Effects of Tribulus terrestris saponins on exercise performance in overtraining rats and the underlying mechanisms.

The objective of this study was to determine the effects of Tribulus terrestris L. (TT) saponins on exercise performance and the underlying mechanisms. A rat overtraining model was established and animals were treated with TT extracts (120 mg/kg body mass) 30 min before each training session. Serum levels of testosterone and corticosterone and levels of androgen receptor (AR) and insulin growth factor-1 receptor (IGF-1R) in the liver, gastrocnemius, and soleus were determined by ELISA and Western blot. Treatment of rats with TT saponins significantly improved the performance of the overtraining rats, reflected by the extension of time to exhaustion, with a concomitant increase in body mass, relative mass, and protein levels of gastrocnemius. Overtraining alone induced a significant decrease in the serum level of testosterone. In contrast, treatment with TT saponins dramatically increased the serum level of testosterone in overtraining rats to about 150% of control and 216% of overtraining groups, respectively. In addition, TT saponins resulted in a further significant increase in AR in gastrocnemius and significantly suppressed the overtraining-induced increase in IGF-1R in the liver. These results indicated that TT saponins increased performance, body mass, and gastrocnemius mass of rats undergoing overtraining, which might be attributed to the changes in androgen-AR axis and IGF-1R signaling.

Overexpression of metabolic markers PKM2 and LDH5 correlates with aggressive clinicopathological features and adverse patient prognosis in tongue cancer.

AIMS: Pyruvate kinase M2 (PKM2) and lactate dehydrogenase 5 (LDH5) are two metabolic and oncogenic markers of cancer. In this study, we sought to investigate their expression patterns and prognostic value in tongue squamous cell carcinoma (TSCC). METHODS AND RESULTS: The expression and subcellular localization of PKM2 and LDH5 in TSCC cell lines were determined by Western blot and immunofluorescence. PKM2 and LDH5 abundance was examined by immunohistochemistry in 63 TSCC tumour specimens; their association with multiple clinicopathological parameters and overall patient survival was assessed. The protein levels of PKM2 and LDH5 were both significantly higher in TSCC cells than in an immortalized oral epithelial cell line. Overexpression of PKM2 associated significantly with cervical node metastasis (P = 0.0373), while elevated LDH5 levels correlated significantly with tumour size (P = 0.0094), pathological grade (P = 0.0052), cervical node metastasis (P = 0.0023) and clinical stage (P = 0.0024). Patients with tumours showing an increase in either PKM2 or LDH5 expression displayed significantly reduced overall survival, while patients with tumours overexpressing both proteins showed the worst prognosis with lowest overall survival. Furthermore, PKM2 and LDH5 were identified as independent prognostic predictors for overall patient survival in TSCC. CONCLUSION: Our data indicate that overexpression of PKM2 and LDH5 associates with key clinicopathological features and unfavourable prognosis in TSCC.

Upregulations of glucocorticoid-induced leucine zipper by hypoxia and glucocorticoid inhibit proinflammatory cytokines under hypoxic conditions in macrophages.

Hypoxia and inflammation often develop concurrently in numerous diseases, and the influence of hypoxia on natural evolution of inflammatory responses is widely accepted. Glucocorticoid-induced leucine zipper (GILZ) is thought to be an important mediator of anti-inflammatory and immune-suppressive actions of glucocorticoid (GC). However, whether GILZ is involved in hypoxic response is still unclear. In this study, we investigated the effects of hypoxic exposure and/or the administration of dexamethasone (Dex), a synthetic GC on GILZ expression both in vitro and in vivo, and further explored the relationship between GILZ and proinflammatory cytokines IL-1ß, IL-6, and TNF-α under normoxic and hypoxic conditions. We found that hypoxia not only remarkably upregulated the expression of GILZ, but also significantly enhanced Dex-induced expression of GILZ in macrophages and the spleen of rats. ERK activity is found involved in the upregulation of GILZ induced by hypoxia. Inhibiting the expression of GILZ in RAW264.7 cells using specific GILZ small interfering RNA led to a significant increase in mRNA production and protein secretion of IL-1ß and IL-6 in hypoxia and abrogated the inhibitory effect of Dex on expression of IL-1ß and IL-6 in hypoxia. We also found that adrenal hormones played pivotal roles in upregulation of GILZ expression in vivo. Altogether, data presented in this study suggest that GILZ has an important role not only in adjusting adaptive responses to hypoxia by negatively regulating the activation of macrophages and the expression of proinflammatory cytokines, but also in mediating the anti-inflammatory action of GC under hypoxic conditions.

Structural and functional interactions of the prostate cancer suppressor protein NKX3.1 with topoisomerase I.

NKX3.1 (NK3 homeobox 1) is a prostate tumour suppressor protein with a number of activities that are critical for its role in tumour suppression. NKX3.1 mediates the cellular response to DNA damage by interacting with ATM (ataxia telangiectasia mutated) and by activation of topoisomerase I. In the present study we characterized the interaction between NKX3.1 and topoisomerase I. The NKX3.1 homeodomain binds to a region of topoisomerase I spanning the junction between the core and linker domains. Loss of the topoisomerase I N-terminal domain, a region for frequent protein interactions, did not affect binding to NKX3.1 as was shown by the activation of Topo70 (N-terminal truncated topoisomerase I) in vitro. In contrast, NKX3.1 interacts with the enzyme reconstituted from peptide fragments of the core and linker active site domains, but inhibits the DNA-resolving activity of the reconstituted enzyme in vitro. The effect of NKX3.1 on both Topo70 and the reconstituted enzyme was seen in the presence and absence of camptothecin. Neither NKX3.1 nor CPT (camptothecin) had an effect on the interaction of the other with topoisomerase I. Therefore the interactions of NKX3.1 and CPT with the linker domain of topoisomerase I are mutually exclusive. However, in cells the effect of NKX3.1 on topoisomerase binding to DNA sensitized the cells to cellular toxicity and the induction of apoptosis by low doses of CPT. Lastly, topoisomerase I is important for the effect of NKX3.1 on cell survival after DNA damage as topoisomerase knockdown blocked the effect of NKX3.1 on clonogenicity after DNA damage. Therefore NKX3.1 and topoisomerase I interact in vitro and in cells to affect the CPT sensitivity and DNA-repair functions of NKX3.1.

Up-regulation of stomatin expression by hypoxia and glucocorticoid stabilizes membrane-associated actin in alveolar epithelial cells.

Stomatin is an important lipid raft-associated protein which interacts with membrane proteins and plays a role in the membrane organization. However, it is unknown whether it is involved in the response to hypoxia and glucocorticoid (GC) in alveolar epithelial cells (AEC). In this study we found that hypoxia and dexamethasone (dex), a synthetic GC not only up-regulated the expression of stomatin alone, but also imposed additive effect on the expression of stomatin in A549 cells, primary AEC and lung of rats. Then we investigated whether hypoxia and dex transcriptionally up-regulated the expression of stomatin by reporter gene assay, and found that dex, but not hypoxia could increase the activity of a stomatin promoter-driven reporter gene. Further deletion and mutational studies demonstrated that a GC response element (GRE) within the promoter region mainly contributed to the induction of stomatin by dex. Moreover, we found that hypoxia exposure did not affect membrane-associated actin, but decreased actin in cytoplasm in A549 cells. Inhibiting stomatin expression by stomatin siRNA significantly decreased dense of peripheral actin ring in hypoxia or dex treated A549 cells. Taken all together, these data indicated that dex and/or hypoxia significantly up-regulated the expression of stomatin in vivo and in vitro, which could stabilize membrane-associated actin in AEC. We suppose that the up-regulation of stomatin by hypoxia and dex may enhance the barrier function of alveolar epithelia and mediate the adaptive role of GC to hypoxia.

Differential modulation of glucocorticoid and progesterone receptor transactivation.

The determinants of the different biological activities of progesterone receptors (PRs) vs. glucocorticoid receptors (GRs), which bind to the same DNA sequences, remain poorly understood. The mechanisms by which differential expression of a common target gene can be achieved by PR and GR include unequal agonist steroid concentrations for half maximal induction (EC50) and dissimilar amounts of residual partial agonist activity for antisteroids in addition to the more common changes in total gene induction, or Vmax. Several factors are known to alter some or all of these three parameters for GR-regulated gene induction and some (i.e., the corepressors NCoR and SMRT) modulate the EC50 and partial agonist activity for GR and PR induction of the same gene in opposite directions. The current study demonstrates that other factors known to modulate GR properties (GME, GMEB-2, Ubc9, and STAMP) can also differentially interact with PRs or alter several of the above induction parameters under otherwise identical conditions. These results support the hypothesis that the modulation of EC50, partial agonist activity, and Vmax by a given factor is not limited to one receptor in a specific cell line. Furthermore, the number of factors that unequally modulate PR and GR induction parameters is now greatly expanded, thereby increasing the possible mechanisms for differential gene regulation by PRs vs. GRs.

Beta-catenin binds to the activation function 2 region of the androgen receptor and modulates the effects of the N-terminal domain and TIF2 on ligand-dependent transcription.

Beta-catenin is a multifunctional molecule that is activated by signaling through WNT receptors. beta-Catenin can also enhance the transcriptional activity of some steroid hormone receptors such as the androgen receptor and retinoic acid receptor alpha. Androgens can affect nuclear translocation of beta-catenin and influence its subcellular distribution. Using mammalian two-hybrid binding assays, analysis of reporter gene transcription, and coimmunoprecipitation, we now show that beta-catenin binds to the androgen receptor ligand-binding domain (LBD) and modulates the transcriptional effects of TIF2 and the androgen receptor N-terminal domain (NTD). In functional assays, beta-catenin bound to androgen receptor only in the presence of ligand agonists, not antagonists. Beta-catenin binding to the androgen receptor LBD was independent of and cooperative with the androgen receptor NTD and the p160 coactivator TIF2, both of which bind to the activation function 2 (AF-2) region of the androgen receptor. Different mutations of androgen receptor helix 3 amino acids disrupted binding of androgen receptor NTD and beta-catenin. beta-Catenin, androgen receptor NTD, and TIF2 binding to the androgen receptor LBD were affected similarly by a subset of helix 12 mutations, but disruption of two sites on helix 12 affected only binding of beta-catenin and not of TIF2 or the androgen receptor NTD. Mutational disruption of each of five LXXLL peptide motifs in the beta-catenin armadillo repeats did not disrupt either binding to androgen receptor or transcriptional coactivation. ICAT, an inhibitor of T-cell factor 4 (TCF-4), and E-cadherin binding to beta-catenin also blocked binding of the androgen receptor LBD. We also demonstrated cross talk between the WNT and androgen receptor signaling pathways because excess androgen receptor could interfere with WNT signaling and excess TCF-4 inhibited the interaction of beta-catenin and androgen receptor. Taken together, the data show that beta-catenin can bind to the androgen receptor LBD and modulate the effects of the androgen receptor NTD and TIF2 on transcription.

Structural determinants of the BRCA1 : estrogen receptor interaction.

Previously, we showed that the BRCA1 protein interacts directly and functionally with estrogen receptor-alpha (ER-alpha), resulting in the inhibition of estradiol (E2)-stimulated ER-alpha transcriptional activity. The interaction sites were mapped to the N-terminus of BRCA1 (within amino acids (aa) 1-302) and the ligand-binding domain/activation function-2 (LBD/AF-2) region (within aa 282-420) of ER-alpha. In this study, we have further characterized the structure/function relationship for the BRCA1 : ER-alpha interaction. We found that the N-terminal RING domain (aa 20-64) is not required for the BRCA1 : ER-alpha interaction. We identified two separate contact points for ER-alpha, one within aa 1-100 and the other within aa 100-200 of BRCA1; and we showed that each of these BRCA1 peptides interacts with BRCA1 in vitro and in vivo. By using different fragments of the BRCA1 N-terminus, we found that aa 67-100 and 101-133 are required for the interaction with ER-alpha, but that aa 1-67 and 134-302 are dispensible. Previously, we showed that BRCA1 aa 1-302 does not inhibit E2-stimulated ER-alpha transcriptional activity but does bind to ER-alpha and acts as a dominant negative inhibitor of the full-length BRCA1 protein. Somewhat surprisingly, we found that BRCA1 aa 1-100 and BRCA1 aa 101-200 (but not aa 201-300) each inhibited ER-alpha activity, although not as efficiently as full-length BRCA1. Mutations within an HIV Rev-like nuclear export signal that resembles a nuclear receptor corepressor motif (aa 86-95) impaired the ability of both truncated (aa 1-100) and full-length (aa 1-1863) BRCA1 proteins to interact with and/or repress ER-alpha activity. Based on these findings, a partial BRCA1 : ER-alpha three-dimensional structure is proposed. The implications of these findings for understanding the BRCA1 : ER-alpha interaction are discussed.

Antiandrogen effects of mifepristone on coactivator and corepressor interactions with the androgen receptor.

Mifepristone is a potent antagonist of steroid hormone receptors such as glucocorticoid and progesterone receptors. We investigated the potential for mifepristone to act as an antiandrogen and compared it with partial androgen receptor (AR) agonists and antagonists, in particular bicalutamide. Mifepristone was an effective antiandrogen in vitro that inhibited transcription from three androgen-responsive promoters and blocked the agonist R1881 in a dose-dependent manner. Like bicalutamide, mifepristone also antagonized the action of androgen receptor with a (T877A) mutation. Mifepristone competed effectively with R1881 with a relative binding affinity comparable to that of cyproterone acetate, and much higher than that of hydroxyflutamide and bicalutamide in a binding assay. Mifepristone could effectively induce the binding of the herpes simplex viral protein 16/AR fusion protein to the hormone response elements in the murine mammary tumor virus-luciferase reporter. With either wild-type or T877A mutant AR, mifepristone alone was unable to induce any detectable interaction with coactivators transcriptional intermediary factor-2 or beta-catenin but could inhibit the R1881-induced binding of AR to transcriptional intermediary factor-2 and beta-catenin. Similarly, mifepristone could inhibit the R1881-induced N/C-terminal interaction in a dose-dependent manner even though mifepristone alone has no effect on the N/C-terminal interaction of AR. We found that mifepristone could induce a strong interaction between AR and corepressors nuclear receptor corepressor and silencing mediator for retinoid and thyroid hormone receptors in both transactivation and two-hybrid assays to a greater degree than hydroxyflutamide, cyproterone acetate, and bicalutamide. The AR-corepressor interaction was also seen in coimmunoprecipitation assays. Finally, mifepristone at high concentrations induced a low level of prostate-specific antigen expression in LNCaP and antagonized prostate-specific antigen expression induced by R1881. Mifepristone also antagonized R1881 action on the growth of LNCaP prostate cancer cells.

Equilibrium interactions of corepressors and coactivators with agonist and antagonist complexes of glucocorticoid receptors.

Corepressors and coactivators can modulate the dose-response curve and partial agonist activity of glucocorticoid receptors (GRs) complexed with agonist and antagonist steroids, respectively, in intact cells. We recently reported that GR-antagonist complexes bind to the coactivator TIF2, (transcriptional intermediary factor 2), which is consistent with the whole-cell effects of coactivators being mediated by direct interactions with GR complexes. We now ask whether the whole-cell modulatory activity of corepressors also entails binding to both GR-agonist and -antagonist complexes and whether the association of corepressors and coactivators with GR complexes involves competitive equilibrium reactions. In mammalian two-hybrid assays with two different cell lines and in cell-free pull-down and whole-cell immunoprecipitation assays, the corepressors NCoR (nuclear receptor corepressor) and SMRT (silencing mediator of retinoid and thyroid hormone receptor) associate with agonist and antagonist complexes of GRs. Both N- and C-terminal regions of GR are needed for corepressor binding, which requires the CoRNR box motifs that mediate corepressor binding to other nuclear/steroid receptors. Importantly, whole-cell GR interactions with corepressors are competitively inhibited by excess coactivator and vice versa. However, the regions of the coactivator TIF2 that compete for GR binding to corepressor and coactivator are not the same, implying a molecular difference in GR association with coactivators and corepressors. Finally, when the whole-cell ratio of coactivators to corepressors is altered by selective cofactor binding to exogenous thyroid receptor beta +/- thyroid hormone, the GR dose-response-curve and partial agonist activity are appropriately modified. Such modifications are independent of histone acetylation. We conclude that mutually antagonistic equilibrium interactions of corepressors and coactivators modulate the dose-response curve and partial agonist activity of GR complexes in a manner that is responsive to the intracellular ratio of these two classes of cofactors. This modulation provides an attractive mechanism for differential control of gene expression during development, differentiation, homeostasis, and endocrine therapies.

The Tumor Suppressor NKX3.1 Is Targeted for Degradation by DYRK1B Kinase.

UNLABELLED: NKX3.1 is a prostate-specific homeodomain protein and tumor suppressor whose expression is reduced in the earliest phases of prostatic neoplasia. NKX3.1 expression is not only diminished by genetic loss and methylation, but the protein itself is a target for accelerated degradation caused by inflammation that is common in the aging prostate gland. NKX3.1 degradation is activated by phosphorylation at C-terminal serine residues that mediate ubiquitination and protein turnover. Because NKX3.1 is haploinsufficient, strategies to increase its protein stability could lead to new therapies. Here, a high-throughput screen was developed using an siRNA library for kinases that mediate NKX3.1 degradation. This approach identified several candidates, of which DYRK1B, a kinase that is subject to gene amplification and overexpression in other cancers, had the greatest impact on NKX3.1 half-life. Mechanistically, NKX3.1 and DYRK1B were shown to interact via the DYRK1B kinase domain. In addition, an in vitro kinase assay showed that DYRK1B phosphorylated NKX3.1 at serine 185, a residue critical for NKX3.1 steady-state turnover. Lastly, small-molecule inhibitors of DYRK1B prolonged NKX3.1 half-life. Thus, DYRK1B is a target for enzymatic inhibition in order to increase cellular NKX3.1. IMPLICATIONS: DYRK1B is a promising and novel kinase target for prostate cancer treatment mediated by enhancing NKX3.1 levels.

The Hippo transducer TAZ promotes epithelial to mesenchymal transition and cancer stem cell maintenance in oral cancer.

The Hippo pathway has emerged as a fundamental regulator in tissue growth, organ size and stem cell functions, and tumorigenesis when deregulated. However, its roles and associated molecular mechanisms underlying oral squamous cell carcinoma (OSCC) initiation and progression remain largely unknown. Here, we identified TAZ, the downstream effector of Hippo signaling, as a novel bona fide oncogene by promoting cell proliferation, migration/invasion and chemoresistance in OSCC. TAZ promoted epithelial-to-mesenchymal transition (EMT) and also was involved in TGF-ß1-induced EMT in oral cancer cells. Furthermore, enriched TAZ sustained self-renewal, maintenance, tumor-seeding potential of oral cancer stem cells (CSCs). Remarkably, enforced TAZ overexpression conferred CSCs-like properties on differentiated non-CSCs and fueled phenotypic transition from non-CSCs to CSCs-like cells. Mechanistically, TAZ-TEADs binding and subsequent transcriptional activation of EMT mediators and pluripotency factors are presumably responsible for TAZ-mediated EMT and non-CSCs-to-CSCs conversion. Importantly, aberrant TAZ overexpression was found to be associated with tumor size, pathological grade and cervical lymph node metastasis, as well as unfavorable prognosis. Pharmacological repression of TAZ by simvastatin resulted in potent anti-cancer effects against OSCC. Taken together, our findings have revealed critical links between TAZ, EMT and CSCs in OSCC initiation and progression, and also established TAZ as a novel cancer biomarker and viable druggable target for OSCC therapeutics.

Dexamethasone enhances cell resistance to chemotherapy by increasing adhesion to extracellular matrix in human ovarian cancer cells.

Glucocorticoids (GCs) are widely used as co-medication in the therapy of solid malignant tumors to relieve some of the side effects of chemotherapeutic drugs. However, recent studies have shown that GCs could render cancer cells more resistant to cytotoxic drug-induced apoptosis, but the mechanism is largely unknown. In the present study, we found that the treatment of human ovarian cancer cell lines HO-8910 and SKOV3 with synthetic GCs dexamethasone (Dex) significantly increased their adhesion to extracellular matrix (ECM) and their resistance to apoptosis induced by cytotoxic drugs cisplatin and paclitaxel. Dex also increased the protein levels of adhesion molecules integrins beta1, alpha 4, and alpha 5 in HO-8910 cells. The neutralizing antibody against integrin beta1 prevented Dex-induced adhesion and significantly abrogated the protective effect of Dex toward cytotoxic agents. We further found that transforming growth factor-beta1 (TGF-beta1) alone not only increased cell adhesion and cell survival of HO-8910 cells in the presence of cisplatin, but also had synergistic pro-adhesion and pro-survival effects with Dex. Moreover, TGF-beta1-neutralizing antibody that could block TGF-beta1-induced cell adhesion and apoptosis resistance markedly abrogated the synergistic pro-adhesion and pro-survival effects of Dex and TGF-beta1. Finally, we further demonstrated that Dex could up-regulate the expression of TGF-beta receptor type II and enhance the responsiveness of cells to TGF-beta1. In conclusion, our results indicate that increased adhesion to ECM through the enhancement of integrin beta1 signaling and TGF-beta1 signaling plays an important role in chemoresistance induced by GCs in ovarian cancer cells.

The cell fate determination factor dachshund inhibits androgen receptor signaling and prostate cancer cellular growth.

Initially isolated as the dominant suppressor of the mutant epidermal growth factor receptor (ellipse), the Dachshund gene plays a key role in metazoan development regulating the Retinal Determination Gene Network. Herein, the DACH1 gene was expressed in normal prostate epithelial cells with reduced expression in human prostate cancer. DACH1 inhibited prostate cancer cellular DNA synthesis, growth in colony forming assays, and blocked contact-independent growth in soft agar assays. DACH1 inhibited androgen receptor (AR) activity, requiring a conserved DS Domain (Dachshund domain conserved with Ski/Sno) that bound NCoR/HDAC and was recruited to an androgen-responsive gene promoter. DACH1 inhibited ligand-dependent activity of AR mutations identified in patients with androgen-insensitive prostate cancer. The DS domain was sufficient for repression of the AR wild-type but failed to repress an AR acetylation site point mutant. These studies show a role for the Retinal Determination Gene Network in regulating cellular growth and signaling in prostate cancer.

Silencing mediator for retinoid and thyroid hormone receptor and nuclear receptor corepressor attenuate transcriptional activation by the beta-catenin-TCF4 complex.

beta-Catenin is a multifunctional mediator of cellular signaling and an oncogene. Nuclear beta-catenin, when complexed with members of the T-cell factor (TCF)/leukocyte enhancer factor family of DNA-binding proteins, mediates transcriptional activation important for embryonic development and adult cell homeostasis. Deregulation of intracellular levels of beta-catenin is an early event in the development of a variety of cancers. We observed that the proteins silencing mediator for retinoid and thyroid hormone receptor (SMRT) and the nuclear receptor corepressor (NCoR) are negative regulators of transcription induced by the beta-catenin-TCF4 complex. Overexpression of SMRT and NCoR attenuated the transcription of beta-catenin-TCF4-specific reporter gene and of CCND1, an endogenous beta-catenin target gene. Knockdown of endogenous SMRT or NCoR by short interfering RNA augmented the beta-catenin-TCF4-mediated reporter gene expression. Glutathione S-transferase pulldown experiments showed there was a direct physical association of SMRT and NCoR with both beta-catenin and TCF4. DNA-protein interaction studies revealed that the interactions between either SMRT or NCoR and beta-catenin or TCF4 occurred at the promoter regions of CCND1 and other target genes. These findings demonstrate an important role for corepressors SMRT and NCoR in the regulation of beta-catenin-TCF4-mediated gene transcription.

Interaction of beta-catenin and TIF2/GRIP1 in transcriptional activation by the androgen receptor.

The multifunctional oncoprotein beta-catenin interacts with the activation function-2 domain of androgen receptor (AR) to stimulate androgen receptor transcriptional activity, increase sensitivity, and broaden specificity of ligand interactions. beta-Catenin interacts with androgen receptor in close proximity to the binding groove for P160 coactivators such as transcriptional intermediary factor-2 (TIF2)/glucocorticoid receptor interacting protein-1 (GRIP1). beta-Catenin can also bind directly to TIF2/GRIP1. Both N- and C-terminal regions of beta-catenin are needed for optimal interaction with TIF2/GRIP1. We show that distinct residues of beta-catenin are responsible for both binding and functional interactions with androgen receptor and with TCF4, thus allowing the introduction of missense mutations that selectively affect these interactions. beta-Catenin and TIF2/GRIP1 are each able to mediate binding between the other and androgen receptor in functional interactions that enhance ligand-dependent transcription. The data strongly imply that AR, beta-catenin, and TIF2/GRIP1 bind in a three-way interaction that mediates transcription. Lastly, we observed that a beta-catenin C-terminal peptide containing 229 amino acids can bind TIF2/GRIP1 and AR but has a profound dominant inhibitory effect on ligand-dependent transcription. We propose that beta-catenin may play an integral role in formation of the androgen-receptor transcriptional complex.

Effects of glucocorticoid on proliferation, differentiation, and glucocorticoid receptor expression in human ovarian carcinoma cell line 3AO.

AIM: To study the effects of dexamethasone (Dex), a synthetic glucocorticoid, on proliferation, differentiation, glucocorticoid receptor expression and regulation in human ovarian cancer cell line 3AO. METHODS: 3AO cells proliferation was evaluated by viable cell count, activity of alkaline phosphatase (AKP) and tumor marker CA125 level were determined; the expression and regulation of glucocorticoid receptor (GR) in 3AO cells was studied with radioligand binding assay. RESULTS: Dex inhibited the proliferation of 3AO cells accompanied by morphological changes in concentration- and time- dependent manner. AKP activity was increased and tumor marker CA125 was decreased in 3AO cells after treatment with Dex. The induction of AKP activity by dexamethasone was blocked by RU486, a potent glucocorticoid antagonist. There existed high affinity and low capacity of GR in 3AO cells, and the GR binding activity could be downregulated by Dex. CONCLUSION: Glucocorticoids play an important role in the regulation of 3AO cell proliferation and differentiation. There existed functional GR in 3AO cells and the cellular effects of dexamethasone on 3AO cells were mediated by GR.