Histone deacetylase inhibitors and transforming growth factor-beta induce 15-hydroxyprostaglandin dehydrogenase expression in human lung adenocarcinoma cells

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.

Anti-Inflammatory Effects of Heat-Processed Artemisia capillaris Thunberg by Regulating IκBα/NF-κB Complex and 15-PGDH in Mouse Macrophage Cells

Growing evidence suggests that dietary nutrients in herbs and plants are beneficial in improving inflammatory disorders. Artemisia capillaris Thunberg (AC) is a traditional herbal medicine widely used in East Asia to treat pain, hepatotoxicity, and inflammatory disorders. Heat processing is a unique pharmaceutical method used in traditional herbal medicine to enhance the pharmacological effects and safety of medicinal plants. This study demonstrates the anti-inflammatory effects of heat-processed AC (HPAC) in lipopolysaccharide- (LPS-) treated mouse macrophage cells. HPAC reduced LPS-induced inflammatory mediators such as IL-6, IL-1β, TNF-α, NO, and PGE2 in RAW 264.7 cells. Interestingly, 15-PGDH appears to play a pivotal role rather than COX-2 and mPGES-1 when HPAC regulated PGE2 levels. Meanwhile, HPAC showed anti-inflammatory effects by blocking IκBα phosphorylation and NF-κB nuclear translocalization. Also, we found that HO-1 upregulation was mediated by the mitogen-activated protein kinase (MAPK) pathways in HPAC-treated RAW 264.7 cells. And, in RAW 264.7 cells challenged with LPS, HPAC restored HO-1 expression, leading to NF-κB inhibition. Through further experiments using specific MAPK inhibitors, we found that, in response to LPS, the phosphorylated IκBα and activated NF-κB were attenuated by p38 MAPK/HO-1 pathway. Therefore, HPAC targeting both the IκBα/NF-κB complex and 15-PGDH may be considered as a potential novel anti-inflammatory agent derived from a natural source.

Nullscript inhibits Cryptosporidium and Toxoplasma growth

Cryptosporidium and Toxoplasma are parasites that have caused problems worldwide. Cryptosporidium causes severe watery diarrhoea and may be fatal in immunocompromised patients and in infants. Nitazoxanide is the only agent currently approved by the FDA, but its efficacy is limited. Toxoplasmosis is also a problem in the immunocompromised, as currently available treatment options have limited efficacy and patient tolerance can be poor. In the present investigation, we screened libraries of epigenetic compounds to identify those that inhibited C. parvum growth. Nullscript was identified as a compound with an inhibitory effect on C. parvum and T. gondii growth, and was less toxic to host cells. Nullscript was also able to significantly decrease oocyst excretion in C. parvum-infected SCID mice.

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A library of epigenetic compounds was used to screen for compounds effective against Cryptosporiium parvum.

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Nullscript has been shown to be effective in inhibiting the growth of C. parvum and T. gondii.

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Nullscript significantly decreased oocyst excretion in C. parvum-infected SCID mice.

Prostaglandin dehydrogenase is a target for successful induction of cervical ripening

The cervix represents a formidable structural barrier for successful induction of labor. Approximately 10% of pregnancies undergo induction of cervical ripening and labor with prostaglandin (PG) E₂ or PGE analogs, often requiring many hours of hospitalization and monitoring. On the other hand, preterm cervical ripening in the second trimester predicts preterm birth. The regulatory mechanisms of this paradoxical function of the cervix are unknown. Here, we show that PGE₂ uses cell-specific EP2 receptor-mediated increases in Ca²⁺ to dephosphorylate and translocate histone deacetylase 4 (HDAC4) to the nucleus for repression of 15-hydroxy prostaglandin dehydrogenase (15-PGDH). The crucial role of 15-PGDH in cervical ripening was confirmed in vivo. Although PGE₂ or 15-PGDH inhibitor alone did not alter gestational length, treatment with 15-PGDH inhibitor + PGE₂ or metabolism-resistant dimethyl-PGE₂ resulted in preterm cervical ripening and delivery in mice. The ability of PGE₂ to selectively autoamplify its own synthesis in stromal cells by signaling transcriptional repression of 15-PGDH elucidates long sought-after molecular mechanisms that govern PG action in the cervix. This report details unique mechanisms of action in the cervix and serves as a catalyst for (i) the use of 15-PGDH inhibitors to initiate or amplify low-dose PGE₂-mediated cervical ripening or (ii) EP2 receptor antagonists, HDAC4 inhibitors, and 15-PGDH activators to prevent preterm cervical ripening and preterm birth.

Epigenetics of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the United States. Epigenetic alterations, including DNA methylation, histone modifications, and noncoding RNA expression, have been reported widely in the literature to play a major role in the genesis of lung cancer. The goal of this review is to summarize the common epigenetic changes associated with lung cancer to give some clarity to its etiology, and to provide an overview of the potential translational applications of these changes, including applications for early detection, diagnosis, prognostication, and therapeutics.

Targeting inflammation: multiple innovative ways to reduce prostaglandin E₂

The PGE2 pathway is important in inflammation-driven diseases and specific targeting of the inducible mPGES-1 is warranted due to the cardiovascular problems associated with the long-term use of COX-2 inhibitors. This review focuses on patents issued on methods of measuring mPGES-1 activity, on drugs targeting mPGES-1 and on other modulators of free extracellular PGE2 concentration. Perspectives and conclusions regarding the status of these drugs are also presented. Importantly, no selective inhibitors targeting mPGES-1 have been identified and, despite the high number of published patents, none of these drugs have yet made it to clinical trials.

Regulation of 15-hydroxyprostaglandin dehydrogenase expression in hepatocellular carcinoma

Cyclooxygenase-2 (COX-2), a rate limiting step in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E2 (PGE2) upon inflammatory stimuli, growth factors, hormones and other cellular stresses. Overproduction of PGE2 stimulates proliferation of various cancer cells, confers resistance to apoptosis and favors metastasis and angiogenesis. The steady-state level of PGE2 is maintained by interplay between the biosynthetic pathway including COX and PGE2 synthases and the catabolic pathways involving nicotinamide adenine dinucleotide (NAD(+))-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). 15-PGDH is a crucial enzyme responsible for the biological inactivation of PGE2. Adult hepatocytes fail to induce COX-2 expression regardless of the pro-inflammatory factors used. COX-2 is induced in hepatocytes after partial hepatectomy (PH), in animal models of cirrhosis, in human hepatoma cell lines, in human HCC and after HBV and HCV infection. However, no data are available regarding 15-PGDH expression in HCC. Our results show that 15-PGDH is downregulated in human hepatoma cells with a high COX-2 expression, in chemical and genetic murine models of HCC and in human HCC biopsies. Moreover, 15-PGDH expression is suppressed by EGF (epidermal growth factor) and HGF (hepatocyte growth factor) mainly involving PI3K (phosphatidylinositol-3-kinase), ERK (extracellular signal-regulated kinase) and p38MAPK (mitogen-activated protein kinase) activation. Conversely, ectopic expression of 15-PGDH induces apoptosis in hepatoma cells and decreases the growth of hepatoma cells in nude mice whereas the silencing of 15-PGDH increases the tumor formation. These data suggest a potential therapeutic application of 15-PGDH in HCC.

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.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

Epigenetic deregulation of the COX pathway in cancer

Inflammation is a major cause of cancer and may condition its progression. The deregulation of the cyclooxygenase (COX) pathway is implicated in several pathophysiological processes, including inflammation and cancer. Although, its targeting with nonsteroidal antiinflammatory drugs (NSAIDs) and COX-2 selective inhibitors has been investigated for years with promising results at both preventive and therapeutic levels, undesirable side effects and the limited understanding of the regulation and functionalities of the COX pathway compromise a more extensive application of these drugs. Epigenetics is bringing additional levels of complexity to the understanding of basic biological and pathological processes. The deregulation of signaling and biosynthetic pathways by epigenetic mechanisms may account for new molecular targets in cancer therapeutics. Genes of the COX pathway are seldom mutated in neoplastic cells, but a large proportion of them show aberrant expression in different types of cancer. A growing body of evidence indicates that epigenetic alterations play a critical role in the deregulation of the genes of the COX pathway. This review summarizes the current knowledge on the contribution of epigenetic processes to the deregulation of the COX pathway in cancer, getting insights into how these alterations may be relevant for the clinical management of patients.

Prostaglandin catabolic enzymes as tumor suppressors

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

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

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

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

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

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

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.

MicroRNA and AU-rich element regulation of prostaglandin synthesis

Many lines of evidence demonstrate that prostaglandins play an important role in cancer, and enhanced synthesis of prostaglandin E(2) (PGE(2)) is often observed in various human malignancies often associated with poor prognosis. PGE(2) synthesis is initiated with the release of arachidonic acid by phospholipase enzymes, where it is then converted into the intermediate prostaglandin prostaglandin H(2) (PGH(2)) by members of the cyclooxygenase family. The synthesis of PGE(2) from PGH(2) is facilitated by three different PGE synthases, and functional PGE(2) can promote tumor growth by binding to four EP receptors to activate signaling pathways that control cell proliferation, migration, apoptosis, and angiogenesis. An integral method of controlling gene expression is by posttranscriptional mechanisms that regulate mRNA stability and protein translation. Messenger RNA regulatory elements typically reside within the 3' untranslated region (3'UTR) of the transcript and play a critical role in targeting specific mRNAs for posttranscriptional regulation through microRNA (miRNA) binding and adenylate- and uridylate-rich element RNA-binding proteins. In this review, we highlight the current advances in our understanding of the impact these RNA sequence elements have upon regulating PGE(2) levels. We also identify various RNA sequence elements consistently observed within the 3'UTRs of the genes involved in the PGE(2) pathway, indicating these binding sites for miRNAs and RNA-binding proteins to be central regulators of PGE(2) synthesis and function. These findings may provide a rationale for the development of new therapeutic approaches to control tumor growth and metastasis promoted by elevated PGE(2) levels.

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.

Interleukin-4 up-regulates 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in human lung cancer cells

IL-4, an anti-inflammatory cytokine, was found to stimulate 15-PGDH activity in A549 and other lung cancer cells. Increase in 15-PGDH activity was due to increased transcription and decreased protein turnover of 15-PGDH. MMP-9 was shown to result in decreased levels of 15-PGDH in A549 cells. IL-4 induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1, an inhibitor of MMP-9. These data suggest that IL-4-induced down-regulation of MMP-9 activity may contribute to up-regulation of 15-PGDH in A549 cells. The role of JAK-STAT6 in IL-4-induced 15-PGDH expression was examined by using inhibitors. Inhibitors of JAKs, kaempferol and JAK inhibitor I, attenuated IL-4-stimulated STAT6 phosphorylation and 15-PGDH activity in a comparable concentration-dependent manner. Furthermore, JAK inhibitor I blocked IL-4-induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1 but not IL-4-stimulated up-regulation of 15-PGDH mRNA. These results indicate that JAK-STAT6 participated in IL-4-induced up-regulation of 15-PGDH through inhibition of MMP-9-mediated degradation. The roles of other signaling kinases in IL-4-induced 15-PGDH expression were also examined by using various inhibitors. Inhibitors of various MAPKs, PI-3K and PKC attenuated significantly IL-4-stimulated 15-PGDH activity indicating that MAPKs, PI-3K/Akt and PKC pathways participated in IL-4-induced up-regulation of 15-PGDH. Our results indicate that IL-4 up-regulates 15-PGDH by increased gene transcription and decreased protein turnover and the up-regulation can be mediated by JAK-STAT6 as well as MAPKs, PI-3K/Akt and PKC pathways.

Designed inhibitors of insulin-degrading enzyme regulate the catabolism and activity of insulin

BACKGROUND

Insulin is a vital peptide hormone that is a central regulator of glucose homeostasis, and impairments in insulin signaling cause diabetes mellitus. In principle, it should be possible to enhance the activity of insulin by inhibiting its catabolism, which is mediated primarily by insulin-degrading enzyme (IDE), a structurally and evolutionarily distinctive zinc-metalloprotease. Despite interest in pharmacological inhibition of IDE as an attractive anti-diabetic approach dating to the 1950s, potent and selective inhibitors of IDE have not yet emerged.

METHODOLOGY/PRINCIPAL FINDINGS

We used a rational design approach based on analysis of combinatorial peptide mixtures and focused compound libraries to develop novel peptide hydroxamic acid inhibitors of IDE. The resulting compounds are approximately 10(6) times more potent than existing inhibitors, non-toxic, and surprisingly selective for IDE vis-à-vis conventional zinc-metalloproteases. Crystallographic analysis of an IDE-inhibitor complex reveals a novel mode of inhibition based on stabilization of IDE's "closed," inactive conformation. We show further that pharmacological inhibition of IDE potentiates insulin signaling by a mechanism involving reduced catabolism of internalized insulin.

CONCLUSIONS/SIGNIFICANCE

The inhibitors we describe are the first to potently and selectively inhibit IDE or indeed any member of this atypical zinc-metalloprotease superfamily. The distinctive structure of IDE's active site, and the mode of action of our inhibitors, suggests that it may be possible to develop inhibitors that cross-react minimally with conventional zinc-metalloproteases. Significantly, our results reveal that insulin signaling is normally regulated by IDE activity not only extracellularly but also within cells, supporting the longstanding view that IDE inhibitors could hold therapeutic value for the treatment of diabetes.

15-hydroxyprostaglandin dehydrogenase is down-regulated in gastric cancer

PURPOSE

We have investigated the expression and regulation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in gastric cancer.

EXPERIMENTAL DESIGN

Clinical gastric adenocarcinoma samples were analyzed by immunohistochemistry and quantitative real-time PCR for protein and mRNA expression of 15-PGDH and for methylation status of 15-PGDH promoter. The effects of interleukin-1beta (IL-1beta) and epigenetic mechanisms on 15-PGDH regulation were assessed in gastric cancer cell lines.

RESULTS

In a gastric cancer cell line with a very low 15-PGDH expression (TMK-1), the 15-PGDH promoter was methylated and treatment with a demethylating agent 5-aza-2'-deoxycytidine restored 15-PGDH expression. In a cell line with a relatively high basal level of 15-PGDH (MKN-28), IL-1beta repressed expression of 15-PGDH mRNA and protein. This effect of IL-1beta was at least in part attributed to inhibition of 15-PGDH promoter activity. SiRNA-mediated knockdown of 15-PGDH resulted in strong increase of prostaglandin E(2) production in MKN-28 cells and increased cell growth of these cells by 31% in anchorage-independent conditions. In clinical gastric adenocarcinoma specimens, 15-PGDH mRNA levels were 5-fold lower in gastric cancer samples when compared with paired nonneoplastic tissues (n = 26) and 15-PGDH protein was lost in 65% of gastric adenocarcinomas (n = 210).

CONCLUSIONS

15-PGDH is down-regulated in gastric cancer, which could potentially lead to accelerated tumor progression. Importantly, our data indicate that a proinflammatory cytokine linked to gastric carcinogenesis, IL-1beta, suppresses 15-PGDH expression at least partially by inhibiting promoter activity of the 15-PGDH gene.

Bioactive food components, inflammatory targets, and cancer prevention

Various dietary components may modify chronic inflammatory processes at the stage of cytokine production, amplification of nuclear factor-kappaB-mediated inflammatory gene expression, and the release of anti-inflammatory cytokine, transforming growth factor-beta. This review provides a synopsis of the strengths and weaknesses of the evidence that specific bioactive food components influence inflammation-related targets linked to cancer. A target repeatedly surfacing as a site of action for several dietary components is transforming growth factor beta. Whereas the use of dietary intervention strategies offers intriguing possibilities for maintaining normal cell function by modifying a process that is essential for cancer development and progression, more information is needed to characterize the minimum quantity of the bioactive food components required to bring about a change in inflammation-mediated cancer, the ideal time for intervention, and the importance of genetics in determining the response. Unquestionably, the societal benefits of using foods and their components to prevent chronic inflammation and associated complications, including cancer, are enormous.

Repression of 15-hydroxyprostaglandin dehydrogenase involves histone deacetylase 2 and snail in colorectal cancer

Prostaglandin E(2) (PGE(2)) promotes cancer progression by modulating proliferation, apoptosis, angiogenesis, and the immune response. Enzymatic degradation of PGE(2) involves the NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). Recent reports have shown a marked diminution of 15-PGDH expression in colorectal carcinomas (CRC). We report here that treatment of CRC cells with histone deacetylase (HDAC) inhibitors, including sodium butyrate and valproic acid, induces 15-PGDH expression. Additionally, we show that pretreatment of CRC cells with HDAC inhibitors can block epidermal growth factor-mediated or Snail-mediated transcriptional repression of 15-PGDH. We show an interaction between Snail and HDAC2 and the binding of HDAC2 to the 15-PGDH promoter. In vivo, we observe increased Hdac2 expression in Apc-deficient mouse adenomas, which inversely correlated with loss of 15-Pgdh expression. Finally, in human colon cancers, elevated HDAC expression correlated with down-regulation of 15-PGDH. These data suggest that class I HDACs, specifically HDAC2, and the transcriptional repressor Snail play a central role in the suppression of 15-PGDH expression. These results also provide a cyclooxygenase-2-independent mechanism to explain increased PGE(2) levels that contribute to progression of CRC.

Targeting histone deacetylases for the treatment of disease

The ‘histone code’ is a well-established hypothesis describing the idea that specific patterns of post-translational modifications to histones act like a molecular ‘code’ recognized and used by non-histone proteins to regulate specific chromatin functions. One modification, which has received significant attention, is that of histone acetylation. The enzymes that regulate this modification are described as lysine acetyltransferases or KATs, and histone deacetylases or HDACs. Due to their conserved catalytic domain HDACs have been actively targeted as a therapeutic target. The pro-inflammatory environment is increasingly being recognized as a critical element for both degenerative diseases and cancer. The present review will discuss the current knowledge surrounding the clinical potential and current development of histone deacetylases for the treatment of diseases for which a pro-inflammatory environment plays important roles, and the molecular mechanisms by which such inhibitors may play important functions in modulating the pro-inflammatory environment.

Inhibition of epidermal growth factor receptor signaling elevates 15-hydroxyprostaglandin dehydrogenase in non-small-cell lung cancer

Evidence indicates that the induction of cyclooxygenase-2 (COX-2) and high prostaglandin E2 (PGE2) levels contribute to the pathogenesis of non-small-cell lung cancer (NSCLC). In addition to overproduction by COX-2, PGE2 concentrations also depend upon the levels of the PGE2 catabolic enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH). We find a dramatic down-regulation of PGDH protein in NSCLC cell lines and in resected human tumors when compared with matched normal lung. Affymetrix array analysis of 10 normal lung tissue samples and 49 resected lung tumors revealed a much lower expression of PGDH transcripts in all NSCLC histologic groups. In addition, treatment with the epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) erlotinib increased the expression of 15-PGDH in a subset of NSCLC cell lines. This effect may be due in part to an inhibition of the extracellular signal-regulated kinase (ERK) pathway as treatment with mitogen-activated protein kinase kinase (MEK) inhibitor U0126 mimics the erlotinib results. We show by quantitative reverse transcription-PCR that the transcript levels of ZEB1 and Slug transcriptional repressors are dramatically reduced in a responsive cell line upon EGFR and MEK/ERK inhibition. In addition, the Slug protein, but not ZEB1, binds to the PGDH promoter and represses transcription. As these repressors function by recruiting histone deacetylases to promoters, it is likely that PGDH is repressed by an epigenetic mechanism involving histone deacetylation, resulting in increased PGE2 activity in tumors. This effect is reversible in a subset of NSCLC upon treatment with an EGFR TKI.

15-hydroxyprostaglandin dehydrogenase (15-PGDH) and lung cancer

15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes NAD(+)-linked oxidation of 15 (S)-hydroxyl group of prostaglandins and lipoxins and is the key enzyme responsible for the biological inactivation of these eicosanoids. The enzyme was found to be under-expressed as opposed to cyclooxygenase-2 (COX-2) being over-expressed in lung and other tumors. A549 human lung adenocarcinoma cells were used as a model system to study the role of 15-PGDH in lung tumorigenesis. Up-regulation of COX-2 expression by pro-inflammatory cytokines in A549 cells was accompanied by a down-regulation of 15-PGDH expression. Over-expression of COX-2 but not COX-1 by adenoviral-mediated approach also attenuated 15-PGDH expression. Similarly, over-expression of 15-PGDH by the same strategy inhibited IL-1beta-induced COX-2 expression. It appears that the expression of COX-2 and 15-PGDH is regulated reciprocally. Adenoviral-mediated transient over-expression of 15-PGDH in A549 cells resulted in apoptosis. Xenograft studies in nude mice also showed tumor suppression with cells transiently over-expressing 15-PGDH. However, cells stably over-expressing 15-PGDH generated tumors faster than those control cells. Examination of different clones of A549 cells stably expressing different levels of 15-PGDH indicated that the levels of 15-PGDH expression correlated positively with those of mesenchymal markers, and negatively with those of epithelial markers. It appears that the stable expression of 15-PGDH induces epithelial-mesenchymal transition (EMT) which may account for the tumor promotion in xenograft studies. A number of anti-cancer agents, such as transforming growth factor-beta1 (TGF-beta1), glucocorticoids and some histone deacetylase inhibitors were found to induce 15-PGDH expression. These results suggest that tumor suppressive action of these agents may, in part, be related to their ability to induce 15-PGDH expression.