Immunohistochemical demonstration of membrane-bound prostaglandin E2 synthase-1 in papillary thyroid carcinoma

mPGES-1 Inhibitor Discovery Based on Computer-Aided Screening: Pharmacophore Models, Molecular Docking, ADMET, and MD Simulations

mPGES-1 is an enzyme, which, when activated by inflammatory factors, can cause prostaglandin E synthesis. Traditional non-steroidal anti-inflammatory drugs are capable of inhibiting prostaglandin production, yet they can also cause gastrointestinal reactions and coagulation disorders. mPGES-1, the enzyme at the conclusion of prostaglandin production, does not cause any adverse reactions when inhibited. Numerous studies have demonstrated that mPGES-1 is more abundant in cancerous cells than in healthy cells, indicating that decreasing the expression of mPGES-1 could be a potential therapeutic strategy for cancer. Consequently, the invention of mPGES-1 inhibitors presents a fresh avenue for the treatment of inflammation and cancer. Incorporating a database of TCM compounds, we collected a batch of compounds that had an inhibitory effect on mPGES-1 and possessed IC50 value. Firstly, a pharmacophore model was constructed, and the TCM database was screened, and the compounds with score cut-off values of more than 1 were retained. Then, the compounds retained after being screened via the pharmacodynamic model were screened for docking at the mPGES-1 binding site, followed by high-throughput virtual screening [HTVS] and standard precision [SP] and super-precision [XP] docking, and the compounds in the top 20% of the XP docking score were selected to calculate the total free binding energy of MM-GBSA. The best ten compounds were chosen by comparing their score against the reference ligand 4U9 and the MM-GBSA_dG_Bind score. ADMET analysis resulted in the selection of ten compounds, three of which had desirable medicinal properties. Finally, the binding energy of the target protein mPGES-1 and the candidate ligand compound was analyzed using a 100 ns molecular dynamics simulation of the reference ligand 4U9 and three selected compounds. After a gradual screening study and analysis, we identified a structure that is superior to the reference ligand 4U9 in all aspects, namely compound 15643. Taken together, the results of this study reveal a structure that can be used to inhibit mPGES-1 compound 15643, thereby providing a new option for anti-inflammatory and anti-tumor drugs.

Sonlicromanol's active metabolite KH176m normalizes prostate cancer stem cell mPGES-1 overexpression and inhibits cancer spheroid growth

Aggressiveness of cancers, like prostate cancer, has been found to be associated with elevated expression of the microsomal prostaglandin E synthase-1 (mPGES-1). Here, we investigated whether KH176m (the active metabolite of sonlicromanol), a recently discovered selective mPGES-1 inhibitor, could affect prostate cancer cells-derived spheroid growth. We demonstrated that KH176m suppressed mPGES-1 expression and growth of DU145 (high mPGES-1 expression)-derived spheroids, while it had no effect on the LNCaP cell line, which has low mPGES-1 expression. By addition of exogenous PGE₂, we found that the effect of KH176m on mPGES-1 expression and spheroid growth is due to the inhibition of a PGE₂-driven positive feedback control-loop of mPGES-1 transcriptional regulation. Cancer stem cells (CSCs) are a subset of cancer cells exhibiting the ability of self-renewal, plasticity, and initiating and maintaining tumor growth. Our data shows that mPGES-1 is specifically expressed in this CSCs subpopulation (CD44⁺CD24^-). KH176m inhibited the expression of mPGES-1 and reduced the growth of spheroids derived from the CSC. Based on the results obtained we propose selective mPGES-1 targeting by the sonlicromanol metabolite KH176m as a potential novel treatment approach for cancer patients with high mPGES-1 expression.

MM-PBSA and per-residue decomposition energy studies on 7-Phenyl-imidazoquinolin-4(5H)-one derivatives: Identification of crucial site points at microsomal prostaglandin E synthase-1 (mPGES-1) active site

The huge therapeutic potential and the market share of painkillers are well-known. Due to the side effects associated with traditional NSAIDs and selective cyclooxygenase (COX-2) inhibitors, a new generation of painkillers is the need of the hour. In this regard, microsomal prostaglandin E synthase-1 (mPGES-1) offers great potential as an alternative drug target against inflammatory disorders. The present study is aimed at identifying the amino acids crucial in effective inhibitor binding at the mPGES-1 active site by performing molecular dynamics based studies on a series of 7-Phenyl-imidazoquinolin-4(5H)-one derivatives. Molecular dynamics (MD) simulations, MM-PBSA, per-residue energy decomposition and Dimensionality Reduction through Covariance matrix Transformation for Identification of Differences in dynamics (DIRECT-ID) analysis were performed to get insights into the structural details that can aid in novel drug design against mPGES-1. The high correlations of electrostatic and polar energy terms with biological activity highlight their importance and applicability in in silico screening studies. Further, per-residue energy decomposition studies revealed that Lys42, Arg52, Arg122, Pro124, Ser127, Val128 and Thr131 were contributing more towards inhibitor binding energy. The results clearly show that MM-PBSA can act as a filter in virtual screening experiments and can play major role in facilitating various mPGES-1 drug discovery studies.

Chemistry and biology of microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitors as novel anti-inflammatory agents: recent developments and current status

Prostaglandin (PG) E₂, a key mediator of inflammatory pain and fever, is biosynthesized from PGH₂ by mPGES-1.

Expression of prostaglandin E2 and EP receptors in human papillary thyroid carcinoma

The objective of the present study is to determine the role of prostaglandin E2 (PGE2) and downstream EP receptors in the development of human papillary thyroid carcinoma (PTC). A total of 90 thyroid specimens excised from patients undergoing total or subtotal thyroidectomy in the Department of General Surgery, the Fifth Affiliated Hospital of Sun Yat-sen University, China, from August 2013 to September 2014, were analyzed. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemical analyses were employed to examine the messenger RNA (mRNA) and protein expression, respectively. The expressions and significances of cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES-1), PGE2, and EP receptors in PTC and nodular goiter were investigated. The COX-2 mRNA and protein expression level significantly increased in the PTC tissues than in the paired noncarcinoma tissues adjacent to the PTC or nodular goiter tissues. The mPGES-1 protein expression was also significantly upregulated in the PTC tissues. All the four subtypes of EP receptors (EP1-4) could express in the thyroid tissues, while only the EP4 mRNA and protein levels significantly increased in the PTC tissues. The local production of PGE2 had a higher-level expression in the PTC tissues than in the noncarcinoma thyroid tissues adjacent to the PTC lesion and the benign nodular goiter tissues. The induction of PGE2 biosynthesis as well as the overexpression of EP4 in PTC suggested that this pathway might play an important role in the carcinogenesis and progression of PTC. These observations raise the possibility that pharmacological inhibition of mPGES-1 and/or EP4 may hold therapeutic promise in this common cancer.

Yamada S, Miyamoto S, Yamada S, Son JH, Nishido H, Ide F, Nagashima H, Sugaya M, Hirohata T, Mizutani A, Okinaga H, Ishii Y, Tahara S, Teramoto A, Osamura RY, Yamazaki K, Ishida Y. Clinicopathological and molecular histochemical review of skull base metastasis from differentiated thyroid carcinoma

Skull base metastasis from differentiated thyroid carcinoma including follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) is a rare clinical entity. Eighteen FTC cases and 10 PTC cases showing skull base metastasis have been reported. The most common symptom of skull base metastasis from FTC and PTC is cranial nerve dysfunction. Bone destruction and local invasion to the surrounding soft tissues are common on radiological imaging. Skull base metastases can be the initial clinical presentation of FTC and PTC in the presence of silent primary sites. The possibility of skull base metastasis from FTC and PTC should be considered in patients with the clinical symptoms of cranial nerve dysfunction and radiological findings of bone destruction. A variety of genetic alterations in thyroid tumors have been identified to have a fundamental role in their tumorigenesis. Molecular histochemical studies are useful for elucidating the histopathological features of thyroid carcinoma. Recent molecular findings may provide novel molecular-based treatment strategies for thyroid carcinoma.

Regional Differences in the Neuronal Expression of Cyclooxygenase-2 (COX-2) in the Newborn Pig Brain

Cyclooxygenase (COX)-2 is the major constitutively expressed COX isoform in the newborn brain. COX-2 derived prostanoids and reactive oxygen species appear to play a major role in the mechanism of perinatal hypoxic-ischemic injury in the newborn piglet, an accepted animal model of the human term neonate. The study aimed to quantitatively determine COX-2 immunopositive neurons in different brain regions in piglets under normoxic conditions (n=15), and 4 hours after 10 min asphyxia (n=11). Asphyxia did not induce significant changes in neuronal COX-2 expression of any studied brain areas. In contrast, there was a marked regional difference in all experimental groups. Thus, significant difference was observed between fronto-parietal and temporo-occipital regions: 59±4% and 67±3% versus 41±2%* and 31±3%* respectively (mean±SEM, data are pooled from all subjects, n=26, *p<0.05, vs. fronto-parietal region). In the hippocampus, COX-2 immunopositivity was rare (highest expression in CA1 region: 14±2%). The studied subcortical areas showed negligible COX-2 staining. Our findings suggest that asphyxia does not significantly alter the pattern of neuronal COX-2 expression in the early reventilation period. Furthermore, based on the striking differences observed in cortical neuronal COX-2 distribution, the contribution of COX-2 mediated neuronal injury after asphyxia may also show region-specific differences.

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 synthases influence thyroid follicular cell proliferation but not carcinogenesis in rats initiated with N-bis(2-hydroxypropyl)nitrosamine

To clarify roles of prostaglandin synthases in rat thyroid follicular carcinogenesis, effects of an antithyroid agent, sulfadimethoxine (SDM), and two prostaglandin H synthase (COX) inhibitors, indomethacin and nimesulide, on prostaglandin synthase expression, follicular cell proliferation, and tumor induction in thyroids of rats with or without N-bis(2-hydroxypropyl)nitrosamine (DHPN) initiation were examined. In experiment 1, F344 male rats were allowed free access to drinking water containing SDM (0.1%), SDM + indomethacin (0.0025% in diet), or SDM + nimesulide (0.04% in diet) for 4 weeks. Both COX inhibitors suppressed goitrogenic activity of SDM, but they did not significantly affect microsomal prostaglandin E synthase-2 (mPGES-2) expression levels enhanced by SDM. In experiment 2, all rats received an injection of DHPN (2800 mg/kg body weight), and starting 1 week later, they were treated as in experiment 1 for 4 or 10 weeks. Cell proliferation was suppressed or showed a tendency for suppression by the COX inhibitors in the follicular preneoplastic/neoplastic lesions and surrounding parenchyma, and this was obviously thyroid stimulating hormone independent at least at week 4. However, neither of the COX inhibitors altered the incidence or multiplicity of preneoplastic/neoplastic lesions. Immunohistochemistry revealed significant reduction and elevation of COX-2 and mPGES-2 expression, respectively, in the lesions, but these were also not changed by the COX inhibitors. These results suggest that COX-2 and PGES, and in turn PGE(2), might play important roles in follicular cell proliferation but do not affect tumor induction in this rat thyroid carcinogenesis model. Further studies are needed to clarify the significance of the reduction of COX-2 expression in preneoplastic/neoplastic lesions.

Identification and development of mPGES-1 inhibitors: where we are at?

Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal synthase responsible for the synthesis of the pro-tumorigenic prostaglandin E(2) (PGE(2)). mPGES-1 is overexpressed in a wide variety of cancers. Since its discovery in 1997 by Bengt Samuelsson and collaborators, the enzyme has been the object of over 200 peer-reviewed articles. Although today mPGES-1 is considered a validated and promising therapeutic target for anticancer drug discovery, challenges in inhibitor design and selectivity are such that up to this date there are only a few published records of small-molecule inhibitors targeting the enzyme and exhibiting some in vivo anticancer activity. This review summarizes the structures, and the in vitro and in vivo activities of these novel mPGES-1 inhibitors. Challenges that have been encountered are also discussed.

mPGES-1 as a target for cancer suppression: A comprehensive invited review "Phospholipase A2 and lipid mediators"

Prostaglandin E(2) (PGE(2)) is a bioactive lipid that can elicit a wide range of biological effects associated with inflammation and cancer. The physiological roles of PGE(2) are diverse, mediated in part through activation of key downstream signaling cascades via transmembrane EP receptors located on the cell surface. Elevated levels of COX-2 and concomitant overproduction of PGE(2) are often found in human cancers. These observations have led to the use of non-steroidal anti-inflammatory drugs (NSAIDs) as chemopreventive agents, particularly for colorectal cancer (CRC). Their long-term use, however, may be associated with gastrointestinal toxicity and increased risk of adverse cardiovascular events, prompting the development of other enzymatic targets in this pathway. This review will focus on recent efforts to target the terminal synthase, mPGES-1, for cancer chemoprevention. The role of mPGES-1 in the pathogenesis of various cancers is discussed. In addition, an overview of recent efforts to develop small molecule inhibitors that target the protein with high selectivity is also be reviewed.