15-Hydroxyprostaglandin dehydrogenase is an in vivo suppressor of colon tumorigenesis

Aspirin, platelet inhibition and cancer prevention

Several lines of evidence are consistent with the hypothesis that activated platelets contribute to colorectal tumorigenesis and metastatization through direct cell-cell interactions and the release of different lipid and protein mediators, and microvesicles. This review examines the clinical pharmacology of low-dose aspirin as a basis for discussing the mechanisms underlying the contribution of platelets to neoplastic transformation and progression of cancer via the development of metastases.

Chemopreventive Efficacy of the Cyclooxygenase-2 (Cox-2) Inhibitor, Celecoxib, Is Predicted by Adenoma Expression of Cox-2 and 15-PGDH

Background: The Adenoma Prevention with Celecoxib (APC) Trial showed that cyclooxygenase-2 (Cox-2) inhibitor, celecoxib, decreased adenoma development in patients at high risk for colorectal cancer. A prospectively planned analysis of the APC Trial tested the hypothesis that expression of target enzymes in adenomas removed before beginning study treatment would identify individuals at high risk of adenoma development, and/or predict response to Cox-2 inhibition.Methods: Pre-treatment adenomas were examined using immunohistochemistry to assess expression of Cox-2 (high vs. low) and 15-prostaglandin dehydrogenase (15-PGDH, presence vs. loss). The Mantel-Cox test evaluated whether these markers predicted benefit from celecoxib for reduction of adenoma detection.Results: Patients whose pre-treatment adenomas demonstrated elevated Cox-2 achieved the greatest adenoma reduction with celecoxib treatment [RR, 0.37; 95% confidence interval (CI), 0.22-0.61; P = 0.0001]. This reduction was less in the low Cox-2 category (RR, 0.64; 95% CI, 0.56-0.73). Patients whose pre-treatment adenomas showed 15-PGDH loss had a similar treatment-associated reduction in adenoma detection (RR, 0.60; 95% CI, 0.52-0.69; P < 0.0001). In contrast, patients with intact tumor 15-PGDH expression did not significantly benefit from celecoxib (RR, 0.73; 95% CI, 0.47-1.12; P = 0.15). However, subset analysis suggested that this lack of response to celecoxib was confined to those patients with 15-PGDH intact tumors who were also using cardioprotective aspirin.Conclusions: The expression of Cox-2 and 15-PGDH in pre-treatment adenomas provides predictive information in patients treated with celecoxib for prevention of colorectal adenomas.Impact: The results of this study show that Cox-2 and 15-PGDH are characteristics of colorectal adenomas that may be used to predict nonsteroidal anti-inflammatory drug chemoprevention efficacy. Cancer Epidemiol Biomarkers Prev; 27(7); 728-36. ©2018 AACR.

Role of prostanoids in gastrointestinal cancer

Chronic inflammation is a risk factor for gastrointestinal cancer and other diseases. Most studies have focused on cytokines and chemokines as mediators connecting chronic inflammation to cancer, whereas the involvement of lipid mediators, including prostanoids, has not been extensively investigated. Prostanoids are among the earliest signaling molecules released in response to inflammation. Multiple lines of evidence suggest that prostanoids are involved in gastrointestinal cancer. In this Review, we discuss how prostanoids impact gastrointestinal cancer development. In particular, we highlight recent advances in our understanding of how prostaglandin E2 induces the immunosuppressive microenvironment in gastrointestinal cancers.

Dietary ALA, EPA and DHA have distinct effects on oxylipin profiles in female and male rat kidney, liver and serum

There is much data on the effects of dietary n-3 fatty acids on tissue fatty acid compositions, but comparable comprehensive data on their oxygenated metabolites (oxylipins) is limited. The effects of providing female and male rats with diets high in α-linolenic acid (ALA), EPA or DHA for 6 weeks on oxylipins and fatty acids in kidney, liver and serum were therefore examined. The oxylipin profile generally reflected fatty acids, but it also revealed unique effects of individual n-3 fatty acids that were not apparent from fatty acid data alone. Dietary ALA increased renal and serum DHA oxylipins even though DHA itself did not increase, while dietary EPA did not increase DHA oxylipins in kidney or liver, suggesting that high EPA may inhibit this conversion. Oxylipin data generally corroborated fatty acid data that indicated that DHA can be retroconverted to EPA and that further retroconversion to ALA is limited. Dietary n-3 fatty acids decreased n-6 fatty acids and their oxylipins (except linoleic acid and its oxylipins), in order of effectiveness of DHA > EPA > ALA, with some exceptions: several arachidonic acid oxylipins modified at carbon 15 were not lower in all three sites, and EPA had a greater effect on 12-hydroxy-eicosatetraenoic acid and its metabolites in the liver. Oxylipins were predominantly higher in males, which was not reflective of fatty acids. Tissue-specific oxylipin profiles, therefore, provide further information on individual dietary n-3 fatty acid and sex effects that may help explain their unique physiological effects and have implications for dietary recommendations.

A potential anti-tumor effect of leukotriene C4 through the induction of 15-hydroxyprostaglandin dehydrogenase expression in colon cancer cells

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. Cyclooxygenase-2, which plays a key role in the biosynthesis of prostaglandin E2 (PGE2), is often up-regulated in CRC and in other types of cancer. PGE2 induces angiogenesis and tumor cell survival, proliferation and migration. The tumor suppressor 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a key enzyme in PGE2 catabolism, converting it into its inactive metabolite 15-keto-PGE2, and is often down-regulated in cancer. Interestingly, CRC patients expressing high levels of the cysteinyl leukotriene 2 (CysLT2) receptor have a good prognosis; therefore, we investigated a potential link between CysLT2 signaling and the tumor suppressor 15-PGDH in colon cancer cells.We observed a significant up-regulation of 15-PGDH after treatment with LTC4, a CysLT2 ligand, in colon cancer cells at both the mRNA and protein levels, which could be reduced by a CysLT2 antagonist or a JNK inhibitor. LTC4 induced 15-PGDH promoter activity via JNK/AP-1 phosphorylation. Furthermore, we also observed that LTC4, via the CysLT2/JNK signaling pathway, increased the expression of the differentiation markers sucrase-isomaltase and mucin-2 in colon cancer cells and that down-regulation of 15-PGDH totally abolished the observed increase in these markers.In conclusion, the restoration of 15-PGDH expression through CysLT2 signaling promotes the differentiation of colon cancer cells, indicating an anti-tumor effect of CysLT2 signaling.

ROS-Mediated 15-Hydroxyprostaglandin Dehydrogenase Degradation via Cysteine Oxidation Promotes NAD+-Mediated Epithelial-Mesenchymal Transition

Nicotinamide adenine dinucleotide (NAD) levels decrease with aging as a result of aging-associated CD38 upregulation. Here, we established a cell model with decreased cellular NAD levels by overexpressing CD38 or treating cells with FK866, an inhibitor of nicotinamide phosphoribosyltransferase. We revealed that decreased NAD triggered reactive oxygen species (ROS)-mediated degradation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which drove cells to undergo epithelial-mesenchymal transition (EMT). Moreover, we showed that oxidation of the Cys44 residue to sulfonic acid in 15-PGDH led to its degradation via non-canonical ubiquitination-proteasome and autophagy pathways. Mutation of Cys44 to alanine abolished ROS-induced 15-PGDH degradation. We demonstrated that 15-PGDH silencing promoted EMT, whereas supplementation with NAD precursors increased NAD and 15-PGDH stability, and reversed the EMT process. Taken together, these results suggest that declining NAD levels contribute to age-dependent increases in cancer incidence, and repletion of NAD precursors is beneficial for increasing 15-PGDH expression.

Integration of pharmacology, molecular pathology, and population data science to support precision gastrointestinal oncology

Precision medicine has a goal of customizing disease prevention and treatment strategies. Under the precision medicine paradigm, each patient has unique pathologic processes resulting from cellular genomic, epigenomic, proteomic, and metabolomic alterations, which are influenced by pharmacological, environmental, microbial, dietary, and lifestyle factors. Hence, to realize the promise of precision medicine, multi-level research methods that can comprehensively analyze many of these variables are needed. In order to address this gap, the integrative field of molecular pathology and population data science (i.e., molecular pathological epidemiology) has been developed to enable such multi-level analyses, especially in gastrointestinal cancer research. Further integration of pharmacology can improve our understanding of drug effects, and inform decision-making of drug use at both the individual and population levels. Such integrative research demonstrated potential benefits of aspirin in colorectal carcinoma with PIK3CA mutations, providing the basis for new clinical trials. Evidence also suggests that HPGD (15-PDGH) expression levels in normal colon and the germline rs6983267 polymorphism that relates to tumor CTNNB1 (β-catenin)/WNT signaling status may predict the efficacy of aspirin for cancer chemoprevention. As immune checkpoint blockade targeting the CD274 (PD-L1)/PDCD1 (PD-1) pathway for microsatellite instability-high (or mismatch repair-deficient) metastatic gastrointestinal or other tumors has become standard of care, potential modifying effects of dietary, lifestyle, microbial, and environmental factors on immunotherapy need to be studied to further optimize treatment strategies. With its broad applicability, our integrative approach can provide insights into the interactive role of medications, exposures, and molecular pathology, and guide the development of precision medicine.

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.

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.

Herbal formula SC-E1 suppresses lipopolysaccharide-stimulated inflammatory responses through activation of Nrf2/HO-1 signaling pathway in RAW 264.7 macrophages

BACKGROUND

SC-E1 is a novel herbal formula consisting of five oriental medicinal herbs used frequently in traditional herbal medicine for the treatment of inflammatory diseases in Korea. This study examined the effects of SC-E1 on lipopolysaccharide (LPS)-stimulated macrophages and the molecular mechanism involved.

METHODS

The cytotoxic effect of the SC-E1 extract was evaluated in RAW 264.7 cells by MTT assay. The effects of SC-E1 on the free radical scavenging and generation of intracellular reactive oxygen species were measured using DPPH and DCFH-DA, respectively. The effects of SC-E1 on the production of pro-inflammatory cytokines, inflammatory mediators, and related products were determined by ELISA and western blotting. The molecular mechanism and the nuclear translocation of nuclear factor-kappa B (NF-κB) and NF-E2-related factor 2 (Nrf2) were examined by western blot analysis and immunocytochemistry.

RESULTS

SC-E1 exhibited strong anti-oxidant activity and inhibited LPS-induced NO secretion as well as iNOS expression and the production of pro-inflammatory cytokines, without affecting the cell viability. SC-E1 also suppressed the LPS-induced NF-κB activation and the mitogen-activated protein kinase (MAPK) pathway. Moreover, SC-E1 induced heme oxygenase-1 (HO-1) expression via the nuclear translocation of Nrf2. The inhibitory effects of SC-E1 on the production of pro-inflammatory cytokines were abrogated by treatment with SnPP, an HO-1 inhibitor.

CONCLUSION

These results suggest that SC-E1 exerts its anti-oxidant and anti-inflammatory effects through the inhibition of NF-κB and MAPK as well as Nrf2-mediated HO-1 induction in macrophages. These findings provide evidences for SC-E1 to be considered as a new prescription for treating inflammatory diseases.

Aspirin and Cancer

The place of aspirin in primary prevention remains controversial, with North American and European organizations issuing contradictory treatment guidelines. More recently, the U.S. Preventive Services Task Force recommended "initiating low-dose aspirin use for the primary prevention of cardiovascular disease (CVD) and colorectal cancer in adults aged 50 to 59 years who have a 10% or greater 10-year CVD risk, are not at increased risk for bleeding, have a life expectancy of at least 10 years, and are willing to take low-dose aspirin daily for at least 10 years." This recommendation reflects increasing evidence for a chemopreventive effect of low-dose aspirin against colorectal (and other) cancer. The intent of this paper is to review the evidence supporting a chemopreventive effect of aspirin, discuss its potential mechanism(s) of action, and provide a conceptual framework for assessing current guidelines in the light of ongoing studies.

Inhibitors of 15-Prostaglandin Dehydrogenase To Potentiate Tissue Repair

The enzyme 15-prostaglandin dehydrogenase (15-PGDH) catalyzes the first step in the degradation of prostaglandins including PGE2. It is a negative regulator of tissue repair and regeneration in multiple organs. Accordingly, inhibitors of 15-PGDH are anticipated to elevate in vivo levels of PGE2 and to promote healing and tissue regeneration. The small molecule SW033291 (1) inhibits 15-PGDH with K_i = 0.1 nM in vitro, doubles PGE2 levels in vivo, and shows efficacy in mouse models of recovery from bone marrow transplantation, ulcerative colitis, and partial hepatectomy. Here we describe optimized variants of 1 with improved solubility, druglike properties, and in vivo activity.

In-vitro Wound Healing Effect of 15-Hydroxyprostaglandin Dehydrogenase Inhibitor from Plant

BACKGROUND

Prostaglandins (PGs) have short existence in vivo because they are rapidly metabolized by NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) to 15-ketoprostaglandins. Inhibition of 15-PGDH causes elevated level of PGE₂ in cellular system. It will be valuable for the therapeutic management of diseases requiring elevated PGE₂ levels, like wound healing.

OBJECTIVE

Ninety-eight plant samples were screened for the discovery of potent 15-PGDH inhibitor. Among them, top five plant extracts as potent 15-PGDH inhibitor were chosen to determine PGE₂ release from HaCaT (Keratinocyte cell line) cell line. Finally, top 15-PGDH inhibitor was selected to evaluate in vitro wound healing effect on HaCaT scratch model.

METHOD

The inhibitory activity for 15-PGDH inhibitors was evaluated using fluorescence spectrophotometer by measuring the formation of NADH at 468 nm following excitation at 340 nm. Cell viability assay and PGE₂ release was evaluated in HaCaT cell line after treatment of 15-PGDH inhibitors. Scratches were made using sterile 200 μL on HaCaT cell and wound-healing effect was evaluated after treatment of 15-PGDH inhibitor.

RESULTS

15-PGDH inhibitors elevated PGE₂ levels in concentration-dependent manner. Ethanol extract of Artocarpus heterophyllus (EEAH), the most potent 15-PGDH inhibitor (IC₅₀ = 0.62 µg/mL) with least cytotoxicity (IC₅₀ = 670 µg/ml), elevated both intracellular and extracellular PGE₂ levels. EEAH facilitated in-vitro wound healing in a HaCaT (Keratinocyte cell line) scratch model.

CONCLUSION

EEAH might apply to treat dermal wounds by elevating PGE₂ levels via COX-1 induction and 15-PGDH inhibition.

SUMMARY

Biological inactivation of 15-PGDH causes elevated level of PGE₂ which will be useful for the management of disease that requires elevated level of PGE₂. Abbreviations used: 15-PGDH: 15-hydroxyprostaglandin dehydrogenase, COX: Cyclooxygenase, DTT: Dithiothreitol, DMEM: Dulbecco's modified Eagle's media, EEAH: Ethanol extract of Artocarpus heterophyllus, MRP4: Multidrug resistance 4, PGs: Prostaglandins, PGT: Prostaglandin transporter, SDS: Sodium dodecylsulfate.

Prostaglandin E2 Activates YAP and a Positive-Signaling Loop to Promote Colon Regeneration After Colitis but Also Carcinogenesis in Mice

BACKGROUND & AIMS

Prostaglandin E₂ (PGE₂) is mediator of inflammation that regulates tissue regeneration, but its continual activation has been associated with carcinogenesis. Little is known about factors in the PGE₂ signaling pathway that contribute to tumor formation. We investigated whether yes-associated protein 1 (YAP1), a transcriptional co-activator in the Hippo signaling pathway, mediates PGE₂ function.

METHODS

DLD-1 and SW480 colon cancer cell lines were transfected with vectors expressing transgenes or small hairpin RNAs and incubated with recombinant PGE₂, with or without pharmacologic inhibitors of signaling proteins, and analyzed by immunoblot, immunofluorescence, quantitative reverse-transcription polymerase chain reaction, transcriptional reporter, and proliferation assays. Dextran sodium sulfate (DSS) was given to induce colitis in C57/BL6 (control) mice, as well as in mice with disruption of the hydroxyprostaglandin dehydrogenase 15 gene (15-PGDH-knockout mice), Yap1 gene (YAP-knockout mice), and double-knockout mice. Some mice also were given indomethacin to block PGE₂ synthesis. 15-PGDH knockout mice were crossed with mice with intestine-specific disruption of the salvador family WW domain containing 1 gene (Sav1), which encodes an activator of Hippo signaling. We performed immunohistochemical analyses of colon biopsy samples from 26 patients with colitis-associated cancer and 51 age-and sex-matched patients with colorectal cancer (without colitis).

RESULTS

Incubation of colon cancer cell lines with PGE₂ led to phosphorylation of cyclic adenosine monophosphate-responsive element binding protein 1 and increased levels of YAP1 messenger RNA, protein, and YAP1 transcriptional activity. This led to increased transcription of the prostaglandin-endoperoxide synthase 2 gene (PTGS2 or cyclooxygenase 2) and prostaglandin E-receptor 4 gene (PTGER4 or EP4). Incubation with PGE₂ promoted proliferation of colon cancer cell lines, but not cells with knockdown of YAP1. Control mice developed colitis after administration of DSS, but injection of PGE₂ led to colon regeneration in these mice. However, YAP-knockout mice did not regenerate colon tissues and died soon after administration of DSS. 15-PGDH-knockout mice regenerated colon tissues more rapidly than control mice after withdrawal of DSS, and had faster recovery of body weight, colon length, and colitis histology scores. These effects were reversed by injection of indomethacin. SAV1-knockout or 15-PGDH-knockout mice did not develop spontaneous tumors after colitis induction, but SAV1/15-PGDH double-knockout mice developed polyps that eventually progressed to carcinoma in situ. Administration of indomethacin to these mice prevented spontaneous tumor formation. Levels of PGE₂ correlated with those of YAP levels in human sporadic colorectal tumors and colitis-associated tumors.

CONCLUSIONS

PGE₂ signaling increases the expression and transcriptional activities of YAP1, leading to increased expression of cyclooxygenase 2 and EP4 to activate a positive signaling loop. This pathway promotes proliferation of colon cancer cell lines and colon tissue regeneration in mice with colitis. Constitutive activation of this pathway led to formation of polyps and colon tumors in mice.

ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED): a study protocol for a randomized controlled trial

BACKGROUND

Although aspirin is recommended for the prevention of colorectal cancer, the specific individuals for whom the benefits outweigh the risks are not clearly defined. Moreover, the precise mechanisms by which aspirin reduces the risk of cancer are unclear. We recently launched the ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED) trial to address these uncertainties.

METHODS/DESIGN

ASPIRED is a prospective, double-blind, multidose, placebo-controlled, biomarker clinical trial of aspirin use in individuals previously diagnosed with colorectal adenoma. Individuals (n = 180) will be randomized in a 1:1:1 ratio to low-dose (81 mg/day) or standard-dose (325 mg/day) aspirin or placebo. At two study visits, participants will provide lifestyle, dietary and biometric data in addition to urine, saliva and blood specimens. Stool, grossly normal colorectal mucosal biopsies and cytology brushings will be collected during a flexible sigmoidoscopy without bowel preparation. The study will examine the effect of aspirin on urinary prostaglandin metabolites (PGE-M; primary endpoint), plasma inflammatory markers (macrophage inhibitory cytokine-1 (MIC-1)), colonic expression of transcription factor binding (transcription factor 7-like 2 (TCF7L2)), colonocyte gene expression, including hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) and those that encode Wnt signaling proteins, colonic cellular nanocytology and oral and gut microbial composition and function.

DISCUSSION

Aspirin may prevent colorectal cancer through multiple, interrelated mechanisms. The ASPIRED trial will scrutinize these pathways and investigate putative mechanistically based risk-stratification biomarkers.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02394769 . Registered on 16 March 2015.

15-Hydroxyprostaglandin dehydrogenase as a marker in colon carcinogenesis: analysis of the prostaglandin pathway in human colonic tissue

Background/Aims

Cyclooxygenase-2 (COX-2), 15-hydroxyprostaglandin dehydrogenase (15-PGDH), and microsomal prostaglandin E synthase-1 (mPGEs-1) regulate prostaglandin E₂ (PGE₂) expression and are involved in colon carcinogenesis. We investigated the expression of PGE₂ and its regulating genes in sporadic human colon tumors and matched normal tissues.

Methods

Twenty colonic adenomas and 27 colonic adenocarcinomas were evaluated. COX-2 and 15-PGDH expression was quantified by real-time polymerase chain reaction. The expression of PGE₂ and mPGEs-1 was measured using enzyme-linked immunosorbent assay and Western blotting, respectively.

Results

The expression of COX-2, mPGEs-1, and PGE₂ did not differ between the adenomas and matched distant normal tissues. 15-PGDH expression was lower in adenomas than in the matched normal colonic tissues (P<0.001). In adenocarcinomas, mPGEs-1 and PGE₂ expression was significantly higher (P<0.001 and P=0.020, respectively), and COX-2 expression did not differ from that in normal tissues (P=0.207). 15-PGDH expression was significantly lower in the normal colonic mucosa from adenocarcinoma patients than in the normal mucosa from adenoma patients (P=0.018).

Conclusions

Early inactivation of 15-PGDH, followed by activation of COX-2 and mPGEs-1, contributes to PGE₂ production, leading to colon carcinogenesis. 15-PGDH might be a novel candidate marker for early detection of field defects in colon carcinogenesis.

Sonic hedgehog inhibitors prevent colitis-associated cancer via orchestrated mechanisms of IL-6/gp130 inhibition, 15-PGDH induction, Bcl-2 abrogation, and tumorsphere inhibition

Sonic hedgehog (SHH) signaling is essential in normal development of the gastrointestinal (GI) tract, whereas aberrantly activated SHH is implicated in GI cancers because it facilitates carcinogenesis by redirecting stem cells. Since colitis-associated cancer (CAC) is associated with inflammatory bowel diseases, in which SHH and IL-6 signaling, inflammation propagation, and cancer stem cell (CSC) activation have been implicated, we hypothesized that SHH inhibitors may prevent CAC by blocking the above SHH-related carcinogenic pathways. In the intestinal epithelial cells IEC-6 and colon cancer cells HCT-116, IL-6 expression and its signaling were assessed with SHH inhibitors and levels of other inflammatory mediators, proliferation, apoptosis, tumorsphere formation, and tumorigenesis were also measured. CAC was induced in C57BL/6 mice by administration of azoxymethane followed by dextran sodium sulfate administration. SHH inhibitors were administered by oral gavage and the mice were sacrificed at 16 weeks. TNF-α–stimulated IEC-6 cells exhibited increased levels of proinflammatory cytokines and enzymes, whereas SHH inhibitors suppressed TNF-α–induced inflammatory signaling, especially IL-6/IL-6R/gp130 signaling. SHH inhibitors significantly induced apoptosis, inhibited cell proliferation, suppressed tumorsphere formation, and reduced stemness factors. In the mouse model, SHH inhibitors significantly reduced tumor incidence and multiplicity, decreased the expression of IL-6, TNF-α, COX-2, STAT3, and NF-κB, and significantly induced apoptosis. In colosphere xenografts, SHH inhibitor significantly suppressed tumorigenesis by inhibiting tumorsphere formation. Taken together, our data suggest that administration of SHH inhibitors could be an effective strategy to prevent colitis-induced colorectal carcinogenesis, mainly by targeting IL-6 signaling, ablating CSCs, and suppressing oncogenic inflammation, achieving chemoquiescence ultimately.

Role of Urinary Biomarkers in the Diagnosis of Adenoma and Colorectal Cancer: A Systematic Review and Meta-Analysis

The growing interest in enhancing and spreading colorectal cancer (CRC) screening has been stimulating the exploration of novel biomarkers with greater sensitivity and specificity than immunochemical faecal occult blood test (iFOBT). The present study provides i) a systematic review of the urinary biomarkers that have been tested to achieve early CRC diagnosis and assess the risk of colorectal adenoma and adenocarcinoma, and ii) a meta-analysis of the data regarding the urinary prostaglandin (PG) metabolite PGE-M. As regard to gene markers, we found significantly different percent methylation of the vimentin gene in CRC patients and healthy controls (HC) (p<0.0001). Respect to metabolism of nitrogenous bases, cytidine, 1-methyladenosine, and adenosine, have higher concentrations in CRC patients than in HC (respectively, p<0.01, p=0.01, and p<0.01). As regard to spermine we found that N1,N12 diacetyl spermine (DiAcSpm) and N1, N8 diacetylspermidine (DiAcSpd) were significantly higher in CRC than in HC (respectively p=0.01 and p<0.01). Respect to PGE-M, levels were higher in CRC than in those with multiple polyposis (p<0.006) and HC subjects (p<0.0004). PGE-M seems to be the most interesting and promising urinary marker for CRC and adenoma risk assessment and for CRC screening. In conclusion, evidence suggests that urinary biomarker could have a potential role as urinary biomarkers in the diagnosis of colorectal cancer. Particularly, PGE-M seems to be the most promising urinary marker for CRC early detection.

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.

YAP Mediates Tumorigenesis in Neurofibromatosis Type 2 by Promoting Cell Survival and Proliferation through a COX-2-EGFR Signaling Axis

The Hippo-YAP pathway has emerged as a major driver of tumorigenesis in many human cancers. YAP is a transcriptional coactivator and while details of YAP regulation are quickly emerging, it remains unknown what downstream targets are critical for the oncogenic functions of YAP. To determine the mechanisms involved and to identify disease-relevant targets, we examined the role of YAP in neurofibromatosis type 2 (NF2) using cell and animal models. We found that YAP function is required for NF2-null Schwann cell survival, proliferation, and tumor growth in vivo Moreover, YAP promotes transcription of several targets including PTGS2, which codes for COX-2, a key enzyme in prostaglandin biosynthesis, and AREG, which codes for the EGFR ligand, amphiregulin. Both AREG and prostaglandin E2 converge to activate signaling through EGFR. Importantly, treatment with the COX-2 inhibitor celecoxib significantly inhibited the growth of NF2-null Schwann cells and tumor growth in a mouse model of NF2. Cancer Res; 76(12); 3507-19. ©2016 AACR.

Aspirin and colorectal cancer: the promise of precision chemoprevention

Aspirin (acetylsalicylic acid) has become one of the most commonly used drugs, given its role as an analgesic, antipyretic and agent for cardiovascular prophylaxis. Several decades of research have provided considerable evidence demonstrating its potential for the prevention of cancer, particularly colorectal cancer. Broader clinical recommendations for aspirin-based chemoprevention strategies have recently been established; however, given the known hazards of long-term aspirin use, larger-scale adoption of an aspirin chemoprevention strategy is likely to require improved identification of individuals for whom the protective benefits outweigh the harms. Such a precision medicine approach may emerge through further clarification of aspirin's mechanism of action.

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.

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.

Genome-wide analysis of microRNAs identifies the lipid metabolism pathway to be a defining factor in adipose tissue from different sheep

MicroRNAs are short (17–24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. In recent years, deep sequencing of the transcriptome is increasingly being utilized with the promise of higher sensitivity for the identification of differential expression patterns as well as the opportunity to discover new transcripts, including new alternative isoforms and miRNAs. Here, we utilized RNA-seq technology to perform a genome-wide analysis of miRNAs from the adipose tissue of the two species of sheep to look for clues that might explain the fat deposition differences between the sheep. The RNA-seq analysis detected 3132 miRNAs from the adipose tissue of the Small-tail Han and Dorset sheep, of which 2893 were defined as potential new miRNAs. In addition, 54 miRNAs were differentially expressed between the two breeds of sheep. Gene ontology and pathway analyses of the predicted target genes that negatively associated with the differentially expressed miRNAs revealed that there was less active lipid metabolism in the adipose tissue of Small Tail Han sheep. This study can help understand the underling mechanisms responsible for the morphological differences related to fat deposition between two breeds of sheep.

Concerted actions of ameliorated colitis, aberrant crypt foci inhibition and 15-hydroxyprostaglandin dehydrogenase induction by sonic hedgehog inhibitor led to prevention of colitis-associated cancer

The sonic hedgehog (Shh) signaling has been known to contribute to carcinogenesis in organ, where hedgehog exerted organogenesis and in cancers, which are developed based on mutagenic inflammation. Therefore, colitis-associated cancer (CAC) can be a good model to prove whether Shh inhibitors can be applied to prevent, as the efforts to discover potent anti-inflammatory agent are active to prevent CAC. Here, under the hypothesis that Shh inhibitors can prevent CAC, mouse model was generated to develop CAC by azoxymethane (AOM)-initiated, dextran sodium sulfate-promoted carcinogenesis. Shh inhibitors, cerulenin and itraconazole were treated by oral gavage and the mice were sacrificed at early phase of 3 weeks and late phase of 16 weeks. Compared to control group, the number of aberrant crypt foci at 3 weeks and tumor incidence at 16 weeks were all significantly decreased with Shh inhibitor. Significant attenuations of macrophage infiltration accompanied with significant decreases of IL-6, COX-2, STAT3 and NF-κB as well as significant ameliorations of β-catenin nuclear translocation, cyclin D1 and CDK4 were imposed with Shh inhibitors. Especially, CAC was accompanied with significant cancellation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), but their levels were significantly preserved with Shh inhibitors. Among inflammatory mediators, significantly decreased levels of IL-6 and TNF-α, regulated with repressed NF-κb and STAT3, were prominent with Shh inhibitor, whereas significant inductions of apoptosis were noted with Shh inhibitors. In conclusion, Shh inhibitors significantly prevented CAC covering either ameliorating oncogenic inflammation or suppressing tumor proliferation, especially supported with significant inhibition of IL-6 and STAT3 signaling, 15-PGDH preservation and apoptosis induction.

The Hen or the Egg: Inflammatory Aspects of Murine MPN Models

It has been known for some time that solid tumors, especially gastrointestinal tumors, can arise on the basis of chronic inflammation. However, the role of inflammation in the genesis of hematological malignancies has not been extensively studied. Recent evidence clearly shows that changes in the bone marrow niche can suffice to induce myeloid diseases. Nonetheless, while it has been demonstrated that myeloproliferative neoplasms (MPN) are associated with a proinflammatory state, it is not clear whether inflammatory processes contribute to the induction or maintenance of MPN. More provocatively stated: which comes first, the hen or the egg, inflammation or MPN? In other words, can chronic inflammation itself trigger an MPN? In this review, we will describe the evidence supporting a role for inflammation in initiating and promoting MPN development. Furthermore, we will compare and contrast the data obtained in gastrointestinal tumors with observations in MPN patients and models, pointing out the opportunities provided by novel murine MPN models to address fundamental questions regarding the role of inflammatory stimuli in the molecular pathogenesis of MPN.

Damage control: Harnessing prostaglandin E2 as a potential healing factor of tissue injuries

Increasing prostaglandin E2 by knocking out its inhibitor 15-hydroxyprostaglandin dehydrogenase (15-PDGH) or administering a compound that inhibits 15-PDGH was recently found to improve healing in hematopoietic stem cell transplants, colitis recovery, and hepatogenesis after transection in mice. These results are suggestive of pharmacologic therapies or even genetic therapy that could improve patient outcomes, especially since the excess PGE2 and the 15-PDGH inhibitor have proven to be non-toxic. However, elevated levels of PGE2 are associated with increased risk of cancer and blood clotting problems. It would be unacceptable to treat a cancer patient with chemotherapy and replenish the hematopoietic stem cells with the help of PGE2, only to have increased expression of PGE2 and induce another cancer. Therefore, to assess the most therapeutic aspects of PGE2, it is important to consider effects that could induce disease.

Expression and Cellular Localization of 15-Hydroxy-Prostaglandin-Dehydrogenase in Abdominal Aortic Aneurysm

PGE₂ has been implicated in abdominal aortic aneurysm (AAA) associated hypervascularization. PGE₂-metabolism involves 15-hydroxyprostaglandin-dehydrogenase (15-PGDH) the expression of which in AAA is unknown. The aim of this study was to examine the expression and cell distribution of 15-PGDH in AAA. Here, we show that 15-PGDH mRNA levels were significantly higher in aorta samples from patients undergoing AAA repair than in those from healthy multiorgan donors. Consequently, the ratio of metabolized PGE₂ secreted by aortic samples was significantly higher in AAA. AAA production of total PGE₂ and PGE₂ metabolites correlated positively with PGI₂ production, while the percentage of metabolized PGE₂ correlated negatively with the total amount of PGE₂ and with PGI₂. Transcript levels of 15-PGDH were statistically associated with leukocyte markers but did not correlate with microvascular endothelial cell markers. Immunohistochemistry revealed 15-PGDH in the areas of leukocyte infiltration in AAA samples, mainly associated with CD45-positive cells, but not in normal aorta samples. We provide new data concerning 15-PGDH expression in human AAA, showing that 15-PGDH is upregulated in AAA and mainly expressed in infiltrating leukocytes. Our data suggest that microvasculature was not involved in PGE₂ catabolism, reinforcing the potential role of microvasculature derived PGE₂ in AAA-associated hypervascularization.

TISSUE REGENERATION. Inhibition of the prostaglandin-degrading enzyme 15-PGDH potentiates tissue regeneration

Agents that promote tissue regeneration could be beneficial in a variety of clinical settings, such as stimulating recovery of the hematopoietic system after bone marrow transplantation. Prostaglandin PGE2, a lipid signaling molecule that supports expansion of several types of tissue stem cells, is a candidate therapeutic target for promoting tissue regeneration in vivo. Here, we show that inhibition of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a prostaglandin-degrading enzyme, potentiates tissue regeneration in multiple organs in mice. In a chemical screen, we identify a small-molecule inhibitor of 15-PGDH (SW033291) that increases prostaglandin PGE2 levels in bone marrow and other tissues. SW033291 accelerates hematopoietic recovery in mice receiving a bone marrow transplant. The same compound also promotes tissue regeneration in mouse models of colon and liver injury. Tissues from 15-PGDH knockout mice demonstrate similar increased regenerative capacity. Thus, 15-PGDH inhibition may be a valuable therapeutic strategy for tissue regeneration in diverse clinical contexts.

Role of microsomal prostaglandin E synthase-1 (mPGES-1)-derived prostaglandin E2 in colon carcinogenesis

Nonsteroidal anti-inflammatory drugs, especially selective cyclooxygenase-2 (COX-2) inhibitors, are among the most promising chemopreventive agents for colorectal cancer. However, recent clinical trials have indicated that these inhibitors pose a significantly increased cardiovascular risk. Microsomal prostaglandin E (PGE) synthase-1 (mPGES-1) and mPGES-1-derived PGE2 have gained attention recently as alternative targets to COX-2 for colorectal cancer chemoprevention and chemotherapy. In this review, we summarize the current understanding of the roles of mPGES-1, a PGE2-inactivating enzyme (15-hydroxyprostagladin dehydrogenase), and PGE2 specific receptors (EPs) in colon carcinogenesis.

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.

Aspirin and the risk of colorectal cancer in relation to the expression of 15-hydroxyprostaglandin dehydrogenase (HPGD)

Aspirin use reduces the risk of colorectal neoplasia, at least in part, through inhibition of prostaglandin-endoperoxide synthase 2 (PTGS2, cyclooxygenase 2)-related pathways. Hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (15-PGDH, HPGD) is down-regulated in colorectal cancers and functions as a metabolic antagonist of PTGS2. We hypothesized that the effect of aspirin may be antagonized by low 15-PGDH expression in the normal colon. In the Nurses' Health Study and the Health Professionals Follow-Up Study, we collected data on aspirin use every 2 years and followed up participants for diagnoses of colorectal cancer. Duplication-method Cox proportional, multivariable-adjusted, cause-specific hazards regression for competing risks data was used to compute hazard ratios (HRs) for incident colorectal cancer according to 15-PGDH mRNA expression level measured in normal mucosa from colorectal cancer resections. Among 127,865 participants, we documented 270 colorectal cancer cases from which we could assess 15-PGDH expression. Compared with nonuse, regular aspirin use was associated with lower risk of colorectal cancer that developed within a background of colonic mucosa with high 15-PGDH expression [multivariable HR, 0.49; 95% confidence interval (CI), 0.34 to 0.71], but not with low 15-PGDH expression (multivariable HR, 0.90; 95% CI, 0.63 to 1.27) (P for heterogeneity = 0.018). Regular aspirin use was associated with lower incidence of colorectal cancers arising in association with high 15-PGDH expression, but not with low 15-PGDH expression in normal colon mucosa. This suggests that 15-PGDH expression level in normal colon mucosa may serve as a biomarker that may predict stronger benefit from aspirin chemoprevention.

15-Hydroxyprostaglandin dehydrogenase generation of electrophilic lipid signaling mediators from hydroxy ω-3 fatty acids

15-Hydroxyprostaglandin dehydrogenase (15PGDH) is the primary enzyme catalyzing the conversion of hydroxylated arachidonic acid species to their corresponding oxidized metabolites. The oxidation of hydroxylated fatty acids, such as the conversion of prostaglandin (PG) E2 to 15-ketoPGE2, by 15PGDH is viewed to inactivate signaling responses. In contrast, the typically electrophilic products can also induce anti-inflammatory and anti-proliferative responses. This study determined that hydroxylated docosahexaenoic acid metabolites (HDoHEs) are substrates for 15PGDH. Examination of 15PGDH substrate specificity was conducted in cell culture (A549 and primary human airway epithelia and alveolar macrophages) using chemical inhibition and shRNA knockdown of 15PGDH. Substrate specificity is broad and relies on the carbon position of the acyl chain hydroxyl group. 14-HDoHE was determined to be the optimal DHA substrate for 15PGDH, resulting in the formation of its electrophilic metabolite, 14-oxoDHA. Consistent with this, 14-HDoHE was detected in bronchoalveolar lavage cells of mild to moderate asthmatics, and the exogenous addition of 14-oxoDHA to primary alveolar macrophages inhibited LPS-induced proinflammatory cytokine mRNA expression. These data reveal that 15PGDH-derived DHA metabolites are biologically active and can contribute to the salutary signaling actions of Ω-3 fatty acids.

Sulindac reversal of 15-PGDH-mediated resistance to colon tumor chemoprevention with NSAIDs

Non-steroidal anti-inflammatory drugs prevent colorectal cancer by inhibiting cyclooxygenase (COX) enzymes that synthesize tumor-promoting prostaglandins. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a tumor suppressor that degrades tumor-promoting prostaglandins. Murine knockout of 15-PGDH increases susceptibility to azoxymethane-induced colon tumors. It also renders these mice resistant to celecoxib, a selective inhibitor of inducible COX-2 during colon neoplasia. Similarly, humans with low colonic 15-PGDH are also resistant to colon adenoma prevention with celecoxib. Here, we used aspirin and sulindac, which inhibit both COX-1 and COX-2, in order to determine if these broader COX inhibitors can prevent colon tumors in 15-PGDH knockout (KO) mice. Unlike celecoxib, sulindac proved highly effective in colon tumor prevention of 15-PGDH KO mice. Significantly, however, aspirin demonstrated no effect on colon tumor incidence in either 15-PGDH wild-type or KO mice, despite a comparable reduction in colonic mucosal Prostaglandin E₂ (PGE₂) levels by both sulindac and aspirin. Notably, colon tumor prevention activity by sulindac was accompanied by a marked induction of lymphoid aggregates and proximal colonic inflammatory mass lesions, a side effect seen to a lesser degree with celecoxib, but not with aspirin. These findings suggest that sulindac may be the most effective agent for colon cancer prevention in humans with low 15-PGDH, but its use may also be associated with inflammatory lesions in the colon.

15-Oxoeicosatetraenoic acid is a 15-hydroxyprostaglandin dehydrogenase-derived electrophilic mediator of inflammatory signaling pathways

Bioactive lipids govern cellular homeostasis and pathogenic inflammatory processes. Current dogma holds that bioactive lipids, such as prostaglandins and lipoxins, are inactivated by 15-hydroxyprostaglandin dehydrogenase (15PGDH). In contrast, the present results reveal that catabolic "inactivation" of hydroxylated polyunsaturated fatty acids (PUFAs) yields electrophilic α,β-unsaturated ketone derivatives. These endogenously produced species are chemically reactive signaling mediators that induce tissue protective events. Electrophilic fatty acids diversify the proteome through post-translational alkylation of nucleophilic cysteines in key transcriptional regulatory proteins and enzymes that govern cellular metabolic and inflammatory homeostasis. 15PGDH regulates these processes as it is responsible for the formation of numerous electrophilic fatty acids including the arachidonic acid metabolite, 15-oxoeicosatetraenoic acid (15-oxoETE). Herein, the role of 15-oxoETE in regulating signaling responses is reported. In cell cultures, 15-oxoETE activates Nrf2-regulated antioxidant responses (AR) and inhibits NF-κB-mediated pro-inflammatory responses via IKKβ inhibition. Inhibition of glutathione S-transferases using ethacrynic acid incrementally increased the signaling capacity of 15-oxoETE by decreasing 15-oxoETE-GSH adduct formation. This work demonstrates that 15PGDH plays a role in the regulation of cell and tissue homeostasis via the production of electrophilic fatty acid signaling mediators.

15-Deoxy-Δ12,14-prostaglandin J2 induces expression of 15-hydroxyprostaglandin dehydrogenase through Elk-1 activation in human breast cancer MDA-MB-231 cells

Overproduction of prostaglandin E2 (PGE2) has been reported to be implicated in carcinogenesis. The intracellular level of PGE2 is maintained not only by its biosynthesis, but also by inactivation/degradation. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the conversion of oncogenic PGE2 to a biologically inactive keto metabolite. In the present study, we demonstrate that 15-deoxy-Δ(12,14)-prostaglandin J2 (15 d-PGJ2), one of the terminal products of cyclooxygenase-2, updregulates the expression and the activity of 15-PGDH in human breast cancer MDA-MB-231 cells. By using deletion constructs of the 15-PGDH promoter, we have found that E-twenty six (Ets) is the most essential determinant for 15-PGDH induction. 15 d-PGJ2 induced phosphorylation of Elk-1, one of Ets transcription factor family members, in the nucleus. Knockdown of Elk-1 abolished the ability of 15 d-PGJ2 to upregulate 15-PGDH expression. Furthermore, 15 d-PGJ2-mediated activation of Elk-1 was found to be dependent on activation of extracellular-signal related kinase (ERK) 1/2. Treatment of U0126, a pharmacological inhibitor of MEK1/2-ERK, abolished phosphorylation and DNA binding of Elk-1 as well as 15-PGDH induction in 15 d-PGJ2-treated MDA-MB-231 cells. Moreover, 15 d-PGJ2 generated reactive oxygen species (ROS), which contribute to the expression of 15-PGDH as well as phosphorylation of ERK1/2 and Elk-1. 15 d-PGJ2 inhibited the migration of MDA-MB-231 cells, which was attenuated by transient transfection with 15-PGDH siRNA. Taken together, these findings suggest that 15 d-PGJ2 induces the expression of 15-PGDH through ROS-mediated activation of ERK1/2 and subsequently Elk-1 in the MDA-MB-231 cells, which may contribute to tumor suppressive activity of this cyclopentenone prostaglandin.

An inflammatory mediator, prostaglandin E2, in colorectal cancer

It is widely accepted that intake of dietary fats and chronic inflammation are risk factors for developing colorectal cancer. Arachidonic acid is a major component of animal fats, and the bioactive lipids produced from this substrate play critical roles in a variety of biologic processes, including cancer. Cyclooxygenase-derived prostaglandin E2 is a known proinflammatory lipid mediator that promotes tumor progression. Metabolism of arachidonic acid by the cyclooxygenase pathway provides one mechanism for the contribution of dietary fats and chronic inflammation to carcinogenesis. In this review, we highlight recent advances in our understanding of how a proinflammatory mediator prostaglandin E2 promotes colorectal cancer immune evasion. These findings may provide a rationale for the development of new therapeutic approaches to subvert tumor-induced immunosuppression.

Discovery of colorectal cancer PIK3CA mutation as potential predictive biomarker: power and promise of molecular pathological epidemiology

Regular use of aspirin reduces incidence and mortality of various cancers, including colorectal cancer. Anticancer effect of aspirin represents one of the 'Provocative Questions' in cancer research. Experimental and clinical studies support a carcinogenic role for PTGS2 (cyclooxygenase-2), which is an important enzymatic mediator of inflammation, and a target of aspirin. Recent 'molecular pathological epidemiology' (MPE) research has shown that aspirin use is associated with better prognosis and clinical outcome in PIK3CA-mutated colorectal carcinoma, suggesting somatic PIK3CA mutation as a molecular biomarker that predicts response to aspirin therapy. The PI3K (phosphatidylinositol-4,5-bisphosphonate 3-kinase) enzyme has a pivotal role in the PI3K-AKT signaling pathway. Activating PIK3CA oncogene mutations are observed in various malignancies including breast cancer, ovarian cancer, brain tumor, hepatocellular carcinoma, lung cancer and colon cancer. The prevalence of PIK3CA mutations increases continuously from rectal to cecal cancers, supporting the 'colorectal continuum' paradigm, and an important interplay of gut microbiota and host immune/inflammatory reaction. MPE represents an interdisciplinary integrative science, conceptually defined as 'epidemiology of molecular heterogeneity of disease'. As exposome and interactome vary from person to person and influence disease process, each disease process is unique (the unique disease principle). Therefore, MPE concept and paradigm can extend to non-neoplastic diseases including diabetes mellitus, cardiovascular diseases, metabolic diseases, and so on. MPE research opportunities are currently limited by paucity of tumor molecular data in the existing large-scale population-based studies. However, genomic, epigenomic and molecular pathology testings (for example, analyses for microsatellite instability, MLH1 promoter CpG island methylation, and KRAS and BRAF mutations in colorectal tumors) are becoming routine clinical practices. In order for integrative molecular and population science to be routine practice, we must first reform education curricula by integrating both population and molecular biological sciences. As consequences, next-generation hybrid molecular biological and population scientists can advance science, moving closer to personalized precision medicine and health care.

Synthetic triterpenoid induces 15-PGDH expression and suppresses inflammation-driven colon carcinogenesis

Colitis-associated colon cancer (CAC) develops as a result of inflammation-induced epithelial transformation, which occurs in response to inflammatory cytokine-dependent downregulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and subsequent suppression of prostaglandin metabolism. Agents that both enhance 15-PGDH expression and suppress cyclooxygenase-2 (COX-2) production may more effectively prevent CAC. Synthetic triterpenoids are a class of small molecules that suppress COX-2 as well as inflammatory cytokine signaling. Here, we found that administration of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-C28-methyl ester (CDDO-Me) suppresses CAC in mice. In a spontaneous, inflammation-driven intestinal neoplasia model, deletion of Smad4 specifically in T cells led to progressive production of inflammatory cytokines, including TNF-α, IFN-γ, iNOS, IL-6, IL-1β; as well as activation of STAT1 and STAT3; along with suppression of 15-PGDH expression. Oral administration of CDDO-Me to mice with SMAD4-deficient T cells increased survival and suppressed intestinal epithelial neoplasia by decreasing production of inflammatory mediators and increasing expression of 15-PGDH. Induction of 15-PGDH by CDDO-Me was dose dependent in epithelial cells and was abrogated following treatment with TGF-β signaling inhibitors in vitro. Furthermore, CDDO-Me-dependent 15-PGDH induction was not observed in Smad3-/- mice. Similarly, CDDO-Me suppressed azoxymethane plus dextran sodium sulfate-induced carcinogenesis in wild-type animals, highlighting the potential of small molecules of the triterpenoid family as effective agents for the chemoprevention of CAC in humans.

Inactivating mutation in the prostaglandin transporter gene, SLCO2A1, associated with familial digital clubbing, colon neoplasia, and NSAID resistance

HPGDand SLCO2A1 genes encode components of the prostaglandin catabolic pathway, with HPGD encoding the degradative enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH), and SLCO2A1 encoding the prostaglandin transporter PGT that brings substrate to 15-PGDH. HPGD-null mice show increased prostaglandin E2 (PGE2), marked susceptibility to developing colon tumors, and resistance to colon tumor prevention by nonsteroidal anti-inflammatory drugs (NSAID). But in humans, HPGD and SLCO2A1 mutations have only been associated with familial digital clubbing. We, here, characterize a family with digital clubbing and early-onset colon neoplasia. Whole-exome sequencing identified a heterozygous nonsense mutation (G104X) in the SLCO2A1 gene segregating in 3 males with digital clubbing. Two of these males further demonstrated notably early-onset colon neoplasia, 1 with an early-onset colon cancer and another with an early-onset sessile serrated colon adenoma. Two females also carried the mutation, and both these women developed sessile serrated colon adenomas without any digital clubbing. Males with clubbing also showed marked elevations in the levels of urinary prostaglandin E2 metabolite, PGE-M, whereas, female mutation carriers were in the normal range. Furthermore, in the male proband, urinary PGE-M remained markedly elevated during NSAID treatment with either celecoxib or sulindac. Thus, in this human kindred, a null SLCO2A1 allele mimics the phenotype of the related HPGD-null mouse, with increased prostaglandin levels that cannot be normalized by NSAID therapy, plus with increased colon neoplasia. The development of early-onset colon neoplasia in male and female human SLCO2A1 mutation carriers suggests that disordered prostaglandin catabolism can mediate inherited susceptibility to colon neoplasia in man.

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.

Genetic variability in key genes in prostaglandin E2 pathway (COX-2, HPGD, ABCC4 and SLCO2A1) and their involvement in colorectal cancer development

The pro-carcinogenic effects of prostaglandin E2 (PGE₂) in colonic mucosa are not only regulated by the rates between Cyclooxygenase-2 (COX-2) biosynthesis and 15-Hydroxyprostaglandin Dehydrogenase (15-PGDH)-dependent degradation but also the steady-state levels of PGE₂ in extracellular microenvironment, maintained by key specific prostaglandin transporters, the Multidrug Resistance Protein (MRP4) (efflux carrier) and Prostaglandin Transporter (PGT) (influx carrier). To understand the contribution of genetic variability in genes coding for COX-2/15-PGDH/MRP4/PGT proteins in CRC development, we conducted a hospital-based case-control study involving 246 CRC patients and 480 cancer-free controls. A total of 51 tagSNPs were characterized using the Sequenom platform through multiplexed amplification followed by mass-spectrometric product separation or allelic discrimination using real-time PCR. Seven tagSNPs were implicated in CRC development: the rs689466 in COX-2 gene, the rs1346271 and rs1426945 in 15-PGDH, the rs6439448 and rs7616492 in PGT and rs1751051 and rs1751031 in MRP4 coding genes. Upon a stratified analysis a measurable gene-environment interaction was noticed between rs689466 and smoking habits, with individuals ever-smokers carriers of rs689466 GG homozygous genotype having a nearly 6-fold increased susceptibility for CRC onset (95%CI: 1.49–22.42, P = 0.011). Furthermore, the multifactor dimensionality reduction (MDR) analysis identified an overall four-factor best gene-gene interactive model, including the rs1426945, rs6439448, rs1751051 and rs1751031 polymorphisms. This model had the highest cross-validation consistency (10/10, P<0.0001) and an accuracy of 0.6957 and was further associated with a 5-fold increased risk for CRC development (95%CI: 3.89–7.02, P<0.0001). In conclusion, specific low penetrance genes in the pro-carcinogenic PGE₂ pathway appear to modulate the genetic susceptibility for CRC development. A clearer understanding on CRC etiology through the identification of biomarkers of colorectal carcinogenesis might allow a better definition of risk models that are more likely to benefit from targeted preventive strategies to reduce CRC burden.

Postnatal regulation of 15-hydroxyprostaglandin dehydrogenase in the rat kidney

Cyclooxygenase 2 (COX-2) has an established role in postnatal kidney development. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is recently identified as an endogenous inhibitor of COX-2, limiting the production of COX-2-derived prostanoids in several pathological conditions. The present study was undertaken to examine the regulation of renal 15-PGDH expression during postnatal kidney development in rats compared with COX-2. qRT-PCR and immunoblotting demonstrated that 15-PGDH mRNA and protein in the kidney were present in neonates, peaked in the second postnatal week, and then declined sharply to very low level in adulthood. Immunostaining demonstrated that at the second postnatal week, renal 15-PGDH protein was predominantly found in the proximal tubules stained positive for Na/H exchanger 3 and brush borders (periodic acid-Schiff), whereas COX-2 protein was restricted to macular densa and adjacent thick ascending limbs. Interestingly, in the fourth postnatal week, 15-PGDH protein was redistributed to thick ascending limbs stained positive for the Na-K-2Cl cotransporter. After 6 wk of age, 15-PGDH protein was found in the granules in subsets of the proximal tubules. Overall, these results support a possibility that 15-PGDH may regulate postnatal kidney development through interaction with COX-2.

Role of inflammation and inflammatory mediators in colorectal cancer

Chronic inflammation is a risk factor for several different cancers including colorectal cancer (CRC). However, the mechanisms underlying the contribution of inflammation to cancer remain elusive. Pro-inflammatory mediators such as cyclooxygenase 2 (COX-2) and prostaglandin E2 (PGE2) contribute to cancer progression. Here, we show that COX-2 is an immediate-early response gene induced by growth factors and pro-inflammatory cytokines and its levels are elevated in human CRCs. Furthermore, we show that COX-2-derived PGE2 promotes colonic tumor growth via silencing certain tumor suppressors and DNA repair genes by DNA methylation in colonic epithelial tumor cells. We also report that C-X-C motif chemokine receptor 2 accelerates colonic inflammation and colitis-associated tumorigenesis by mediating myeloid-derived suppressor cell recruitment to the tumor microenvironment. These findings not only support a rationale to target these pro-inflammatory pathways for cancer prevention and treatment but also provide support for developing new therapeutic approaches to subvert chronic inflammation- and tumor-induced immunosuppression.

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.