Reduction of 15-hydroxyprostaglandin dehydrogenase expression is an independent predictor of poor survival associated with enhanced cell proliferation in gastric adenocarcinoma

The role of microRNA-21 (miR-21) in pathogenesis, diagnosis, and prognosis of gastrointestinal cancers: A review

MicroRNAs (miRNAs) are small non-coding RNAs regulating the expression of several target genes. miRNAs play a significant role in cancer biology, as they can downregulate their corresponding target genes by impeding the translation of mRNA (at the mRNA level) as well as degrading mRNAs by binding to the 3'-untranslated (UTR) regions (at the protein level). miRNAs may be employed as cancer biomarkers. Therefore, miRNAs are widely investigated for early detection of cancers which can lead to improved survival rates and quality of life. This is particularly important in the case of gastrointestinal cancers, where early detection of the disease could substantially impact patients' survival. MicroRNA-21 (miR-21 or miRNA-21) is one of the most frequently researched miRNAs, where it is involved in the pathophysiology of cancer and the downregulation of several tumor suppressor genes. In gastrointestinal cancers, miR-21 regulates phosphatase and tensin homolog (PTEN), programmed cell death 4 (PDCD4), mothers against decapentaplegic homolog 7 (SMAD7), phosphatidylinositol 3-kinase /protein kinase B (PI3K/AKT), matrix metalloproteinases (MMPs), β-catenin, tropomyosin 1, maspin, and ras homolog gene family member B (RHOB). In this review, we investigate the functions of miR-21 in pathogenesis and its applications as a diagnostic and prognostic cancer biomarker in four different gastrointestinal cancers, including colorectal cancer (CRC), pancreatic cancer (PC), gastric cancer (GC), and esophageal cancer (EC).

Prostaglandin E2 Pathway Is Dysregulated in Gastric Adenocarcinoma in a Caucasian Population

Gastric cancer (GC) represents the third leading cause of cancer-related deaths worldwide. The levels of prostaglandin E₂, a key player in the hallmarks of cancer, are mainly regulated by prostaglandin-endoperoxide synthase 2 (PTGS2) and ATP-binding cassette subfamily C member 4 (ABCC4), involved in its synthesis and exportation, respectively, and 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and solute carrier organic anion transporter family member 2A1 (SLCO2A1), responsible for its inactivation. Even though there are distinct molecular signatures across ethnic populations, most published studies focus on Asian populations. Our main aim was to explore the genetic expression of the aforementioned molecules in a Caucasian population. 94 “Normal” and 89 tumoral formalin-fixed paraffin-embedded (FFPE) samples from GC patients were used to assess the mRNA expression of PTGS2, ABCC4, hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD), SLCO2A1 by Real-Time PCR. We found an upregulation for the PTGS2 gene mean factor of 2.51 and a downregulation for the HPGD and SLCO2A1 genes (mean factor of 0.10 and 0.37, respectively) in tumorous mucosa in a gender-independent manner. In females, we observed an ABCC4 downregulation and a PTGS2 mRNA upregulation compared to males in tumoral mucosa (mean factor of 0.61 and 1.64, respectively). We reported dysregulation of the inflammation triggered PGE₂ pathway in a Caucasian population with an intermediate risk for GC, which might highlight the applicability of aspirin in the treatment of GC patients.

15-PGDH Expression in Gastric Cancer: A Potential Role in Anti-Tumor Immunity

Introduction

Host immunity plays a vital role in tumorigenesis, including in tumor invasion and metastasis. However, the precise underlying mechanism remains to be explored. The enzyme 15-PGDH, which plays a key role in prostaglandin degradation, is a critical inflammatory mediator in gastric cancer (GC) tumorigenesis.

Materials and Methods

Immunohistochemistry was performed to determine 15-PGDH expression in GC and the corresponding adjacent non-neoplastic tissues (n=92).

Results

The expression of 15-PGDH in GC tissues was significantly lower than that in paracancerous tissues (P<0.001) and found to correspond inversely with GC differentiation (P=0.043) and lymph node metastasis (P=0.046). In contrast, FOXP3 expression was increased in poorly differentiated GC tissues (P=0.001). Kaplan–Meier analysis revealed that GC patients with low expression of 15-PGDH (Log rank test, P=0.007) and high expression of FOXP3 (Log rank test, P=0.009) had shorter overall survival (OS) than those with high 15-PGDH and low FOXP3 expression. OS was also correlated with pathological tumor-node-metastasis stage (Log rank test, P=0.014). Furthermore, using Cox proportional hazard regression, 15-PGDH expression [hazard ratio (HR): 0.605 (0.440–0.833); P=0.002] was identified as an independent factor for OS.

Conclusion

Our data suggest that 15-PGDH may contribute to anti-tumor immunity by regulating FOXP3⁺ Treg cells. The findings are useful for the identification of therapeutic targets for the management of GC.

Ki-67/MKI67 as a Predictive Biomarker for Clinical Outcome in Gastric Cancer Patients: an Updated Meta-analysis and Systematic Review involving 53 Studies and 7078 Patients

Gastric cancer (GC) threatens human health worldwide and we performed this meta-analysis to evaluate the clinical value of Ki-67/MKI67 in patients with GC. The combined hazard ratio (HR), odds ratio (OR) and 95% confidence interval (95% CI) were calculated to assess the relationships of Ki-67/MKI67 expression with prognoses and clinicopathological characteristics. Genes co-expressed with MKI67 were collected for Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and protein-protein interaction (PPI) network analyses. In total, 53 studies with 7078 patients were included in this study. The pooled HRs indicated that an elevated expression of Ki-67/MKI67 predicted an unfavorable overall survival (HR: 1.54, 95% CI: 1.33-1.78, P<0.0001) and disease-free survival (HR: 2.28, 95% CI: 1.43-3.64, P<0.0001) in GC patients. Additionally, in patients with advanced GC, a high Ki-67/MKI67 expression was also significantly connected with OS (HR: 1.37, 95% CI: 1.18-1.60, P<0.0001). The combined ORs showed that Ki-67/MKI67 expression was related to TNM stage (stage III/IV versus stage I/II: OR=1.93, 95% CI=1.34-2.78, P<0.0001), tumor differentiation (poor versus well/moderate: OR=1.94, 95% CI=1.32-2.85, P=0.001), lymph node metastasis (yes versus no: OR=1.67, 95% CI=1.23-2.25, P=0.001), distant metastasis (yes versus no: OR=1.67, 95% CI=1.24-2.26, P=0.001) and tumor invasion depth (T3/T4 versus T_is/T1/T2: OR=1.98, 95% CI=1.60-2.44, P<0.0001). The results of GO, KEGG pathway and PPI network analyses indicated that Ki-67/MKI67 may be involved in the development of GC via influencing P53 signaling pathway. Ki-67/MKI67 could be a potential indicator to predict the prognosis of patients with GC and identify high-risk cases. Detecting Ki-67/MKI67 expression in clinic may be helpful in optimizing individual treatment and further improving the survival expectancy of patients with GC.

miR-21-mediated regulation of 15-hydroxyprostaglandin dehydrogenase in colon cancer

Elevated prostaglandin E₂ (PGE₂) levels are observed in colorectal cancer (CRC) patients, and this increase is associated with poor prognosis. Increased synthesis of PGE₂ in CRC has been shown to occur through COX-2-dependent mechanisms; however, loss of the PGE₂-catabolizing enzyme, 15-hydroxyprostaglandin dehydrogenase (15-PGDH, HPGD), in colonic tumors contributes to increased prostaglandin levels and poor patient survival. While loss of 15-PGDH can occur through transcriptional mechanisms, we demonstrate that 15-PGDH can be additionally regulated by a miRNA-mediated mechanism. We show that 15-PGDH and miR-21 are inversely correlated in CRC patients, with increased miR-21 levels associating with low 15-PGDH expression. 15-PGDH can be directly regulated by miR-21 through distinct sites in its 3′ untranslated region (3′UTR), and miR-21 expression in CRC cells attenuates 15-PGDH and promotes increased PGE₂ levels. Additionally, epithelial growth factor (EGF) signaling suppresses 15-PGDH expression while simultaneously enhancing miR-21 levels. miR-21 inhibition represses CRC cell proliferation, which is enhanced with EGF receptor (EGFR) inhibition. These findings present a novel regulatory mechanism of 15-PGDH by miR-21, and how dysregulated expression of miR-21 may contribute to loss of 15-PGDH expression and promote CRC progression via increased accumulation of PGE₂.

MicroRNA-21 induces loss of 15-hydroxyprostaglandin dehydrogenase in early gastric tubular adenocarcinoma

15-hydroxyprostaglandin dehydrogenase (15-PGDH), the rate-limiting enzyme in prostaglandin E2 degradation, is decreased in gastric cancers and microRNA (miR)-21 is one of the regulators. We investigated the expression and regulation of 15-PGDH in eary gastric carcinogenesis utilizing endoscopic submucosal dissection (ESD) and gastric cancer cell lines. Expression of 15-PGDH and cyclooxygenase-2 as well as the promoter methylation of 15-PGDH were evaluted. CRISPR, miR-21 transfection, proliferation and apoptosis assays were also done. We observed significant decreases in 15-PGDH expression but no promoter methylation was detected in any ESDs. 15-PGDH suppression by CRISPR induced enhanced growth kinetics. miR-21, which was detected in high level in gastric tumors from the TGCA data, caused increased proliferation, decreased apoptosis. miR-21 overexpression was confirmed with CISH and RT-PCR in the ESDs. Loss of 15-PGDH occurs at the very early stage of gastric adenocarcinoma by miR-21. H. pylori infection may affect miR-21 up regulation. Maintaining 15-PGDH enzyme activity could be a new strategic measure in preventing gastric cancer especially tubular adenocarcinoma.

Clinicopathologic significance and prognostic value of Ki-67 expression in patients with gastric cancer: a meta-analysis

BACKGROUND

The prognostic value and clinicopathologic significance of Ki-67 expression in gastric cancer patients was controversial. This meta-analysis was performed to clarify the prognostic value and clinicopathologic significance of Ki-67 expression in gastric cancer patients.

MATERIALS AND METHODS

Several electronic databases were searched for eligible studies. The pooled odds ratio (OR), hazard ratios (HR) and 95% confidence interval(CI) were calculated to explore the prognostic value and clinicopathologic significance of Ki-67 expression for disease free survival and overall survival.

RESULTS

Totally 5600 gastric cancer patients from 29 studies were included in this study. High Ki-67 expression was significantly related with Lauren's classification (OR = 1.70; P = 0.001; 95%CI: 1.40-2.06) and tumor size(OR = 1.54; P = 0.006; 95%CI: 1.14-2.09). However, high Ki-67 expression was not significantly associated with lymph node metastasis (OR = 1.37; P = 0.138; 95% CI: 0.90-2.08) , tumor stage (OR = 1.31; P = 0.296; 95% CI: 0.79-2.16) and tumor differentiation (OR = 1.03; P = 0.839; 95% CI: 0.78-1.35). The pooled HRs were 1.87(P = 0.001; 95% CI 1.30-2.69) for disease free survival and 1.23(P = 0.005; 95% CI 1.06-1.42) for overall survival.

CONCLUSIONS

High Ki-67 expression may serve as a predictive biomarker for poor prognosis in gastric cancer patients. Stratification by Ki-67 expression may be a consideration for selection of therapeutic regimen and integrated managements.

Distinct differences in serum eicosanoids in healthy, enteritis and colorectal cancer individuals

BACKGROUND

Eicosanoids as inflammatory mediators take part in the regulation of disease progression. However, the application of serum eicosanoid in disease progression identification was still uncertain.

METHODS

Serum from 52 healthy volunteers, 34 enteritis patients and 55 colorectal cancer (CRC) patients were collected. Ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was used to analyze the change of serum eicosanoids.

RESULTS

Of 158 eicosanoids, we found that lower levels of anti-inflammatory eicosanoids 13-HOTrE, 9-HOTrE, DHA, 11-HETE and 12-HHT were observed in enteritis and CRC group compared with healthy group, meanwhile the content of 5-iPF2α-VI as oxidative stress mediator in enteritis and CRC group was greater than that in healthy groups. Moreover, 9-HODE, 13-HODE, 12,13-diHOME, 8-HETE and 15-HETE were dramatically decrease in CRC group compared with non-CRC group. Additionally, the change of 5-, 12- and 15-HETE content in serum sample was associated with progression from healthy to enteritis, finally to CRC. No significant difference between serum eicosanoids and the expression of CerbB-2 and Ki67 were observed.

CONCLUSION

Serum eicosanoids might be used as a possible biomarker for identifying among health, enteritis and CRC.

miR-21 modulates prostaglandin signaling and promotes gastric tumorigenesis by targeting 15-PGDH

miR-21 is an abundantly expressed miRNA in mammalian cells, and evolutionarily conserved across a wide range of vertebrate species. The previous study found that miR-21 is significantly upregulated in gastric cancer. However, the detail mechanisms remain to be largely unknown. In current study, quantitative real-time PCR was applied to examine the expression of miR-21 in gastric cancer tissue and cell lines. The roles of miR-21 in cell proliferation and cell cycle were analyzed by cck8 cell viability assays, flow cytometry cell cycle assays and clone formation assays. As to detail mechanisms, we investigate the relationship between miR-21 and 15-PGDH in gastric cell lines, AGS and BGC-823 treated with In-miR-21, and found that miR-21 is negatively correlated with 15-PGDH. The reduced 15-PGDH may result in PGE2 accumulation which sustains carcinogenesis and tumor progression. We further found that miR-21 exert its oncogenic role through PGE₂/PI3K/Akt/Wnt/β-catenin axis in gastric cell proliferation. In conclusion, our findings enlarged our knowledge in the roles of miR-21 in the progression of gastric cancer.

MicroRNA-21 regulates prostaglandin E2 signaling pathway by targeting 15-hydroxyprostaglandin dehydrogenase in tongue squamous cell carcinoma

Background

Oral tongue squamous cell carcinoma (OTSCC) is one of the most aggressive forms of head and neck/oral cancer (HNOC), and is a complex disease with extensive genetic and epigenetic defects, including microRNA deregulation. Identifying the deregulation of microRNA-mRNA regulatory modules (MRMs) is crucial for understanding the role of microRNA in OTSCC.

Methods

A comprehensive bioinformatics analysis was performed to identify MRMs in HNOC by examining the correlation among differentially expressed microRNA and mRNA profiling datasets and integrating with 12 different sequence-based microRNA target prediction algorithms. Confirmation experiments were performed to further assess the correlation among MRMs using OTSCC patient samples and HNOC cell lines. Functional analyses were performed to validate one of the identified MRMs: miR-21-15-Hydroxyprostaglandin Dehydrogenase (HPGD) regulatory module.

Results

Our bioinformatics analysis revealed 53 MRMs that are deregulated in HNOC. Four high confidence MRMs were further defined by confirmation experiments using OTSCC patient samples and HNOC cell lines, including miR-21-HPGD regulatory module. HPGD is a known anti-tumorigenic effecter, and it regulates the tumorigenic actions of Prostaglandin E2 (PGE2) by converts PGE2 to its biologically inactive metabolite. Ectopic transfection of miR-21 reduced the expression of HPGD in OTSCC cell lines, and the direct targeting of the miR-21 to the HPGD mRNA was confirmed using a luciferase reporter gene assay. The PGE2-mediated upregulation of miR-21 was also confirmed which suggested the existence of a positive feed-forward loop that involves miR-21, HPGD and PGE2 in OTSCC cells that contribute to tumorigenesis.

Conclusions

We identified a number of high-confidence MRMs in OTSCC, including miR-21-HPGD regulatory module, which may play an important role in the miR-21-HPGD-PGE2 feed-forward loop that contributes to tumorigenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2716-0) contains supplementary material, which is available to authorized users.

Reduction of prostaglandin transporter predicts poor prognosis associated with angiogenesis in gastric adenocarcinoma

BACKGROUND AND AIM

Prostaglandin (PG) E2 promotes gastrointestinal carcinogenesis and tumor progression. The total amount of biologically active PGE2 in tissues is determined by a balance of PG biosynthesis and degradation pathways, which involve the PG transporter (PGT). We investigated PGT in gastric adenocarcinoma by determining its expression pattern and examining associations of PGT with prognosis and tumor angiogenesis.

METHODS

PGT expression was determined by immunohistochemistry in advanced gastric adenocarcinoma specimens obtained from 96 patients who underwent surgical resection. Correlations between PGT expression level and clinicopathological factors were statistically analyzed. Angiogenesis in the tumor tissue was evaluated by counting the number of microvessels. The role of PGT in mRNA and protein expression of vascular endothelial growth factor (VEGF) was examined in gastric cancer cells stimulated by PGE2 .

RESULTS

Based on multivariate and Kaplan-Meier analyses, negativity for PGT expression was an independent poor prognostic factor. There were more microvessels in PGT-negative tumors than in PGT-positive tumors. Transfection of AGS and MKN7 gastric cancer cells with PGT-specific siRNA led to increased VEGF mRNA and protein expression accompanied by increased PGE2 in the culture media.

CONCLUSIONS

PGT expression is an independent predictor of poor survival and is associated with tumor angiogenesis in gastric adenocarcinoma.

Correlation of 15-prostagladin dehydrogenase expression with clinicopathological factors and survival rate in gastric adenocarcinoma

INTRODUCTION

The prostaglandin (PG) E2 level, which is associated with oncogenesis, progression and metastasis in various types of cancer, is determined by reciprocal regulation of 15-prostaglandin dehydrogenase (15-PGDH) and cyclooxygenase-2. This study investigated 15-PGDH expression in gastric adenocarcinoma, the associations between 15-PGDH expression and clinicopathological factors, and the correlation between 15-PGDH expression and the 5-year gastric-cancer-specific survival rate (5-year GCSS).

METHODS

From 175 patients who underwent gastrectomy, we obtained biopsies of gastric adenocarcinoma tissues and adjacent normal tissues for preparation as formalin-fixed, paraffin-embedded specimens and conducted an immunohistochemical analysis.

RESULTS

15-PGDH expression was low in 65.1% of cases. 15-PGDH expression showed no relationship with age or gender, but was significantly correlated with the pathologic type, T stage, N stage, TNM stage, positive lymph node metastasis, metastasis to a larger quantity of lymph nodes, positive lymphatic invasion, positive vascular invasion, positive perineural invasion, and palliative gastrectomy. The 5-year GCSS of the low-expression group was 77.19% and a lower level of 15-PGDH expression correlated to a lower 5-year GCSS. 15-PGDH expression significantly influenced the 5-year GCSS on univariate but not multivariate analysis.

CONCLUSION

Our findings indicate that 15-PGDH expression was low in gastric adenocarcinoma and was correlated with the clinicopathological factors associated with prognosis and a more advanced stage of gastric adenocarcinoma. Also, 15-PGDH expression was significantly associated with the 5-year GCSS, but was not an independent prognostic factor thereof.

Expression of 15-hydroxyprostaglandin dehydrogenase and cyclooxygenase-2 in non-small cell lung cancer: Correlations with angiogenesis and prognosis

The aim of the present study was to investigate the function of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and cyclooxygenase-2 (COX-2) in angiogenesis and their association with the prognosis of non-small cell lung cancer (NSCLC). Using immunohistochemical staining, the expression of 15-PGDH and COX-2, and the microvessel density (MVD) levels were evaluated in 35 NSCLC specimens. Paracancerous normal lung tissue was collected as control samples from six patients. The correlation of 15-PGDH with COX-2, clinicopathological characteristics, MVD and overall survival (OS) was studied. NSCLC tissues showed a significantly lower expression level of 15-PGDH (P=0.009) and a significantly higher expression level of COX-2 (P=0.004) compared with normal lung tissue. The expression level of 15-PGDH was negatively correlated with MVD (P<0.001) and COX-2 expression (P=0.032). A low expression level of 15-PGDH, a high expression level of COX-2 and high levels of MVD were significantly correlated with a shorter OS time (15-PGDH, P<0.0001; COX-2, P=0.038; MVD, P<0.0001). This study provided clinical evidence that a low expression level of 15-PGDH is associated with a poor prognosis in NSCLC. Furthermore, it was shown that 15-PGDH and COX-2 reciprocally regulate cancer angiogenesis, which may affect the prognosis of patients with NSCLC.

Relationship between 15-hydroxyprostaglandin dehydrogenase and gastric adenocarcinoma

Purpose

Prostaglandin E2 (PGE2) is a contributory carcinogen in gastric adenocarcinoma. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) catabolizes PGE2 by oxidizing its 15(s)-hydroxy group. The aim of this study was to investigate the expression of 15-PGDH in gastric adenocarcinoma tissue and the relationship between 15-PGDH expression and clinicopathologic features of gastric adenocarcinoma.

Methods

Ninety-nine patients who underwent surgical resection for gastric adenocarcinoma between January 2007 and December 2007 were enrolled and evaluated retrospectively.

Results

In 62 patients (62.6%), 15-PGDH expression was lower in gastric adenocarcinoma tissue than in nonneoplastic tissue. Regarding the relationship between 15-PGDH expression and clinicopathological features, 15-PGDH expression was significantly lower in tissues with poor differentiation (P = 0.002), advanced T stage (P = 0.0319), a higher number of lymph node metastases (P = 0.045), lymphatic invasion (P = 0.031), and vascular invasion (P = 0.036).

Conclusion

15-PGDH expression was associated with a subset of clinicopathologic features such as differentiation grade, T stage, lymphatic invasion, and vascular invasion.

miR-21 targets 15-PGDH and promotes cholangiocarcinoma growth

miRNAs are a group of small, noncoding RNAs that modulate the translation of genes by binding to specific target sites in the target mRNA. This study investigated the biologic function and molecular mechanism of miR-21 in human cholangiocarcinoma. In situ hybridization analysis of human cholangiocarcinoma specimens showed increased miR-21 in cholangiocarcinoma tissue compared with the noncancerous biliary epithelium. Lentiviral transduction of miR-21 enhanced human cholangiocarcinoma cell growth and clonogenic efficiency in vitro, whereas inhibition of miR-21 decreased these parameters. Overexpression of miR-21 also promoted cholangiocarcinoma growth using an in vivo xenograft model system. The NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH/HPGD), a key enzyme that converts the protumorigenic prostaglandin E2 (PGE2) to its biologically inactive metabolite, was identified as a direct target of miR-21 in cholangiocarcinoma cells. In parallel, cyclooxygenase-2 (COX2) overexpression and PGE2 treatment increased miR-21 levels and enhanced miR-21 promoter activity in human cholangiocarcinoma cells.

IMPLICATIONS

Cholangiocarcinogenesis and tumor progression are regulated by a novel interplay between COX-2/PGE2 and miR-21 signaling, which converges at 15-PGDH.

Cyclooxygenase-2 expression is associated with poor overall survival of patients with gastric cancer: a meta-analysis

BACKGROUND

Cyclooxygenase-2 (COX-2) is believed to be involved in gastric carcinogenesis. However, it is still controversial whether COX-2 expression can be regarded as a prognostic factor for gastric cancer patients.

AIM

To obtain a more accurate relationship between COX-2 overexpression and prognosis in gastric cancer by meta-analysis.

METHOD

Relevant articles published up to May 2013 were searched by use of several keywords in electronic databases. Separate hazard ratio (HR) estimates and 95 % confidence intervals (95 % CI) for COX-2 overexpression and overall survival (OS) and disease-free survival (DFS) with gastric cancer were extracted. Combined HR with 95 % CI was calculated by use of Stata11.0 software to estimate the size of the effect. Publication bias testing and sensitivity analysis were also performed.

RESULTS

A total of 27 studies which included 3,891 gastric cancer patients were combined in the final analysis. Combined results suggested that COX-2 overexpression was associated with an unfavorable OS (HR 1.58, 95 % CI 1.36-1.84) but not DFS (HR 1.15, 95 % CI 0.93-1.43) among patients with gastric cancer. Publication bias was absent. Sensitivity analysis suggested that the results of this meta-analysis were robust.

CONCLUSIONS

The results of this meta-analysis suggest that high COX-2 expression may be an independent risk factor for poor OS of patients with gastric cancer. More large prospective studies are now needed to further clarify the prognostic value of COX-2 expression for DFS in gastric cancer.

Cellular uptake and antiproliferative effects of 11-oxo-eicosatetraenoic acid

Cyclooxygenases (COX) metabolize arachidonic acid (AA) to hydroxyeicosatetraenoic acids (HETE), which can then be oxidized by dehydrogenases, such as 15-hydroxyprostaglandin dehydrogenase (15-PGDH), to oxo-eicosatetraenoic acids (ETE). We have previously established that 11-oxo-eicosatetraenoic acid (oxo-ETE) and 15-oxo-ETE are COX-2/15-PGDH-derived metabolites. Stable isotope dilution (SID) chiral liquid chromatography coupled with electron capture atmospheric pressure chemical ionization (ECAPCI) single reaction monitoring (SRM) MS has been used to quantify uptake of 11-oxo-ETE and 15-oxo-ETE in both LoVo cells and human umbilical vein endothelial cells (HUVEC). Intracellular 11-oxo- and 15-oxo-ETE concentrations reached maximum levels within 1 h and declined rapidly, with significant quantitative differences in uptake between the LoVo cells and the HUVECs. Maximal intracellular concentrations of 11-oxo-ETE were 0.02 ng/4 × 10⁵ cells in the LoVo cells and 0.58 ng/4 × 10⁵ cells in the HUVECs. Conversely, maximal levels of 15-oxo-ETE were 0.21 ng/4 × 10⁵ in the LoVo cells and 0.01 ng/4 × 10⁵ in the HUVECs. The methyl esters of both 11-oxo- and 15-oxo-ETE increased the intracellular concentrations of the corresponding free oxo-ETEs by 3- to 8-fold. 11-oxo-ETE, 15-oxo-ETE, and their methyl esters inhibited proliferation in both HUVECs and LoVo cells at concentrations of 2–10 μM, with 11-oxo-ETE methyl ester being the most potent inhibitor. Cotreatment with probenecid, an inhibitor of multiple drug resistance transporters (MRP)1 and 4, increased the antiproliferative effect of 11-oxo-ETE methyl ester in LoVo cells and increased the intracellular concentration of 11-oxo-ETE from 0.05 ng/4 × 10⁵ cells to 0.18 ng/4 × 10⁵ cells. Therefore, this study has established that the COX-2/15-PGDH-derived eicosanoids 11-oxo- and 15-oxo-ETE enter target cells, that they inhibit cellular proliferation, and that their inhibitory effects are modulated by MRP exporters.

15-hydroxyprostaglandin dehydrogenase-derived 15-keto-prostaglandin E2 inhibits cholangiocarcinoma cell growth through interaction with peroxisome proliferator-activated receptor-γ, SMAD2/3, and TAP63 proteins

Prostaglandin E2 (PGE2) is a potent lipid mediator that plays a key role in inflammation and carcinogenesis. NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of the 15(S)-hydroxyl group of PGE2, which leads to PGE2 biotransformation. In this study, we showed that the 15-PGDH-derived 15-keto-PGE2 is an endogenous peroxisome proliferator-activated receptor-γ (PPAR-γ) ligand that causes PPAR-γ dissociation from Smad2/3, allowing Smad2/3 association with the TGF-β receptor I and Smad anchor for receptor activation and subsequent Smad2/3 phosphorylation and transcription activation in human cholangiocarcinoma cells. The 15-PGDH/15-keto-PGE2-induced Smad2/3 phosphorylation resulted in the formation of the pSmad2/3-TAP63-p53 ternary complex and their binding to the TAP63 promoter, inducing TAP63 autotranscription. The role of TAP63 in 15-PGDH/15-keto-PGE2-induced inhibition of tumor growth was further supported by the observation that knockdown of TAP63 prevented 15-PGDH-induced inhibition of tumor cell proliferation, colony formation, and migration. These findings disclose a novel 15-PGDH-mediated 15-keto-PGE2 signaling cascade that interacts with PPAR-γ, Smad2/3, and TAP63.

15-PGDH inhibits hepatocellular carcinoma growth through 15-keto-PGE2/PPARγ-mediated activation of p21WAF1/Cip1

15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a key enzyme in prostaglandin metabolism. This study provides important evidence for inhibition of hepatocellular carcinoma (HCC) growth by 15-PGDH through the 15-keto-PGE₂/PPARγ/p21^WAF1/Cip1 signaling pathway. Forced overexpression of 15-PGDH inhibited HCC cell growth in vitro, whereas knockdown of 15-PGDH enhanced tumor growth parameters. In a tumor xenograft model in SCID mice, inoculation of human HCC cells (Huh7) with overexpression of 15-PGDH led to significant inhibition of tumor growth, while knockdown of 15-PGDH enhanced tumor growth. In a separate tumor xenograft model in which mouse HCC cells (Hepa1-6) were inoculated into syngeneic C57BL/6 mice, intratumoral injection of adenovirus vector expressing 15-PGDH (pAd-15-PGDH) significantly inhibited xenograft tumor growth. The anti-tumor effect of 15-PGDH is mediated through its enzymatic product, 15-keto-PGE₂, which serves as an endogenous PPARγ ligand. Activation of PPARγ by 15-PGDH-derived 15-keto-PGE₂ enhanced the association of PPARγ with the p21^WAF1/Cip1 promoter and increased p21 expression and association with CDK2, CDK4 and PCNA. Depletion of p21 by shRNA reversed 15-PGDH-induced inhibition of HCC cell growth; overexpression of p21 prevented 15-PGDH knockdown-induced tumor cell growth. These results demonstrate a key 15-PGDH/15-keto-PGE₂-mediated activation of PPARγ and p21^WAF1/Cip1 signaling cascade that regulates hepatocarcinogenesis and tumor progression.

Celecoxib enhances the efficacy of 15-hydroxyprostaglandin dehydrogenase gene therapy in treating murine breast cancer

PURPOSE

The overexpression of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) has been proved to inhibit tumor growth and metastasis through degradation of prostaglandin E2 (PGE2), which is often overexpressed in various cancers and accelerates tumor progression. Cyclooxygenase-2 (COX-2), a synthase of PGE2, actively produces much PGE2 to counteract the 15-PGDH-induced antitumor efficacy. Here, we investigated the combinational effect by using pcDNA3.1(+) encoding mouse 15-PGDH gene therapy and celecoxib, a COX-2 inhibitor, in mouse breast cancers.

METHODS

Mice bearing 4T1 were treated with short-term administration of the COX-2 inhibitor celecoxib (40 mg/kg/day) plus liposome-encapsulated mouse 15-PGDH in order to determine their synergistic antitumor activity in vivo. And the possible mechanisms were investigated.

RESULTS

We observed that the combination treatment of 15-PGDH and celecoxib significantly inhibited tumor growth and lung metastases than monotherapy or controls. Moreover, the effect of combination treatment was associated with significant reduction of PGE2 in serum, which resulted from increased 15-PDGH and decreased COX-2 in tumor tissues. The tumor tissues in combination treatment presented more apoptotic cells and less microvessel density. Notably, the number of myeloid-derived suppressor cells in the spleen was also significantly decreased in the combination treatment than others.

CONCLUSIONS

Our findings suggested that celecoxib increased the antitumor activity of 15-PGDH by synergistically blocking PGE2 pathway, which might be a new feasible way for cancer therapy.

Prognostic implication of 15-hydroxyprostaglandin dehydrogenase down-regulation in patients with colorectal cancer

PURPOSE

Prostaglandin (PG) E2 is known to be closely related to cancer progression and is inactivated by 15-hydroxyprostaglandin dehydrogenase (PGDH). 15-PGDH is shown to have tumor suppressor activity and to be down-regulated in various cancers, including colorectal cancer (CRC). Therefore, we evaluated the expression of 15-PGDH and its prognostic effect in patients with CRC.

METHODS

15-PGDH expression was examined by using immunohistochemistry in 77 patients with CRC. Its prognostic significance was statistically evaluated.

RESULTS

Negative 15-PGDH expression was noted in 55.8% of the 77 cases of CRC. 15-PGDH expression showed no correlation with any of the various clinicopathologic parameters. The status of lymph node metastasis, tumor-node-metastasis stages, and pre-operative carcinoembryonic antigen levels showed significant prognostic effect. However, univariate analysis revealed down-regulation of 15-PGDH not to be a predictor of poor survival. The 5-year overall survival rate was 71.7% in the group with positive expression of 15-PGDH and 67.1% in the group with negative expression of 15-PGDH, but this difference was not statistically significant (P = 0.751).

CONCLUSION

15-PGDH was down-regulated in 55.8% of the colorectal cancer patients. However, down-regulation of 15-PGDH showed no prognostic value in patients with CRC. Further larger scale or prospective studies are needed to clarify the prognostic effect of 15-PGDH down-regulation in patients with colorectal cancer.

Cyclooxygenase-2 and gastric cancer

Gastric cancer remains a leading cause of cancer-related deaths worldwide, although its incidence has been steadily declining during recent decades. Expression of cyclooxygenase-2 (COX-2) is elevated in gastric carcinomas and in their precursor lesions. COX-2 expression associates with reduced survival in gastric cancer patients, and it has also been shown to be an independent factor of poor prognosis. Several molecular mechanisms are involved in the regulation of COX-2 expression in gastric cancer cell lines, including signal transduction pathways activated by Helicobacter pylori. In gastric tumor models in vivo the role of COX-2 seems to be predominantly to facilitate tumor promotion and growth.

Prostaglandin catabolic enzymes as tumor suppressors

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is a key prostaglandin catabolic enzyme catalyzing the oxidation and inactivation of prostaglandin E(2) (PGE(2)) synthesized from the cyclooxygenase (COX) pathway. Accumulating evidence indicates that 15-PGDH may function as a tumor suppressor antagonizing the action of COX-2 oncogene. 15-PGDH has been found to be down-regulated contributing to elevated levels of PGE(2) in most tumors. The expression of 15-PGDH and COX-2 appears to be regulated reciprocally in cancer cells. Down-regulation of 15-PGDH in tumors is due, in part, to transcriptional repression and epigenetic silencing. Numerous agents have been found to up-regulate 15-PGDH by down-regulation of transcriptional repressors and by attenuation of the turnover of the enzyme. Up-regulation of 15-PGDH may provide a viable approach to cancer chemoprevention. Further catabolism of 15-keto-prostaglandin E(2) is catalyzed by 15-keto-prostaglandin-∆(13)-reductase (13-PGR), which also exhibits LTB(4)-12-hydroxydehydrogenase (LTB(4)-12-DH) activity. 13-PGR/LTB(4)-12-DH behaves as a tumor suppressor as well. This review summarizes current knowledge of the expression and function of 15-PGDH and 13-PGR/LTB(4)-12-DH in lung and other tissues during tumor progression. Future directions of research on these prostaglandin catabolic enzymes as tumor suppressors are also discussed.

15-PGDH is reduced and induces apoptosis and cell cycle arrest in gastric carcinoma

AIM: To investigate the expression of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in human gastric cancer and it’s mechanism in apoptosis and cell cycle arrest.

METHODS: Expression of 15-PGDH mRNA and protein was examined by immunohistochemistry, immunocytochemistry, reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting in tissue from human gastric cancer, gastric precancerous state (gastric polyps and atrophic gastritis), normal stomach, and gastric cancer cell lines. The relationship between gastric cancer, gastric precancerous state and 15-PGDH expression was determined. The association between expression of 15-PGDH and various clinicopathological parameters in gastric cancer was evaluated. Human gastric cancer cell line SGC-7901 was transfected with 15-PGDH expression plasmids. The effect of 15-PGDH on the cell cycle was examined by flow cytometry. The effect of 15-PGDH on apoptosis was examined by transmission electron microscopy, flow cytometry and transferase mediated nick end labeling (TUNEL) assay. Expression of cell cycle (p21, p27, p16 and p53) and apoptosis (Survivin, BCL-2, BCL-X_L, BAK and BAX) genes was analyzed by RT-PCR.

RESULTS: Expression of 15-PGDH mRNA and protein in human gastric cancer tissues was significantly lower than in normal gastric tissues (P < 0.01). Expression in human gastric cancer cell lines MKN-28 and MKN-45 was reduced, and absent in SGC-7901 cells (P < 0.05). Reduction of 15-PGDH expression was also found in precancerous tissues, such as gastric polyps and atrophic gastritis (P < 0.01). There was a significant difference in expression of 15-PGDH among various gastric cancer pathological types (P < 0.05), with or without distant metastasis (P < 0.05) and different TNM stage (P < 0.01). Flow cytometry demonstrated a significant increase in apoptotic cells in SGC-7901 cells transfected with pcDNA3/15-PGDH plasmid for 24 h and 48 h (P < 0.01), and an increased fraction of sub-G1 phase after transfection (P < 0.05). TUNEL assay showed an increased apoptotic index in cells overexpressing 15-PGDH (P < 0.01). After transfection, expression of proapoptotic genes, such as BAK (P < 0.05), BAX and p53 (P < 0.01), was increased. Expression of antiapoptotic genes was decreased, such as Survivin, BCL-2 and BCL-X_L (P < 0.01). Expression of cyclin-dependent kinase inhibitors p21 and p16 (P < 0.01) was significantly upregulated in cells overexpressing 15-PGDH.

CONCLUSION: Reduction of 15-PGDH is associated with carcinogenesis and development of gastric carcinoma. 15-PGDH induces apoptosis and cell cycle arrest in SGC-7901 cells.

Regulation of inflammation in cancer by eicosanoids

Inflammation in the tumor microenvironment is now recognized as one of the hallmarks of cancer. Endogenously produced lipid autacoids, locally acting small molecule lipid mediators, play a central role in inflammation and tissue homeostasis, and have recently been implicated in cancer. A well-studied group of autacoid mediators that are the products of arachidonic acid metabolism include: the prostaglandins, leukotrienes, lipoxins and cytochrome P450 (CYP) derived bioactive products. These lipid mediators are collectively referred to as eicosanoids and are generated by distinct enzymatic systems initiated by cyclooxygenases (COX 1 and 2), lipoxygenases (5-LOX, 12-LOX, 15-LOXa, 15-LOXb), and cytochrome P450s, respectively. These pathways are the target of approved drugs for the treatment of inflammation, pain, asthma, allergies, and cardiovascular disorders. Beyond their potent anti-inflammatory and anti-cancer effects, non-steroidal anti-inflammatory drugs (NSAIDs) and COX-2 specific inhibitors have been evaluated in both preclinical tumor models and clinical trials. Eicosanoid biosynthesis and actions can also be directly influenced by nutrients in the diet, as evidenced by the emerging role of omega-3 fatty acids in cancer prevention and treatment. Most research dedicated to using eicosanoids to inhibit tumor-associated inflammation has focused on the COX and LOX pathways. Novel experimental approaches that demonstrate the anti-tumor effects of inhibiting cancer-associated inflammation currently include: eicosanoid receptor antagonism, overexpression of eicosanoid metabolizing enzymes, and the use of endogenous anti-inflammatory lipid mediators. Here we review the actions of eicosanoids on inflammation in the context of tumorigenesis. Eicosanoids may represent a missing link between inflammation and cancer and thus could serve as therapeutic target(s) for inhibiting tumor growth.

COX-derived prostanoid pathways in gastrointestinal cancer development and progression: novel targets for prevention and intervention

Arachidonic acid metabolism through cyclooxygenase (COX) pathways leads to the generation of biologically active eicosanoids. Eicosanoid expression levels vary during development and progression of gastrointestinal (GI) malignancies. COX-2 is the major COX-isoform responsible for G.I. cancer development/progression. COX-2 expression increases during progression from a normal to cancerous state. Evidence from observational studies has demonstrated that chronic NSAID use reduces the risk of cancer development, while both incidence and risk of death due to G.I. cancers were significantly reduced by daily aspirin intake. A number of randomized controlled trials (APC trial, Prevention of Sporadic Adenomatous Polyps trial, APPROVe trial) have also shown a significant protective effect in patients receiving selective COX-2 inhibitors. However, chronic use of selective COX-2 inhibitors at high doses was associated with increased cardiovascular risk, while NSAIDs have also been associated with increased risk. More recently, downstream effectors of COX-signaling have been investigated in cancer development/progression. PGE(2), which binds to both EP and PPAR receptors, is the major prostanoid implicated in the carcinogenesis of G.I. cancers. The role of TXA(2) in G.I. cancers has also been examined, although further studies are required to uncover its role in carcinogenesis. Other prostanoids investigated include PGD(2) and its metabolite 15d-PGJ2, PGF(1α) and PGI(2). Targeting these prostanoids in G.I. cancers has the promise of avoiding cardiovascular toxicity associated with chronic selective COX-2 inhibition, while maintaining anti-tumor reactivity. A progressive sequence from normal to pre-malignant to a malignant state has been identified in G.I. cancers. In this review, we will discuss the role of the COX-derived prostanoids in G.I. cancer development and progression. Targeting these downstream prostanoids for chemoprevention and/or treatment of G.I. cancers will also be discussed. Finally, we will highlight the latest pre-clinical technologies as well as avenues for future investigation in this highly topical research field.

Oncolytic herpes simplex virus 1 encoding 15-prostaglandin dehydrogenase mitigates immune suppression and reduces ectopic primary and metastatic breast cancer in mice

Oncolytic herpes simplex virus 1 (HSV-1) viruses armed with immunomodulatory transgenes have shown potential for enhanced antitumor therapy by overcoming tumor-based immune suppression and promoting antitumor effector cell development. Previously, we reported that the new oncolytic HSV-1 virus, OncSyn (OS), engineered to fuse tumor cells, prevented tumor growth and metastasis to distal organs in the 4T1/BALB/c immunocompetent breast cancer mouse model, suggesting the elicitation of antitumor immune responses (Israyelyan et al., Hum. Gen. Ther. 18:5, 2007, and Israyelyan et al., Virol. J. 5:68, 2008). The OSV virus was constructed by deleting the OS viral host shutoff gene (vhs; UL41) to further attenuate the virus and permit dendritic cell activation and antigen presentation. Subsequently, the OSVP virus was constructed by inserting into the OSV viral genome a murine 15-prostaglandin dehydrogenase (15-PGDH) expression cassette, designed to constitutively express 15-PGDH upon infection. 15-PGDH is a tumor suppressor protein and the primary enzyme responsible for the degradation of prostaglandin E2 (PGE2), which is known to promote tumor development. OSVP, OSV, and OS treatment of 4T1 tumors in BALB/c mice effectively reduced primary tumor growth and inhibited metastatic development of secondary tumors. OSVP was able to significantly inhibit the development and accumulation of 4T1 metastatic tumor cells in the lungs of treated mice. Ex vivo analysis of immune cells following treatment showed increased inflammatory cytokine production and the presence of mature dendritic cells for the OSVP, OSV, and OS viruses. A statistically significant decrease in splenic myeloid-derived suppressor cells (MDSC) was observed only for OSVP-treated mice. These results show that intratumoral oncolytic herpes is highly immunogenic and suggest that 15-PGDH expression by OSVP enhanced the antitumor immune response initiated by viral infection of primary tumor cells, leading to reduced development of pulmonary metastases. The availability of the OSVP genome as a bacterial artificial chromosome allows for the rapid insertion of additional immunomodulatory genes that could further assist in the induction of potent antitumor immune responses against primary and metastatic tumors.

Rebamipide, a mucoprotective drug, inhibits NSAIDs-induced gastric mucosal injury: possible involvement of the downregulation of 15-hydroxyprostaglandin dehydrogenase

Prostaglandin E₂ plays an important role in the maintenance of gastric mucosal integrity. The level of biologically active prostaglandin E₂ in the tissue is regulated by the balanced expression of its synthetic enzymes, such as cyclooxygenase, and its catabolic enzyme, 15-hydroxyprostaglandin dehydrogenase. We examined the effect of rebamipide, a mucoprotective drug, on prostaglandin E₂ production and metabolism in the gastric tissue and its effect on indomethacin-induced gastric mucosal injury in mice. Rebamipide suppressed indomethacin-induced gastric mucosal injury. Suppressive effect of rebamipide on indomethacin-induced gastric mucosal injury was also observed in cyclooxygenase-2-knockout mice. The mice that were treated with rebamipide showed a 2-fold increase in cyclooxygenase-2 mRNA expression in the gastric tissue, whereas 15-hydroxyprostaglandin dehydrogenase mRNA expression markedly decreased as compared to vehicle-treated control mice. Rebamipide did not affect the expression of cyclooxygenase-1 in the gastric tissue. Rebamipide did not increase prostaglandin E₂ production in the gastric tissue; however, it induced a 1.4-fold increase in the concentration of prostaglandin E₂ in the gastric tissue as compared to vehicle-treated control mice. These results suggest that the suppressive effect of rebamipide on non-steroidal anti-inflammatory drugs-induced gastric mucosal injury can be attributed to reduced 15-hydroxyprostaglandin dehydrogenase expression, which increases the prostaglandin E₂ concentration in the gastric tissue.

Gene expression changes in patient-matched gastric normal mucosa, adenomas, and carcinomas

A subset of gastric carcinomas shows histologic evidence of a multistep process, progressing from gastric adenoma to gastric carcinoma. We examined gene expression changes during the gastric adenoma-carcinoma sequence in 26 snap-frozen samples (normal mucosa, adenoma, and carcinoma samples from eight patients and two additional carcinomas) by oligonucleotide microarray. Unsupervised hierarchical clustering analysis demonstrated differential gene expression between gastric normal mucosa, adenomas and carcinomas. We identified 319 and 422 genes differentially regulated in adenoma and carcinoma, respectively, relative to normal mucosa, using a combination of Welch's t-test and fold-change analysis. Applying a combination of robust multi-category support vector machines to the data, reveal that 39 and 21 genes were gradually up- and down-regulated, respectively, in succession in normal mucosa, adenoma, and carcinoma samples. We validated gene expression levels of four genes: hydroxyprostaglandin dehydrogenase 15 (HPGD), follistatin-like 1, trefoil factor 1 (TTF1) and trefoil factor 2 (TFF2) by RT-PCR and found direct correlation with microarray results. The expressions of the TFF2 and HPGD genes were further evaluated by immunohistochemistry in 103 adenomas and 70 carcinomas; expression of both proteins was decreased in these tissues. The progressive alteration in gene expression in the transition from normal mucosa to carcinoma suggests that these changes may play critical roles in gastric carcinogenesis.