Loss of 15-hydroxyprostaglandin dehydrogenase expression contributes to bladder cancer progression

The tumor suppressor role and epigenetic regulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in cancer and tumor microenvironment (TME)

Oxidative stress and inflammation may initiate carcinogenesis and facilitate metastasis via activation of pro-inflammatory signaling network. The side product of arachidonic acid processing by cyclooxygenase-2 (COX-2), the prostaglandin E2 (PGE2), plays a key role in various metabolic disorders and during inflammation-mediated tumorigenesis. It has been demonstrated that PGE2 increases the proliferation, migration, invasion, metastasis, and resistance of cancer cells to apoptosis and other forms of programmed cell death. The expression level of PGE2 metabolizing enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is often decreased in various malignancies. However, the role of 15-PGDH and PGE2 in the regulation of carcinogenesis remains controversial. Numerous cancer cell lines and mouse models have demonstrated the role of 15-PGDH as a tumor suppressor. Downregulation of 15-PGDH increased cancer cell proliferation, migration, anchorage independent growth, colony formation while overexpression reversed these effects, by inducing apoptosis and cell cycle arrest in vitro and in vivo. The expression of 15-PGDH is regulated by various mechanisms, including (a) epigenetic alterations (methylation of promoter region, histone deacetylases, microRNAs (miR-21, miR-26a/b, miR-106b-5p, miR-146b-3p, miR-155, miR-218-5p, and miR-620)); and (b) dysregulated oxidative stress and associated mediators (elevated levels of growth factors and proinflammatory cytokines (such as IL1β and TNFα)). Several transcription factors, such as HNF3β, β-catenin, Snail, Slug, can bind to 15-PGDH promoter region and downregulate the enzyme expression. In contrast, the expression of 15-PGDH can be upregulated by several anti-inflammatory cytokines and anti-cancer agents, such as IL10 and vitamin D. The functional activity of 15-PGDH protein can be modulated by signaling effectors and oxidative stress, including increased production of reactive oxygen species (ROS). However, the role of oxidative stress regulator protein, i.e., nuclear factor erythroid 2-related factor 2 (Nrf2), in the control of 15-PGDH expression remains unclear. This article provides insights and comprehensive overview of the tumor suppressor role of 15-PGDH in various cancers. Epigenetic and post-translational mechanisms regulating 15-PGDH expression and the role of novel ROS-Nrf2-15-PGDH axis were discussed and accented as potential drug targets.

Insights into the molecular mechanisms and signalling pathways of epithelial to mesenchymal transition (EMT) in colorectal cancer: A systematic review and bioinformatic analysis of gene expression

Colorectal cancer (CRC) is ranked as the second leading cause of mortality worldwide, mainly due to metastasis. Epithelial to mesenchymal transition (EMT) is a complex cellular process that drives CRC metastasis, regulated by changes in EMT-associated gene expression. However, while numerous genes have been identified as EMT regulators through various in vivo and in vitro studies, little is known about the genes that are differentially expressed in CRC tumour tissue and their signalling pathway in regulating EMT. Using an integration of systematic search and bioinformatic analysis, gene expression profiles of CRC tumour tissues were compared to non-tumour adjacent tissues to identify differentially expressed genes (DEGs), followed by performing systematic review on common identified DEGs. Fifty-eight common DEGs were identified from the analysis of 82 tumour tissue samples obtained from four gene expression datasets (NCBI GEO). These DEGS were then systematically searched for their roles in modulating EMT in CRC based on previously published studies. Following this, 10 common DEGs (CXCL1, CXCL8, MMP1, MMP3, MMP7, TACSTD2, VIP, HPGD, ABCG2, CLCA4) were included in this study and subsequently subjected to further bioinformatic analysis. Their roles and functions in modulating EMT in CRC were discussed in this review. This study enhances our understanding of the molecular mechanisms underlying EMT and uncovers potential candidate genes and pathways that could be targeted in CRC.

Comparative proteomics analysis in different stages of urothelial bladder cancer for identification of potential biomarkers: highlighted role for antioxidant activity

BACKGROUND

Non-muscle-invasive bladder cancer (NMIBC) has a high recurrence rate and muscle-invasive bladder cancer (MIBC) has unfavorable outcomes in urothelial bladder cancer (UBC) patients. Complex UBC-related protein biomarkers for outcome prediction may provide a more efficient management approach with an improved clinical outcome. The aim of this study is to recognize tumor-associated proteins, which are differentially expressed in different stages of UBC patients compared non-cancerous tissues.

METHODS

The proteome of tissue samples of 42 UBC patients (NMIBC n = 25 and MIBC n = 17) was subjected to two-dimensional electrophoresis (2-DE) combined with Liquid chromatography-mass spectrometry (LC-MS) system to identify differentially expressed proteins. The intensity of protein spots was quantified and compared with Prodigy SameSpots software. Functional, pathway, and interaction analyses of identified proteins were performed using geneontology (GO), PANTHER, Reactome, Gene MANIA, and STRING databases.

RESULTS

Twelve proteins identified by LC-MS showed differential expression (over 1.5-fold, p < 0.05) by LC-MS, including 9 up-regulated in NMIBC and 3 up-regulated in MIBC patients. Proteins involved in the detoxification of reactive oxygen species and cellular responses to oxidative stress showed the most significant changes in UBC patients. Additionally, the most potential functions related to these detected proteins were associated with peroxidase, oxidoreductase, and antioxidant activity.

CONCLUSION

We identified several alterations in protein expression involved in canonical pathways which were correlated with the clinical outcomes suggested might be useful as promising biomarkers for early detection, monitoring, and prognosis of UBC.

Treatment of acromegaly by rosiglitazone via upregulating 15-PGDH in both pituitary adenoma and liver

Rosiglitazone, a synthetic peroxisome proliferator-activated receptor γ (PPARγ) ligand, has been reported to reduce growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in 10 patients with acromegaly. However, the mechanisms remain unknown. Here, we reveal that PPARγ directly enhances 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression, whose expression is decreased and negatively correlates with tumor size in acromegaly. Rosiglitazone decreases GH production and promotes apoptosis and autophagy in GH3 and primary somatotroph adenoma cells and suppresses hepatic GH receptor (GHR) expression and IGF-1 secretion in HepG2 cells. Activating the PGE2/cAMP/PKA pathway directly increases GHR expression. Rosiglitazone suppresses tumor growth and decreases GH and IGF-1 levels in mice inoculated subcutaneously with GH3 cells. The above effects are all dependent on 15-PGDH expression. Rosiglitazone as monotherapy effectively decreases GH and IGF-1 levels in all nineteen patients with active acromegaly. Evidence suggests that rosiglitazone may be an alternative pharmacological approach for acromegaly by targeting both pituitary adenomas and liver.

Downregulation of 15-hydroxyprostaglandin dehydrogenase during acquired tamoxifen resistance and association with poor prognosis in ERα-positive breast cancer

Aim:

Tamoxifen (TAM) resistance remains a clinical issue in breast cancer. The authors previously reported that 15-hydroxyprostaglandin dehydrogenase (HPGD) was significantly downregulated in tamoxifen-resistant (TAMr) breast cancer cell lines. Here, the authors investigated the relationship between HPGD expression, TAM resistance and prediction of outcome in breast cancer.

Methods:

HPGD overexpression and silencing studies were performed in isogenic TAMr and parental human breast cancer cell lines to establish the impact of HPGD expression on TAM resistance. HPGD expression and clinical outcome relationships were explored using immunohistochemistry and in silico analysis.

Results:

Restoration of HPGD expression and activity sensitised TAMr MCF-7 cells to TAM and 17β-oestradiol, whilst HPGD silencing in parental MCF-7 cells reduced TAM sensitivity. TAMr cells released more prostaglandin E₂ (PGE₂) than controls, which was reduced in TAMr cells stably transfected with HPGD. Exogenous PGE₂ signalled through the EP4 receptor to reduce breast cancer cell sensitivity to TAM. Decreased HPGD expression was associated with decreased overall survival in ERα-positive breast cancer patients.

Conclusions:

HPGD downregulation in breast cancer is associated with reduced response to TAM therapy via PGE₂-EP4 signalling and decreases patient survival. The data offer a potential target to develop combination therapies that may overcome acquired tamoxifen resistance.

Concordant expression pattern across multiple immune tissues of commercial broilers in response to avian pathogenic Escherichia coli (APEC)

In this study, RNA-seq gene expression data were obtained for three different immune tissues (bone marrow, thymus, and bursa) at two time points from birds with three phenotypes (non-infected, resistant, and susceptible birds). A total of 380 significant differentially expressed genes (DEGs) were commonly expressed in each of the three tissues in the contrast of susceptible vs. non-infected birds at 5 days post-infection (dpi) and 106 significant DEGs were shared in susceptible vs. resistant birds at 5 dpi. For the co-expressed DEGs, a relatively high consistency in expression pattern was identified in the three tissues for the two contrasts. These co-expressed DEGs were involved in the biological process of response to stimulus, regulation of cell proliferation, signal transduction, and immune system. Moreover, three gene networks were identified for the co-expressed DEGs, showing the activation of the humoral immune response, cell survival, growth and death were the concordant response for the three lymphocyte tissues. Several potential biomarker genes, HPGD, PROX1, FOSL2, E2F1, and ANP32A were found, which may have critical functions in resistant birds to resist APEC infection. Taken together, this study provides a novel insight that may elucidate the molecular mechanisms underlying host response to systemic APEC infection, as well as enhances the probability of advancement in biomedical research.

The first case of primary hypertrophic osteoarthropathy with soft tissue giant tumors caused by HPGD loss-of-function mutation

BACKGROUND

Primary hypertrophic osteoarthropathy (PHO) is a rare genetic multi-organic disease characterized by digital clubbing, periostosis and pachydermia. Two genes, HPGD and SLCO2A1, which encodes 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and prostaglandin transporter (PGT), respectively, have been reported to be related to PHO. Deficiency of aforementioned two genes leads to failure of prostaglandin E2 (PGE2) degradation and thereby elevated levels of PGE2. PGE2 plays an important role in tumorigenesis. Studies revealed a tumor suppressor activity of 15-PGDH in tumors, such as lung, bladder and breast cancers. However, to date, no HPGD-mutated PHO patients presenting concomitant tumor has been documented. In the present study, we reported the first case of HPGD-mutated PHO patient with soft tissue giant tumors at lower legs and evaluated the efficacy of selective COX-2 inhibitor (etoricoxib) treatment in the patient.

METHODS

In this study, we summarized the clinical data, collected the serum and urine samples for biochemical test and analyzed the HPGD gene in our patient.

RESULTS

A common HPGD mutation c.310_311delCT was identified in the patient. In addition to typical clinical features (digital clubbing, periostosis and pachydermia), the patient demonstrated a new clinical manifestation, a giant soft tissue tumor on the left lower leg which has not been reported in HPGD-mutated PHO patient before. After 6-month treatment with etoricoxib, the patient showed decreased PGE2 levels and improved PHO-related symptoms. Though the soft tissue tumor persisted, it seemed to be controlled under the etoricoxib treatment.

CONCLUSION

This finding expanded the clinical spectrum of PHO and provided unique insights into the HPGD-mutated PHO.

15-Keto prostaglandin E2 suppresses STAT3 signaling and inhibits breast cancer cell growth and progression

Overproduction of prostaglandin E₂ (PGE₂) has been linked to enhanced tumor cell proliferation, invasiveness and metastasis as well as resistance to apoptosis. 15-Keto prostaglandin E₂ (15-keto PGE₂), a product formed from 15-hydroxyprostaglandin dehydrogenase-catalyzed oxidation of PGE₂, has recently been shown to have anti-inflammatory and anticarcinogenic activities. In this study, we observed that 15-keto PGE₂ suppressed the phosphorylation, dimerization and nuclear translocation of signal transducer and activator of transcription 3 (STAT3) in human mammary epithelial cells transfected with H-ras (MCF10A-ras). 15-Keto PGE₂ inhibited the migration and clonogenicity of MCF10A-ras cells. In addition, subcutaneous injection of 15-keto PGE₂ attenuated xenograft tumor growth and phosphorylation of STAT3 induced by breast cancer MDA-MB-231 cells. However, a non-electrophilic analogue, 13,14-dihydro-15-keto PGE₂ failed to inhibit STAT3 signaling and was unable to suppress the growth and transformation of MCF10A-ras cells. These findings suggest that the α,β-unsaturated carbonyl moiety of 15-keto PGE₂ is essential for its suppression of STAT3 signaling. We observed that the thiol reducing agent, dithiothreitol abrogated 15-keto PGE₂-induced STAT3 inactivation and disrupted the direct interaction between 15-keto PGE₂ and STAT3. Furthermore, a molecular docking analysis suggested that Cys251 and Cys259 residues of STAT3 could be preferential binding sites for this lipid mediator. Mass spectral analysis revealed the covalent modification of recombinant STAT3 by 15-keto PGE₂ at Cys259. Taken together, thiol modification of STAT3 by 15-keto PGE₂ inactivates STAT3 which may account for its suppression of breast cancer cell proliferation and progression.

Cinobufacini promotes apoptosis of bladder cancer cells by influencing the expression of autophagy-related genes

The effects of cinobufacini on apoptosis of human bladder cancer T24 cells and the expression of autophagy-related genes and proteins were studied. The human bladder cancer T24 cells were selected, and the inhibitory effect of cinobufacini on the proliferation of human bladder cancer cells was detected by cell viability assay. Flow cytometry and Hoechst staining were used to detect the changes in the apoptosis of bladder cancer cells after being treated with cinobufacini; the changes in the expression levels of human bladder cancer cell apoptosis-related genes and proteins, cleaved caspase-3, Bax, B-cell lymphoma-2 (Bcl-2) and autophagy-related genes and proteins, p62, light chain 3 (LC3) and autophagy-related protein 7 (Atg7) after treatment with cinobufacini were detected by western blot analysis and reverse transcription polymerase chain reaction (RT-PCR). 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The results showed that 0.1 mg/ml cinobufacini significantly inhibited the proliferation of human bladder cancer cells cultured in vitro (P<0.01), and it was dose- and time-dependent. Both flow cytometry and Hoechst staining showed that cinobufacini promoted the apoptosis of cells (P<0.01), and the level of cell apoptosis increased with the increase of drug concentration. Both western blot analysis and RT-PCR showed that cinobufacini could decrease the expression level of Bcl-2 in T24 cells (P<0.01), increase the expression levels of Bax and cleaved caspase-3 (P<0.01), increase the ratio of Bax/Bcl-2 (P<0.01), upregulate the expression level of the angiotensin-related protein p62 (P<0.01), reduce the ratio of LC3-II/I (P<0.01) and decrease the expression level of Atg7 (P<0.01). After treatment with rapamycin, the expression levels of Bcl-2, Bax, cleaved caspase-3, autophagy-related genes and proteins, p62, LC3-II/I and Atg7 were similar to those in the control group. Cinobufacini can inhibit the autophagy activation of bladder cancer cells, thus promoting apoptosis of bladder cancer T24 cells and inhibiting the proliferation of T24 cells, which may provide a theoretical basis for the development of new anti-bladder cancer drugs.

A Single Nucleotide Polymorphism in HPGD Gene Is Associated with Prostate Cancer Risk

Introduction: The HPGD gene was associated with some cancers, such as colorectal, breast, prostate, and bladder. However, detailed role of 15-hydroxyprostaglandin dehydrogenase (HPGD) gene remain unclear in prostate cancer. The study was to investigate the correlation between rs8752 that located in the 3'untranslated region (UTR) of the 15-hydroxyprostaglandin dehydrogenase (HPGD) gene and prostate cancer (PCa) risk.

Materials and Methods: 109 patients from the First Affiliate Hospital of Soochow University were recruited. According to the results of pathologic diagnosis, all patients were divided into two groups (prostate cancer and benign prostatic hyperplasia). The single-nucleotide polymorphism (SNP) rs8752 was genotyped in all samples by direct sequencing.

Results: 54 prostate cancer and 55 BPH patients were included with a median age of 70.41 and 67.62 years, respectively. No statistically significant difference between two groups in patient criteria. The frequency of the GG homozygote and AG+GG genotype were 37.74% and 62.26% in 54 prostate cancer samples, while in 55BPH patients, values were 62.50% and 37.50%. Compared with the GG genotype, the combined GA+AA genotypes had a significantly higher risk of prostate cancer (OR = 2.750; 95% CI: 1.266-5.971, p = 0.011). Furthermore, the risk effect was obtained in subgroups of PCa patient group, the AA+AG genotypes significantly associated with the higher Gleason score samples (AA+AG vs GG: OR = 3.50, 95%CI = 1.106-11.072, p = 0.033) and the risk of pathological stage (AA+AG vs GG: OR = 4.00, 95%CI = 1.253-12.767, p = 0.019).

Conclusions: rs8752 in the 3'untranslated region (UTR) of the 15-hydroxyprostaglandin dehydrogenase (HPGD) gene was found to be responsible for the susceptibility to prostate cancer in Chinese individuals.

A nonrandomized trial of vitamin D supplementation for Barrett's esophagus

Background

Vitamin D deficiency may increase esophageal cancer risk. Vitamin D affects genes regulating proliferation, apoptosis, and differentiation and induces the tumor suppressor 15-hydroxyprostaglandin dehydrogenase (PGDH) in other cancers. This nonrandomized interventional study assessed effects of vitamin D supplementation in Barrett’s esophagus (BE). We hypothesized that vitamin D supplementation may have beneficial effects on gene expression including 15-PGDH in BE.

Methods

BE subjects with low grade or no dysplasia received vitamin D₃ (cholecalciferol) 50,000 international units weekly plus a proton pump inhibitor for 12 weeks. Esophageal biopsies from normal plus metaplastic BE epithelium and blood samples were obtained before and after vitamin D supplementation. Serum 25-hydroxyvitamin D was measured to characterize vitamin D status. Esophageal gene expression was assessed using microarrays.

Results

18 study subjects were evaluated. The baseline mean serum 25-hydroxyvitamin D level was 27 ng/mL (normal ≥30 ng/mL). After vitamin D supplementation, 25-hydroxyvitamin D levels rose significantly (median increase of 31.6 ng/mL, p<0.001). There were no significant changes in gene expression from esophageal squamous or Barrett’s epithelium including 15-PGDH after supplementation.

Conclusion

BE subjects were vitamin D insufficient. Despite improved vitamin D status with supplementation, no significant alterations in gene expression profiles were noted. If vitamin D supplementation benefits BE, a longer duration or higher dose of supplementation may be needed.

Helicobacter pylori modulates cyclooxygenase-2 and 15-hydroxy prostaglandin dehydrogenase in gastric cancer

Persistent infection with Helicobacter pylori may contribute to the carcinogenesis of gastric cancer through modulating local prostaglandin E₂ (PGE₂) levels. Cyclooxygenase-2 (COX-2) and 15-hydroxy prostaglandin dehydrogenase (15-PGDH) are two key enzymes that regulate PGE₂ synthesis and inactivation, respectively. The present study was designed to investigate the expression of COX-2 and 15-PGDH in gastric cancer specimens (n=66) in comparison to that of control specimens (n=70) and, furthermore, to semi-quantitatively assess the level of COX-2 and 15-PGDH mRNA and protein in tissues with or without H. pylori infection by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. It was revealed that COX-2 was expressed in almost all gastric cancer specimens infected with H. pylori (32 out of 33 specimens), but it was also expressed in 2/3 gastric cancers without H. pylori infection (22 out of 33 specimens). By contrast, COX-2 was expressed in <1/6 control subjects regardless of H. pylori infection. Furthermore, 15-PGDH was expressed in control samples but significantly downregulated in gastric cancer specimens. H. pylori infection resulted in slight inhibition of 15-PGDH in control subjects, but significant inhibition of 15-PGDH mRNA expression and protein synthesis in the gastric cancer specimens. These findings indicated that COX-2 and 15-PGDH, the two enzymes that regulate PGE₂ levels, were significantly altered in gastric cancer, and that H. pylori may contribute to gastric carcinogenesis through modulating COX-2 and 15-PGDH mRNA expression and protein synthesis.

Proteomics analysis of bladder cancer invasion: Targeting EIF3D for therapeutic intervention

Patients with advanced bladder cancer have poor outcomes, indicating a need for more efficient therapeutic approaches. This study characterizes proteomic changes underlying bladder cancer invasion aiming for the better understanding of disease pathophysiology and identification of drug targets. High resolution liquid chromatography coupled to tandem mass spectrometry analysis of tissue specimens from patients with non-muscle invasive (NMIBC, stage pTa) and muscle invasive bladder cancer (MIBC, stages pT2+) was conducted. Comparative analysis identified 144 differentially expressed proteins between analyzed groups. These included proteins previously associated with bladder cancer and also additional novel such as PGRMC1, FUCA1, BROX and PSMD12, which were further confirmed by immunohistochemistry. Pathway and interactome analysis predicted strong activation in muscle invasive bladder cancer of pathways associated with protein synthesis e.g. eIF2 and mTOR signaling. Knock-down of eukaryotic translation initiation factor 3 subunit D (EIF3D) (overexpressed in muscle invasive disease) in metastatic T24M bladder cancer cells inhibited cell proliferation, migration, and colony formation in vitro and decreased tumor growth in xenograft models. By contrast, knocking down GTP-binding protein Rheb (which is upstream of EIF3D) recapitulated the effects of EIF3D knockdown in vitro, but not in vivo. Collectively, this study represents a comprehensive analysis of NMIBC and MIBC providing a resource for future studies. The results highlight EIF3D as a potential therapeutic target.

COX2/mPGES1/PGE2 pathway regulates PD-L1 expression in tumor-associated macrophages and myeloid-derived suppressor cells

In recent years, it has been established that programmed cell death protein ligand 1 (PD-L1)-mediated inhibition of activated PD-1⁺ T lymphocytes plays a major role in tumor escape from immune system during cancer progression. Lately, the anti-PD-L1 and -PD-1 immune therapies have become an important tool for treatment of advanced human cancers, including bladder cancer. However, the underlying mechanisms of PD-L1 expression in cancer are not fully understood. We found that coculture of murine bone marrow cells with bladder tumor cells promoted strong expression of PD-L1 in bone marrow-derived myeloid cells. Tumor-induced expression of PD-L1 was limited to F4/80⁺ macrophages and Ly-6C⁺ myeloid-derived suppressor cells. These PD-L1-expressing cells were immunosuppressive and were capable of eliminating CD8 T cells in vitro. Tumor-infiltrating PD-L1⁺ cells isolated from tumor-bearing mice also exerted morphology of tumor-associated macrophages and expressed high levels of prostaglandin E₂ (PGE₂)-forming enzymes microsomal PGE₂ synthase 1 (mPGES1) and COX2. Inhibition of PGE₂ formation, using pharmacologic mPGES1 and COX2 inhibitors or genetic overexpression of PGE₂-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH), resulted in reduced PD-L1 expression. Together, our study demonstrates that the COX2/mPGES1/PGE₂ pathway involved in the regulation of PD-L1 expression in tumor-infiltrating myeloid cells and, therefore, reprogramming of PGE₂ metabolism in tumor microenvironment provides an opportunity to reduce immune suppression in tumor host.

miR-620 promotes tumor radioresistance by targeting 15-hydroxyprostaglandin dehydrogenase (HPGD)

MicroRNA contribute to tumor radiation resistance, which is an important clinical problem, and thus we are interested in identifying and characterizing their function. We demonstrate that miR-620 contributes to radiation resistance in cancer cells by increasing proliferation, and decreasing the G2/M block. We identify the hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (HPGD/15-PGDH) tumor suppressor gene as a direct miR-620 target, which results in increased prostaglandin E2 (PGE2) levels. Furthermore, we show that siRNA targeting of HPGD or administration of exogenous PGE2 recapitulates radioresistance. Targeting of the EP2 receptor that responds to PGE2 using pharmacological or genetic approaches, abrogates radioresistance. Tumor xenograft experiments confirm that miR-620 increases proliferation and tumor radioresistance in vivo. Regulation of PGE2 levels via targeting of HPGD by miR-620 is an innovative manner by which a microRNA can induce radiation resistance.

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.

Non-canonical WNT5A signaling up-regulates the expression of the tumor suppressor 15-PGDH and induces differentiation of colon cancer cells

The tumor suppressor 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme in prostaglandin E₂ catabolism and is down-regulated in colorectal cancer (CRC) tissue. Canonical Wnt signaling is frequently elevated in colon cancers and has been shown to down-regulate 15-PGDH expression. Therefore, we have in the current study investigated if the non-canonical ligand WNT5A relates to increased expression of 15-PGDH in colon cancer cells. In the same cohort of patients, we demonstrated a parallel and significant loss of 15-PGDH and WNT5A protein expression in CRC tissues compared with matched normal colon tissues. Furthermore, patients with low 15-PGDH/WNT5A expression in their tumors showed reduced survival compared with patients with high 15-PGDH/WNT5A expression. To investigate if WNT5A signaling directly affects 15-PGDH expression, we performed in vitro analyses of colon cancer cells (HT-29 and Caco-2). Both cell lines, when treated with recombinant WNT5A (rWNT5A) or Foxy-5, a WNT5A-mimicking peptide, responded by increasing their expression of 15-PGDH mRNA and protein. Our investigations showed that rWNT5A and Foxy-5 induced this increased expression of 15-PGDH through reduced β-catenin signaling as well as increased JNK/AP-1 signaling in colon cancer cells. WNT5A signaling also induced increased 15-PGDH expression in a breast cancer cell line both in vitro and in vivo. In agreement, WNT5A signaling also increased the expression of the differentiation markers sucrose-isomaltase and mucin-2 in colon cancer cells. Our results show that WNT5A signaling regulates 15-PGDH expression, thus uncovering a novel mechanism by which WNT5A acts as a tumor suppressor and suggests that increased 15-PGDH expression could be used as an indicator of a positive response to Foxy-5 in patients treated with this WNT5A agonist.

Seminal Fluid-Mediated Inflammation in Physiology and Pathology of the Female Reproductive Tract

Inflammation is a multifaceted process involving a host of resident and recruited immune cells that eliminate the insult or injury and initiate tissue repair. In the female reproductive tract (FMRT), inflammation-mediated alterations in epithelial, vascular, and immune functions are important components of complex physiological processes and many local and systemic pathologies. It is well established that intracoital and postcoital function of seminal fluid (SF) goes beyond nutritive support for the spermatozoa cells. SF, in particular, the inflammatory bioactive lipids, and prostaglandins present in vast quantities in SF, have a role in localized immune modulation and regulation of pathways that can exacerbate inflammation in the FMRT. In sexually active women SF-mediated inflammation has been implicated in physiologic processes such as ovulation, implantation, and parturition while also enhancing tumorigenesis and susceptibility to infection. This review highlights the molecular mechanism by which SF regulates inflammatory pathways in the FMRT and how alterations in these pathways contribute to physiology and pathology of the female reproductive function. In addition, based on findings from TaqMan® 96-Well Plate Arrays, on neoplastic cervical cells treated with SF, we discuss new findings on the role of SF as a potent driver of inflammatory and tumorigenic pathways in the cervix.

Inhibition of Prostaglandin Reductase 2, a Putative Oncogene Overexpressed in Human Pancreatic Adenocarcinoma, Induces Oxidative Stress-Mediated Cell Death Involving xCT and CTH Gene Expressions through 15-Keto-PGE2

Prostaglandin reductase 2 (PTGR2) is the enzyme that catalyzes 15-keto-PGE₂, an endogenous PPARγ ligand, into 13,14-dihydro-15-keto-PGE₂. Previously, we have reported a novel oncogenic role of PTGR2 in gastric cancer, where PTGR2 was discovered to modulate ROS-mediated cell death and tumor transformation. In the present study, we demonstrated the oncogenic potency of PTGR2 in pancreatic cancer. First, we observed that the majority of the human pancreatic ductal adenocarcinoma tissues was stained positive for PTGR2 expression but not in the adjacent normal parts. In vitro analyses showed that silencing of PTGR2 expression enhanced ROS production, suppressed pancreatic cell proliferation, and promoted cell death through increasing 15-keto-PGE₂. Mechanistically, silencing of PTGR2 or addition of 15-keto-PGE₂ suppressed the expressions of solute carrier family 7 member 11 (xCT) and cystathionine gamma-lyase (CTH), two important providers of intracellular cysteine for the generation of glutathione (GSH), which is widely accepted as the first-line antioxidative defense. The oxidative stress-mediated cell death after silencing of PTGR2 or addition of 15-keto-PGE₂ was further abolished after restoring intracellular GSH concentrations and cysteine supply by N-acetyl-_L-cysteine and 2-Mercaptomethanol. Our data highlight the therapeutic potential of targeting PTGR2/15-keto-PGE₂ for pancreatic cancer.

Suppressive Effect of Matrine on Tumor Invasion in N-Butyl-N-(4-Hydroxybutyl)Nitrosamine-Induced Urinary Bladder Carcinogenesis

AIMS

This study was designed to investigate the mechanisms and suppressive effects of matrine on the development of urinary bladder cancers induced by N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in rats.

METHODS

Male Sprague-Dawley rats were given BBN (200 mg/rat) twice a week for a period of 8 weeks. Oral administration of matrine (50 and 100 mg/kg) was started 1 week before BBN exposure for 35 weeks. Half of each bladder was histopathologically analyzed and the remainder was extracted for protein analysis by Western blot.

RESULTS

The bladders of BBN-treated rats demonstrated progression from epithelial hyperplasia to papillary urothelial neoplasia and even poorly differentiated invasive cancer. Matrine (50 and 100 mg/kg) treatment decreased the formation of large bladder tumors by 31.6 and 21.1%, respectively. An incidence of cancer cells was detected in rats given BBN [70% (14/20)] and matrine [50 mg/kg: 68.4% (13/19) and 100 mg/kg: 57.9% (11/19), respectively]. The frequency of invasive tumors in the matrine treatment groups [50 mg/kg: 15.4% (2/13), 100 mg/kg: 9.1% (1/11)] was significantly lower than in the BBN-alone group [57% (8/14)]. Furthermore, oral administration of matrine (50 and 100 mg/kg) markedly attenuated the BBN-induced upregulation of bladder cyclooxygenase-2 (COX-2) expression and the elevation of bladder cytosolic phospholipase A2 (cPLA2) levels. Although the contents of 15-prostaglandin dehydrogenase (PGDH), which degrades PGE2, were dramatically reduced by BBN, matrine exerted no effects on reduced PGDH contents.

CONCLUSION

Our results suggest that matrine suppressed bladder tumor invasion in a rat model, and this might be primarily mediated through regulation of the protein contents, COX-2 and cPLA2 in the bladder.

15-hydroxyprostaglandin dehydrogenase is upregulated by hydroxychloroquine in rheumatoid arthritis fibroblast-like synoviocytes

15-Hydroxyprostaglandin dehydrogenase (HPGD) is the key enzyme responsible for the metabolic inactivation of prostaglandin E2 (PGE₂) catabolism. PGE₂ is one of the predominant catabolic factors involved in rheumatoid arthritis (RA). However, the expression and regulation of HPGD in RA fibroblast-like synoviocyte (FLS) remain to be elucidated. Disease-modifying anti-rheumatic drugs (DMARDs) are the most important anti-arthritic drugs, which reduce the effect of joint injury. The aim of the present study was to assess the expression of HPGD in RA tissues and cells, and normal synovial tissues and cells. The effect of the most popular DMARDs, hydroxychloroquine, on the expression of HPGD in RA-FLS was also investigated. Western blotting and immuno-histochemical analysis demonstrated that the expression levels of HPGD in human synovium were lower in RA synovium compared with the normal and OA synovium. In RA-FLS, the expression of HPGD was increased following treatment with several DMARDs, including sulfasalazine, methotrexate, and hydroxychloroquine. Hydroxychloroquine (10 µM) treatment induced the phosphorylation of ERK, SAPK/JNK and p38. Hydroxychloroquine induced a decrease in the release of PGE₂, which was restored by mitogen-activated protein (MAP) kinase pathway inhibitors. Hydroxychloroquine may therefore, affect the pathogenesis of RA through the MAP kinase pathway by regulating the expression of HPGD.

Hypoxia activates 15-PGDH and its metabolite 15-KETE to promote pulmonary artery endothelial cells proliferation via ERK1/2 signalling

BACKGROUND AND PURPOSE

Dysfunction and injury of endothelial cells in the pulmonary artery play critical roles in the hypertension induced by chronic hypoxia. One consequence of hypoxia is increased activity of 15-hydroxyprostaglandin dehydrogenase (PGDH). Here, we have explored, in detail, the effects of hypoxia on the proliferation of pulmonary artery endothelial cells.

EXPERIMENTAL APPROACH

We used bromodeoxyuridine incorporation, cell-cycle analysis, immunohistochemistry and Western blot analysis to study the effects of hypoxia, induced 15-PGDH) activity and its product, 15-keto-6Z, 8Z, 11Z, 13E-eicosatetraenoic acid (15-KETE), on endothelial cell proliferation. Scratch-wound and tube formation assays were also used to study migration of endothelial cells.

KEY RESULTS

15-KETE increased DNA synthesis and enhanced the transition from the G0 /G1 phase to the S phase in hypoxia. Inhibition of 15-PGDH or siRNA for 15-PGDH reversed these effects. 15-KETE also activated the ERK1/2 signalling pathway. 15-KETE-induced cell migration and tube formation were reversed by blocking ERK1/2, but not the p38 MAPK pathway.

CONCLUSIONS AND IMPLICATIONS

Hypoxia-induced endothelial proliferation and migration, an important underlying mechanism contributing to hypoxic pulmonary vascular remodelling, appears to be mediated by 15-PGDH and 15-KETE, via the ERK1/2 signalling pathway.

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.

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.

Effect of 15-hydroxyprostaglandin dehydrogenase gene on the proliferation of gastric cancer cell murine forestomach carcinoma

The aim of the present study was to construct the eukaryotic expression vector pcDNA3.1/15-PGDH. The vector was used to transfect mouse murine forestomach carcinoma (MFC) cancer cells and observe the effects of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) on the proliferation of MFC. pcDNA3.1/15-PGDH was constructed using gene recombination technology and the vector was used to transfect MFC cells to build a stable transfected cell strain. The expression levels of 15-PGDH in the transfected cells were detected using reverse transcription polymerase chain reaction. Optical Density (OD) values were determined using an MTT assay and used to draw cell growth curves. The effects of 15-PGDH on the proliferation of MFC were observed using a clone formation experiment. Following successful transfection by 15-PGDH, the relative expression levels of 15-PGDH in the MFC/15-PGDH cells were significantly higher (1.06±0.08) (P<0.01) compared with the empty plasmid-transfected group (0.22±0.01) and the untransfected group (0.21±0.01). Following transfection by 15-PGDH, cell growth was markedly inhibited. The MTT results showed that on days 4, 6 and 8, the 15-PGDH-transfected group had a low OD on average, which was significantly different (P<0.05) from the empty plasmid-transfected group or the untransfected group. The 15-PGDH-transfected group had a plating efficiency of 18%, and compared with the untransfected group (63%) and the empty plasmid-transfected group (59%), clone formation was significantly inhibited (P<0.01). Results of the present study indicate that transfection by 15-PGDH may significantly inhibit the proliferation and clone formation of MFC cells.

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.

Inhibition of 15-hydroxyprostaglandin dehydrogenase by Helicobacter pylori in human gastric carcinogenesis

Helicobacter pylori (H. pylori) infection induces a chronic inflammatory response, which promotes gastric carcinogenesis. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) plays a key role as a tumor suppressor in gastrointestinal cancers. The aim of this study was to elucidate the role of 15-PGDH in gastric carcinogenesis associated with H. pylori. 15-PGDH expression in gastric biopsies from H. pylori-infected (n = 25) and noninfected (n = 15) subjects was analyzed by quantitative real-time PCR, Western blot analysis, and immunohistochemistry. 15-PGDH DNA methylation was evaluated by methylation-specific PCR and pyrosequencing. The expression of 15-PGDH, Snail, extracellular signal-regulated kinase (ERK)1/2, TLR4, and MyD88 in response to H. pylori infection was assessed by immunoblot analysis. Compared with negative specimens, H. pylori-positive specimens had 2-fold lower 15-PGDH mRNA levels and significantly less 15-PGDH protein. In four H. pylori-infected subjects with longitudinal follow-up, the suppression of 15-PGDH expression was reversed by H. pylori eradication therapy. In parallel with suppressing 15-PGDH expression, H. pylori infection activated expression of TLR4 and MyD88 expression, increased levels of phospho-ERK1/2, and increased expression of EGF receptor (EGFR)-Snail. Inhibition of Snail and MyD88 reversed suppression of 15-PGDH expression, and siMyD88 reduced phosphorylated ERK1/2. Similarly, treatment with an ERK1/2 and EGFR inhibitor also restored 15-PGDH expression. H. pylori appeared to promote gastric carcinogenesis by suppressing 15-PGDH. This process is mediated by the TLR4/MyD88 pathway via ERK1/2 or EGFR-Snail transcriptional regulation. 15-PGDH may be a useful marker and a potential therapeutic target in H. pylori-induced gastric carcinogenesis.

Loss of 15-hydroxyprostaglandin dehydrogenase indicates a tumor suppressor role in pituitary adenomas

15-hydroxyprostaglandin dehydrogenase (15-PGDH) may function as a tumor suppressor that antagonizes the action of the cyclooxygenase-2 (COX-2) oncogene in several types of tumors. However, it is unknown if it has a role in the pituitary. Recently, our group found that 15-PGDH expression was low in prolactin (PRL) secreting adenomas (prolactinomas) and growth hormone (GH) secreting adenomas (GHomas) using fiber-optic BeadArray technology. In this study, we examined the relative expression of 15-PGDH and COX-2 mRNA in clinical specimens and examined the effects of 15-PGDH on GH3 rat pituitary tumor cell proliferation, apoptosis and hormone secretion. 15-PGDH expression was lower and COX-2 expression was higher in prolactinomas and GHomas compared with normal controls. Overexpressed 15-PGDH inhibited tumor cell proliferation and induced apoptosis. It had a significant suppressive effect on mRNA levels and on the secretion of PRL and GH in GH3 cells. The inhibition of cell proliferation was accompanied by the decreased expression of cox-2, matrix metalloproteinase-9 (MMP-9) and B cell leukemia/lymphoma-2 (Bcl-2). These data are suggestive of a previously unrecognized pathway in pituitary tumorigenesis, and this novel observation may shed light on therapeutic strategies for pituitary tumors.

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.

Regulation of immune responses by prostaglandin E2

PGE(2), an essential homeostatic factor, is also a key mediator of immunopathology in chronic infections and cancer. The impact of PGE(2) reflects the balance between its cyclooxygenase 2-regulated synthesis and 15-hydroxyprostaglandin dehydrogenase-driven degradation and the pattern of expression of PGE(2) receptors. PGE(2) enhances its own production but suppresses acute inflammatory mediators, resulting in its predominance at late/chronic stages of immunity. PGE(2) supports activation of dendritic cells but suppresses their ability to attract naive, memory, and effector T cells. PGE(2) selectively suppresses effector functions of macrophages and neutrophils and the Th1-, CTL-, and NK cell-mediated type 1 immunity, but it promotes Th2, Th17, and regulatory T cell responses. PGE(2) modulates chemokine production, inhibiting the attraction of proinflammatory cells while enhancing local accumulation of regulatory T cells cells and myeloid-derived suppressor cells. Targeting the production, degradation, and responsiveness to PGE(2) provides tools to modulate the patterns of immunity in a wide range of diseases, from autoimmunity to cancer.

15-Hydroxyprostaglandin dehydrogenase associates with poor prognosis in breast cancer, induces epithelial-mesenchymal transition, and promotes cell migration in cultured breast cancer cells

Breast cancer is the most frequent cancer and the leading cause of cancer-related deaths in women worldwide. The prognosis of breast cancer is tightly correlated with the degree of spread beyond the primary tumour. Arachidonic acid (AA) and prostaglandin E(2) (PGE(2)) are known to regulate tumour metastasis enabling epithelial-mesenchymal transition (EMT). However, the detailed role of 15-hydroxyprostaglandin dehydrogenase (HPGD), the key enzyme degrading prostaglandin E(2) , remains unclear in breast cancer. Here, we show that HPGD mRNA is overexpressed in a subset of clinical breast cancers compared to normal breast tissue samples and that high HPGD mRNA expression associates with poor prognosis. Immunohistochemical staining of primary breast cancer and lymph node metastasis tissue samples confirmed high HPGD protein expression in 20% of the samples, as well as associated HPGD expression with aggressive characteristics, such as increased risk of disease relapse and shorter disease-free survival. Results from cultured cells indicated abundant HPGD expression in highly metastatic breast cancer cells, and impairment of HPGD expression using RNA interference led to a significant decrease in transforming growth factor-β signalling, in cellular arachidonic acid levels as well as in cell migration. Furthermore, gene expression microarray analysis followed by quantitative RT-PCR validation showed that HPGD silencing decreased aryl hydrocarbon receptor signalling and induced mesenchymal-epithelial transition. In conclusion, our results indicate that HPGD is highly expressed in metastatic and aggressive breast cancer and promotes EMT and migration in breast cancer 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.

11-Oxoeicosatetraenoic acid is a cyclooxygenase-2/15-hydroxyprostaglandin dehydrogenase-derived antiproliferative eicosanoid

Previously, we established that 11(R)-hydroxy-5,8,12,14-(Z,Z,E,Z)-eicosatetraenoic acid (HETE) was a significant cyclooxygenase (COX)-2-derived arachidonic acid (AA) metabolite in epithelial cells. Stable isotope dilution chiral liquid chromatography (LC)-electron capture atmospheric pressure chemical ionization (ECAPCI)/mass spectrometry (MS) was used to quantify COX-2-derived eicosanoids in the human colorectal adenocarcinoma (LoVo) epithelial cell line, which expresses both COX-2 and 15-hydroxyprostaglandin dehydrogenase (15-PGDH). 11(R)-HETE secretion reached peak concentrations within minutes after AA addition before rapidly diminishing, suggesting further metabolism had occurred. Surprisingly, recombinant 15-PGDH, which is normally specific for oxidation of eicosanoid 15(S)-hydroxyl groups, was found to convert 11(R)-HETE to 11-oxo-5,8,12,14-(Z,Z,E,Z)-eicosatetraenoic acid (ETE). Furthermore, LoVo cell lysates converted 11(R)-HETE to 11-oxo-ETE and inhibition of 15-PGDH with 5-[[4-(ethoxycarbonyl)phenyl]azo]-2-hydroxy-benzeneacetic acid (CAY10397) (50 μM) significantly suppressed endogenous 11-oxo-ETE production with a corresponding increase in 11(R)-HETE. These data confirmed COX-2 and 15-PGDH as enzymes responsible for 11-oxo-ETE biosynthesis. Finally, addition of AA to the LoVo cells resulted in rapid secretion of 11-oxo-ETE into the media, reaching peak levels within 20 min of starting the incubation. This was followed by a sharp decrease in 11-oxo-ETE levels. Glutathione (GSH) S-transferase (GST) was found to metabolize 11-oxo-ETE to the 11-oxo-ETE-GSH (OEG)-adduct in LoVo cells, as confirmed by LC–MS/MS analysis. Bromodeoxyuridine (BrdU)-based cell proliferation assays in human umbilical vein endothelial cells (HUVECs) revealed that the half-maximal inhibitory concentration (IC₅₀) of 11-oxo-ETE for inhibition of HUVEC proliferation was 2.1 μM. These results show that 11-oxo-ETE is a novel COX-2/15-PGDH-derived eicosanoid, which inhibits endothelial cell proliferation with a potency that is similar to that observed for 15d-PGJ₂.

15-Hydroxyprostaglandin dehydrogenase as a novel molecular target for cancer chemoprevention and therapy

Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E(2) (PGE(2)) upon inflammatory insults. Overproduction of PGE(2) stimulates proliferation of various cancer cells, confers resistance to apoptosis of cancerous or transformed cells, and accelerates metastasis and angiogenesis. Excess PGE(2) undergoes metabolic inactivation which is catalyzed by NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). In this context, 15-PGDH has been speculated as a physiological antagonist of COX-2 and a tumor suppressor. Thus, overexpression of 15-PGDH has been known to protect against experimentally induced carcinogenesis and renders the cancerous or transformed cells susceptible to apoptosis by counteracting oncogenic action of PGE(2). In contrast, silence of 15-PGDH is observed in some cancer cells, which is associated with epigenetic modification, such as DNA methylation and histone deacetylation, in the promoter region of 15-PGDH. A variety of compounds capable of inducing the expression of 15-PGDH have been reported, which include the histone deacetylase inhibitors, nonsteroidal anti-inflammatory drugs, and peroxisome proliferator-activated receptor-gamma agonists. Therefore, 15-PGDH may be considered as a novel molecular target for cancer chemoprevention and therapy. This review highlights the role of 15-PGDH in carcinogenesis and its regulation.

Aberrant PGE₂ metabolism in bladder tumor microenvironment promotes immunosuppressive phenotype of tumor-infiltrating myeloid cells

Bladder cancer is associated with enhanced inflammation and characterized by deregulated prostanoid metabolism. Here we examined prostaglandin E₂ (PGE₂) metabolism and myeloid cell subsets that infiltrate tumor tissue using two xenograft models of human bladder cancer. Human bladder tumor xenografts implanted into athymic nude mice become highly infiltrated with host CD11b myeloid cells of bone marrow origin. Fast growing SW780 bladder tumor xenografts were infiltrated with heterogeneous CD11b myeloid cell subsets including tumor-associated macrophages and myeloid-derived suppressor cells. In contrast, majority of myeloid cells in tumor tissue from slow growing bladder cancer Urothel 11 displayed more immature, homogenous phenotype and comprised mostly MHC II class-negative myeloid-derived suppressor cells. We demonstrate that human bladder tumors secrete substantial amounts of PGE₂. Normal bone marrow myeloid cell progenitors cultured in the presence of a bladder tumor-conditioned medium, which is enriched for PGE₂, failed to differentiate into mature APCs and acquired phenotype of the myeloid-derived suppressor cells or inflammatory macrophages with up-regulated chemokine receptor CXCR4. Collectively our data demonstrate that enhanced cancer-related inflammation and deregulated PGE₂ metabolism in tumor microenvironment promote immunosuppressive pro-tumoral phenotype of myeloid cells in bladder cancer. These data also suggest that not only local tumor microenvironment but other factors such as stage of cancer disease and pace of tumor growth could markedly influence the phenotype, differentiation and immune function of myeloid cells in tumor tissue.

Circulating and tumor-infiltrating myeloid cell subsets in patients with bladder cancer

Both cancer-related inflammation and tumor-induced immune suppression are associated with expansion of myeloid cell subsets including myeloid-derived suppressor cells. However, little known regarding characteristics of myeloid cells in patients with bladder cancer. In this study, we analyzed myeloid cells from peripheral blood (PBMC) and tumor tissue that were collected from patients with superficial noninvasive and invasive urothelial carcinomas. Our results demonstrate that PBMC from bladder cancer patients contain two major CD11b myeloid cell subsets: granulocyte-type CD15(high) CD33(low) cells and monocyte-type CD15(low) CD33(high) cells. The number of circulating granulocytic but not monocytic myeloid cells in cancer patients was markedly increased when compared to healthy individuals. Both myeloid cell subsets from cancer patients were highly activated and produced substantial amounts of proinflammatory chemokines/cytokines including CCL2, CCL3, CCL4, G-CSF, IL-8 and IL-6. Granulocytic myeloid cells were able to inhibit in vitro T cell proliferation through induction of CD4(+) Foxp3(+) T regulatory cells. Analysis of bladder cancer tissues revealed that tumors were infiltrated with monocyte-macrophage CD11b(+) HLA-DR(+) and granulocytic CD11b(+) CD15(+) HLA-DR(-) myeloid cells. Collectively, this study identifies myeloid cell subsets in patients with bladder cancer. We demonstrate that these highly activated inflammatory myeloid cells represent a source of multiple chemokines/cytokines and may contribute to inflammation and immune dysfunction in bladder cancer.

Arachidonic acid pathway members PLA2G7, HPGD, EPHX2, and CYP4F8 identified as putative novel therapeutic targets in prostate cancer

The arachidonic acid and prostaglandin pathway has been implicated in prostate carcinogenesis, but comprehensive studies of the individual members in this key pathway are lacking. Here, we first conducted a systematic bioinformatic study of the expression of 36 arachidonic acid pathway genes across 9783 human tissue samples. The results showed that the PLA2G7, HPGD, EPHX2, and CYP4F8 genes are highly expressed in prostate cancer. Functional studies using RNA interference in prostate cancer cells indicated that all four genes are also essential for cell growth and survival. Clinical validation confirmed high PLA2G7 expression, especially in ERG oncogene-positive prostate cancers, and its silencing sensitized ERG-positive prostate cancer cells to oxidative stress. HPGD was highly expressed in androgen receptor (AR)-overexpressing advanced tumors, as well as in metastatic prostate cancers. EPHX2 mRNA correlated with AR in primary prostate cancers, and its inhibition in vitro reduced AR signaling and potentiated the effect of antiandrogen flutamide in cultured prostate cancer cells. In summary, we identified four novel putative therapeutic targets with biomarker potential for different subtypes of prostate cancer. In addition, our results indicate that inhibition of these enzymes may be particularly powerful when combined with other treatments, such as androgen deprivation or induction of oxidative stress.

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.

Role of COX-2 and 15-PGDH expression in colorectal tumorigenesis

AIM: To investigate the role of cyclooxygenase (COX)-2 and 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression in colorectal tumorigenesis.

METHODS: Dissected samples of colorectal polyps from 48 consecutive patients with adenomatous polyps and 25 patients with hyperplastic polyps, who underwent colonoscopy at our hospital from February 2009 to October 2009, were used in this study. Carcinomatous tissue samples surgically dissected from 15 patients with colorectal adenocarcinoma and 15 endoscopically taken normal colorectal mucosal samples were used as controls. The protein and mRNA expression of COX-2 and 15-PGDH was analyzed by RT-PCR and Western blot, respectively.

RESULTS: Colorectal adenocarcinoma showed the highest expression level of COX-2 mRNA and protein, followed by adenomatous polyps, hyperplastic polyps, and normal mucosa (429.184 ± 45.721 vs 9.859 ± 1.151, 83.387 ± 15.957, 155.732 ± 28.395; 0.772 ± 1.054 vs 0.138 ± 0.025, 0.557 ± 0.131, 0.509 ± 0.087, all P < 0.05). There was no significant difference in COX-2 protein expression level between adenomatous polyps and hyperplastic polyps though significant differences were noted among normal mucosa, polyps, and carcinoma. Normal colorectal mucosa showed the highest expression level of 15-PGDH mRNA and protein, followed by hyperplastic polyps, adenomatous polyps and adenocarcinoma (5.234 ± 0.358 vs 918.260 ± 82.116, 125.380 ± 28.713, 12.036 ± 3.509; 0.186 ± 0.058 vs 0.762 ± 0.165, 0.443 ± 0.085, 0.202 ± 0.042, all P < 0.05). The absence of 15-PGDH protein expression was found in both adenocarcinoma and adenomatous polyps. There was no significant difference in 15-PGDH protein expression level between adenomatous polyps and adenocarcinoma though significant differences were noted in 15-PGDH protein expression levels among normal mucosa, hyperplastic polyps, and carcinoma.

CONCLUSION: Increased COX-2 expression and decreased 15-PGDH expression may be involved in colorectal carcinogenesis.

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.

Association of hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) variants and colorectal cancer risk

A recent study examined associations of tagging single nucleotide polymorphisms (tagSNPs) in 43 fatty acid metabolism-related genes and risk of colorectal cancer (CRC), showing rs8752, rs2612656 and a haplotype [comprising both of the single nucleotide polymorphisms (SNPs)] in the hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) gene to be positively associated with CRC risk. In the present study, we attempted to replicate these single marker and haplotype associations, using 1795 CRC cases and 1805 controls from the German Darmkrebs: Chancen der Verhütung durch Screening study (DACHS). In addition to rs8752 and rs2612656, HPGD tagSNPs rs9312555, rs17360144 and rs7349744 were genotyped for haplotype analyses. Except for a marginally significant inverse association of HPGD rs8752 with CRC risk [odds ratio (OR) = 0.85; 95% confidence interval (CI) = 0.74, 0.98; P = 0.03], none of the analyzed tagSNPs showed any association with CRC. Subset analyses for colon and rectal cancers yielded similar, yet non-significant risk estimates at all five loci. Also, none of the haplotypes was found to be associated with CRC, colon or rectal cancers. However, rs8752 was significantly associated with a decreased risk of CRC among individuals with a body mass index < 30 (OR = 0.82, 95% CI = 0.70, 0.95, P = 0.01) as well as among smokers (OR = 0.74, 95% CI = 0.61, 0.90, P = 0.003). Yet, our data do not support the previously reported associations of HPGD tagSNPs and risk of CRC.