Physical interaction and mutual transrepression between CCAAT/enhancer-binding protein beta and the p53 tumor suppressor

Inside the Endometrial Cell Signaling Subway: Mind the Gap(s)

Endometrial cells perceive and respond to their microenvironment forming the basis of endometrial homeostasis. Errors in endometrial cell signaling are responsible for a wide spectrum of endometrial pathologies ranging from infertility to cancer. Intensive research over the years has been decoding the sophisticated molecular means by which endometrial cells communicate to each other and with the embryo. The objective of this review is to provide the scientific community with the first overview of key endometrial cell signaling pathways operating throughout the menstrual cycle. On this basis, a comprehensive and critical assessment of the literature was performed to provide the tools for the authorship of this narrative review summarizing the pivotal components and signaling cascades operating during seven endometrial cell fate “routes”: proliferation, decidualization, implantation, migration, breakdown, regeneration, and angiogenesis. Albeit schematically presented as separate transit routes in a subway network and narrated in a distinct fashion, the majority of the time these routes overlap or occur simultaneously within endometrial cells. This review facilitates identification of novel trajectories of research in endometrial cellular communication and signaling. The meticulous study of endometrial signaling pathways potentiates both the discovery of novel therapeutic targets to tackle disease and vanguard fertility approaches.

UBR2 Enriched in p53 Deficient Mouse Bone Marrow Mesenchymal Stem Cell-Exosome Promoted Gastric Cancer Progression via Wnt/β-Catenin Pathway

The deficiency or mutation of p53 has been linked to several types of cancers. The mesenchymal stem cell (MSC) is an important component in the tumor microenvironment, and exosomes secreted by MSCs can transfer bioactive molecules, including proteins and nucleic acid, to other cells in the tumor microenvironment to influence the progress of a tumor. However, whether the state of p53 in MSCs can impact the bioactive molecule secretion of exosomes to promote cancer progression and the regulatory mechanism remains elusive. Our study aimed to investigate the regulation of ubiquitin protein ligase E3 component n-recognin 2 (UBR2) enriched in exosomes secreted by p53 deficient mouse bone marrow MSC (p53^-/- mBMMSC) in gastric cancer progression in vivo and in vitro. We found that the concentration of exosome was significantly higher in p53^-/- mBMMSC than that in p53 wild-type mBMMSC (p53^+/+ mBMMSC). In particular, UBR2 was highly expressed in p53^-/- mBMMSC cells and exosomes. P53^-/- mBMMSC exosomes enriched UBR2 could be internalized into p53^+/+ mBMMSC and murine foregastric carcinoma (MFC) cells and induce the overexpression of UBR2 in these cells which elevated cell proliferation, migration, and the expression of stemness-related genes. Mechanistically, the downregulation of UBR2 in p53^-/- mBMMSC exosomes could reverse these actions. Moreover, a majority of Wnt family members, β-catenin, and its downstream genes (CD44, CyclinD1, CyclinD3, and C-myc) were significantly decreased in MFC knockdown UBR2 and β-catenin depletion, an additional depletion of UBR2 had no significant difference in the expression of Nanog, OCT4, Vimentin, and E-cadherin. Taken together, our findings indicated that p53^-/- mBMMSC exosomes could deliver UBR2 to target cells and promote gastric cancer growth and metastasis by regulating Wnt/β-catenin pathway. Stem Cells 2017;35:2267-2279.

Association of MMP-2, RB and PAI-1 with decreased recurrence-free survival and overall survival in bladder cancer patients

Background

We previously reported an accurate urine-based bladder cancer (BCa)-associated diagnostic signature that can be used to non-invasively detect BCa. In this study, we investigated whether a component of this signature could risk stratify patients with BCa.

Methods

Utilizing immunohistochemistry, we investigated angiogenin, MMP-2, p53, RB and PAI-1 expression from 939 patients with BCa. The expression levels were scored by assigning a proportion score and an intensity score to yield a total staining score for each protein. The expressions of each protein individually and as an aggregate were then correlated with progression-free survival (PFS), cancer-specific survival (CSS) and overall survival (OS).

Results

Differential expressions of these markers were noted in BCa. With multivariate analysis in non-muscle invasive bladder cancer (NMIBC) age, tumor grade portended a worse PFS, while age, tumor grade, nodal status, MMP2, RB and PAI-1 expression portended a worse OS. As for multivariate analysis in muscle invasive bladder cancer (MIBC), age MMP-2 and RB were associated with a worse PFS, while age, nodal status, MMP-2, RB and PAI-1 were associated with a worse OS. Using Kaplan-Meier survival analysis, we noted a significant reduction in OS as more of the five biomarkers were expressed in a tumor. Thus, overall, high expressions of MMP-2, RB and/or PAI-1 in bladder tumors were markers of poor prognosis.

Conclusion

Individually, MMP-2, RB and PAI-1, as well as in aggregate correlated with poor survival in patients with BCa. Thus, patients whose bladder tumors express these biomarkers may benefit from early radical treatment and/or neoadjuvant or adjuvant therapies.

Long Non-coding RNAs and Their Roles in Non-small-cell Lung Cancer

As a leading cause of cancer deaths worldwide, lung cancer is a collection of diseases with diverse etiologies which can be broadly classified into small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC). Lung cancer is characterized by genomic and epigenomic alterations; however, mechanisms underlying lung tumorigenesis remain to be elucidated. Long non-coding RNAs (lncRNAs) are a group of non-coding RNAs that consist of ⩾200 nucleotides but possess low or no protein-coding potential. Accumulating evidence indicates that abnormal expression of lncRNAs is associated with tumorigenesis of various cancers, including lung cancer, through multiple biological mechanisms involving epigenetic, transcriptional, and post-transcriptional alterations. In this review, we highlight the expression and roles of lncRNAs in NSCLC and discuss their potential clinical applications as diagnostic or prognostic biomarkers, as well as therapeutic targets.

Long-time treatment by low-dose N-acetyl-L-cysteine enhances proinflammatory cytokine expressions in LPS-stimulated macrophages

N-acetyl-L-cysteine is known to act as a reactive oxygen species scavenger and used in clinical applications. Previous reports have shown that high-dose N-acetyl-L-cysteine treatment inhibits the expression of proinflammatory cytokines in activated macrophages. Here, we have found that long-time N-acetyl-L-cysteine treatment at low-concentration increases phosphorylation of extracellular signal-regulated kinase 1/2 and AKT, which are essential for the induction of proinflammatory cytokines including interleukin 1β and interleukin 6 in lipopolysaccharide-stimulated RAW264.7 cells. Furthermore, long-time N-acetyl-L-cysteine treatment decreases expressions of protein phosphatases, catalytic subunit of protein phosphatase-2A and dual specificity phosphatase 1. On the other hand, we have found that short-time N-acetyl-L-cysteine treatment at low dose increases p53 expression, which inhibits expressions of proinflammatory cytokines. These observations suggest that long-time low-dose N-acetyl-L-cysteine treatment increases expressions of proinflammatory cytokines through enhancement of kinase phosphorylation.

Transcriptome profiling of gill tissue in regionally bred and globally farmed rainbow trout strains reveals different strategies for coping with thermal stress

Thermal stress can pose a major challenge to salmonid fish. A 4x44K oligonucleotide microarray approach was used to screen for genetically determined variations of a temperature stress response during acclimation in fish gills, a highly specialized and complex organ responsible for gas and electrolyte exchange as well as excretion. The comparison addressed transcriptional changes in the local breeding strain BORN and imported (TCO) rainbow trout after graded 2-week acclimation to 8 and 23 °C. Besides well-characterized mediators of thermoregulation such as genes encoding cold-inducible RNA-binding protein and heat shock proteins, the present microarray study suggests several new candidate genes commonly regulated in gills of the two trout lines. Having identified the differential expression of thermoregulated genes as duplicated paralogues, they were subsequently validated in a gill cell model. Moreover, the comparison of transcriptome profiles provides evidence for distinctively employed expression patterns. The induction of genes encoding factors of the early innate immunity in BORN trout upon warming contrasts with the increased expression of adaptive immune genes in import trout. Cold acclimation induced genes assigned to the functional categories "cell death" and "ion channel activity" in import trout, but repressed "lipid metabolism." This manuscript provides an overview of the genes of the multifunctional gills in rainbow trout that are mandated after temperature change, suggesting links between the different temperature-dependent pathways and gene networks.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Mechanisms of endometrial progesterone resistance

Throughout the reproductive years, the rise and fall in ovarian hormones elicit in the endometrium waves of cell proliferation, differentiation, recruitment of inflammatory cells, apoptosis, tissue breakdown and regeneration. The activated progesterone receptor, a member of the superfamily of ligand-dependent transcription factors, is the master regulator of this intense tissue remodelling process in the uterus. Its activity is tightly regulated by interaction with cell-specific transcription factors and coregulators as well as by specific posttranslational modifications that respond dynamically to a variety of environmental and inflammatory signals. Endometriosis, a chronic inflammatory disorder, disrupts coordinated progesterone responses throughout the reproductive tract, including in the endometrium. This phenomenon is increasingly referred to as 'progesterone resistance'. Emerging evidence suggests that progesterone resistance in endometriosis is not just a consequence of perturbed progesterone signal transduction caused by chronic inflammation but associated with epigenetic chromatin changes that determine the intrinsic responsiveness of endometrial cells to differentiation cues.

Specific recognition of p53 tetramers by peptides derived from p53 interacting proteins

Oligomerization plays a major role in regulating the activity of many proteins, and in modulating their interactions. p53 is a homotetrameric transcription factor that has a pivotal role in tumor suppression. Its tetramerization domain is contained within its C-terminal domain, which is a site for numerous protein-protein interactions. Those can either depend on or regulate p53 oligomerization. Here we screened an array of peptides derived from proteins known to bind the tetrameric p53 C-terminal domain (p53CTD) and identified ten binding peptides. We quantitatively characterized their binding to p53CTD using fluorescence anisotropy. The peptides bound tetrameric p53CTD with micromolar affinities. Despite the high charge of the binding peptides, electrostatics contributed only mildly to the interactions. NMR studies indicated that the peptides bound p53CTD at defined sites. The most significant chemical shift deviations were observed for the peptides WS100B(81-92), which bound directly to the p53 tetramerization domain, and PKCα(281-295), which stabilized p53CTD in circular dichroism thermal denaturation studies. Using analytical ultracentrifugation, we found that several of the peptides bound preferentially to p53 tetramers. Our results indicate that the protein-protein interactions of p53 are dependent on the oligomerization state of p53. We conclude that peptides may be used to regulate the oligomerization of p53.

A half-site of the p53-binding site on the keratin 14 promoter is specifically activated by p63

Three members of p53 family, p53, p63 and p73, can transactivate their specific target genes through a p53 consensus sequence-binding motif which consists with direct repeats of PuPuPuC(T/A)(T/A)GPyPyPy as a whole-site of p53-binding site. p63, an epidermal stem cells marker, can regulate epidermal development and differentiation, but p53 has no similar biological activity. One isoform of p63, TAp63α, can active an epidermal basal cell marker, keratin 14. However, the p53-binding site does not exist as a whole-site in the K14 promoter region, although it contains three putative p53 half-binding sites at -269 to -1 of the K14 promoter. Two of three putative half-sites of the p53-binding site can be bound by p63α by electrophoresis mobility shift assay and DNA affinity purification assay. Only mutation of the p53 half-binding site at -140 to -131, the TAp63α induced K14 promoter activity can be abolished. This half-site was specifically activated by p63, but not by p53. Once we extend this p53 half-site to a whole p53-binding site in K14 promoter, both p53 and p63 expression vectors can activate its activity. Therefore, we propose that the different length of p53-binding site would determinate the gene regulated by different p53 family proteins.

Cell cycle regulation of human endometrial stromal cells during decidualization

OBJECTIVE

Differentiation of endometrial stromal cells into decidual cells is crucial for optimal endometrial receptivity. Data from our previous microarray study implied that expression of many cell cycle regulators are changed during decidualization and inhibition of DNA methylation in vitro. In this study, we hypothesized that both the classic progestin treatment and DNA methylation inhibition would inhibit stromal cell proliferation and cell cycle transition.

METHODS

The human endometrial stromal cell line (HESC) was treated from 2 days to 18 days with the DNA methylation inhibitor, 5-aza-2'-deoxycytidine (AZA), a mixture of estradiol/progestin/cyclic adenosine monophosphate ([cAMP]; medroxy-progesterone acetate [MPA mix]) or both. Cell growth was measured by cell counting, cell cycle transition and apoptosis were analyzed by flow cytometry, expression of cell cycle regulators were analyzed by quantitative polymerase chain reaction (qPCR) and Western blotting, and change in DNA methylation profiles were detected by methylation-specific PCR.

RESULTS

Both AZA and MPA mix inhibited the proliferation of HESC for at least 7 days. Treatment with MPA mix resulted in an early G0/G1 inhibition followed by G2/M phase inhibition at 18 days. In contrast, AZA treatment inhibited cell cycle progression at the G2/M phase throughout. The protein levels of p21(Cip1)and 14-3-3σ were increased with both AZA and MPA mix treatments without any change in the DNA methylation profiles of the genes.

CONCLUSIONS

Our data imply that the decidualization of HESC is associated with cell cycle arrest at G0/G1 phase initially and G2/M phase at later stages. Our results also suggest that p53 pathway members play a role in the cell cycle regulation of endometrial stromal cells.

Negative regulation of miR-145 by C/EBP-β through the Akt pathway in cancer cells

MicroRNAs are master gene regulators that can also be under the control of transcriptional regulation. We have previously shown that miR-145 is a tumor suppressor capable of silencing c-Myc and the tumor suppressor p53 induces miR-145 by directly binding to the miR-145 promoter, demonstrating the role of miR-145 in p53-mediated c-Myc repression. However, little is known as to why miR-145 is often downregulated in tumors. In this study, we identify CCAAT/enhancer binding protein beta (C/EBP-β) as a negative regulator for miR-145 expression by direct interaction with the putative C/EBP-β binding site in the miR-145 promoter. In the wild-type p53 background, C/EBP-β counteracts the ability of p53 to induce miR-145. Moreover, C/EBP-β is able to suppress miR-145 in the mutant p53 background, suggesting the p53 independent regulation of miR-145. Of interest, both the large isoform (LAP-2) and the small isoform (LIP) of C/EBP-β can exert suppressive function for miR-145. Finally, we further show that, like serum starvation and PI3K inhibitor LY29, the antioxidant resveratrol suppresses pAkt and phosphorylation of C/EBP-β and at the same time, it induces miR-145. Together, these results suggest a miR-145 regulatory system involving the Akt and C/EBP-β, which may contribute to the downregulation of miR-145 in cancer cells.

Increased activation of the PI3K/AKT pathway compromises decidualization of stromal cells from endometriosis

CONTEXT

Endometriosis affects approximately 10% of women in the United States and causes pain and infertility. Decidualization of endometrial stromal cells from women with endometriosis is aberrant.

OBJECTIVE

The objective of this study was to investigate a potential mechanism for the inadequate decidual response in stromal cells from ovarian endometriomas.

DESIGN

Stromal cells of the endometrium from women without endometriosis (HSC) or from ovarian endometriomas (OsisSC) were grown in culture and treated with 10 μm LY294002 or 250 nm MK2206, 100 nm medroxyprogesterone acetate (M), and 0.5 mm dibutyryl cAMP (A) or infection with 100 multiplicity of infection adenoviral constructs containing wild-type Forkhead box O1 or triple-mutant FOXO1. Real-time PCR was used to measure the expression of FOXO1, IGF binding protein-1 (IGFBP1), and prolactin (PRL) mRNA, and Western blot and immunohistochemical staining were used to detect the levels of progesterone receptor (PR), FOXO1, AKT, and p(Ser473)-AKT protein in vitro or in vivo.

RESULTS

Expression of the decidua-specific genes, IGFBP1 and PRL, were significantly lower in OsisSC compared with normal HSC in response to M+A treatment. Basal expression levels of PRA, PRB, and FOXO1 proteins were dramatically lower in OsisSC. Overexpression of triple-mutant FOXO1 increased mRNA levels of IGFBP1 and PRL in OsisSC in the presence of M+A, whereas the overexpression of wild-type FOXO1 had no effect. AKT was highly phosphorylated in OsisSC compared with HSC and inhibition of phosphatidylinositol 3-kinase, with LY294002, increased levels of FOXO1 protein as well as IGFBP1 mRNA in the presence of M+A. Moreover, inhibition of AKT with MK2206, an allosteric AKT inhibitor, dramatically increased the accumulation of nuclear FOXO1 as well as expression of IGFBP1. Finally, immunohistochemical staining demonstrated higher p(Ser473)-AKT and lower FOXO1 levels in endometriosis tissues, compared with normal endometrial tissues.

CONCLUSIONS

In endometriotic stromal cells, overactivation of the phosphatidylinositol 3-kinase/AKT signaling pathway contributes to the reduced expression of the decidua-specific gene, IGFBP1, potentially through reduced levels of nuclear FOXO1.

NADPH oxidase-derived reactive oxygen species mediate decidualization of human endometrial stromal cells in response to cyclic AMP signaling

Differentiation of human endometrial stromal cells into specialized decidual cells is critical for embryo implantation and survival of the conceptus. Initiation of this differentiation process is strictly dependent on elevated cAMP levels, but the signal intermediates that control the expression of decidual marker genes, such as prolactin (PRL) and IGFBP1, remain poorly characterized. Here we show that cAMP-dependent decidualization can be attenuated or enhanced upon treatment of primary cultures with a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor (diphenylen iodonium) or activator (apocynin), respectively. Time-course analysis demonstrated that cAMP enhances endogenous reactive oxygen species production, apparent after 12 h of stimulation, which coincides with a dramatic increase in decidual PRL and IGFBP1 expression. Knockdown of the Rho GTPase RAC1, which disables activation of the NADPH oxidase homologs NADPH oxidase (NOX)-1, NOX-2, and NOX-3, had no effect on PRL or IGFBP1 expression. In contrast, silencing of NOX-4, or its cofactor p22(PHOX), inhibited the expression of both decidual markers. Finally, we show that the NOX-4/p22(PHOX) complex regulates the DNA-binding activity of CCAAT/enhancer binding protein-β, a key regulator of human endometrial stromal cell differentiation. Thus, NOX-4 activation and reactive oxygen species signaling play an integral role in initiating the endometrial decidual response in preparation of pregnancy.

The CCAAT/enhancer binding protein beta is a critical regulator of steroid-induced mitotic expansion of uterine stromal cells during decidualization

During early pregnancy, the concerted actions of the maternal steroid hormones, estrogen and progesterone, promote a unique process known as decidualization, which involves extensive proliferation and differentiation of uterine stromal cells. The molecular pathways underlying this hormonally induced cellular transformation, an essential prerequisite for embryo implantation, remain poorly understood. We previously identified CCAAT/enhancer binding protein beta (C/EBPbeta) as a target of steroid regulation in the uterus. Uteri of mice lacking C/EBPbeta failed to undergo decidualization. In the present study, analyses of C/EBPbeta-null uteri indicated that loss of this factor leads to a block in stromal cell proliferation in response to a decidual stimulation. The mutant stromal cells entered S phase of the cell cycle and completed DNA synthesis but were unable to execute mitosis. Further analysis revealed that C/EBPbeta facilitates the transition of these cells into mitosis by binding directly to the cyclin B2 promoter to regulate its expression. The expression of cdc25C, a phosphatase that maintains the active state of the cyclin B-cyclin-dependent kinase complex during mitosis, is also strongly suppressed in C/EBPbeta-null stromal cells. Furthermore, the expression of the tumor suppressor p53 and the cell cycle inhibitors p21 and p27 was markedly elevated in C/EBPbeta-null stromal cells before the mitotic phase, uncovering additional mechanisms by which C/EBPbeta controls G2 to M transition. Collectively, these results revealed that C/EBPbeta mediates the effects of steroid hormones during decidualization by modulating the expression of multiple key cell cycle regulatory factors that control the G2 to M transition of the proliferating uterine stromal cells.

Regulation of p53--insights into a complex process

The p53 protein is one of the most important tumor suppressor proteins. Normally, the p53 protein is in a latent state. However, when its activity is required, e.g. upon DNA damage, nucleotide depletion or hypoxia, p53 becomes rapidly activated and initiates transcription of pro-apoptotic and cell cycle arrest-inducing target genes. The activity of p53 is regulated both by protein abundance and by post-translational modifications of pre-existing p53 molecules. In the 30 years of p53 research, a plethora of modifications and interaction partners that modulate p53's abundance and activity have been identified and new ones are continuously discovered. This review will summarize our current knowledge on the regulation of p53 abundance and activity.

Regulation of SIV mac 239 basal long terminal repeat activity and viral replication in macrophages: functional roles of two CCAAT/enhancer-binding protein beta sites in activation and interferon beta-mediated suppression

CCAAT/enhancer-binding protein (C/EBP) beta and C/EBP sites in the HIV-1 long terminal repeat (LTR) are crucial for HIV-1 replication in monocyte/macrophages and for the ability of interferon beta (IFN beta) to inhibit ongoing active HIV replication in these cells. This IFN beta-mediated down-regulation involves induction of the truncated, dominant-negative isoform of C/EBP beta referred to as liver-enriched transcriptional inhibitory protein (LIP). Although binding of the C/EBP beta isoform to C/EBP sites in the simian immunodeficiency virus (SIV) LTR has previously been examined, the importance of these sites in core promoter-mediated transcription, virus replication, IFN beta-mediated regulation, and the relative binding of the two isoforms (C/EBP beta and LIP) has not been investigated. Here, we specifically examine two C/EBP sites, JC1 (-100 bp) and DS1 (+134 bp), located within the minimal region of the SIV LTR, required for core promoter-mediated transcription and virus replication in macrophages. Our studies revealed that the JC1 but not DS1 C/EBP site is important for basal level transcription, whereas the DS1 C/EBP site is imperative for productive virus replication in primary macrophages. In contrast, either JC1 or DS1 C/EBP site is sufficient to mediate IFN beta-induced down-regulation of SIV LTR activity and virus replication in these cells. We also characterized the differential binding properties of C/EBP beta and LIP to the JC1 and DS1 sites. In conjunction with previous studies from our laboratory, we demonstrate the importance of these sites in virus gene expression, and we propose a model for their role in establishing latency and persistence in macrophages in the brain.

Molecular and cellular mechanisms for differentiation and regeneration of the uterine endometrium

The human endometrium undergoes cyclical changes including proliferation, differentiation, tissue breakdown, and shedding (menstruation) throughout a woman's reproductive life. The postovulatory rise in ovarian progesterone induces profound remodeling and differentiation of the estradiol-primed endometrium. This change, termed decidualization, is crucial for embryo implantation and maintenance of the pregnancy. To date, activation and crosstalk of cAMP- and progesterone-mediated signaling pathways have emerged as key cellular events to drive integrated changes at both the transcriptome and the proteome levels. This results in the induction and maintenance of the decidual phenotype and function. Our recent series of studies highlights the critical role of SRC kinase activation (v-src sarcoma viral oncogene homolog) and STAT5 (signal transducer and activator of transcription 5) phosphorylation in decidualization. After separation of the functional layer of the differentiated endometrium that follows progesterone withdrawal, i.e., menstruation, the basal layer of the endometrium, under the influence of estradiol, regrows and initiates a unique form of angiogenesis and regenerates a new functional layer. The molecular and cellular mechanisms for this process remain elusive, mainly because of difficulties in reproducing menstrual tissue breakdown, shedding, and subsequent tissue regeneration in vitro. We have recently developed a "humanized" mouse model in which a functional human endometrium is reconstituted. It may be used as an in vivo experimental tool for the study of endometrial angiogenesis and regeneration. This model may also be used to identify and test new therapeutic strategies for endometriosis, endometrial cancer, implantation failure, and infertility related to endometrial dysfunction.

Steroidogenic enzyme and key decidualization marker dysregulation in endometrial stromal cells from women with versus without endometriosis

Identification of mechanisms underlying endometriosis pathogenesis will facilitate understanding and treatment of infertility and pain associated with this disorder. Herein, we investigated the expression of steroidogenic pathway enzymes and key decidualization biomarkers in endometrial tissue and in eutopic endometrial stromal fibroblasts (hESFs) from women with vs. those without endometriosis, and subsequently treated in vitro with 8-bromo-cAMP (8-Br-cAMP) or progesterone (P4). Real-time quantitative PCR, immunohistochemistry, ELISA, and radiometric aromatase activity assay were used. The results demonstrate significantly increased (14.5-fold; P=0.037) expression of aromatase in eutopic endometrium of women with disease. In 8-Br-cAMP-treated hESF from eutopic endometrium of women with endometriosis, the balance in estradiol (E2) and P4 biosynthetic and metabolizing enzymes is disturbed (decreased HSD3B1 and HSD17B2, and increased HSD17B1 and aromatase), with the equilibrium being shifted towards an E2-enriched milieu. However, hESF from the same group of women treated with P4 did not demonstrate such responsiveness. Lower expression of IGFBP1 and prolactin mRNA and protein was observed in hESF from women with vs. those without endometriosis in response to 8-Br-cAMP, but not P4, suggesting a blunted response of these decidual biomarkers to activation of the PKA pathway in eutopic endometrium in women with disease. The dichotomy of 8-Br-cAMP regulation of select steroidogenic enzymes leading to an enriched E2 milieu within the endometrium and a blunted response of decidual biomarkers to this decidualizing agent of hESF from women with endometriosis suggests resistance to full decidualization of the stromal fibroblasts and mechanisms underlying implantation failure and the pathophysiology of this disorder.

C/EBPbeta represses p53 to promote cell survival downstream of DNA damage independent of oncogenic Ras and p19(Arf)

CCAAT/enhancer-binding protein-beta (C/EBPbeta) is a mediator of cell survival and tumorigenesis. When C/EBPbeta(-/-) mice are treated with carcinogens that produce oncogenic Ras mutations in keratinocytes, they respond with abnormally elevated keratinocyte apoptosis and a block in skin tumorigenesis. Although this aberrant carcinogen-induced apoptosis results from abnormal upregulation of p53, it is not known whether upregulated p53 results from oncogenic Ras and its ability to induce p19(Arf) and/or activate DNA-damage response pathways or from direct carcinogen-induced DNA damage. We report that p19(Arf) is dramatically elevated in C/EBPbeta(-/-) epidermis and that C/EBPbeta represses a p19(Arf) promoter reporter. To determine whether p19(Arf) is responsible for the proapoptotic phenotype in C/EBPbeta(-/-) mice, C/EBPbeta(-/-);p19(Arf-/-) mice were generated. C/EBPbeta(-/-);p19(Arf-/-) mice responded to carcinogen treatment with increased p53 and apoptosis, indicating p19(Arf) is not essential. To ascertain whether oncogenic Ras activation induces aberrant p53 and apoptosis in C/EBPbeta(-/-) epidermis, we generated K14-ER:Ras;C/EBPbeta(-/-) mice. Oncogenic Ras activation induced by 4-hydroxytamoxifen did not produce increased p53 or apoptosis. Finally, when C/EBPbeta(-/-) mice were treated with differing types of DNA-damaging agents, including alkylating chemotherapeutic agents, they displayed aberrant levels of p53 and apoptosis. These results indicate that C/EBPbeta represses p53 to promote cell survival downstream of DNA damage and suggest that inhibition of C/EBPbeta may be a target for cancer cotherapy to increase the efficacy of alkylating chemotherapeutic agents.

The tumour suppressor gene p53 modulates the severity of antigen-induced arthritis and the systemic immune response

p53 is a transcription factor with a well-described role in the induction of apoptosis and cell cycle arrest as part of a protective response to a variety of stressful stimuli. Expansion of inflamed tissue in rheumatoid arthritis has been related to the loss of functioning p53, and the severity of collagen-induced arthritis is increased in p53-/- mice. Our objective was to assess the role of p53 in a model of adaptive immunity, antigen-induced arthritis (AIA). AIA was induced in p53-/- and wild-type mice by priming with methylated bovine serum albumin followed by intra-articular challenge. Severity of arthritis was assessed using a standardized scoring system and synovial apoptosis was detected by TdT-mediated biotin-dUTP nick-end labelling. Splenocyte proliferation was measured by [H(3)] incorporation and interferon (IFN)-gamma release. Splenocyte viability was assessed using Titreglow. Splenic T cell activation status was assessed by flow cytometry. Serum cytokines were measured using enzyme-linked immunosorbent assay. Increased severity of AIA in p53-/- mice was associated with decreased synovial apoptosis and with increased delayed-type hypersensitivity response, increased mitogen and antigen-induced splenocyte proliferation and increased IFN-gamma release in p53-/- mice compared with wild-type mice. Antigen-specific immunoglobulin responses were equivalent in both groups. Splenocyte viability was increased in p53-/- mice but T cell apoptosis was equivalent. T cell activation markers were increased in p53-/- mice compared with wild-type mice. Lipopolysaccharide-induced tumour necrosis factor release was increased in p53-/- mice with a trend to increased interleukin-6 in p53-/- mice compared with littermates. p53 is involved in the modulation of adaptive and innate immune responses relevant to arthritis models and is also involved in the modulation of severity of AIA by both cell-cycle dependent and cell-cycle-independent mechanisms.

Loss of c/EBP-beta activity promotes the adaptive to apoptotic switch in hypoxic cortical neurons

Understanding the mechanisms governing the switch between hypoxia-induced adaptive and pathological transcription may reveal novel therapeutic targets for stroke. Using an in vitro hypoxia model that temporally separates these divergent responses, we found apoptotic signaling was preceded by a decline in c/EBP-beta activity and was associated with markers of ER-stress including transient eIF2alpha phosphorylation, and the delayed induction of the bZIP proteins ATF4 and CHOP-10. Pretreatment with the eIF2alpha phosphatase inhibitor salubrinal blocked the activation of caspase-3, indicating that ER-related stress responses are integral to this transition. Delivery of either full-length, or a transcriptionally inactive form of c/EBP-beta protected cultures from hypoxic challenge, in part by inducing levels of the anti-apoptotic protein Bcl-2. These data indicate that the pathologic response in cortical neurons induced by hypoxia involves both the loss of c/EBP-beta-mediated survival signals and activation of pro-death pathways originating from the endoplasmic reticulum.

Inhibition of CCAAT/enhancer binding protein family DNA binding in mouse epidermis prevents and regresses papillomas

The CCAAT/enhancer binding proteins (C/EBP) are a family of B-ZIP DNA binding proteins that act as transcription factors to regulate growth and differentiation of many cell types, including keratinocytes. To examine the consequences of inhibiting the C/EBP family of transcription factors in skin, we generated transgenic mice that use the tetracycline system to conditionally express A-C/EBP, a dominant negative that inhibits the DNA binding of C/EBP family members. We expressed A-C/EBP in the basal layer of the skin epidermis during a two-step skin carcinogenesis protocol. A-C/EBP expression caused hyperplasia of the basal epidermis and increased apoptosis in the suprabasal epidermis. The mice developed fewer papillomas and had systemic hair loss. A-C/EBP expression caused C/EBPbeta protein to disappear whereas C/EBPalpha, p53, Bax, and caspase-3 protein levels were dramatically up-regulated in the suprabasal layer. Primary keratinocytes recapitulate the A-C/EBP induction of cell growth and increase in p53 protein. A-C/EBP expression after papilloma development caused the papillomas to regress with an associated increase in apoptosis and up-regulation of p53 protein. Furthermore, A-C/EBP-expressing mice heterozygous for p53 were more susceptible to papilloma formation, suggesting that the suppression of papilloma formation has a p53-dependent mechanism. These results implicate DNA binding of C/EBP family members as a potential molecular therapeutic target.