Glucocorticoids inhibit lung cancer cell growth through both the extracellular signal-related kinase pathway and cell cycle regulators

The influence of fluticasone inhalation on markers of carcinogenesis in bronchial epithelium

RATIONALE

Bronchial epithelium exposed to cigarette smoke undergoes a series of histologic changes that may ultimately lead to invasive cancer. Inhaled corticosteroids reduce the number of lung tumors developing in rats exposed to cigarette smoke.

OBJECTIVES

We studied the effect of inhaled fluticasone on premalignant lesions in smokers and patients curatively treated for head and neck cancer or lung cancer.

METHODS

Participants were screened for premalignant lesions by bronchoscopy. Biopsies were taken from three to five locations and classified using WHO criteria. In case of a metaplasia index of > 15%, participants were randomized to receive a powder inhalation device containing either fluticasone 500 microg or a placebo, to be used twice a day. After 6 months, biopsies were obtained from the same locations as previously sampled. Efficacy of treatment was assessed by reversal of metaplasia/dysplasia; secondary endpoints were reversal of increased p53 and KI-67 immunoreactivity and expression of human telomerase reverse transcriptase.

MEASUREMENTS AND MAIN RESULTS

Of the 201 subjects that were screened, 108 were included. Mean age was 53 yr (35-71), mean number of pack-years 48 (18-99), mean metaplasia index 48%, and 32% had some degree of dysplasia at baseline. The two treatment arms did not differ with respect to response or change in either metaplasia index or the expression of the markers p53, KI-67, or human telomerase reverse transcriptase.

CONCLUSIONS

Inhaled fluticasone in a dose of 500 mug twice a day does not affect the natural course of premalignant lesions in the central airways.

Differential proteomic analysis of the anti-proliferative effect of glucocorticoid hormones in ST1 rat glioma cells

Glucocorticoid hormones (GCs) exert a potent anti-proliferative activity on several cell types. The classic molecular mechanism of GCs involves modulation of the activity of the glucocorticoids receptor, a transcriptional regulator. However, the anti-proliferative effect of GCs may also involve modulation of processes such as translation, subcellular localization and post-translational modifications, which are not reflected at the mRNA level. To investigate these potential effects of GCs, we employed the proteomic approach (two-dimensional electrophoresis and mass spectrometry) and the ST1 cells, obtained from the C6 rat glioma cell line, as a model. GC treatment leads ST1 cells to a complete transformed-to-normal phenotypic reversion and loss of their tumorigenic potential. By comparing sets of 2D nuclear protein profiles of ST1 cells treated (or not) with hydrocortisone (Hy), 13 polypeptides displaying >or=two-fold difference in abundance upon Hy treatment were found. Five of these polypeptides were identified by peptide mass fingerprinting, including Annexin 2 (ANX2), hnRNP A3 and Ubiquitin. Evidence obtained by Western blot analysis indicates that ANX2 is present in the nucleus and has its subcellular localization modulated by GC-treatment of ST1 cells. Our findings indicate complementary mechanisms contributing to the regulation of gene expression associated with ST1 cells' response to GCs.

15-hydroxyprostaglandin dehydrogenase (15-PGDH) and lung cancer

15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes NAD(+)-linked oxidation of 15 (S)-hydroxyl group of prostaglandins and lipoxins and is the key enzyme responsible for the biological inactivation of these eicosanoids. The enzyme was found to be under-expressed as opposed to cyclooxygenase-2 (COX-2) being over-expressed in lung and other tumors. A549 human lung adenocarcinoma cells were used as a model system to study the role of 15-PGDH in lung tumorigenesis. Up-regulation of COX-2 expression by pro-inflammatory cytokines in A549 cells was accompanied by a down-regulation of 15-PGDH expression. Over-expression of COX-2 but not COX-1 by adenoviral-mediated approach also attenuated 15-PGDH expression. Similarly, over-expression of 15-PGDH by the same strategy inhibited IL-1beta-induced COX-2 expression. It appears that the expression of COX-2 and 15-PGDH is regulated reciprocally. Adenoviral-mediated transient over-expression of 15-PGDH in A549 cells resulted in apoptosis. Xenograft studies in nude mice also showed tumor suppression with cells transiently over-expressing 15-PGDH. However, cells stably over-expressing 15-PGDH generated tumors faster than those control cells. Examination of different clones of A549 cells stably expressing different levels of 15-PGDH indicated that the levels of 15-PGDH expression correlated positively with those of mesenchymal markers, and negatively with those of epithelial markers. It appears that the stable expression of 15-PGDH induces epithelial-mesenchymal transition (EMT) which may account for the tumor promotion in xenograft studies. A number of anti-cancer agents, such as transforming growth factor-beta1 (TGF-beta1), glucocorticoids and some histone deacetylase inhibitors were found to induce 15-PGDH expression. These results suggest that tumor suppressive action of these agents may, in part, be related to their ability to induce 15-PGDH expression.

Interleukin-31 and oncostatin-M mediate distinct signaling reactions and response patterns in lung epithelial cells

Lung epithelial cells are primary targets of oncostatin M (OSM) and, to a lower degree, of interleukin (IL)-6 and IL-31, all members of the IL-6 cytokine family. The OSM receptor (OSMR) signals through activation of STAT and mitogen-activated protein kinase pathways to induce genes encoding differentiated cell functions, reduce cell-cell interaction, and suppress cell proliferation. IL-31 functions through the heteromeric IL-31 receptor, which shares with OSMR the OSMRbeta subunit, but does not engage gp130, the common subunit of all other IL-6 cytokine receptors. Because the response of epithelial cells to IL-31 is unknown, the action of IL-31 was characterized in the human alveolar epithelial cell line A549 in which the expression of the ligand-binding IL-31Ralpha subunit was increased. IL-31 initiated signaling that differed from other IL-6 cytokines by the particularly strong recruitment of the STAT3, ERK, JNK, and Akt pathways. IL-31 was highly effective in suppressing proliferation by altering expression of cell cycle proteins, including up-regulation of p27(Kip1) and down-regulation of cyclin B1, CDC2, CDK6, MCM4, and retinoblastoma. A single STAT3 recruitment site (Tyr-721) in the cytoplasmic domain of IL-31Ralpha exerts a dominant function in the entire receptor complex and is critical for gene induction, morphological changes, and growth inhibition. The data suggest that inflammatory and immune reactions involving activated T-cells regulate functions of epithelial cells by IL-6 cytokines through receptor-defined signaling reactions.

Up-regulation of RhoB by glucocorticoids and its effects on the cell proliferation and NF-kappaB transcriptional activity

Although there is ample evidence that glucocorticoids (GCs) have an antiproliferative effect on many cell types, the molecular mechanism remains elusive. We reported in our previous study that Dex treatment led to cell growth arrest in a human ovarian cancer cell HO-8910. RhoB, as a member of Rho GTPases, have been implicated to be a negative regulator of cell proliferation. In this study, we provided novel evidence that Dex induced the expressions of small GTPase RhoB mRNA and protein, but not RhoA and RhoC mRNA in a dose- and time-dependent fashion via glucocorticoid receptor (GR). Over-expression of RhoB increased while inhibition of RhoB expression by RNA interference reversed Dex-induced growth arrest, indicating that RhoB signaling is involved in Dex-induced proliferation inhibition. We also presented the novel observation that over-expression or activation of RhoB signaling elevated the basal transcriptional activity of the transcription factor NF-kappaB in HO-8910 cells. Furthermore, elevating RhoB signaling enhanced the inhibitory effect of Dex on NF-kappaB activity, while attenuating RhoB signaling almost abrogated Dex suppression of NF-kappaB signaling, indicating that RhoB pathway is involved in the regulation of NF-kappaB activity and is essential for Dex transcriptional repression on NF-kappaB signaling in HO-8910 cells.

Tumor suppressor activity of glucocorticoid receptor in the prostate

Glucocorticoids are extensively used in combination chemotherapy of advanced prostate cancer (PC). Little is known, however, about the status of the glucocorticoid receptor (GR) in PC. We evaluated over 200 prostate samples and determined that GR expression was strongly decreased or absent in 70-85% of PC. Similar to PC tumors, some PC cell lines, including LNCaP, also lack GR. To understand the role of GR, we reconstituted its expression in LNCaP cells using lentiviral approach. Treatment of LNCaP-GR cells with the glucocorticoids strongly inhibited proliferation in the monolayer cultures and blocked anchorage-independent growth. This was accompanied by upregulation of p21 and p27, down-regulation of cyclin D1 expression and c-Myc phosphorylation. Importantly, the activation of GR resulted in normalized expression of PC markers hepsin, AMACR, and maspin. On the signaling level, GR decreased expression and inhibited activity of the MAP-kinases (MAPKs) including p38, JNK/SAPK, Mek1/2 and Erk1/2. We also found that activation of GR inhibited activity of numerous transcription factors (TF) including AP-1, SRF, NF-kappaB, p53, ATF-2, CEBPalpha, Ets-1, Elk-1, STAT1 and others, many of which are regulated via MAPK cascade. The structural analysis of hepsin and AMACR promoters provided the mechanistic rationale for PC marker downregulation by glucocorticoids via inhibition of specific TFs. Our data suggest that GR functions as a tumor suppressor in prostate, and inhibits multiple signaling pathways and transcriptional factors involved in proliferation and transformation.

Functional interaction between the glucocorticoid receptor and GANP/MCM3AP

Glucocorticoids are widely used to treat inflammatory diseases but have a number of side effects that partly are connected to inhibition of cell proliferation. Glucocorticoids mediated their action by binding to the glucocorticoid receptor. In the present study, we have identified by two-hybrid screens the germinal center-associated protein (GANP) and MCM3-associated protein (MCM3AP), a splicing variant of GANP, as glucocorticoid receptor interacting proteins. GANP and MCM3AP can bind to the MCM3 protein involved in initiation of DNA replication. Glutathione-S-transferase-pull-down and co-immunoprecipitation assays showed that the C-terminal domain of GANP, encompassing MCM3AP, interacts with the ligand-binding domain of the glucocorticoid receptor. Characterization of the intracellular localization of GANP revealed that GANP is shuttling between the nucleus and the cytoplasm. Furthermore, we show that glucocorticoids are unable to inhibit DNA replication in HeLa cells overexpressing MCM3AP suggesting a role for both glucocorticoid receptor and GANP/MCM3AP in regulating cell proliferation.

Glucocorticoid receptor expression in advanced non-small cell lung cancer: clinicopathological correlation and in vitro effect of glucocorticoid on cell growth and chemosensitivity

The current study aimed to immunohistochemically examine the tumor glucocorticoids receptor (GR) expression in patients with advanced non-small cell lung cancer (NSCLC) and to examine the effect of glucocorticoids (GCs) on the in vitro NSCLC cells growth and chemosensitivity. High GR expression was detected in 51% of the tumor specimens. The difference in tumor GR expression was not associated with cell type, gender, age, or stage. The outcome was significantly superior for patients whose tumor showed high GR expression compared to those with either low expression or non-expression. The median progression-free survival was 8.0 versus 5.6 months (p=0.039) and overall survival was 18.1 versus 10.2 months, (p=0.003), respectively. Almost all these patients have received GC as antiemetics or allergic preventive treatment during chemotherapy courses, therefore, the effect of GC on the chemosensitivity in vivo was not evaluable. However, in vitro cytotoxicity assay showed that dexamethasone (DEX) had heterogeneous effects on the growth and chemosensitivity of the NSCLC cell lines. These findings suggest that tumor samples express high levels of GR in about half of the patients with advanced NSCLC, and this high expression of GR may be associated with better outcome. The effect of GC treatment on the chemosensitivity in NSCLC patients remains to be established.

Adverse neurodevelopmental effects of dexamethasone modeled in PC12 cells: identifying the critical stages and concentration thresholds for the targeting of cell acquisition, differentiation and viability

The use of dexamethasone (DEX) to prevent respiratory distress in preterm infants is suspected to produce neurobehavioral deficits. We used PC12 cells to model the effects of DEX on different stages of neuronal development, utilizing exposures from 24 h up to 11 days and concentrations from 0.01 to 10 microM, simulating subtherapeutic, therapeutic, and high-dose regimens. In undifferentiated cells, even at the lowest concentration, DEX inhibited DNA synthesis and produced a progressive deficit in the number of cells as evaluated by DNA content, whereas cell growth (evaluated by the total protein to DNA ratio) and cell viability (Trypan blue exclusion) were promoted. When cell differentiation was initiated with nerve growth factor, the simultaneous inclusion of DEX still produced a progressive deficit in cell numbers and promoted cell growth and viability while retarding the development of neuritic projections as monitored by the membrane/total protein ratio. Again, even 0.01 microM DEX was effective. We next assessed effects at mid-differentiation by introducing nerve growth factor for 4 days followed by coexposure to DEX. Although effects on cell number, growth, and neurite extension were still detectable, the outcomes were generally less notable. DEX also shifted the fate of PC12 cells away from the cholinergic phenotype and toward the adrenergic phenotype, with the maximum effect achieved at the outset of differentiation. Our results indicate that DEX directly disrupts neuronal cell replication, differentiation, and phenotype at concentrations below those required for the therapy of preterm infants, providing a mechanistic link between glucocorticoid use and neurodevelopmental sequelae.

Inhibition of 11beta-hydroxysteroid dehydrogenase eliminates impaired glucocorticoid suppression and induces apoptosis in corticotroph tumor cells

Cushing's disease is characterized by persistent ACTH secretion under hypercortisolemia. In an attempt to clarify the molecular mechanism, we examined the effect of 11beta-hydroxysteroid dehydrogenase (HSD) inhibition on glucocorticoid suppression of ACTH release using murine corticotroph tumor cells. We found that 11beta-HSD2, as well as -HSD1, was expressed in the cells and that its inhibition by carbenoxolone significantly improved the negative feedback effect of glucocorticoid. Carbenoxolone also enhanced apoptosis induced by cortisol. These effects are most likely attributable to inhibition of 11beta-HSD2 because only cortisol, a substrate of 11beta-HSD2, was present in these experimental conditions. We conclude that ectopic expression of 11beta-HSD2 is, at least in part, responsible for the impaired glucocorticoid suppression in corticotroph adenoma. Inhibition of 11beta-HSD2 may be applicable to the medical therapy for Cushing's disease.

Effects of glucocorticoids on the growth and chemosensitivity of carcinoma cells are heterogeneous and require high concentration of functional glucocorticoid receptors

AIM: To determine how glucocorticoids (GCs) may affect the growth and chemosensitivity of common carcinoma cells.

METHODS: The effect of dexamethasone (DEX) on growth and chemosensitivity was assessed in 14 carcinoma cell lines. The function of GC receptors (GR) was assessed by MMTV reporter assay. Overexpression of GR was done by in vitro transfection and expression of a GR-expressing vector. Immunohistochemical stain of tissues and cells were done by PA1-511A, an anti-GR monoclonal antibody.

RESULTS: DEX inhibited cell growth of four (MCF-7, MCF-7/MXR1, MCF-7/TPT300, and HeLa), increased cisplatin cytotoxicity of one (SiHa), and decreased cisplatin cytotoxicity of two (H460 and Hep3B) cell lines. The GR content of the seven cell lines affected by DEX was significantly higher than those of the seven cell lines unaffected by DEX (5.2±2.5×104 sites/cell vs 1.3±1.4×104 sites/cell, P = 0.005). Only two DEX-unresponsive cell lines (NPC-TW01 and NPC-TW04) contained high GR amounts in the range (1.9-8.1×104 sites/cell) of the seven DEX-responsive cell lines. The GR function of NPC-TW01 and NPC-TW04, however, was found to be impaired. The importance of high cellular amount of GR in mediating DEX susceptibility of the cells was further exemplified by GR dose-dependent drug resistance to cisplatin of AGS, a cell line with low GR content and was unaffected by DEX before transfection of GR-expressing vector. Immunohistochemical studies of human cancer tissues showed that 5 of the 45 (11.1%) breast cancer and 43 of the 85 (50.6%) non-small cell lung cancer had high GR contents at the ranges of the GC-responsive carcinoma cell lines.

CONCLUSION: The growth and chemosensitivity of human carcinomas with high GR contents may be affected by GC. However, in light of the heterogeneous and even contradictive effects of GC on these cells, routine examination of GR contents of human carcinoma tissues may not be clinically useful until other markers that help predict the ultimate effect of GC on individual patients are identified.

Is macrophage migration inhibitory factor (MIF) the "control point" of vascular hypo-responsiveness in septic shock?

Macrophage migration inhibitory factor (MIF), a member of the cytokine family, is beginning to be recognized as a pleiotropic proinflammatory molecule. MIF exerts function via antagonistic regulation of glucocorticoids, inhibition to apoptosis-mediated p53, influence on vasodilator gas NO and inducible nitric oxide synthase (iNOS), feedback counter-regulation of complement C5a controlling MIF release, and interaction with major cations as well. Interestingly, aforementioned glucocorticoids, apoptosis, NO, iNOS, C5a, Ca2+, Mg2+, Na+, K+, and H+ that are greatly associated with vascular tone or vasomotion. Nevertheless, the elevated serum and cytosolic concentrations of MIF exactly affect all above facets in septic shock models and patients, during which vasodilation of the peripheral resistance vessels occurs, and accompanied with decreased responsiveness to vascular pressors. Thus MIF may bring into play as one of point-controlling proteins in the onset of sustained vascular hypo-reactivity during the process of septic shock.

Differential regulation of the human MRP2 and MRP3 gene expression by glucocorticoids

Multidrug resistance proteins, which catalyse the detoxification of xenobiotics and excretion of metabolites, are very often controlled at the transcriptional level by interaction of exogenous compounds or hormones with nuclear receptors. Since synthetic glucocorticoids have found extensive use as anti-inflammatory drugs, also in the inhaled form in the treatment of asthma, lung cancer is potentially highly prone to transcriptional induction of multidrug resistance proteins by these steroids. MRP3 and MRP2 are major active anionic conjugate transporters in human cells and play a significant role in clinical multidrug resistance in cancer. A549 cells (non-small-cell lung cancer cell line) were challenged with glucocorticoids (dexamethasone, hydrocortisone and prednisone) at physiologically and therapeutically relevant concentrations for 24h and changes in MRP2 and MRP3 expression were followed on four levels: promoter regulation (luciferase reporter constructs), mRNA level (semi-quantitative real-time PCR), protein level (Western blotting) and activity (drug resistance and cellular transport of the model substrate calcein). DEX and HCT in the submicromolar concentration range caused a 2-fold induction of transcriptional activity at the MRP3 promoter construct, while MRP2 expression was not activated. All investigated glucocorticoids caused a modest stimulation of organic anion transport activity. We conclude that glucocorticoids used in clinical practice have the ability to transcriptionally upregulate human MRP3 gene expression in lung-derived cells where this protein is a major component of the organic anion extrusion system. This phenomenon has to be taken into account when designing treatments for lung cancer, especially for patients treated simultaneously with glucocorticoids against inflammatory symptoms.

Regulation of human airway mesenchymal cell proliferation by glucocorticoids and beta2-adrenoceptor agonists

Altered rates of cell proliferation play important roles in the pathogenesis of a variety of conditions, including cancer, inflammation and several airway and cardiovascular diseases. One of the most consistently observed changes in asthmatic airways is an increased volume of airway smooth muscle (ASM), that has been explained by proliferation, hypertrophy, extracellular matrix deposition within the smooth muscle bundles, and more recently, the migration of mesenchymal precursor cells to the airways. The best characterised of these is proliferation of ASM cells. In vitro studies suggest that the proliferation is driven by various mitogens, and ECM proteins found in asthma, such as collagen type I. Therefore, we compared the anti-mitogenic actions of two classes of anti-asthma agents, the glucocorticoids and the beta2-adrenoceptor agonists, in ASM cells grown on collagen type I. Culture on collagen type I prevented the anti-mitogenic actions of glucocorticoids, but not beta2-adrenoceptor agonists. In contrast, glucocorticoids are efficacious in regulating ASM production of GM-CSF, whereas beta2-adrenoceptor agonists are without effect. Therefore, combination therapy may have increased efficacy over glucocorticoids alone in controlling remodelling events due to complementary actions of the two classes of compounds.

A randomized phase IIb trial of pulmicort turbuhaler (budesonide) in people with dysplasia of the bronchial epithelium

PURPOSE

Preclinical studies suggest that inhaled budesonide may be an effective chemopreventive agent for lung cancer. We conducted a phase IIb study to determine the effects of inhaled budesonide in smokers with bronchial dysplasia.

EXPERIMENTAL DESIGN

A total of 112 smokers with more than or equal to one site of bronchial dysplasia > 1.2 mm in size identified by autofluorescence bronchoscopy-directed biopsy was randomly assigned to receive placebo or budesonide (Pulmicort Turbuhaler) 800 microg twice daily inhalation for 6 months. The primary end point was change in the histopathologic grade on repeat biopsy of the same sites at the end of 6 months.

RESULTS

There were no significant differences in the regression or progression rates of bronchial dysplasia between the two groups. There was a statistically significant but modest decrease in p53 and BclII expression in the bronchial biopsies after 6 months of Pulmicort Turbuhaler versus placebo (P = 0.01 and P = 0.001, respectively). There was a small but statistically significant decrease in the proportion of computed tomography-detected lung nodules after Pulmicort Turbuhaler compared with placebo (P = 0.024).

CONCLUSIONS

Our results suggest that in smokers, inhaled budesonide in the dose of 1600 microg daily for 6 months had no effect in regression of bronchial dysplastic lesions or prevention of new lesions. Budesonide treatment resulted in a modest decrease in p53 and BclII protein expression in bronchial biopsies and a slightly higher rate of resolution of computed tomography-detected lung nodules. Whether budesonide truly has an effect in preneoplastic lesions in the peripheral airways and alveoli requires additional investigation.

Early lymphoid progenitors in mouse and man are highly sensitive to glucocorticoids

Glucocorticoids are extensively used in anti-inflammatory therapy and may contribute to the normal regulation of lymphopoiesis. This study utilized new information about the early stages of lymphopoiesis in mouse and man to determine precisely which cell types are hormone sensitive. Cycling B lineage precursors were depleted in dexamethasone-treated mice, while mature, non-dividing CD45R(Hi) CD19(Hi) lymphocytes, myeloid progenitors and stem cells with the potential for lymphocyte generation on transplantation were spared. Lineage marker-negative (Lin(-)) IL-7R(+) Flk-2(+) pro-lymphocytes also declined, but not as rapidly as the terminal deoxynucleotidyl transferase-positive cells within an early Lin(-) c-kit(Hi) Sca-1(Hi) fraction of bone marrow. Hormone-sensitive cells with additional properties of early lymphoid progenitors (ELP) were identified within the same Lin(-) c-kit(Hi) Sca-1(Hi) subset using human mu transgenic mice and recombination-activating gene 1 (RAG1)/green fluorescent protein knock-in animals. Furthermore, cells with a recent history of RAG1 expression were more glucocorticoid sensitive than mature lymphocytes in marrow and spleen. Lymphocyte progenitors in mice bearing a human bcl-2 transgene were protected from dexamethasone treatment. However, isolated progenitors from either wild-type or bcl-2 transgenic mice were directly sensitive to the hormone in stromal cell-free cultures, suggesting that additional factors must determine vulnerability to glucocorticoids. B lineage lymphocyte precursors were found to be abnormally elevated in the bone marrow of adrenalectomized or RU486-treated mice. This suggests that glucocorticoids may normally contribute to steady-state regulation of lymphopoiesis. Finally, parallel studies revealed that the earliest events in human lymphopoiesis are susceptible to injury during glucocorticoid therapy.

Glucocorticoids induce G1 cell cycle arrest in human neoplastic thymic epithelial cells

PURPOSE

Glucocorticoids exert anti-proliferative effects in various cell types and have long been known to induce apoptosis in thymocytes. Although a few reports have described the regression of human thymoma with glucocorticoid therapy, its effects on neoplastic thymic epithelial cells (TECs) have not been reported. In the present study, we investigated glucocorticoid receptor (GR) expression on neoplastic TECs and the effects of glucocorticoids in vitro on the cell cycle progression of tumor cells.

PATIENTS AND METHODS

Thymoma specimens were obtained during surgery from 21 patients. Three of the specimens with glucocorticoid therapy were examined using the TdT-mediated dUTP-biotin nick-end labeling method. Primary tumor specimens from ten untreated thymomas were examined for GR expression by immunohistochemistry. Isolated neoplastic TECs from the remaining eight untreated thymomas were examined using immunohistochemistry, flow cytometric and cell cycle analysis.

RESULTS

GR are expressed on neoplastic TECs as well as on non-neoplastic thymocytes in thymomas, regardless of WHO histological classification. Glucocorticoids caused an accumulation of TEC in G0/G1 phase in all cases examined (n = 6), and also induced apoptosis in the three with the lowest levels of Bcl-2 expression.

CONCLUSIONS

Our results indicate that neoplastic TECs express GR and that glucocorticoids directly suppress their in vitro proliferation.

Glucocorticoid-Induced Changes in the Global Gene Expression of Lens Epithelial Cells

AIMS

Clinically, steroid use is accompanied by a risk for posterior subcapsular cataracts (PSCs). PSC possibly involves perturbation of lens epithelial cell proliferation and differentiation; however, the underlying mechanism is unknown. In this study, we aimed to characterize changes in gene expression in human lens epithelial cells exposed to glucocorticoid using DNA microarray hybridization.

METHODS

Human lens epithelial cells (HLE B-3) were treated with dexamethasone (1 microM) for 24 or 48 hours or with vehicle (0.01% dimethylsulfoxide) and the derived cRNA was hybridized to U133A microarrays. Data were processed using the Affymetrix program Micro Array Suite, and ontological analyses were performed using the software dChip, filtering to exclude transcripts up- or down-regulated by less than 2-fold.

RESULTS

At 24 hours, 57 transcripts were upregulated relative to controls by greater than 2- fold and 50 were downregulated by greater than 2-fold. At 48 hours, 92 transcripts were upregulated and 42 were downregulated. Twenty-two upregulated and 2 downregulated transcripts were shared between the 24-hour and 48-hour data sets. The predominant ontological groupings were: signal transduction, transcription factor activity, cytoskeleton/ECM/adhesion, transport, and cell cycle/development. Alternate ontological interpretations are possible.

CONCLUSIONS

The data indicate steroid treatment of lens epithelial cells is associated with significant changes in gene expression in several functional categories and these include transcripts related to cell proliferation.

Airway mucosal thickening and bronchial hyperresponsiveness induced by inhaled beta 2-agonist in mice

BACKGROUND

Patients with chronic persistent asthma require frequent use of inhaled beta(2)-agonist, which may result in aggravation of asthma symptoms. Our recent in vitro study has shown that beta(2)-agonist stimulates the growth of human airway epithelial cell lines.

STUDY OBJECTIVE

To determine whether beta(2)-agonist likewise affects airway epithelial cell proliferation in vivo and, if so, what the mechanism of action is, we examined the effect of salbutamol on the morphology of murine airways.

METHODS

Seventy-two BALB/c mice were administered aerosolized salbutamol using "flow-through" nose-only inhalation chambers at daily doses of 0.2 to 20 microg for up to 6 weeks. Morphology of tracheal mucosa, labeling of epithelial cells with 5-bromo-2'-deoxyuridine (BrdU), and bronchial responsiveness were assessed.

RESULTS

Exposure to salbutamol increased the thickness of tracheal epithelial layer and the number of BrdU-positive epithelial cells in a dose- and time-dependent manner: the values in mice receiving 20 microg salbutamol for 6 weeks were 247% and 642%, respectively, of those in control animals receiving saline solution alone. These effects were inhibited by the mitogen-activated protein (MAP) kinase kinase inhibitors PD98059 and U0126. Salbutamol also caused a decrease in the provocative concentration of methacholine to achieve 400% of baseline enhanced pause. Combined treatment with inhaled budesonide attenuated salbutamol-induced airway morphologic changes and bronchial hyperresponsiveness.

CONCLUSION

beta(2)-agonist stimulates proliferation of airway epithelial cells and produces airway wall thickening in vivo via MAP kinase-dependent pathway, and these effects are prevented by inhaled corticosteroid.

Increased expression of Apaf-1 and procaspase-3 and the functionality of intrinsic apoptosis apparatus in non-small cell lung carcinoma

The intrinsic apoptosis apparatus plays a significant role in generating and amplifying cell death signals. In this study we examined whether there are differences in the expression of its components and in its functioning in non-small cell lung carcinoma (NSCLC) and the lung. We show that NSCLC cell lines express Apaf-1 and procaspase-9 and -3 proteins and that the expression of Apaf-1 and procaspase-3, but not of procaspase-9 and -7, is frequently up-regulated in NSCLC tissues as compared to the lung. NSCLC tissues and lungs and some NSCLC cell lines expressed also caspase-9S(b) and displayed a high caspase-9S(b)/procaspase-9 expression ratio. Procaspase-3 from NSCLCs and lungs was readily processed to caspase-3 by granzyme B or caspase-8, and the granzyme B-generated caspase-3-like activity was significantly higher in tumor tissues and cells than in lungs. By contrast, cytochrome c plus dATP could induce a significant increase of caspase-3-like activity in cytosol only in some NSCLC cell lines and in subsets of studied NSCLC tissues and lungs, while procaspase-3 and -7 were detectably processed only in NSCLC tissues which showed a high (cytochrome c+dATP)-induced caspase-3-like activity. Taken together, the present study provides evidence that the expression of Apaf-1 and procaspase-3 is up-regulated in NSCLCs and indicates that the tumors have a capability to suppress the apoptosome-driven caspase activation in their cytosol.

Increased P27KIP1 protein expression in the dentate gyrus of chronically stressed rats indicates G1 arrest involvement

Various chronic stress paradigms decrease new cell proliferation in the hippocampal dentate gyrus, yet the exact underlying mechanism is still unclear. In the first gap (G1) phase of the cell cycle, both stimulatory and inhibitory signals derived from the extracellular environment converge. Corticosteroids, which increase during stress and are well-known anti-mitotics, cause cells in vitro to arrest in the G1 phase. Following 3 weeks of unpredictable stress, we therefore expected a change in protein expression of various important G1 cell cycle regulators in the adult rat subgranular zone. Using quantitative immunocytochemistry, we show that particularly cyclin-dependent kinase inhibitor p27Kip1 expression is significantly increased. In addition, 3 weeks of recovery after stress normalized the numbers of p27Kip1-expressing cells, consistent with the recovered adult cell proliferation in these animals. P27Kip1-positive cells do not overlap with GFAP-staining and only to a limited extent with Ki-67-expressing cells. Numbers of cyclin E- and cyclin D1-expressing cells did not change after chronic stress. These results indicate that chronic stress causes cycling cells in the adult hippocampus to arrest in G1, thereby providing more mechanistic insight in the stress-induced decrease in cell proliferation.

Induction of apoptosis in nasal polyp fibroblasts by glucocorticoids in vitro

OBJECTIVE

To examine the possible mechanisms underlying the therapeutic mode of action of glucocorticoids (GCs) in nasal polyposis.

MATERIAL AND METHODS

The effects of GCs on nasal polyps were firstly evaluated by examining the growth of fibroblasts derived from 10 nasal polyps in vitro. Subsequently, the ability of GCs to induce apoptotic cell death in fibroblasts was examined.

RESULTS

Addition of betamethasone 21-phosphate (BET) at a concentration of > 1 x 10(-3) M to cell cultures inhibited cell growth in all cases examined. BET and dexamethasone 21-phosphate, but not testosterone or estradiol, caused apoptotic cell death in 2/10 nasal polyp fibroblasts, as assessed by agarose gel electrophoresis, when the cells were cultured with the agents for > 96 h. The minimum concentration of agent needed to cause apoptosis was 1 x 10(-3) M, which is half of the recommended therapeutic dose.

CONCLUSION

The present findings suggest that topical application of GCs in nasal polyposis patients suppresses proliferation of fibroblasts in polyps and results in favorable modification of the clinical status of these patients.