Guanylate Binding Protein-1 Research Articles

Dueling nucleosides: cross-regulation of extracellular adenosine by guanosine. Focus on “Extracellular guanosine regulates extracellular adenosine levels”

<i>Dueling nucleosides: cross-regulation of extracellular adenosine by guanosine</i>. Focus on “Extracellular guanosine regulates extracellular adenosine levels”

Knockout of the 15 kDa Selenoprotein Protects against Chemically-Induced Aberrant Crypt Formation in Mice

Evidence suggests that selenium has cancer preventive properties that are largely mediated through selenoproteins. Our previous observations demonstrated that targeted down-regulation of the 15 kDa selenoprotein (Sep15) in murine colon cancer cells resulted in the reversal of the cancer phenotype. The present study investigated the effect of Sep15 knockout in mice using a chemically-induced colon cancer model. Homozygous Sep15 knockout mice, and wild type littermate controls were given four weekly subcutaneous injections of azoxymethane (10 mg/kg). Sep15 knockout mice developed significantly (p<0.001) fewer aberrant crypt foci than controls demonstrating that loss of Sep15 protects against aberrant crypt foci formation. Dietary selenium above adequate levels did not significantly affect aberrant crypt foci formation in Sep15 knockout mice. To investigate molecular targets affected by loss of Sep15, gene expression patterns in colonic mucosal cells of knockout and wild type mice were examined using microarray analysis. Subsequent analyses verified that guanylate binding protein-1 (GBP-1) mRNA and protein expression were strongly upregulated in Sep15 knockout mice. GBP-1, which is expressed in response to interferon-γ, is considered to be an activation marker during inflammatory diseases, and up-regulation of GBP-1 in humans has been associated with a highly significant, increased five-year survival rate in colorectal cancer patients. In agreement with these studies, we observed a higher level of interferon-γ in plasma of Sep15 knockout mice. Overall, our results demonstrate for the first time, that Sep15 knockout mice are protected against chemically-induced aberrant crypt foci formation and that Sep15 appears to have oncogenic properties in colon carcinogenesis in vivo.

Guanylate-binding protein 1 expression from embryonal endothelial progenitor cells reduces blood vessel density and cellular apoptosis in an axially vascularised tissue-engineered construct

BackgroundGuanylate binding protein-1 (GBP-1) is a large GTPase which is actively secreted by endothelial cells. It is a marker and intracellular inhibitor of endothelial cell proliferation, migration, and invasion. We previously demonstrated that stable expression of GBP-1 in murine endothelial progenitor cells (EPC) induces their premature differentiation and decreases their migration capacity in vitro and in vivo. The goal of the present study was to assess the antiangiogenic capacity of EPC expressing GBP-1 (GBP-1-EPC) and their impact on blood vessel formation in an axially vascularized 3-D bioartificial construct in vivo.ResultsFunctional in vitro testing demonstrated a significant increase in VEGF secretion by GBP-1-EPC after induction of cell differentiation. Undifferentiated GBP-1-EPC, however, did not secrete increased levels of VEGF compared to undifferentiated control EPC expressing an empty vector (EV-EPC). In our In vivo experiments, we generated axially vascularized tissue-engineered 3-D constructs. The new vascular network arises from an arterio-venous loop (AVL) embedded in a fibrin matrix inside a separation chamber. Total surface area of the construct as calculated from cross sections was larger after transplantation of GBP-1-EPC compared to control EV-EPC. This indicated reduced formation of fibrovascular tissue and less resorption of fibrin matrix compared to constructs containing EV-EPC. Most notably, the ratio of blood vessel surface area over total construct surface area in construct cross sections was significantly reduced in the presence of GBP-1-EPC. This indicates a significant reduction of blood vessel density and thereby inhibition of blood vessel formation from the AVL constructs caused by GBP-1. In addition, GBP-1 expressed from EPC significantly reduced cell apoptosis compared to GBP-1-negative controls.ConclusionTransgenic EPC expressing the proinflammatory antiangiogenic GTPase GBP-1 can reduce blood vessel density and inhibit apoptosis in a developing bioartificial vascular network and may become a new powerful tool to manipulate angiogenetic processes in tissue engineering and other pathological conditions such as tumour angiogenesis.

Molecular Characterization of EGFR and EGFRvIII Signaling Networks in Human Glioblastoma Tumor Xenografts

Glioblastoma multiforme (GBM) is a malignant primary brain tumor with a mean survival of 15 months with the current standard of care. Genetic profiling efforts have identified the amplification, overexpression, and mutation of the wild-type (wt) epidermal growth factor receptor tyrosine kinase (EGFR) in ≈ 50% of GBM patients. The genetic aberration of wtEGFR is frequently accompanied by the overexpression of a mutant EGFR known as EGFR variant III (EGFRvIII, de2-7EGFR, ΔEGFR), which is expressed in 30% of GBM tumors. The molecular mechanisms of tumorigenesis driven by EGFRvIII overexpression in human tumors have not been fully elucidated. To identify specific therapeutic targets for EGFRvIII driven tumors, it is important to gather a broad understanding of EGFRvIII specific signaling. Here, we have characterized signaling through the quantitative analysis of protein expression and tyrosine phosphorylation across a panel of glioblastoma tumor xenografts established from patient surgical specimens expressing wtEGFR or overexpressing wtEGFR (wtEGFR+) or EGFRvIII (EGFRvIII+). S100A10 (p11), major vault protein, guanylate-binding protein 1(GBP1), and carbonic anhydrase III (CAIII) were identified to have significantly increased expression in EGFRvIII expressing xenograft tumors relative to wtEGFR xenograft tumors. Increased expression of these four individual proteins was found to be correlated with poor survival in patients with GBM; the combination of these four proteins represents a prognostic signature for poor survival in gliomas. Integration of protein expression and phosphorylation data has uncovered significant heterogeneity among the various tumors and has highlighted several novel pathways, related to EGFR trafficking, activated in glioblastoma. The pathways and proteins identified in these tumor xenografts represent potential therapeutic targets for this disease.

Guanylate-binding protein 1 participates in cellular antiviral response to dengue virus

BackgroundDengue virus (DENV), the causative agent of human Dengue hemorrhagic fever, is a mosquito-borne virus found in tropical and sub-tropical regions around the world. Vaccines against DENV are currently unavailable. Guanylate-binding protein 1 (GBP1) is one of the Interferon (IFN) stimulated genes (ISGs) and has been shown important for host immune defense against various pathogens. However, the role of GBP1 during DENV infection remains unclarified. In this study, we evaluated the relevance of GBP1 to DENV infection in in vitro model.FindingsQuantitative RT-PCR (qRT-PCR) and Western blot showed that the expression of mouse Gbp1 was dramatically upregulated in DENV-infected RAW264.7 cells. The intracellular DENV loads were significantly higher in Gbp1 silenced cells compared with controls. The expression levels of selective anti-viral cytokines were decreased in Gbp1 siRNA treated cells, while the transcription factor activity of NF-κB was impaired upon GBP1 silencing during infection.ConclusionsOur data suggested that GBP1 plays an antiviral role during DENV infection.

GBP-1 acts as a tumor suppressor in colorectal cancer cells

The human guanylate-binding protein 1 (GBP-1) is among the proteins the most highly induced by interferon-γ (IFN-γ) in every cell type investigated as yet. In vivo, GBP-1 expression is associated with the presence of inflammation and has been observed in autoimmune diseases, inflammatory bowel diseases (IBD) and cancer. In colorectal carcinoma (CRC), the expression of GBP-1 in the desmoplastic stroma has been previously reported to correlate with the presence of an IFN-γ-dominated T helper type 1 (Th1) micromilieu and with an increased cancer-related 5-year survival. In the present study, the analysis of GBP-1 expression in a series of 185 CRCs by immunohistochemistry confirmed that GBP-1 is expressed in stroma cells of CRCs and revealed a significantly less frequent expression in tumor cells, which was contradictory with the broad inducibility of GBP-1. Furthermore, three of six CRC cell lines treated with IFN-γ were unable to express GBP-1 indicating that colorectal tumor cells tend to downregulate GBP-1. On the contrary, non-transformed colon epithelial cells strongly expressed GBP-1 in vitro in presence of IFN-γ and in vivo in inflammatory bowel diseases. Reconstitution of GBP-1 expression in a negative CRC cell line inhibited cell proliferation, migration and invasion. Using RNA interference, we showed that GBP-1 mediates the antitumorigenic effects of IFN-γ in CRC cells. In addition, GBP-1 was able to inhibit tumor growth in vivo. Altogether, these results suggested that GBP-1 acts directly as a tumor suppressor in CRC and the loss of GBP-1 expression might indicate tumor evasion from the IFN-γ-dominated Th1 immune response.

Insight into temperature dependence of GTPase activity in human guanylate binding protein-1.

Interferon-γ induced human guanylate binding protein-1(hGBP1) belongs to a family of dynamin related large GTPases. Unlike all other GTPases, hGBP1 hydrolyzes GTP to a mixture of GDP and GMP with GMP being the major product at 37°C but GDP became significant when the hydrolysis reaction was carried out at 15°C. The hydrolysis reaction in hGBP1 is believed to involve with a number of catalytic steps. To investigate the effect of temperature in the product formation and on the different catalytic complexes of hGBP1, we carried out temperature dependent GTPase assays, mutational analysis, chemical and thermal denaturation studies. The Arrhenius plot for both GDP and GMP interestingly showed nonlinear behaviour, suggesting that the product formation from the GTP-bound enzyme complex is associated with at least more than one step. The negative activation energy for GDP formation and GTPase assay with external GDP together indicate that GDP formation occurs through the reversible dissociation of GDP-bound enzyme dimer to monomer, which further reversibly dissociates to give the product. Denaturation studies of different catalytic complexes show that unlike other complexes the free energy of GDP-bound hGBP1 decreases significantly at lower temperature. GDP formation is found to be dependent on the free energy of the GDP-bound enzyme complex. The decrease in the free energy of this complex at low temperature compared to at high is the reason for higher GDP formation at low temperature. Thermal denaturation studies also suggest that the difference in the free energy of the GTP-bound enzyme dimer compared to its monomer plays a crucial role in the product formation; higher stability favours GMP but lower favours GDP. Thus, this study provides the first thermodynamic insight into the effect of temperature in the product formation of hGBP1.

IFN-γ and TNF-α-induced GBP-1 inhibits epithelial cell proliferation through suppression of β-catenin/TCF signaling.

Proinflammatory cytokines induce Guanylate Binding Protein 1 (GBP-1) protein expression in intestinal epithelial tissues. GBP-1 has been described as influencing a number of cellular processes important for epithelial homeostasis, including cell proliferation. However, many questions remain as to the role of GBP-1 in intestinal mucosal homeostasis. We therefore sought to investigate the function of proinflammatory cytokine induced GBP-1 during intestinal epithelial cell proliferation. Through the use of complementary GBP-1 overexpression and siRNA-mediated knockdown studies, we now show that GBP-1 acts to inhibit pro-mitogenic β-catenin/T cell factor (TCF) signaling. Interestingly, proinflammatory cytokine induced GBP-1 was found to be a potent suppressor of β-catenin protein levels and β-catenin serine 552 phosphorylation. Neither GSK3-β nor proteasomal inhibition alleviated GBP-1-mediated suppression of cell proliferation or β- catenin/TCF signaling, indicating a non-canonical mechanism of β-catenin inhibition. Together, these data show that cytokine-induced GBP-1 retards cell proliferation by forming a negative feedback loop that suppresses β-catenin/TCF signaling.

Class III β‐tubulin and the cytoskeletal gateway for drug resistance in ovarian cancer

The Class III β-tubulin isotype (βIII-tubulin) is a predictive biomarker in ovarian cancer and other solid tumor malignancies. We discovered that βIII-tubulin function is linked to two GTPases: guanylate-binding protein 1 (GBP1), which activates its function, and GNAI1, which inhibits it. This finding was demonstrated in a panel of ovarian cancer cells resistant to several chemotherapeutic agents. Using a protein microarray, we identified PIM1 as the downstream partner of GBP1, recruited into the cytoskeleton under hypoxic conditions. The clinical value of these observations was tested by performing an archive study of 98 ovarian cancer patients, which demonstrated that the βIII-tubulin -/PIM1- cohort responded to treatment, exhibiting long overall survival (OS), while βIII-tubulin +/PIM+ patients experienced poor outcomes and OS times similar to patients receiving palliation alone. βIII-tubulin expression is commonly believed responsible for paclitaxel resistance due to its enhancement of the dynamic instability of microtubules, which counteracts the activity of taxanes. In contrast, our research reveals that βIII-tubulin behaves as a gateway for prosurvival signals, such as PIM1, to move into the cytoskeleton. When cells are exposed to microenvironmental stressors, they activate this pathway by telling the cytoskeleton to incorporate PIM1 through GBP1 and βIII-tubulin, which ultimately leads to drug resistance. This discovery reveals that βIII-tubulin does not act alone but requires partners to play its role. The discovery of such protein:protein interactions underlying this prosurvival cascade makes feasible the development of therapeutic approaches using novel compounds that are capable of inhibiting the transmission of prosurvival signals into the cytoskeleton.

Guanylate binding protein 1 is a novel effector of EGFR-driven invasion in glioblastoma

Although GBP1 (guanylate binding protein 1) was among the first interferon-inducible proteins identified, its function is still largely unknown. Epidermal growth factor receptor (EGFR) activation by amplification or mutation is one of the most frequent genetic lesions in a variety of human tumors. These include glioblastoma multiforme (GBM), which is characterized by independent but interrelated features of extensive invasion into normal brain parenchyma, rapid growth, necrosis, and angiogenesis. In this study, we show that EGFR activation promoted GBP1 expression in GBM cell lines through a signaling pathway involving Src and p38 mitogen-activated protein kinase. Moreover, we identified YY1 (Yin Yang 1) as the downstream transcriptional regulator regulating EGFR-driven GBP1 expression. GBP1 was required for EGFR-mediated MMP1 (matrix metalloproteinase 1) expression and glioma cell invasion in vitro. Although deregulation of GBP1 expression did not affect glioma cell proliferation, overexpression of GBP1 enhanced glioma cell invasion through MMP1 induction, which required its C-terminal helical domain and was independent of its GTPase activity. Reducing GBP1 levels by RNA interference in invasive GBM cells also markedly inhibited their ability to infiltrate the brain parenchyma of mice. GBP1 expression was high and positively correlated with EGFR expression in human GBM tumors and cell lines, particularly those of the neural subtype. Together, these findings establish GBP1 as a previously unknown link between EGFR activity and MMP1 expression and nominate it as a novel potential therapeutic target for inhibiting GBM invasion.

GBP1 (guanylate binding protein 1, interferon-inducible, 67kDa)

Review on GBP1 (guanylate binding protein 1, interferon-inducible, 67kDa), with data on DNA, on the protein encoded, and where the gene is implicated.

Identification of Guanylate-Binding Protein 1 as a Potential Oral Cancer Marker Involved in Cell Invasion Using Omics-Based Analysis

Oral cavity squamous cell carcinoma (OSCC) is a devastating disease that accounts for 3% of all cancer cases diagnosed annually. OSCC is usually diagnosed at advanced clinical stages, resulting in poor outcomes. To identify effective biomarkers for improved OSCC diagnosis and/or management, we simultaneously analyzed the OSCC cell secretome and tissue transcriptome. Among the 19 candidates isolated, guanylate-binding protein 1 (GBP1) was selected for further validation using serum samples from OSCC patients and healthy controls. Notably, the serum level of GBP1 was higher in OSCC patients, compared to that in healthy controls. Immunohistochemical analysis further revealed GBP1 overexpression in OSCC tissues, compared with adjacent noncancerous epithelia. Importantly, the higher GBP1 level in OSCC tissue was associated with higher overall pathological stage, positive perineural invasion, and poorer prognosis. Moreover, GBP1 modulated the migration and invasion of OSCC cells in vitro. Our results collectively indicate that integrated analysis of the cancer secretome and transcriptome is a feasible strategy for the efficient identification of novel OSCC markers.

Role of guanylate binding protein-1 in vascular defects associated with chronic inflammatory diseases

Rheumatic autoimmune disorders are characterized by a sustained pro-inflammatory microenvironment associated with impaired function of endothelial progenitor cells (EPC) and concomitant vascular defects. Guanylate binding protein-1 (GBP-1) is a marker and intracellular regulator of the inhibition of proliferation, migration and invasion of endothelial cells induced by several pro-inflammatory cytokines. In addition, GBP-1 is actively secreted by endothelial cells. In this study, significantly increased levels of GBP-1 were detected in the sera of patients with chronic inflammatory disorders. Accordingly we investigated the function of GBP-1 in EPC. Interestingly, stable expression of GBP-1 in T17b EPC induced premature differentiation of these cells, as indicated by a robust up-regulation of both Flk-1 and von Willebrand factor expression. In addition, GBP-1 inhibited the proliferation and migration of EPC in vitro. We confirmed that GBP-1 inhibited vessel-directed migration of EPC at the tissue level using the rat arterio-venous loop model as a novel quantitative in vivo migration assay. Overall, our findings indicate that GBP-1 contributes to vascular dysfunction in chronic inflammatory diseases by inhibiting EPC angiogenic activity via the induction of premature EPC differentiation.

Abstract 1193: Guanylate binding protein-1, a novel oncogenic gene in glioblastoma

Abstract Glioblastoma multiforme (GBM) is the most common and deadly primary malignant brain tumor in adults. The most frequent genetic lesion associated with GBM, found at 40-60% frequency, is amplification and mutation of the EGFR gene. Here we report that guanylate binding protein-1 (GBP1), an immune response large GTPase, is involved in EGFR-mediated glioblatoma invasion through the modulation of matrix metallopeptidase-1 (MMP1) expression and show that GBP1 is upregulated in human GBM tumors relative to normal brain tissues, especially in EGFRvIII-positive samples. We further show that EGFRvIII promotes GBP1 expression at the transcriptional level through stimulation of the p38 MAPK signaling pathway and targeting GBP1 by lentivirus shRNA transduction significantly reduces EGFRvIII-mediated tumorigenicity of orthotopic xenografts in the mouse. Reciprocally, overexpression of GBP1 alone in glioma cells was sufficient to enhance glioma tumorigenesis by increasing cell proliferation, angiogenesis and decreasing cell apoptosis. Taken together, these results reveal that GBP1 is a novel oncogenic gene downstream of EGFRvIII signaling and suggest that GBP1 may serve as a promising therapeutic target for the treatment of GBM patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1193. doi:10.1158/1538-7445.AM2011-1193

Abstract 780: Immune escape in colorectal carcinoma: role of the IFN-γ pathway

Abstract The presence of a Th1 adaptive immune response in colorectal carcinoma (CRC) has been associated with improved clinical outcome and survival of patients. The Th1 adaptive immune response is mediated by IFN-γ, a known anti-proliferative, pro-apoptotic and pro-immunogenic cytokine. We have previously identified the guanylate-binding protein 1 (GBP-1), one of the proteins the most highly induced by IFN-γ, as a sensitive marker for the detection of this immune response in CRC in vivo. In a tissue microarray study with 388 CRC tumors, 30% showed GBP-1 expression. Interestingly, in these tumors the expression of GBP-1 was only induced in the cells of the desmoplastic stroma and not observed in adjacent tumor cells. This suggested that CRC tumor cells might undergo an immune escape from the Th1 adaptive immune response, characterized by the loss of IFN-γ responsiveness. Therefore, we investigated the responsiveness to IFN-γ in sixth different CRC cell lines and in normal colon epithelial cells. After treatment with IFN-γ, three of the sixth CRC cell lines (DLD-1, SW480 and HCT116) failed to express GBP-1 as well as other IFN-induced proteins such as caspase-1 and MxA. On the contrary, a robust GBP-1 induction was present in normal colon epithelial cells, in T84, WiDr and HT29 cells. We then investigated whether the loss of expression of IFN-γ target genes was associated with phenotypic changes in CRC cells. In fact, we found that DLD-1, HCT116 and SW480 were resistant to IFN-γ-induced apoptosis. Furthermore, the loss of IFN-γ responsiveness correlated in SW480 and HCT116 with the absence of expression of the IFN-γ receptor alpha chain (IFNγRα). Tumor xenotransplant experiments using DLD-1 cells with reconstituted GBP-1 expression resulted in significantly reduced tumor growth as compared to xentotransplants with control vector transfected DLD-1 cells. This indicated that GBP-1 expression may mediate the anti-tumorigenic effects of the Th1 response. Overall, these data suggested that loss of IFN-γ responsiveness may be a common event in CRC and may protect tumor cells against the anti-tumorigenic (e.g. pro-apoptotic) effects of IFN-γ. The presence of an immune escape from the Th1 adaptive immune response may have important repercussions for prognosis and patients recruitment for immune-based therapy in CRC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 780. doi:10.1158/1538-7445.AM2011-780

Abstract 1868: Sep15 knockout in mice provides protection against chemically-induced aberrant crypt formation

Abstract The essential nutrient selenium appears to have cancer preventive properties that are partly mediated through selenoproteins. This study investigated the role of the 15 kDa selenoprotein (Sep15) in cancer by examining Sep15 knockout in mice. Weanling homozygous Sep15 knockout, heterozygote and wild type littermate controls (N=12/genotype) were given four weekly subcutaneous injections of the known colon carcinogen azoxymethane (10 mg/kg). Sep15 knockout mice developed significantly (p&amp;lt;0.001) fewer aberrant crypt foci (ACF) than controls. Dietary selenium (0, 0.1 or 2.0 μg selenium/g diet) did not significantly affect ACF formation in Sep15 knockout mice. To investigate molecular targets affected by Sep15 knockout, gene expression patterns in colonic mucosal cells of knockout and wild type mice were compared with microarrays and Ingenuity Pathway Analysis. Quantitative PCR and western blot analysis revealed guanylate binding protein-1 (GBP1) mRNA and protein expression to be strongly upregulated in Sep15 knockout mice. Furthermore, serum analysis indicated significant differences in cytokine expression in Sep15 knockout mice. Our results suggest that Sep15 knockout mice are protected against chemically-induced ACF formation possibly through alterations in inflammatory pathways. Funded by NCI Intramural support, the Cancer Prevention Fellowship Program, NIH grants and the Division of Cancer Prevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1868. doi:10.1158/1538-7445.AM2011-1868

Sep15 knockout in mice provides protection against chemically‐induced aberrant crypt formation

The essential nutrient selenium appears to have cancer preventive properties that are partly mediated through selenoproteins. This study investigated the role of the 15 kDa selenoprotein (Sep15) in cancer by examining Sep15 knockout (k.o.) in mice. Weanling homozygous Sep15 k.o., heterozygote and wild type littermate controls (N=12/genotype) were given four weekly subcutaneous injections of the colon carcinogen azoxymethane (10 mg/kg). Sep15 k.o. mice developed significantly (p<0.001) fewer aberrant crypt foci (ACF) than controls. Dietary selenium (0, 0.1 or 2.0 ug selenium/g diet) did not significantly affect ACF formation in Sep15 k.o. mice. To investigate molecular targets affected by Sep15 k.o., gene expression patterns in colonic mucosal cells of k.o. and wild type mice were compared with microarrays and Ingenuity Pathway Analysis. Quantitative PCR and western blot analysis revealed guanylate binding protein-1 (GBP1) mRNA and protein expression to be strongly upregulated in Sep15 k.o. mice. Furthermore, serum analysis indicated significant differences in cytokine expression in Sep15 k.o. mice. Our results suggest that Sep15 k.o. mice are protected against chemically-induced ACF formation possibly through alterations in inflammatory pathways. Funded by NCI Intramural support, the Cancer Prevention Fellowship Program, NIH grants and the Division of Cancer Prevention.

Increased expression of guanylate binding protein‐1 in lesional skin of patients with cutaneous lupus erythematosus

The large GTPase human guanylate binding protein-1 (GBP-1) is a key mediator of angiostatic effects of inflammation and is induced by interferon (IFN)-α and IFN-γ in endothelial cells (ECs). The aim of this study was to investigate whether GBP-1 is a marker of skin lesions in patients with cutaneous lupus erythematosus (CLE). Western blotting revealed that GBP-1 was in vitro induced by IFN-α and -γ in primary keratinocytes obtained from healthy controls. Moreover, we found that this protein was expressed by keratinocytes and ECs in primary and ultraviolet (UV)-induced skin lesions from patients with various subtypes of CLE, when compared to non-lesional skin. No GBP-1 expression was noted in skin biopsy specimens 24 or 72 h after UV irradiation prior to lesion formation in patients with CLE or in healthy control specimens with or without UV irradiation. Initial findings suggest that GBP-1 is not expressed in other skin diseases with different inflammatory aetiology, such as atopic dermatitis. We conclude that GBP-1 expression is closely associated with skin lesions in patients with CLE, suggesting a contribution of GBP-1 in the pathogenesis of this disease.

Commensal Escherichia coli Reduces Epithelial Apoptosis through IFN-αA–Mediated Induction of Guanylate Binding Protein-1 in Human and Murine Models of Developing Intestine

Appropriate microbial colonization protects the developing intestine by promoting epithelial barrier function and fostering mucosal tolerance to luminal bacteria. Commensal flora mediate their protective effects through TLR9-dependent activation of cytokines, such as type I IFNs (alpha, beta) and IL-10. Although IFN-beta promotes apoptosis, IFN-alpha activates specific antiapoptotic target genes whose actions preserve epithelial barrier integrity. We have recently identified guanylate binding protein-1 (GBP-1) as an antiapoptotic protein, regulated by both type I and type II IFNs, that promotes intestinal epithelial barrier integrity in mature intestine. However, the mechanisms by which commensal bacteria regulate epithelial apoptosis during colonization of immature intestine and the contributions of GBP-1 are unknown. The healthy newborn intestine is initially colonized with bacterial species present in the maternal gastrointestinal tract, including nonpathogenic Escherichia coli. Therefore, we examined the influence of commensal E. coli on cytokine expression and candidate mediators of apoptosis in preweaned mice. Specifically, enteral exposure of 2 wk-old mice to commensal E. coli for 24 h selectively increased both IFN-alphaA and GBP-1 mRNA expression and prevented staurosporine-induced epithelial apoptosis. Exogenous IFN-alphaA treatment also induced GBP-1 expression and protected against staurosporine-induced apoptosis in a GBP-1 dependent manner, both in vitro and ex vivo. These findings identify a role for IFN-alphaA-mediated GBP-1 expression in the prevention of intestinal epithelial apoptosis by commensal bacteria. Thus IFN-alphaA mediates the beneficial effects of commensal bacteria and may be a promising therapeutic target to promote barrier integrity and prevent the inappropriate inflammatory responses seen in developing intestine as in necrotizing enterocolitis.

Abstract 265: EGFR positively regulates GBP1 expression to promote glioma cell invasion

Abstract Glioma is the most common and deadly human brain tumor. Epidermal growth factor receptor (EGFR) amplification or constitutively active mutation (EGFRVIII) is one of the most frequent genetic lesions in gliomas. To identify target genes regulated by EGFR signaling, we performed expression array analysis and found that human guanylate binding protein-1 (GBP1), a large GTPase that is induced by inflammatory cytokines, is one of the predominant genes induced by EGFR/EGF or EGFR VIII kinase activity. Our results demonstrate that EGF/EGFR signaling could dramatically induce GBP1 expression at both the mRNA and protein level through the p38 MAPK signaling cascade that is distinct from Stat1 signaling used by interferon γ. Moreover, we identified IRF1 and YY1 as downstream transcriptional regulator for GBP1 enhancement by EGFR/p38 signaling. Interestingly, we show that GBP1 is required for EGFR-mediated matrix metallopeptidase-1 (MMP1) expression, and plays a role in glioma cell invasion in vitro. Overexpression of GBP1 enhances glioma cell invasion through MMP1 induction, which was independent of GBP1 GTPase activity. In contrast, siRNA-mediated knockdown of GBP1 inhibited MMP1 expression and in turn blocked cell invasion as well. Consistently, we found that GBP1 is overexpressed and positively correlated with EGFR/EGFRVIII and MMP1 expression in human glioma clinical samples and glioma cell lines, particularly in neural subtypes of GBM as demonstrated by TCGA database analysis. Therefore, Our results suggest that the dysregulation of EGFR-mediated GBP1 expression may contribute to glioma invasion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 265.