characterization of a cDNA clone overexpressed tenfold during the induction of apoptosis in the glucocorticoid-sensitive human leukaemia cell line CEM C7. This clone was shown by DNA sequence analysis to represent the human HL14 gene, encoding a beta-galactoside binding protein, the mouse homologue of which has recently been reported to act as a cell growth inhibitory factor.

Cortivazol mediated induction of glucocorticoid receptor messenger ribonucleic acid in wild-type and dexamethasone-resistant human leukemic (CEM) cells

Cortivazol is a phenylpyrazolo glucocorticoid of high potency and unusual structure. In both wild-type and highly dexamethasone(dex)-resistant clones of the human leukemic cell line CEM, exposure to cortivazol leads to cell death. It has been shown recently that in wild-type CEM cells but not in a dex-resistant, glucocorticoid receptor(GR)-defective clone ICR-27 TK-3, dex induces GR mRNA. To test the hypothesis that cortivazol acts in dex-resistant cells by making use of the residual GR found there, wild-type and dex-resistant clones were treated with various concentrations of cortivazol and induction of GR mRNA was studied. Cortivazol significantly induced GR mRNA in the normal CEM-C7 as well as in two classes of dex-resistant clones, although the dex-resistant clones needed at least 10 times more cortivazol than the normal cells for significant GR mRNA induction. Increased levels of GR mRNA were noticed as early as 3 h after treatment. A general correlation between induction of GR mRNA and lysis of the normal and dex-resistant cells was found. Positive induction of GR mRNA might be one of the earliest crucial steps in the lysis of normal and dex-resistant CEM cells, or might serve as a marker for the process. However, the lysis pathway in the dex-resistant cells is defective in that dex-resistant clones needed significantly more cortivazol than the normal cells for lysis of the cells.

Modulation of nucleotide pyrophosphatase in plasmacytoma cells

The effect of glucocorticoid hormones on the protein responsible for both nucleotide pyrophosphatase (EC 3.6.1.9) and alkaline phosphodiesterase I (EC 3.1.4.1) activities was examined in murine MOPC 315 plasmacytoma cells. Incubation of these cells with dexamethasone resulted in parallel increases in pyrophosphatase and phosphodiesterase specific activities. The incorporation of [3H]mannose into N-linked oligosaccharide precursors was also analyzed in cells following hormone modulation. In cells treated for 36 hours or cultured continuously with dexamethasone, the resulting increase in enzyme specific activities was accompanied by a decrease in [3H]mannose incorporation, consistent with the hypothesis that in some cell types, nucleotide pyrophosphatase activity is involved in the regulation of glycoprotein synthesis.

Glutamine-synthesizing activity in lungs of fed, starved, acidotic, diabetic, injured and septic rats

The maximal catalytic activity of glutamine synthetase was measured in lung homogenates of the rat (being 5.46 +/- 0.29 mumol/min per g wet wt. or 31.70 +/- 2.62 nmol/min per mg of protein at 37 degrees C, in fed animals). The activity is similar to that of liver, but 16-fold higher than that in quadriceps muscles. Chronic (NH4Cl-induced) or acute (HCl-induced) metabolic acidosis had no effects on enzyme activity, but there was a marked increase in the activity of glutamine synthetase in starved (30-40%), streptozotocin-diabetic (17%), dexamethasone-treated (18-22%), laparotomized (25-27%) and septic rats (24-45%).

A study of glutamine synthetase in normal human brain and intracranial tumours

Glutamine synthetase (GS) activity was measured in selected areas of three normal brains and in 262 biopsies from patients with suspected intracranial tumours. In general, levels were higher in grey matter than in white matter and the highest activities of all were found in the hypothalamus which is consistent with its high glutamatergic activity. In the biopsy material, GS activity was greatest in gliotic brain, in keeping with the predominantly astrocytic localization of the enzyme. High levels were also found in astrocytomas and oligodendrogliomas but there was considerable variation between tumours, suggesting a random loss of GS expression during neoplastic transformation or heterogeneity in their cellular origin. The immunocytochemical demonstration of GS in neoplastic oligodendrocytes and in meningioma cells argues against absolute cell-type specificity for this enzyme.

Increased glucocorticoid responsiveness of CD4+ T-cell clonal lines grown in serum-free media

CEM-C7, a human leukemic CD4+ T-lymphocyte cell line and three of its subclones, CEM-4R4, CEM-3R43, and ICR-27, previously cultured in a medium supplemented with 5 to 10% fetal bovine serum, have been adapted to serum-free media. The best medium of those tested was RPMI 1640 supplemented with 5 micrograms/ml each transferrin and insulin + 5 ng/ml sodium selenite +/- 0.1% bovine serum albumin. While growing either with or without albumin, the several clonal lines of CEM cells displayed growth similar to serum-supplemented cultures. Cell proliferation of CEM-C7 cells cultured in both serum-free media has been sustained for 3 mo. with culture doubling times of about 25 h for both serum-supplemented and serum-free cultures (viability greater than or equal to 90%). Cell morphology remained essentially the same in serum-free or serum containing media. The expression of CD4, a marker for T-derived lymphoid cells, was not significantly different in serum-free medium. When grown in serum-free medium, CEM-C7 cells exhibited increased steroid responsiveness as evidenced by increased glucocorticoid receptor binding sites, increased induction of glutamine synthetase, and cell lysis at lower concentrations of steroid. Receptor mutant subclones of CEM-C7, which are proven to be completely unresponsive to micromolar concentrations of dexamethasone when grown in serum-supplemented medium, become partially sensitive to the hormone after growth in defined medium. The increased sensitivity of CEM-C7 cells and its subclones to dexamethasone in serum-free medium returned to previous levels when these cells were recultured in serum-containing medium. Our results suggest that substances in serum influence steroid effects on these cells and that the molecular details of glucocorticoid hormone action may be pursued more precisely in a clearly defined culture medium.

Steroid mediated lysis of lymphoblasts requires the DNA binding region of the steroid hormone receptor

Glucocorticoids kill certain types of lymphoblasts, but the mechanisms are unknown. It is clear that sufficient numbers of functional glucocorticoid receptors are required to mediate lysis, but whether they do so through the classical model of steroid hormone activation and modulation of gene expression has not been established. In this report we have asked which region(s) of the steroid receptor are important for mediating lysis in leukemic T lymphoblasts. CEM-ICR 27 leukemic lymphoblasts, a clone of CEM cells which lack functional glucocorticoid receptors and therefore are neither lysed by dexamethasone nor capable of showing glutamine synthetase induction, were provided with steroid receptors by DNA transfections of various receptor gene constructs. We measured steroid mediated lysis, receptor number and induction of glutamine synthetase in the transfected cells. Our results provide evidence that the lysis mechanism in the ICR27 lymphoblasts is restored when functional receptor number is restored. The DNA binding region specifying high affinity for GRE sites is required. Lysis is mediated by any steroid that allows for activation of the receptor containing such a region. Our data support the view that steroid-mediated cell death occurs by a process requiring direct interaction of steroid-receptor complexes with the genome.

Isolation and characterization of glucocorticoid- and cyclic AMP-induced genes in T lymphocytes

Glucocorticoids and cyclic AMP exert dramatic effects on the proliferation and viability of murine T lymphocytes through unknown mechanisms. To identify gene products which might be involved in glucocorticoid-induced responses in lymphoid cells, we constructed a lambda cDNA library prepared from murine thymoma WEHI-7TG cells treated for 5 h with glucocorticoids and forskolin. The library was screened with a subtracted cDNA probe enriched for sequences induced by the two drugs, and cDNA clones representing 11 different inducible genes were isolated. The pattern of expression in BALB/c mouse tissues was examined for each cDNA clone. We have identified two clones that hybridized to mRNAs detected exclusively in the thymus. Other clones were identified that demonstrated tissue-specific gene expression in heart, brain, brain and thymus, or lymphoid tissue (spleen and thymus). The kinetics of induction by dexamethasone and forskolin were examined for each gene. The majority of the cDNA clones hybridized to mRNAs that were regulated by glucocorticoids and forskolin, two were regulated only by glucocorticoids, and three hybridized to mRNAs that required both drugs for induction. Inhibition of protein synthesis by cycloheximide resulted in the induction of all mRNAs that were inducible by glucocorticoids. Preliminary sequence analysis of four of the 11 cDNAs suggests that two cDNAs represent previously undescribed genes while two others correspond to the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein.

Isolation and characterization of glucocorticoid- and cyclic AMP-induced genes in T lymphocytes

Glucocorticoids and cyclic AMP exert dramatic effects on the proliferation and viability of murine T lymphocytes through unknown mechanisms. To identify gene products which might be involved in glucocorticoid-induced responses in lymphoid cells, we constructed a lambda cDNA library prepared from murine thymoma WEHI-7TG cells treated for 5 h with glucocorticoids and forskolin. The library was screened with a subtracted cDNA probe enriched for sequences induced by the two drugs, and cDNA clones representing 11 different inducible genes were isolated. The pattern of expression in BALB/c mouse tissues was examined for each cDNA clone. We have identified two clones that hybridized to mRNAs detected exclusively in the thymus. Other clones were identified that demonstrated tissue-specific gene expression in heart, brain, brain and thymus, or lymphoid tissue (spleen and thymus). The kinetics of induction by dexamethasone and forskolin were examined for each gene. The majority of the cDNA clones hybridized to mRNAs that were regulated by glucocorticoids and forskolin, two were regulated only by glucocorticoids, and three hybridized to mRNAs that required both drugs for induction. Inhibition of protein synthesis by cycloheximide resulted in the induction of all mRNAs that were inducible by glucocorticoids. Preliminary sequence analysis of four of the 11 cDNAs suggests that two cDNAs represent previously undescribed genes while two others correspond to the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein.

Phorbol esters potentiate glucocorticoid-induced cytotoxicity in CEM-C7 human T-leukemia cell line

Phorbol ester tumor promoter, such as 12-O-tetradecanoylphorbol-13-acetate (TPA), is synergistic with dexamethasone to cause growth inhibition of CEM-C7 human T-leukemia cell line. A specific saturable binding component which may mediate the phorbol ester effects has been identified by using [20-(3)H]phorbol 12,13-dibutyrate in a whole cell binding assay. Saturation of the specific binding occurs at a concentration (approx. 100 nM) consistent with causing maximal cytotoxicity. Scatchard analysis of the binding after 15 min at 37 degrees C demonstrates a single class of binding sites. The number is 194,000 sites per cell. Other phorbol esters are also cytotoxic to CEM-C7 cell in the presence of 30 nM dexamethasone in an approximate proportion to their activity in competing for [20-(3)H]phorbol 12,13-dibutyrate binding. Phorbol 12, 13-didecanoate, 4-O-methyl PMA, 4-beta-phorbol do not compete for specific binding. The synergism of phorbol esters and dexamethasone on CEM-C7 cells is reversible by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine(H-7). However, by treating CEM-C7 cells with TPA for 48 h there is not any increase in the affinity or levels of glucocorticoid receptor. It is tentatively concluded that phorbol esters may play an important role linked to the glucocorticoid-induced growth inhibition in CEM-C7 human T-leukemic cell.

Ketoconazole inhibition and glucocorticoid action in the human lymphoblastic leukemia cell line CEM-C7

The antifungal drug, ketoconazole, was reported to antagonize the induction of the enzyme tyrosine aminotransferase (TAT) by glucocorticoids in hepatoma tissue culture (HTC) cells, and to compete with glucocorticoids for binding to the glucocorticoid receptor. Since glucocorticoids inhibit the growth of the human leukemia cell line CEM-C7, ketoconazole might be expected to reverse this inhibition. Unexpectedly, ketoconazole inhibited CEM-C7 cell growth without utilizing glucocorticoid receptors. This was confirmed by ketoconazole inhibition of the growth of a receptor-less subline of CEM-C7 cells which are insensitive to glucocorticoids. Ketoconazole competed with triamcinolone acetonide (TA) for binding to the glucocorticoid receptor in cell-free supernatant prepared from CEM-C7 cells, but this was greatly reduced if ketoconazole and TA were incubated with intact cells prior to preparation of the cell-free supernatant. Ketoconazole inhibited induction by TA of the enzyme glutamine synthetase only at concentrations of 45-90 microM. We conclude that ketoconazole antagonism of glucocorticoid activity in CEM-C7 cells is probably not of pharmacologic significance due to the large concentrations required, and its reduced interaction with receptors in intact cells. The growth inhibitory activity of ketoconazole may be of interest in cancer chemotherapy.

Mechanisms of glucocorticoid function in human leukemic cells: analysis of receptor gene mutants of the activation-labile type using the covalent affinity ligand dexamethasone mesylate

In the cultured acute lymphoblastic leukemic (ALL) cell line, clones of sensitive cells are killed by receptor-occupying concentrations of glucocorticoids. In addition, several types of resistance have been identified. The types of resistance are r- (glucocorticoid binding site loss), ract/l (activation labile receptors) and r+ly- (defective lysis mechanism). The two types of receptor mutants have been examined for the presence and expression of the glucocorticoid receptor (GR) gene. Southern blot analysis, using a full-length cDNA probe for human GR, shows that the gene in both is grossly intact. Examination of the expression of the gene by Northern blots reveals the presence of normal, 7-kb message in both types of receptor mutants, though in amounts somewhat reduced from wild-type. This report focuses on the activation labile mutants. Since characterization of these mutants suggests that they can bind ligand but not retain it during activation, we hypothesized that they would respond normally to a ligand that could not be lost during activation. This seems to be the case. When the covalent affinity ligand dexamethasone mesylate, itself a partial glucocorticoid agonist/antagonist, is used, the ract/l cells are killed to an extent corresponding to that evoked by a sub-optimal concentration of the full agonist dexamethasone. We conclude: (1) that the ract/l receptors can function to kill cells if provided a ligand that they do not lose during activation; (2) that the partial agonist activity of dexamethasone mesylate for cell killing is not due to release of a small amount of free dexamethasone; (3) that the poor agonist activity of dexamethasone mesylate receptor complexes suggests that the role of steroid is strictly to participate in conversion of the receptor to its DNA binding form, after which presence of the steroid actually interferes with proper receptor action.

The antiglucocorticoid, cortexolone, fails to promote in vitro activation of cytoplasmic glucocorticoid receptors from the human leukemic cell line CEM-C7

Cortexolone functions as an antiglucocorticoid in the human leukemic cell line CEM-C7, since it blocks the growth inhibition and cell lysis mediated by the potent agonist triamcinolone acetonide (TA). At high concentrations (10(-5) M) cortexolone alone is inactive. The ability of cortexolone to block the TA-mediated biological effects is reflected in its ability (1000-fold molar excess) to effectively block the binding of [3H]TA to the cytoplasmic unactivated form of the receptors eluted from DEAE-cellulose at approx. 180 mM potassium phosphate (KP). Likewise a 1000-fold molar excess of TA inhibits the specific binding of [3H]cortexolone to the unactivated receptors and to a peak which elutes at low salt concentration (35 mM KP) but does not appear to represent activated [3H]cortexolone-receptor complexes. Thermal activation/transformation (25 degrees C for 30 min +/- 10 mM ATP) of the [3H]TA-receptor complexes significantly enhances the subsequent DNA-cellulose binding capacity of these complexes and also results in their elution from DEAE-cellulose at the low salt (50 mM KP) activated position. In contrast, exposure of the cytoplasmic [3H]cortexolone-receptor complexes to identical in vitro activating (transforming) conditions fails to enhance subsequent DNA-cellulose binding capacity or to result in the appropriate shift in DEAE-cellulose elution profile. This inability of [3H]cortexolone to facilitate activation/transformation of receptors was also verified using cytosol prepared from the glucocorticoid-resistant 'activation-labile' mutant, 3R7. Taken collectively the data suggest that cortexolone, unlike an agonist such as TA, fails to promote in vitro activation/transformation, a conformational change which also occurs in vivo under physiological conditions and is a prerequisite for nuclear binding.

Complementation between glucocorticoid receptor and lymphocytolysis in somatic cell hybrids of two glucocorticoid-resistant human leukemic clonal cell lines

Somatic hybrids between two glucocorticoid-resistant clonal cell lines, CEM C1 and ICR-27, isolated independently from the CCRF-CEM human lymphoblastoid cell line, were constructed to investigate the complementation effect between the glucocorticoid receptor and the gene product(s) for inducing receptor-mediated lymphocytolysis. CEM C1 (r+ly-) has a normal amount of functional glucocorticoid receptor as compared to the steroid-sensitive clonal line CEM C7. Clone ICR-27 (r-ly?), which was originally isolated following mutagenesis of CEM C7 with the mutagen ICR 191, has few glucocorticoid receptors as determined by whole-cell receptor assay. The eight randomly selected CEM C1 X ICR-27 hybrid clones all showed sensitivity to 10(-6) M dexamethasone (ly+). The receptor site content of two near-tetraploid hybrids chosen for analysis was close to that of CEM C1 (r+). Hybrids constructed between CEM C1 and the receptor-bearing, steroid-sensitive clone, CEM C7 (r+ly+) also showed glucocorticoid sensitivity, and their receptor sites corresponded to the sum of those of CEM C1 and CEM C7 (r+r+ly+). These results indicate: that CEM C1 has no trans-active inhibitor of lysis; that CEM C1 has intact glucocorticoid receptor; and that ICR-27 and CEM C1 complement one another to restore lymphocytolysis. Therefore, CEM C1 cells can serve as a donor of human glucocorticoid receptors.

In vitro activation and DNA binding affinity of human lymphoid (CEM-C7) cytoplasmic receptors labeled with the antiglucocorticoid RU 38486

The data reported here demonstrate that the synthetic steroid RU 38486 functions as an optimal antagonist in the glucocorticoid-sensitive human leukemic cell line CEM-C7. This steroid blocks the ability of the potent agonist triamcinolone acetonide (TA) to induce glutamine synthetase activity and to ultimately cause cell lysis, but when given alone does not exhibit partial agonist activity. Both [3H]RU 38486 and [3H]TA bind with high affinity and specificity to cytosolic glucocorticoid receptors in this cell line. However, under a variety of in vitro conditions (elevated temperature and presence of exogenous ATP), [3H]TA promotes receptor activation more effectively than [3H]RU 38486. This difference in the extent of activation was verified by two independent techniques: DEAE-cellulose chromatography and DNA-cellulose binding. [3H]RU 38486 and [3H]TA dissociate at the same rate from the unactivated receptors but at 25 degrees C (not 0 degree C) [3H]RU 38486 dissociates slightly more rapidly from the activated receptors. The defective receptors in the glucocorticoid-resistant subclone 3R7 appear to be "activation labile" (rapid dissociation of ligand from activated form) using either tritiated steroid. Once activated in vivo, the CEM-C7 [3H]TA- and [3H]RU 38486-receptor complexes undergo similar nuclear translocation and those activated complexes generated in vitro appear to bind to nonspecific DNA-cellulose with the same relative affinities. Thus the precise mechanism(s) by which RU 38486 exerts its potent antiglucocorticoid effect in this human cell line cannot be easily explained in terms of a defect in one of the crucial steps (specific high affinity binding, activation, translocation, DNA binding) required to elicit a physiological response. However, the data presented here do suggest that when comparing an antagonist and agonist which both bind to receptors with the same relative high affinity, the agonist may be more effective in facilitating the conformational change associated with in vitro activation.

Glucocorticoid receptors and glucocorticoid resistance in human leukemia in vivo and in vitro

Clinical measurements quantitating glucocorticoid receptor sites in leukemic blasts may give useful prognostic information. In childhood ALL, where the most data is available, "high" receptor content in peripheral or marrow blasts correlated with likelihood of remission on therapy, longer durations of remission and better prognosis generally. In lymphomas and CLL as well, high receptor content correlated with likelihood of response to steroid therapy, though the number of studies is less. In AML the correlation with receptor site content is moot, and in other leukemias the reports are less complete. A model system for childhood ALL is provided by CEM cells, a glucocorticoid sensitive human cell line from a patient with the disease. These cells have glucocorticoid receptors which must be filled by hormone for greater than 24 hr for cell lysis to begin. Four types of glucocorticoid resistance have been identified thus far in clones of these cells. Their distinctive properties are described and their relevance to clinical situations briefly discussed.

The karyotype of the glucocorticoid-sensitive, lymphoblastic human T-cell line CCRF-CEM shows a unique deleted and inverted chromosome 9

Chromosome karyotypes were prepared from the highly glucocorticoid-sensitive clone C7 of the human acute lymphoblastic leukemia T-cell line CCRF-CEM. The modal number of chromosomes is 47, and one chromosome #9 has a pericentric inversion of the heterochromatin region (9qh) plus a deletion of the short arm. In most cells, there is an extra chromosome #20. All other chromosomes appear to be normal. Examination of the uncloned line CCRF-CEM (ATCC CCL 119), which was frozen away shortly after the line was originated and has undergone fewer passages than CEM C7, also revealed the same abnormality of chromosome #9. Each of 10 other clones isolated from CCRF-CEM in this laboratory also contained the abnormal chromosome #9.

Expression of differentiated functions in dexamethasone-resistant hepatoma cells

The expression of liver-specific functions of different dexamethasone-resistant variants derived from a well-differentiated dexamethasone-sensitive Reuber H35 rat hepatoma cell line (Faza 967) was examined during long-term cultivation. The dexamethasone-sensitive Faza 967 cells are characterized by the activity of tyrosine aminotransferase (TAT) and gluconeogenic enzymes, secretion of serum albumin, and the presence of liver isozymes of alcohol dehydrogenase (L-ADH), aldolase (aldolase-B), and five isoenzymes of lactate dehydrogenase (LDH). The hormone-resistant cells undergo a very dramatic change in expression of most liver-specific functions (dedifferentiation) during long-term culture, in contrast to the sensitive cells in which only certain functions (TAT activity, inducibility, and synthesis of serum albumin) exhibit considerable changes. The hormone-dependent growth sensitivity and the expression of other differentiated functions is not controlled in coordinated way in Faza 967 cells. The time course of the expression of liver-specific functions shows that the cells are resistant before they became 'dedifferentiated', i.e., loss of these liver-specific functions is not a prerequisite of the establishment of the hormone-resistant state.

Glutamine synthetase activity of muscle in acidosis

Metabolic acidosis stimulates the rate of glutamine release from muscle, and this in turn is used by the kidney in acid-base balance. NH4Cl, HCl or diabetic ketoacidosis increases the maximum activity of glutamine synthetase in skeletal muscle. Starvation and administration of adrenal steroids also increase the activity of the enzyme in muscle.

Presence and steroid inducibility of glutamine synthetase in human leukemic cells

Glutamine synthetase (EC 6.3.1.2; GS) is present in lymphoblasts from patients with acute lymphoblastic leukemia (ALL) as well as in normal peripheral blood lymphocytes. In 16 out of 20 ALL patients studied exposure of the cells to physiological concentrations of dexamethasone in vitro increased enzyme activity above the control levels. The increase was specific for glucocorticoid receptor ligands. A direct correlation was found between the magnitude of glucocorticoid-mediated increase of GS activity and the cellular levels of specific glucocorticoid receptors assayed in the same cell specimen. Moreover, the basal levels of the enzyme measured in cells prior to exposure to dexamethasone correlated negatively with receptor density. It is suggested that the presence of steroid-inducible GS in ALL cells may prove to be a marker for functional receptor sites.

Messenger RNA for glutamine synthetase. Review article

Of the various eucaryotic tissues, where glutamine synthetase (GS) mRNA and its regulation have been investigated, the induction of GS by glucocorticoids in the embryonic chick retina represents one of the systems most extensively studied. GS mRNA was first identified at the polysomal level by immunochemical precipitation of fractionated polysomes containing nascent GS chains with anti-GS gamma-globulin. The mRNA has been shown to be polyadenylated at the 3' end; on this basis, it has been partially purified from embryonic chick retina as well as from N. Crassa by chromatography on oligo(dT)-cellulose or poly(U)-sepharose and translated in cell-free protein synthesizing systems derived from wheat germ. Hormonal regulation of GS activity studied in the embryonic retina, hepatoma tissue culture cells, or in other tissues is always shown to be mediated by GS mRNA. In the retina, hydrocortisone (HC) elicits an age-related and transcription-dependent induction of GS by enhancing the level of GS mRNA in the polysomes through an increased supply of this mRNA from the nucleus. Comparative studies of three inhibitors of transcription, viz. actinomycin D, leucanthone and proflavine on the induction of GS by HC indicate that the latter inhibits GS mRNA selectively and reversibly with minimal effects on other RNA synthesis. Since proflavine acts by competing with HC-receptor binding sites in the nuclei, further studies on its interaction with the retina genome are likely to help identify the DNA sequences involved in the GS induction. In bacteria, studies on the genetics and physiology of various mutants with lesions in the structural gene for GS show that the transcription of the GS gene (gln A) is regulated both positively and negatively by GS and the product of another gene gln F. Purification of GS mRNA to homogeneity cloning of its cDNA and development of assay systems for cell-free transcription of GS are other studies likely to advance our knowledge on GS mRNA and its regulation.