Overexpression Of mPGES-1 Research Articles

5-methyl-2-carboxamidepyrrole-based novel dual mPGES-1/sEH inhibitors as promising anticancer candidates.

Inhibiting microsomal prostaglandin E2 synthase-1 (mPGES-1), an inducible enzyme involved in prostaglandin E2 (PGE2) biosynthesis and tumor microenvironment (TME) homeostasis, is a valuable strategy for treating inflammation and cancer. In this work, 5-methylcarboxamidepyrrole-based molecules were designed and synthesized as new compounds targeting mPGES-1. Remarkably, compounds 1f, 2b, 2c, and 2d were able to significantly reduce the activity of the isolated enzyme, showing IC50 values in the low micromolar range. With the aim of further profiling the synthesized molecules, their ability to interfere with the activity of soluble epoxide hydrolase (sEH), whose inhibition blocks the loss of the anti-inflammatory mediators epoxyeicosatrienoic acids (EETs or epoxyicosatrienoic acids), was investigated in silico and by employing specific biological assays. Among the set of tested compounds, 1f, 2b, 2c, and 2d emerged as mPGES-1/sEH dual inhibitors. Moreover, given that overexpression of mPGES-1 has been observed in many human tumors, we finally explored the biological effect of our compounds in an in vitro model of human colorectal cancer (CRC). The obtained outcomes pave the way for future investigation to optimize and further characterize anticancer pharmacological profile of the carboxamidepyrrole-based molecules.

Microsomal Prostaglandin E2 Synthase-1 Deletion Attenuates Isoproterenol-Induced Myocardial Fibrosis in Mice.

Deletion of microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibits inflammation and protects against atherosclerotic vascular diseases but displayed variable influence on pathologic cardiac remodeling. Overactivation of β-adrenergic receptors (β-ARs) causes heart dysfunction and cardiac remodeling, whereas the role of mPGES-1 in β-AR-induced cardiac remodeling is unknown. Here we addressed this question using mPGES-1 knockout mice, subjecting them to isoproterenol, a synthetic nonselective agonist for β-ARs, at 5 or 15 mg/kg per day to induce different degrees of cardiac remodeling in vivo. Cardiac structure and function were assessed by echocardiography 24 hours after the last of seven consecutive daily injections of isoproterenol, and cardiac fibrosis was examined by Masson trichrome stain in morphology and by real-time polymerase chain reaction for the expression of fibrosis-related genes. The results showed that deletion of mPGES-1 had no significant effect on isoproterenol-induced cardiac dysfunction or hypertrophy. However, the cardiac fibrosis was dramatically attenuated in the mPGES-1 knockout mice after either low-dose or high-dose isoproterenol exposure. Furthermore, in vitro study revealed that overexpression of mPGES-1 in cultured cardiac fibroblasts increased isoproterenol-induced fibrosis, whereas knocking down mPGES-1 in cardiac myocytes decreased the fibrogenesis of fibroblasts. In conclusion, mPGES-1 deletion protects against isoproterenol-induced cardiac fibrosis in mice, and targeting mPGES-1 may represent a novel strategy to attenuate pathologic cardiac fibrosis, induced by β-AR agonists. SIGNIFICANCE STATEMENT: Inhibitors of microsomal prostaglandin E2 synthase-1 (mPGES-1) are being developed as alternative analgesics that are less likely to elicit cardiovascular hazards than cyclooxygenase-2 selective nonsteroidal anti-inflammatory drugs. We have demonstrated that deletion of mPGES-1 protects inflammatory vascular diseases and promotes post-myocardial infarction survival. The role of mPGES-1 in β-adrenergic receptor-induced cardiomyopathy is unknown. Here we illustrated that deletion of mPGES-1 alleviated isoproterenol-induced cardiac fibrosis without deteriorating cardiac dysfunction. These results illustrated that targeting mPGES-1 may represent an efficacious approach to the treatment of inflammatory cardiovascular diseases.

MPGES-1 as a new target to overcome acquired resistance to gefitinib in non-small cell lung cancer cell lines

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) as gefitinib are standard treatment of non-small cell lung cancer (NSCLC), but resistance often occurs. This study demonstrates that NSCLC cells resistant to gefitinib (GR cells) displayed a significantly higher microsomal prostaglandin E synthase-1 (mPGES-1) expression and activity than parental cells. Overexpression of mPGES-1/prostaglandin E-2 (PGE-2) signaling in GR cells was associated with acquisition of mesenchymal and stem-like cell properties, nuclear EGFR translocation and tolerance to cisplatin. mPGES-1 inhibition reduced mesenchymal and stem-like properties, and nuclear EGFR translocation in GR cells. Consistently, inhibition of mPGES-1 activity enhanced sensitivity to cisplatin and responsiveness to gefitinib in GR cells. We propose the mPGES-1/PGE-2 signaling as a potential target for treating aggressive and resistant lung cancers.

Regulation of mPGES-1 composition and cell growth via the MAPK signaling pathway in jurkat cells.

Previous studies have suggested that microsomal prostaglandin E synthase-1 (mPGES-1) is highly expressed and closely associated with mitogen-activated protein kinase (MAPK) signaling pathways in various types of malignant cells. However, their expression patterns and function with respect to T-cell acute lymphoblastic leukemia (T-ALL) remain largely unknown. The present study investigated whether mPGES-1 served a crucial role in T-ALL and aimed to identify interactions between mPGES-1 and the MAPK signaling pathway in T-ALL. The results indicated that mPGES-1 overexpression in T-ALL jurkat cells was significantly decreased by RNA silencing. Decreasing mPGES-1 on a consistent basis may inhibit cell proliferation, induce apoptosis and arrest the cell cycle in T-ALL jurkat cells. Microarray and western blot analyses revealed that c-Jun N-terminal kinase served a role in the mPGES-1/prostaglandin E2/EP4/MAPK positive feedback loops. In addition, P38 and extracellular signal-regulated kinase 1/2 exhibited negative feedback effects on mPGES-1. In conclusion, the results suggested that cross-talk between mPGES-1 and the MAPK signaling pathway was very complex. Therefore, the combined regulation of mPGES-1 and the MAPK signaling pathway may be developed into a new candidate therapy for T-ALL in the future.

Linking of mPGES-1 and iNOS activates stem-like phenotype in EGFR-driven epithelial tumor cells

Inflammatory prostaglandin E-2 (PGE-2) favors cancer progression in epithelial tumors characterized by persistent oncogene input. However, its effects on tumor cell stemness are poorly understood at molecular level. Here we describe two epithelial tumor cells A431 and A459, originating from human lung and skin tumors, in which epithelial growth factor (EGF) induces sequential up-regulation of mPGES-1 and iNOS enzymes, producing an inflammatory intracellular milieu. We demonstrated that concerted action of EGF, mPGES-1 and iNOS causes sharp changes in cell phenotype demonstrated by acquisition of stem-cell features and activation of the epithelial-mesenchymal transition (EMT). When primed with EGF, epithelial tumor cells transfected with mPGES-1 or iNOS to ensure steady enzyme levels display major stem-like and EMT markers, such as reduction in E-cadherin with a concomitant rise in vimentin, ALDH-1, CD133 and ALDH activity. Tumorsphere studies with these cells show increased sphere number and size, enhanced migratory and clonogenic capacity and sharp changes in EMT markers, indicating activation of this process. The concerted action of the enzymes forms a well-orchestrated cascade where expression of iNOS depends on overexpression of mPGES-1. Indeed, we show that through its downstream effectors (PGE-2, PKA, PI3K/Akt), mPGES-1 recruits non-canonical transcription factors, thus facilitating iNOS production.In conclusion, we propose that the initial event leading to tumor stem-cell activation may be a leveraged intrinsic mechanism in which all players are either inherent constituents (EGF) or highly inducible proteins (mPGES-1, iNOS) of tumor cells. We suggest that incipient tumor aggressiveness may be moderated by reducing pivotal input of mPGES-1.

Krüppel-like Factor 5 Transcription Factor Promotes Microsomal Prostaglandin E2 Synthase 1 Gene Transcription in Breast Cancer

The KLF5 (Krüppel-like factor 5) transcription factor is specifically expressed in a subset of estrogen receptor α-negative breast cancers. Although KLF5 promotes breast cancer cell cycle progression, survival, and tumorigenesis, the mechanism by which KLF5 promotes breast cancer is still not entirely understood. Here, we demonstrate that mPGES1, encoding microsomal prostaglandin E2 synthase 1 (mPGES1), is a KLF5 direct downstream target gene. KLF5 overexpression or knockdown positively altered the levels of mPGES1 mRNA and protein in multiple breast cell lines. 12-O-Tetradecanoylphorbol-13-acetate induced the expression of both KLF5 and mPGES1 in dosage- and time-dependent manners. The induction of KLF5 was essential for 12-O-tetradecanoylphorbol-13-acetate to induce mPGES1 expression. Additionally, KLF5 bound to the mPGES1 gene proximal promoter and activated its transcription. Both KLF5 and mPGES1 promoted prostaglandin E2 production; regulated p21, p27, and Survivin downstream gene expression; and likewise stimulated cell proliferation. Overexpression of mPGES1 partially rescued the KLF5 knockdown-induced downstream gene expression changes and growth arrest in MCF10A cells. Finally, we demonstrate that the expression of mPGES1 was positively correlated with the estrogen receptor α/progesterone receptor/HER2 triple-negative status. These findings suggest that mPGES1 is a target gene of KLF5, making it a new biomarker and a potential therapeutic target for triple-negative breast cancers.

Genetic deletion of microsomal prostaglandin E synthase-1 suppresses mouse mammary tumor growth and angiogenesis

The cyclooxygenase/prostaglandin (COX/PG) signaling pathway is of central importance in inflammation and neoplasia. COX inhibitors are widely used for analgesia and also have demonstrated activity for cancer prophylaxis. However, cardiovascular toxicity associated with this drug class diminishes their clinical utility and motivates the development of safer approaches both for pain relief and cancer prevention. The terminal synthase microsomal PGE synthase-1 (mPGES-1) has attracted considerable attention as a potential target. Overexpression of mPGES-1 has been observed in both colorectal and breast cancers, and gene knockout and overexpression approaches have established a role for mPGES-1 in gastrointestinal carcinogenesis. Here we evaluate the contribution of mPGES-1 to mammary tumorigenesis using a gene knockout approach. Mice deficient in mPGES-1 were crossed with a strain in which breast cancer is driven by overexpression of human epidermal growth factor receptor 2 (HER2/neu). Loss of mPGES-1 was associated with a substantial reduction in intramammary PGE2 levels, aromatase activity, and angiogenesis in mammary glands from HER2/neu transgenic mice. Consistent with these findings, we observed a significant reduction in multiplicity of tumors ≥1mm in diameter, suggesting that mPGES-1 contributes to mammary tumor growth. Our data identify mPGES-1 as a potential anti-breast cancer target.

Expression and Significance of Microsomal Prostaglandin Synthase-1 (mPGES-1) and Beclin-1 in the Development of Prostate Cancer

The aim of this study was to investigate the expression and significance of microsomal prostaglandin synthase-1 (mPGES-1) and Beclin-1 in the development of prostate cancer (PCa). Immunohistochemistry was performed on paraffin-embedded sections with rabbit polyclonal against mPGES-1 and Beclin-1 in 40 PCa, 40 benign prostatic hyperplasia (BPH) and 10 normal prostate specimens for this purpose. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied for mRNA expression of mPGES-1 and Beclin-1, while MTT assays were used to ascertain the best working concentration of the mPGES-1 inhibitor (CAY10526). The effect of CAY10526 treatment on expression of Beclin-1 in DU-145 cells was studied using Western blot analysis. Localization of Beclin-1 and mPGES-1 was in endochylema. Significant differences in expression was noted among PCa, BPH and normal issues (P<0.05). Beclin-1 expression inversely correlated with mPGES-1 expression in PCa tissue (P<0.05). CAY10526 could significantly block mPGES-1 expression and the proliferation of DU-145 cells (P<0.05), while increasing Beclin-1 levels (P<0.05). Overexpression of mPGES-1 could decrease the autophagic PCa cell death. Inhibiting the expression of mPGES-1 may lead to DU-145 cell death and up-regulation of Beclin-1. The results suggest that inhibition of mPGES-1 may have therapeutic potential for PCa in the future.

EGFR signaling upregulates expression of microsomal prostaglandin E synthase-1 in cancer cells leading to enhanced tumorigenicity

In this report we describe the contribution of prostaglandin E(2) (PGE(2)) derived from the inducible microsomal PGE-synthase type-1 (mPGES-1) to the epidermal growth factor receptor (EGFR) oncogenic drive in tumor epithelial cells and in tumor-bearing mice. EGFR stimulation upregulated expression of mPGES-1 in HT-29, A431 and A549 cancer cells. Egr-1, a transcription factor induced by EGF, mediated this response. The Egr-1 rise provoked the overexpression of mPGES-1 messenger and protein, and enhanced PGE(2) formation. These changes were suppressed either by silencing Egr-1, or by upstream blockade of EGFR or ERK1/2 signals. Further, in a clonogenic assay on tumor cells, EGF induced a florid tumorigenic phenotype, which regressed when mPGES-1 was silenced or knocked down. EGF-induced mPGES-1 overexpression in epithelial cell reduced E-cadherin expression, whereas enhancing that of vimentin, suggesting an incipient mesenchymal phenotype. Additionally, inhibiting the EGFR in mice bearing the A431 tumor, the mPGES-1 expression and the tumor growth, exhibited a parallel decline. In conclusion, these findings provide novel evidence that a tight cooperation between the EGF/EGFR and mPGES-1 leads to a significant tumorigenic gain in epithelial cells, and provide clues for controlling the vicious association.

Microsomal prostaglandin E synthase-1 promotes hepatocarcinogenesis through activation of a novel EGR1/β-catenin signaling axis

Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme that couples with cyclooxygenase-2 (COX-2) for the production of PGE2. Although COX-2 is known to mediate the growth and progression of several human cancers including hepatocellular carcinoma (HCC), the role of mPGES-1 in hepatocarcinogenesis is not well established. This study provides novel evidence for a key role of mPGES-1 in HCC growth and progression. Forced overexpression of mPGES-1 in two HCC cell lines (Hep3B and Huh7) increased tumor cell growth, clonogenic formation, migration and invasion, whereas knockdown of mPGES-1 inhibited these parameters, in vitro. In a SCID mouse tumor xenograft model, mPGES-1 overexpressed cells formed palpable tumors at earlier time points and developed larger tumors when compared to the control (p<0.01); in contrast, mPGES-1 knockdown delayed tumor development and reduced tumor size (p<0.01). Mechanistically, mPGES-1-induced HCC cell proliferation, invasion and migration involve PGE2 production and activation of early growth response 1 (EGR1) and β-catenin. Specifically, mPGES-1-derived PGE2 induces the formation of EGR1-β-catenin complex, which interacts with TCF4/LEF1 transcription factors and activates the expression of β-catenin downstream genes. Our findings depict a novel crosstalk between mPGES-1/PGE2 and EGR1/β-catenin signaling that is critical for hepatocarcinogenesis.

Role of mPGES-1 in the occurrence, progression, metastasis and invasion of hepatocellular carcinoma

To study the expression of mPGES-1 in hepatocellular carcinoma (HCC), observe the effect of MK886 on down-regulation of mPGES-1 gene expression on the biology of human hepatocarcinoma cell line HepG2 and to investigate its significance in the occurrence, progression, metastasis and invasion. HCC tissues, para-carcinoma tissues, far-carcinoma tissues and normal liver tissues were collected. The expressions of mPGES-1 were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The proliferation, adherence, migration and invasion abilities of HepG2 cells interfered by MK886 were assessed by MTT and transwell technique respectively. The expression of mPGES-1 in HCCs was higher than that in normal liver tissues (P < 0.01), which increased following histological grade. Furthermore, mPGES-1 expression level was higher in the capsule invasion and metastasis tumor than in primary locus. A significant dose-dependent down-regulation of expressions of mPGES-1 gene mRNA and protein were observed in HepG2 cells when MK886 was given for 48 h (F = 140.402, P < 0.01; a'= 0.00714, P < 0.01). Compared with the control group, the growth inhibitory rate of HepG2 cell was observed significantly time and dose-dependent when MK886 was given. The rate of adhesion cells in experimental groups were 85.3% ± 1.3%, 70.5% ± 1.5% and 45.8% ± 2.4%, respectively, less than that in control group 100.0% ± 0 (F = 626.313, P < 0.01). The migration cells was 92.47 ± 1.90, 62.63 ± 1.96 and 37.33 ± 0.83 respectively in the experimental groups after 24 h, lower than that in the control group 128.93 ± 2.60 (F = 1253.805, P < 0.01). The invasion assay revealed that the invading cells were 41.67 ± 1.30, 25.47 ± 1.30 and 13.93 ± 1.66 in the experimental groups, in contrast to 55.67 ± 2.08 in control group after 24 h. The difference between these groups was significant (F = 372.615, P < 0.01). The numbers of adhesion, migration and invasion of HepG2 cells were dose-dependent in MK886 groups. Over-expression of mPGES-1 was associated with the tumorigenesis and progression of HCC. The down-regulation of mPGES-1 gene expression might indicated the decrease of the invasion and metastasis of HCC.

Abstract 247: A novel mPGES-1/EGR1/beta-catenin signaling axis in hepatocarcinogenesis

Abstract Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme that couples with cyclooxygenase-2 (COX-2) for the production of PGE2. Although COX-2-derived PGE2 is known to participate in the development and progression of several human cancers including hepatocellular carcinoma (HCC), the role of mPGES-1 in carcinogenesis remains poorly understood. This study provides novel evidence for an important role of mPGES-1 in human HCC. Forced overexpression of mPGES-1 in two HCC cell lines (Hep3B and Huh7) promoted tumor cell growth and increased clonogenic formation capacity, in vitro. Conversely, mPGES-1 knockdown inhibited tumor cell growth and prevented clonogenic formation. Overexpression of mPGES-1 in Hep3B and Huh7 cells also increased cell invasion and migration/repair capacity, whereas knockdown of mPGES-1 reduced these parameters. Flowcytometric analysis revealed that mPGES-1 knockdown caused cell cycle arrest at G1/S checkpoint. In SCID mouse tumor xenograft model, mPGES-1 overexpressed cells formed palpable tumors at earlier time points and developed larger tumor nodules when compared to the control cells (p&amp;lt;0.01); in contrast, mPGES-1 knockdown delayed tumor development and reduced tumor growth in SCID mice (p&amp;lt;0.01). Mechanistically, mPGES-1-induced HCC cell proliferation, invasion and migration involve activation of EGR1 and beta-catenin. mPGES-1 induced the formation of EGR1-beta-catenin complex, which interacted with TCF4 transcription factors in HCC cells. Our findings depict a novel mPGES1/EGR1/beta-catenin signaling axis that is crucial in hepatocarcinogenesis. 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 247. doi:10.1158/1538-7445.AM2011-247

Microsomal prostaglandin E synthase‐1 (mPGES‐1) promotes human cholangiocarcinogenesis through inhibition of PTEN pathway

Microsomal prostaglandin E synthase-1 (mPGES-1) is a rate-limiting key enzyme that is coupled with cyclooxygenase-2 (COX-2) to synthesize prostaglandin E2 (PGE2). Although COX-2 is implicated in the development of various human cancers, the role of mPGES-1 in carcinogenesis has not been defined. This study was designed to determine the role of mPGES-1 in human cholangiocarcinoma growth. Forced overexpression of mPGES-1 in human cholangiocarcinoma cells enhanced tumor cell proliferation, migration/invasion and colony formation; in contrast, RNAi knockdown of mPGES-1 inhibited tumor growth parameters. In SCID mouse tumor xenograft model, mPGES-1 overexpression accelerated tumor formation and increased tumor weight (p<0.01), whereas mPGES-1 knockdown delayed tumor formation and reduced tumor weight (p<0.01). mPGES-1 inhibited the expression of PTEN, leading to activation of the EGFR-PI3K-AKT-mTOR signaling pathways in cholangiocarcinoma cells. mPGES-1-mediated inhibition of PTEN is regulated at transcriptional level (via blocking EGR1 sumoylation and binding to 5′-UTR of PTEN gene) as well as at posttranscriptional level (via miR21-mediated degradation of PTEN mRNA). This study provides novel evidence for an important role of mPGES-1-mediated PTEN pathway in cholangiocarcinogenesis.

Microsomal Prostaglandin E Synthase-1 Inhibits PTEN and Promotes Experimental Cholangiocarcinogenesis and Tumor Progression

Microsomal prostaglandin E synthase-1 (mPGES-1) is a rate-limiting enzyme that is coupled with cyclooxygenase (COX)-2 in the synthesis of prostaglandin E2. Although COX-2 is involved in the development and progression of various human cancers, the role of mPGES-1 in carcinogenesis has not been determined. We investigated the role of mPGES-1 in human cholangiocarcinoma growth. We used immunohistochemical analyses to examine the expression of mPGES-1 in formalin-fixed, paraffin-embedded human cholangiocarcinoma tissues. The effects of mPGES-1 on human cholangiocarcinoma cells were determined in vitro and in SCID mice. Immunoblotting and immunoprecipitation assays were performed to determine the levels of PTEN and related signaling molecules in human cholangiocarcinoma cells with overexpression or knockdown of mPGES-1. mPGES-1 is overexpressed in human cholangiocarcinoma tissues. Overexpression of mPGES-1 in human cholangiocarcinoma cells increased tumor cell proliferation, migration, invasion, and colony formation; in contrast, RNA interference knockdown of mPGES-1 inhibited tumor growth parameters. In SCID mice with tumor xenografts, mPGES-1 overexpression accelerated tumor formation and increased tumor weight (P<.01), whereas mPGES-1 knockdown delayed tumor formation and reduced tumor weight (P<.01). mPGES-1 inhibited the expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), leading to activation of the epidermal growth factor/phosphoinositide 3-kinase/AKT/mammalian target of rapamycin signaling pathways in cholangiocarcinoma cells. mPGES-1-mediated inhibition of PTEN is regulated through blocking of early growth response-1 sumoylation and binding to the 5'-untranslated region of the PTEN gene. mPGES-1 promotes experimental cholangiocarcinogenesis and tumor progression by inhibiting PTEN.

Increase in PGE2 biosynthesis induces a Bax dependent apoptosis correlated to patients’ survival in glioblastoma multiforme

Prostaglandin E(2) plays multiple roles both in the physiology and the physiopathology of human brain, which are not completely understood. We have identified in a subset of human glioblastoma multiforme (GBM) tumors, the most common form of adult brain cancer, an increased expression of mPGES-1, the enzyme which catalyses the isomerization of PGH(2) into PGE(2) downstream of cyclooxygenase 2 (COX-2). The sensitivity of primary cultures of GBM to apoptosis was augmented by the overexpression of mPGES-1, whereas the knockdown of its expression by shRNA decreased the apoptotic threshold in vitro and stimulated tumor growth in vivo. Adding extracellular PGE(2) in the culture medium failed to reproduce mPGES-1 effect on the cell viability in vitro. However, the intracellular injection of PGE(2) induced a dose-dependent apoptosis in GBM cultures, which was dependent on the presence of Bax, a pro-apoptotic protein. We show that PGE(2) physically associates with Bax, triggering its apoptotic-like change in conformation and its subsequent association with mitochondria. Our results raise questions about the role of PGE(2) in the control of apoptosis and in its potential impact in central nervous system pathologies.

Clinical Implications of Microsomal Prostaglandin E Synthase-1 Overexpression in Human Non–Small-Cell Lung Cancer

Microsomal prostaglandin E synthase-1 (mPGES-1) has recently been found to overexpress in human cancers, including non-small-cell lung cancer (NSCLC). However, the clinical value is largely unknown. The aim of this study was to investigate the associations between mPGES-1 expression in NSCLC and the clinical characteristics and survival outcome. Between 2001 and 2003, paired fresh tumorous and nontumorous samples were prospectively procured from patients undergoing surgery for NSCLC. The expression of mPGES-1 was assessed by using Western blot in 93 subjects and reverse transcriptase-polymerase chain reaction in 35. Overexpression of mPGES-1 was defined as a more than 2-fold expression in the tumorous sample compared with the corresponding nontumorous one. Immunohistochemistry was used to confirm its localization to the tumor cells. In a subset of 30 cases, cyclooxygenase-2 (COX-2) was also analyzed to assess its association with mPGES-1. The protein and messenger RNA of mPGES-1 were both expressed at higher levels in the tumor samples (P < .001 and P = .006, respectively). The expressions of mPGES-1 and COX-2 were unrelated (P = .715). Overexpression of mPGES-1 protein was observed in 61 (65.6%) of 93 patients, but it was not significantly associated with the clinicopathologic characteristics or overall and disease-free survivals. However, mPGES-1 overexpression seemed to be associated with the likelihood of subsequent pulmonary metastases and a lower tendency for developing bony metastases (P = .001 and P = .006, respectively). Our results demonstrated that mPGES-1 was overexpressed in NSCLC, unassociated with COX-2. Overexpression of mPGES-1 per se was not a prognostic indicator, but it might be implicated in the organ preference of metastasis.

Targeted over-expression of mPGES-1 and elevated PGE2 production is not sufficient for lung tumorigenesis in mice.

There is a significant body of evidence suggesting that enzymes involved in arachidonic acid metabolism and their eicosanoid products play a role in various cancers, having both pro- and antitumorigenic effects. The goal of this study was to further define the role microsomal prostaglandin E synthases (mPGES-1) play in lung tumorigenesis. Transgenic mice were created with targeted over-expression of human mPGES-1 in the alveolar and airway epithelial cells using an SP-C promoter driven construct. Transgene positive (mPGES-1+) mice were shown to significantly over-express functional mPGES-1 in the lung and more specifically in alveolar type II cells. To study the effects of mPGES-1 over-expression in lung tumor formation, mice were exposed to a complete carcinogen protocol with a single injection of urethane or an initiation/promotion model with a single injection of 3-methylcholanthrene (MCA) followed by multiple injections of butylated hydroxytoluene (BHT). mPGES-1+ mice did not show a significant difference in tumor multiplicity or tumor size at 10, 16, 19 or 30 weeks after urethane injection compared with mPGES-1- mice. No significant difference was seen in tumor incidence, multiplicity or size at 19 weeks after treatment with MCA/BHT. Western blots verified that mPGES-1 expression was increased in tumors versus uninvolved tissue of both mPGES-1+ and mPGES-1- mice with overall expression being significantly higher in mPGES-1+ mice. Cyclooxygenase-2 levels were elevated in tumors in both groups. From these studies we conclude that over-expression of mPGES-1 and highly elevated PGE2 production are not sufficient to induce lung tumors.

Microsomal Prostaglandin E Synthase-1 Is Overexpressed in Inflammatory Bowel Disease: EVIDENCE FOR INVOLVEMENT OF THE TRANSCRIPTION FACTOR Egr-1

Microsomal prostaglandin E synthase-1 (mPGES-1) catalyzes the conversion of cyclooxygenase-derived prostaglandin (PG) H(2) to PGE(2). Increased amounts of mPGES-1 were detected in inflamed intestinal mucosa from patients with inflammatory bowel disease (IBD). Treatment with tumor necrosis factor (TNF)-alpha stimulated mPGES-1 transcription in human colonocytes, resulting in increased amounts of mPGES-1 mRNA and protein. The inductive effect of TNF-alpha localized to the GC box region of the mPGES-1 promoter. Binding of Egr-1 to the GC box region of the mPGES-1 promoter was enhanced by treatment with TNF-alpha. Notably, increased Egr-1 expression and binding activity were also detected in inflamed mucosa from IBD patients. Treatment with TNF-alpha induced the activities of phosphatidylcholine-phospholipase C (PC-PLC) and protein kinase (PK) C and enhanced NO production. A pharmacological approach was used to implicate PC-PLC --> PKC --> NO signaling as being important for the induction of mPGES-1 by TNF-alpha. TNF-alpha also enhanced guanylate cyclase activity and inhibitors of guanylate cyclase activity blocked the induction of mPGES-1 by TNF-alpha. YC-1, an activator of guanylate cyclase, induced mPGES-1. Overexpressing a dominant negative form of PKG blocked TNF-alpha-mediated stimulation of the mPGES-1 promoter. Taken together, these results suggest that overexpression of mPGES-1 in IBD is the result of Egr-1-mediated activation of transcription. Moreover, TNF-alpha induced mPGES-1 by stimulating PC-PLC --> PKC --> NO --> cGMP --> PKG signal transduction pathway.

Potential Role of Microsomal Prostaglandin E Synthase-1 in Tumorigenesis

Microsomal prostaglandin E2 synthase-1 (mPGES-1) is a stimulus-inducible enzyme that functions downstream of cyclooxygenase (COX)-2 in the PGE2-biosynthetic pathway. Given the accumulating evidence that COX-2-derived PGE2 participates in the development of various tumors, including colorectal cancer, we herein examined the potential involvement of mPGES-1 in tumorigenesis. Immunohistochemical analyses demonstrated the expression of both COX-2 and mPGES-1 in human colon cancer tissues. HCA-7, a human colorectal adenocarcinoma cell line that displays COX-2- and PGE2-dependent proliferation, expressed both COX-2 and mPGES-1 constitutively. Treatment of HCA-7 cells with an mPGES-1 inhibitor or antisense oligonucleotide attenuated, whereas overexpression of mPGES-1 accelerated, PGE2 production and cell proliferation. Moreover, cotransfection of COX-2 and mPGES-1 into HEK293 cells resulted in cellular transformation manifested by colony formation in soft agar culture and tumor formation when implanted subcutaneously into nude mice. cDNA array analyses revealed that this mPGES-1-directed cellular transformation was accompanied by changes in the expression of a variety of genes related to proliferation, morphology, adhesion, and the cell cycle. These results collectively suggest that aberrant expression of mPGES-1 in combination with COX-2 can contribute to tumorigenesis.