Cyclooxygenases and lipoxygenases in cancer

miR-146a suppresses 5-lipoxygenase activating protein (FLAP) expression and Leukotriene B4 production in lung cancer cells

Arachidonic acid (AA) can be converted into prostaglandins (PGs) or leukotrienes (LTs) by the enzymatic actions of cyclooxygenases (COX-1 and COX-2) or 5-lipoxygenase (5-LO), respectively. PGs and LTs are lipid signaling molecules that have been implicated in various diseases, including multiple cancers. 5-LO and its activating protein (FLAP) work together in the first two conversion steps of LT production. Previous work has suggested a role for LTs in cancer development and progression. MicroRNAs (miRNAs) are small RNA molecules that negatively regulate gene expression post-transcriptionally, and have previously been shown to be involved in cancer. Here, we show that high FLAP expression is associated with lower overall survival in lung adenocarcinoma patients, and FLAP protein is overexpressed in lung cancer cells compared to normal lung cells. Our lab has previously shown that miR-146a regulates COX-2 in lung cancer cells, and this miRNA is also predicted to target FLAP. Transient and stable transfections of miR-146a repress endogenous FLAP expression in lung cancer cells, and reporter assays show this regulation occurs through a direct interaction between the FLAP 3′ untranslated region (UTR) and miR-146a. Restoration of miR-146a also results in decreased cancer cell Leukotriene B4 (LTB₄) production. Additionally, methylation analysis indicates the miR-146a promoter is hypermethylated in lung cancer cell lines. Taken together, this study and previous work from our lab suggest miR-146a is an endogenous dual inhibitor of AA metabolism in lung cancer cells by regulating both PG and LT production through direct targeting of the COX-2 and FLAP 3’ UTRs.

Cyclooxygenase and lipoxygenase gene expression in the inflammogenesis of breast cancer

We examined the expression of major inflammatory genes, cyclooxygenase-1 and 2 (COX1, COX2) and arachidonate 5-lipoxygenase (ALOX5) in 1090 tumor samples of invasive breast cancer from The Cancer Genome Atlas (TCGA). Mean cyclooxygenase expression (COX1 + COX2) ranked in the upper 99th percentile of all 20,531 genes and surprisingly, the mean expression of COX1 was more than tenfold higher than COX2. Highly significant correlations were observed between COX2 with eight tumor-promoting genes (EGR2, IL6, RGS2, B3GNT5, SGK1, SLC2A3, SFRP1 and ETS2) and between ALOX5 and ten tumor promoter genes (CD33, MYOF1, NLRP1, GAB3, CD4, IFR8, CYTH4, BTK, FGR, CD37). Expression of CYP19A1 (aromatase) was significantly correlated with COX2, but only in tumors positive for ER, PR and HER2. Tumor-promoting genes correlated with the expression of COX1, COX2, and ALOX5 are known to effectively increase mitogenesis, mutagenesis, angiogenesis, cell survival, immunosuppression and metastasis in the pathogenesis of breast cancer.

DuCLOX-2/5 Inhibition Attenuates Inflammatory Response and Induces Mitochondrial Apoptosis for Mammary Gland Chemoprevention

The present study is a pursuit to define implications of dual cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) (DuCLOX-2/5) inhibition on various aspects of cancer augmentation and chemoprevention. The monotherapy and combination therapy of zaltoprofen (COX-2 inhibitor) and zileuton (5-LOX inhibitor) were validated for their effect against methyl nitrosourea (MNU) induced mammary gland carcinoma in albino wistar rats. The combination therapy demarcated significant effect upon the cellular proliferation as evidenced through decreased in alveolar bud count and restoration of the histopathological architecture when compared to toxic control. DuCLOX-2/5 inhibition also upregulated levels of caspase-3 and caspase-8, and restored oxidative stress markers (GSH, TBARs, protein carbonyl, SOD and catalase). The immunoblotting and qRT-PCR studies revealed the participation of the mitochondrial mediated death apoptosis pathway along with favorable regulation of COX-2, 5-LOX. Aforementioned combination restored the metabolic changes to normal when scrutinized through ¹H NMR studies. Henceforth, the DuCLOX-2/5 inhibition was recorded to import significant anticancer effects in comparison to either of the individual treatments.

Nordihydroguaiaretic acid impairs prostate cancer cell migration and tumor metastasis by suppressing neuropilin 1

Tumor metastasis is a major cause leading to the deaths of cancer patients. Nordihydroguaiaretic acid (NDGA) is a natural product that has been demonstrated to show therapeutic values in multiple diseases. In this study, we report that NDGA can inhibit cell migration and tumor metastasis via a novel mechanism. NDGA suppresses NRP1 function by downregulating its expression, which leads to attenuated cell motility, cell adhesion to ECM and FAK signaling in cancer cells. Moreover, due to its cross-cell type activity on NRP1 suppression, NDGA also impairs angiogenesis function of endothelial cells and fibronectin assembly by fibroblasts, both of which are critical to promote metastasis. Based on these comprehensive effects, NDGA effectively suppresses tumor metastasis in nude mice model. Our findings reveal a novel mechanism underlying the anti-metastasis function of NDGA and indicate the potential value of NDGA in NRP1 targeting therapy for selected subtypes of cancer.

Inhibition of COX-2 and 5-LOX regulates the progression of colorectal cancer by promoting PTEN and suppressing PI3K/AKT pathway

For colorectal cancer (CRC) patients, local and systemic inflammatory responses have been extensively reported to closely associate with patient survival. However, the specific signaling pathways responsible for carcinogenic responses are unclear. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a negative regulator of PI3K/AKT pathway that is gradually inactivated in cancers through mutation, loss of heterozygosity and others epigenetic mechanisms. In addition, COX and LOX metabolic pathways of arachidonic acid (AA) play a crucial role in promoting adenoma development. The aim of this study is to clarify the relationship of COX, LOX and PTEN/PI3K/AKT pathway. Results showed that the over-expressed COX and LOX in cancer cells can be targeted to decrease the expression of PTEN. After using corresponding inhibitors, this condition was significantly improved and promoted apoptosis, inhibited invasion, proliferation and the production of reactive oxygen species. And for COX-2-/- or 5-LOX-/- Apc^Min/+ mice, the PI3K/AKT pathway was further inhibited via promoting PTEN. Furthermore, weakened oxidative stress, inhibited adenoma growth, and improved survival rate. All findings indicated that PTEN was indirectly targeted by these enzyme inhibitors and acted as the potential therapeutic target for colorectal cancer therapy. In short, COX-2 or 5-LOX deletion and its inhibitors enhanced activity of PTEN and suppressed cell and adenoma progression through PI3K/AKT pathway in colorectal cancer.

Arachidonic Acid Induces the Migration of MDA-MB-231 Cells by Activating Raft-associated Leukotriene B4 Receptors

BACKGROUND

The migration of tumor cells is critical in spreading cancers through the lymphatic nodes and circulatory systems. Although arachidonic acid (AA) and its soluble metabolites have been shown to induce the migration of breast and colon cancer cells, the mechanism by which it induces such migration has not been fully understood.

OBJECTIVE

The effect of AA on migratory responses of the MDA-MB-231 cell line (a triple-negative breast cancer cell) was examined and compared with MCF-7 (estrogen-receptor positive) breast cancer cells to elucidate the mechanism of AA-induced migration.

METHODS

Migrations of breast cancer cells were examined with the help of wound-healing assays. AA-induced eicosanoid synthesis was monitored by RP-HPLC. Cellular localizations of lipoxygenase and lipid rafts were assessed by immunoblot and confocal microscopy.

RESULTS

AA treatment stimulated the synthesis of leukotriene B4 (LTB4) and HETE-8, but lowered the levels of prostaglandin E2 (PGE2), prostaglandin D2 (PGD2), and HETE-5 in MDA-MB-231 cells. Further analysis indicated that AA increased the expression of 5-lipoxygenase (5-LOX) in this cell line and inhibiting its expression by small molecule inhibitors lowered the production of LTB4 and reduced migration. In contrast, MCF-7 cells did not show any appreciable changes in eicosanoid synthesis, 5-LOX expression, or cellular migration.

CONCLUSION

Our results suggest that AA treatment activates the BLT1 receptor (present in membrane microdomains) and stimulates the synthesis of LTB4 production, which is likely to be associated with the migration of MDA-MB-231 cells.

The Impact of Dietary Polyphenols on COX-2 Expression in Colorectal Cancer

Polyphenols are natural compounds with high structural diversity whose common occurrence in plants renders them intrinsic dietary components. They are known to be secondary metabolites characterized by a wide spectrum of biological activities, and a growing body of evidence indicates they have anti-inflammatory potential. It is well known that inflammation plays a key role in many chronic diseases such as circulatory diseases, pulmonary diseases, autoimmune diseases, diabetes, cancer, and neurodegenerative diseases. Polyphenols influence the inflammatory process by controlling and inhibiting pro-inflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α, and cyclooxygenase-2 (COX-2) enzyme involved in the metabolism of arachidonic acid. Furthermore, polyphenols exhibit anti-inflammatory activity on many levels via NF-κB inhibition, and MAPK, iNOS, and growth factors regulation. This paper reviews the current state of knowledge concerning the potential of various dietary polyphenols to inhibit the effects of COX-2 in colon cancer, by examining the available evidence regarding the efficacy and safety of these compounds obtained from in vitro and animal studies.

Regulation of cell signaling pathways by dietary agents for cancer prevention and treatment

Although it is widely accepted that better food habits do play important role in cancer prevention and treatment, how dietary agents mediate their effects remains poorly understood. More than thousand different polyphenols have been identified from dietary plants. In this review, we discuss the underlying mechanism by which dietary agents can modulate a variety of cell-signaling pathways linked to cancer, including transcription factors, nuclear factor κB (NF-κB), signal transducer and activator of transcription 3 (STAT3), activator protein-1 (AP-1), β-catenin/Wnt, peroxisome proliferator activator receptor- gamma (PPAR-γ), Sonic Hedgehog, and nuclear factor erythroid 2 (Nrf2); growth factors receptors (EGFR, VEGFR, IGF1-R); protein Kinases (Ras/Raf, mTOR, PI3K, Bcr-abl and AMPK); and pro-inflammatory mediators (TNF-α, interleukins, COX-2, 5-LOX). In addition, modulation of proteasome and epigenetic changes by the dietary agents also play a major role in their ability to control cancer. Both in vitro and animal based studies support the role of dietary agents in cancer. The efficacy of dietary agents by clinical trials has also been reported. Importantly, natural agents are already in clinical trials against different kinds of cancer. Overall both in vitro and in vivo studies performed with dietary agents strongly support their role in cancer prevention. Thus, the famous quote "Let food be thy medicine and medicine be thy food" made by Hippocrates 25 centuries ago still holds good.

Bystander signaling via oxidative metabolism

The radiation-induced bystander effect (RIBE) is the initiation of biological end points in cells (bystander cells) that are not directly traversed by an incident-radiation track, but are in close proximity to cells that are receiving the radiation. RIBE has been indicted of causing DNA damage via oxidative stress, besides causing direct damage, inducing tumorigenesis, producing micronuclei, and causing apoptosis. RIBE is regulated by signaling proteins that are either endogenous or secreted by cells as a means of communication between cells, and can activate intracellular or intercellular oxidative metabolism that can further trigger signaling pathways of inflammation. Bystander signals can pass through gap junctions in attached cell lines, while the suspended cell lines transmit these signals via hormones and soluble proteins. This review provides the background information on how reactive oxygen species (ROS) act as bystander signals. Although ROS have a very short half-life and have a nanometer-scale sphere of influence, the wide variety of ROS produced via various sources can exert a cumulative effect, not only in forming DNA adducts but also setting up signaling pathways of inflammation, apoptosis, cell-cycle arrest, aging, and even tumorigenesis. This review outlines the sources of the bystander effect linked to ROS in a cell, and provides methods of investigation for researchers who would like to pursue this field of science.

Role of 20-Hydroxyeicosatetraenoic Acid (20-HETE) in Androgen-Mediated Cell Viability in Prostate Cancer Cells

20-Hydroxyeicosatetraenoic acid (20-HETE) is generated intracellularly through the ω-hydroxylation of arachidonic acid by the cytochrome P450 (in humans, CYP4A11 and CYP4F2). 20-HETE induces mitogenic responses in different cancer cells. The aim of this study was to analyze how 20-HETE impacts cell survival, proliferation, and apoptosis in prostate cancer cells. Incubation of the human androgen-sensitive cells (LNCaP) with 1-10 μM HET0016 (a selective inhibitor of 20-HETE synthesis) reduced cell viability by 49*-64%* (*p < 0.05 vs. control). This was explained by a reduction in cell proliferation (vehicle, 46 ± 3%; 1 μM, 23 ± 3%*; 10 μM, 28 ± 3%*) and by an increase in apoptosis (vehicle, 2.1 ± 0%; 1 μM, 16 ± 4%*; 10 μM, 31 ± 3%*). Furthermore, the increase in LNCaP cell viability induced by dihydrotestosterone (DHT, 0.1 nM) was abrogated by 30*-42%* by 1-10 μM HET0016. Incubation with 20-HETE (5-1000 nM) increased LNCaP cell viability up to 50%*, together with a 70%* reduction in apoptosis. PC-3 (androgen-insensitive) cell viability was not affected by either HET0016 or 20-HETE. In LNCaP cells, HET0016 (10 μM) diminished the expression of androgen receptors (AR): messenger RNA (mRNA) (40%*) and protein (50%*). DHT (10 nM) augmented CYP4F2 protein expression (1.9-fold*) and 20-HETE levels (50%*). Oppositely, enzalutamide (AR antagonist) reduced CYP4F2 mRNA and protein expressions by 30 and 25%, respectively. Thus, intracellular availability of 20-HETE is necessary to sustain LNCaP cell viability. 20-HETE may act as a signaling molecule in the pathways involved in LNCaP cell viability upon stimulation of the AR. This effect may be partially attributed to its role on securing normal AR expression levels that in turn contribute to maintain intracellular levels of 20-HETE.

Genetic variation in the eicosanoid pathway is associated with non-small-cell lung cancer (NSCLC) survival

Globally, lung cancer results in more deaths worldwide than any other cancer, indicating a need for better treatments. Members of the eicosanoid metabolism pathway represent promising therapeutic targets, as several enzymes involved in the generation of these lipids are dysregulated in many cancers and their inhibition reduces lung cancer growth in mouse models. However, genetic variation of enzymes involved in eicosanoid metabolism has not been adequately examined for association with lung cancer. The goal of this study was to determine whether germline genetic variation altering eicosanoid producing enzyme function and/or expression are associated with differences in lung cancer survival. We examined the association of genetic variation with mortality within eicosanoid metabolism genes in 395 non-small-cell lung cancer (NSCLC) cases from the Southern Community Cohort Study (SCCS). A total of 108 SNPs, both common and rare, in 19 genes, were examined for association. No common or rare variants were associated with lung cancer survival across the entire study population. However, rare variants in ALOX15B (arachidonate 15-lipoxygenase, type B) and the common variant rs12529 in AKR1C3 (prostaglandin F synthase) were associated with NSCLC mortality in women and African Americans, respectively. Rare variants in ALOX15B were associated with greater mortality in women (HR = 2.10, 95% CI = 1.25–3.54, p-value = 0.005). The major allele of rs12529 in AKCR1C3 associated with improved survival in African Americans (HR = 0.74, 95% CI = 0.59–0.92, p-value = 0.008). The lack of genetic associations among all NSCLC cases and the association among women only for rare variants in ALOX15B may, in part, explain the better NSCLC survival observed among women. These results raise the possibility that some subgroups within the NSCLC population may benefit from drugs targeting eicosanoid metabolism.

Inhibition of COX2 enhances the chemosensitivity of dichloroacetate in cervical cancer cells

Dichloroacetate (DCA), a traditional mitochondria-targeting agent, has shown promising prospect as a sensitizer in fighting against malignancies including cervical cancer. But it is unclear about the effect of DCA alone on cervical tumor. Moreover, previous reports have demonstrated that the increased cyclooxygenase-2 (COX2) expression is associated with chemoresistance and poor prognosis of cervical cancer. However, it is still unknown whether COX2 can affect the sensitivity of DCA in cervical cancer cells. In this study, we found that cervical cancer cells were insensitive to DCA. Furthermore, we for the first time revealed that DCA could upregulate COX2 which impeded the chemosensitivity of DCA in cervical cancer cells. Mechanistic study showed that DCA reduced the level of RNA binding protein quaking (QKI), leading to the decay suppression of COX2 mRNA and the subsequent elevation of COX2 protein. Inhibition of COX2 using celecoxib could sensitize DCA in repressing the growth of cervical cancer cells both in vitro and in vivo. These results indicate that COX2 is a novel resistance factor of DCA, and combination of celecoxib with DCA may be beneficial to the treatment of cervical cancer.

Cell biology-metabolic crosstalk in glioma

The renewed interest in cancer metabolism in recent years has been fuelled by the identification of the involvement of key oncogenes and tumour suppressor genes in the control of metabolic pathways. Many of these alterations lead to dramatic changes in bioenergetics, biosynthesis and redox balance within tumour cells. The complex relationship between tumour cell metabolism and the tumour microenvironment has turned this field of biochemistry and cell biology into a challenging and exciting area for study. In the case of gliomas the involvement of altered metabolic pathways including glycolysis, oxidative phosphorylation and glutaminolysis are pointing the way to new possibilities for treatment. The tumour-promoting effects of inflammation are an emerging hallmark of cancer and the role of the eicosanoids in gliomas is an area of active research to elucidate the importance of individual eicosanoids in glioma cell proliferation, migration and immune escape. In this review, the different aspects of metabolic reprogramming which occur in gliomas are highlighted and their relationship to glioma cell biology and the wider tumour microenvironment is described.

Catalytic Conversion of Lipophilic Substrates by Phase constrained Enzymes in the Aqueous or in the Membrane Phase

Both soluble and membrane-bound enzymes can catalyze the conversion of lipophilic substrates. The precise substrate access path, with regard to phase, has however, until now relied on conjecture from enzyme structural data only (certainly giving credible and valuable hypotheses). Alternative methods have been missing. To obtain the first experimental evidence directly determining the access paths (of lipophilic substrates) to phase constrained enzymes we here describe the application of a BODIPY-derived substrate (PS1). Using this tool, which is not accessible to cytosolic enzymes in the presence of detergent and, by contrast, not accessible to membrane embedded enzymes in the absence of detergent, we demonstrate that cytosolic and microsomal glutathione transferases (GSTs), both catalyzing the activation of PS1, do so only within their respective phases. This approach can serve as a guideline to experimentally validate substrate access paths, a fundamental property of phase restricted enzymes. Examples of other enzyme classes with members in both phases are xenobiotic-metabolizing sulphotransferases/UDP-glucuronosyl transferases or epoxide hydrolases. Since specific GSTs have been suggested to contribute to tumor drug resistance, PS1 can also be utilized as a tool to discriminate between phase constrained members of these enzymes by analyzing samples in the absence and presence of Triton X-100.

Targeting arachidonic acid pathway by natural products for cancer prevention and therapy

Arachidonic acid (AA) pathway, a metabolic process, plays a key role in carcinogenesis. Hence, AA pathway metabolic enzymes phospholipase A₂s (PLA₂s), cyclooxygenases (COXs) and lipoxygenases (LOXs) and their metabolic products, such as prostaglandins and leukotrienes, have been considered novel preventive and therapeutic targets in cancer. Bioactive natural products are a good source for development of novel cancer preventive and therapeutic drugs, which have been widely used in clinical practice due to their safety profiles. AA pathway inhibitory natural products have been developed as chemopreventive and therapeutic agents against several cancers. Curcumin, resveratrol, apigenin, anthocyans, berberine, ellagic acid, eugenol, fisetin, ursolic acid, [6]-gingerol, guggulsteone, lycopene and genistein are well known cancer chemopreventive agents which act by targeting multiple pathways, including COX-2. Nordihydroguaiaretic acid and baicalein can be chemopreventive molecules against various cancers by inhibiting LOXs. Several PLA₂s inhibitory natural products have been identified with chemopreventive and therapeutic potentials against various cancers. In this review, we critically discuss the possible utility of natural products as preventive and therapeutic agents against various oncologic diseases, including prostate, pancreatic, lung, skin, gastric, oral, blood, head and neck, colorectal, liver, cervical and breast cancers, by targeting AA pathway. Further, the current status of clinical studies evaluating AA pathway inhibitory natural products in cancer is reviewed. In addition, various emerging issues, including bioavailability, toxicity and explorability of combination therapy, for the development of AA pathway inhibitory natural products as chemopreventive and therapeutic agents against human malignancy are also discussed.

Effect of β-sitosterol against methyl nitrosourea-induced mammary gland carcinoma in albino rats

BACKGROUND

The present study was in quested to study the effects of β-sitosterol on methyl nitrosourea (MNU) induced mammary gland carcinoma in albino wistar rats.

METHODS

Animals were randomized and divided into four groups of eight animals each. Group I (sham control 1 % CMC in normal saline p.o.); Group II (toxic control, MNU 47 mg/kg, i.v); Group III (MNU 47 mg/kg, i.v + β-sitosterol, 10 mg/kg, p.o); Group IV (MNU 47 mg/kg, i.v + β-sitosterol, 20 mg/kg, p.o). Toxicity was induced by single i.v. injection of MNU followed by β-sitosterol supplementation therapy for 115 days at the dose mentioned above.

RESULTS

Treatment with β-sitosterol evidenced decrease in the alveolar bud and lobule score in the whole mount of the mammary gland. β-sitosterol exhibited diminishing effect on oxidative stress through synchronizing lipid and enzymatic antioxidant defense. A significant decrease in the saturated and unsaturated fatty acid was evident with the MNU treatment and β-sitosterol demonstrated a marked effect on it. Pgp 9.5 expression was dose dependently upregulated by β-sitosterol treatment in comparison to MNU treatment. On the contrary, downregulated NF-kB expression was perceived, when β-sitosterol was concomitantly administered with MNU.

CONCLUSION

β-sitosterol afforded significant protection against the deleterious effects of MNU.

Serum 5-LOX: a progressive protein marker for breast cancer and new approach for therapeutic target

Lipoxygenase (LOX) pathway has emerged to have a role in carcinogenesis. There is an evidence that both 12-LOX and 5-LOX have procarcinogenic role. We have previously reported the elevated level of serum 12-LOX in breast cancer patients. This study evaluated the serum level of 5-LOX in breast cancer patients and its in vitro inhibition assessment with peptide inhibitor YWCS. The level of 5-LOX was determined by surface plasmon resonance (SPR). The peptide inhibitor of 5-LOX was designed by molecular modeling and kinetic assay was performed by spectrophotometry. The siRNA mediated 5-LOX gene silencing was performed to investigate the effect on proliferation of MDA-MB-231, breast cancer cell line. The serum 5-LOX level in breast cancer (5.69±1.97ng/µl) was almost 2-fold elevated compared to control (3.53±1.0ng/µl) (P < 0.0001). The peptide YWCS had shown competitive inhibitory effects with IC50, 2.2 µM and dissociation constant (K D), 4.92×10(-8) M. The siRNA mediated knockdown of 5-LOX, resulted in the decreased gene expression for 5-LOX and increased cell death in MDA-MB-231 cell line and thereby play a key role in reducing tumor proliferation. Thus, it can be concluded that 5-LOX is one of the potential serum protein marker for breast cancer and a promising therapeutic target for the same.

Evolutionary alteration of ALOX15 specificity optimizes the biosynthesis of antiinflammatory and proresolving lipoxins

ALOX15 (12/15-lipoxygenase) orthologs have been implicated in maturational degradation of intracellular organelles and in the biosynthesis of antiinflammatory and proresolving eicosanoids. Here we hypothesized that lower mammals (mice, rats, pigs) express 12-lipoxygenating ALOX15 orthologs. In contrast, 15-lipoxygenating isoforms are found in higher primates (orangutans, men), and these results suggest an evolution of ALOX15 specificity. To test this hypothesis we first cloned and characterized ALOX15 orthologs of selected Catarrhini representing different stages of late primate evolution and found that higher primates (men, chimpanzees) express 15-lipoxygenating orthologs. In contrast, lower primates (baboons, rhesus monkeys) express 12-lipoxygenating enzymes. Gibbons, which are flanked in evolution by rhesus monkeys (12-lipoxygenating ALOX15) and orangutans (15-lipoxygenating ALOX15), express an ALOX15 ortholog with pronounced dual specificity. To explore the driving force for this evolutionary alterations, we quantified the lipoxin synthase activity of 12-lipoxygenating (rhesus monkey, mouse, rat, pig, humIle418Ala) and 15-lipoxygenating (man, chimpanzee, orangutan, rabbit, ratLeu353Phe) ALOX15 variants and found that, when normalized to their arachidonic acid oxygenase activities, the lipoxin synthase activities of 15-lipoxygenating ALOX15 variants were more than fivefold higher (P < 0.01) [corrected]. Comparative molecular dynamics simulations and quantum mechanics/molecular mechanics calculations indicated that, for the 15-lipoxygenating rabbit ALOX15, the energy barrier for C13-hydrogen abstraction (15-lipoxygenation) was 17 kJ/mol lower than for arachidonic acid 12-lipoxygenation. In contrast, for the 12-lipoxygenating Ile418Ala mutant, the energy barrier for 15-lipoxygenation was 10 kJ/mol higher than for 12-lipoxygenation. Taken together, our data suggest an evolution of ALOX15 specificity, which is aimed at optimizing the biosynthetic capacity for antiinflammatory and proresolving lipoxins.

Role of phospholipases in adrenal steroidogenesis

Phospholipases are lipid-metabolizing enzymes that hydrolyze phospholipids. In some cases, their activity results in remodeling of lipids and/or allows the synthesis of other lipids. In other cases, however, and of interest to the topic of adrenal steroidogenesis, phospholipases produce second messengers that modify the function of a cell. In this review, the enzymatic reactions, products, and effectors of three phospholipases, phospholipase C, phospholipase D, and phospholipase A2, are discussed. Although much data have been obtained concerning the role of phospholipases C and D in regulating adrenal steroid hormone production, there are still many gaps in our knowledge. Furthermore, little is known about the involvement of phospholipase A2, perhaps, in part, because this enzyme comprises a large family of related enzymes that are differentially regulated and with different functions. This review presents the evidence supporting the role of each of these phospholipases in steroidogenesis in the adrenal cortex.

Lipoxygenase directed anti-inflammatory and anti-cancerous secondary metabolites: ADMET-based screening, molecular docking and dynamics simulation

Lipoxygenases (LOXs), key enzymes involved in the biosynthesis of leukotrienes, are well known to participate in the inflammatory and immune responses. With the recent reports of involvement of 5-LOX (one of the isozymes of LOX in human) in cancer, there is a need to find out selective inhibitors of 5-LOX for their therapeutic application. In the present study, plant-derived 300 anti-inflammatory and anti-cancerous secondary metabolites (100 each of alkaloids, flavonoids and terpenoids) have been screened for their pharmacokinetic properties and subsequently docked for identification of potent inhibitors of 5-LOX. Pharmacokinetic analyses revealed that only 18 alkaloids, 26 flavonoids, and 9 terpenoids were found to fulfill all the absorption, distribution, metabolism, excretion, and toxicity descriptors as well as those of Lipinski's Rule of Five. Docking analyses of pharmacokinetically screened metabolites and their comparison with a known inhibitor (drug), namely zileuton revealed that only three alkaloids, six flavonoids and three terpenoids were found to dock successfully with 5-LOX with the flavonoid, velutin being the most potent inhibitor among all. The results of the docking analyses were further validated by performing molecular dynamics simulation and binding energy calculations for the complexes of 5-LOX with velutin, galangin, chrysin (in order of LibDock scores), and zileuton. The data revealed stabilization of all the complexes within 15 ns of simulation with velutin complex exhibiting least root-mean-square deviation value (.285 ± .007 nm) as well as least binding energy (ΔG_bind = -203.169 kJ/mol) as compared to others during the stabilization phase of simulation.

Production of cross-kingdom oxylipins by pathogenic fungi: An update on their role in development and pathogenicity

Oxylipins are a class of molecules derived from the incorporation of oxygen into polyunsaturated fatty acid substrates through the action of oxygenases. While extensively investigated in the context of mammalian immune responses, over the last decade it has become apparent that oxylipins are a common means of communication among and between plants, animals, and fungi to control development and alter host-microbe interactions. In fungi, some oxylipins are derived nonenzymatically while others are produced by lipoxygenases, cyclooxygenases, and monooxygenases with homology to plant and human enzymes. Recent investigations of numerous plant and human fungal pathogens have revealed oxylipins to be involved in the establishment and progression of disease. This review highlights oxylipin production by pathogenic fungi and their role in fungal development and pathogen/host interactions.

Plasma Vasoprotective Eicosanoid Concentrations in Healthy Greyhounds and Non-Greyhound Dogs

BACKGROUND

Hypertension and albuminuria often coexist in Greyhounds, suggesting generalized vascular dysfunction that could contribute to the development of a variety of diseases in this breed. Eicosanoid metabolites of arachidonic acid (AA) mediate endothelial function, vascular reactivity, and proteinuria in humans and in rodent models.

HYPOTHESIS

The eicosanoid profile of Greyhounds is shifted toward metabolites that promote vascular dysfunction, hypertension, and proteinuria.

ANIMALS

Healthy Greyhounds (n = 20) and non-Greyhound (n = 20) dogs that were consecutively enrolled in a blood donor program.

METHODS

Prospective study. Plasma eicosanoid metabolites were assayed by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI/MS) and compared to systolic blood pressure (SP) measurements and urine albumin concentration.

RESULTS

Isomers of hydroxyeicosatetraenoic acid (HETE) were higher in Greyhounds than non-Greyhounds (median, range in pmol/mL: 5(S)HETE 19.82, 8.55-32.95 versus 13.54, 4.33-26.27, P = .033; 8(S)HETE 9.39, 3.28-19.84 versus 5.80, 2.25-17.66, P = .002; 9(S)HETE 9.46, 2.43-13.79 versus 5.82, 1.50-17.16, P = .026; 12(S)HETE 10.17, 3.81-40.06 versus 7.24, 2.9-16.16, P = .022). Dihydroxyeicosatrienoic acid (DHET) isomers also were higher in Greyhounds compared to non-Greyhounds (mean ± SD in pmol/mL: 8,9DHET 5.78 ± 2.13 versus 4.03 ± 1.36, P = .004; 11,12DHET 11.98 ± 2.86 versus 8.90 ± 3.48, P = .004; 14,15DHET 7.23 ± 2.19 versus 5.76 ± 1.87, P = .028). Albuminuria correlated with total DHET (rs = 0.46, P = .003). SP was positively correlated with 11,12EET (rs = 0.42, P = .006) and 20(S)HETE (rs = 0.38, P = .017). SP and 8,9EET were inversely correlated (rs = -0.49, P = .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Plasma eicosanoid profile in Greyhounds was consistent with activation of metabolic pathways known to promote vascular dysfunction and might contribute to higher blood pressures and albuminuria. Inhibition of these eicosanoid pathways should be evaluated as therapeutic targets in Greyhounds.

Environmental immune disruptors, inflammation and cancer risk

An emerging area in environmental toxicology is the role that chemicals and chemical mixtures have on the cells of the human immune system. This is an important area of research that has been most widely pursued in relation to autoimmune diseases and allergy/asthma as opposed to cancer causation. This is despite the well-recognized role that innate and adaptive immunity play as essential factors in tumorigenesis. Here, we review the role that the innate immune cells of inflammatory responses play in tumorigenesis. Focus is placed on the molecules and pathways that have been mechanistically linked with tumor-associated inflammation. Within the context of chemically induced disturbances in immune function as co-factors in carcinogenesis, the evidence linking environmental toxicant exposures with perturbation in the balance between pro- and anti-inflammatory responses is reviewed. Reported effects of bisphenol A, atrazine, phthalates and other common toxicants on molecular and cellular targets involved in tumor-associated inflammation (e.g. cyclooxygenase/prostaglandin E2, nuclear factor kappa B, nitric oxide synthesis, cytokines and chemokines) are presented as example chemically mediated target molecule perturbations relevant to cancer. Commentary on areas of additional research including the need for innovation and integration of systems biology approaches to the study of environmental exposures and cancer causation are presented.

Advances in Our Understanding of Oxylipins Derived from Dietary PUFAs

Oxylipins formed from polyunsaturated fatty acids (PUFAs) are the main mediators of PUFA effects in the body. They are formed via cyclooxygenase, lipoxygenase, and cytochrome P450 pathways, resulting in the formation of prostaglandins, thromboxanes, mono-, di-, and tri-hydroxy fatty acids (FAs), epoxy FAs, lipoxins, eoxins, hepoxilins, resolvins, protectins (also called neuroprotectins in the brain), and maresins. In addition to the well-known eicosanoids derived from arachidonic acid, recent developments in lipidomic methodologies have raised awareness of and interest in the large number of oxylipins formed from other PUFAs, including those from the essential FAs and the longer-chain n-3 (ω-3) PUFAs. Oxylipins have essential roles in normal physiology and function, but can also have detrimental effects. Compared with the oxylipins derived from n-3 PUFAs, oxylipins from n-6 PUFAs generally have greater activity and more inflammatory, vasoconstrictory, and proliferative effects, although there are notable exceptions. Because PUFA composition does not necessarily reflect oxylipin composition, comprehensive analysis of the oxylipin profile is necessary to understand the overall physiologic effects of PUFAs mediated through their oxylipins. These analyses should include oxylipins derived from linoleic and α-linolenic acids, because these largely unexplored bioactive oxylipins constitute more than one-half of oxylipins present in tissues. Because collated information on oxylipins formed from different PUFAs is currently unavailable, this review provides a detailed compilation of the main oxylipins formed from PUFAs and describes their functions. Much remains to be elucidated in this emerging field, including the discovery of more oxylipins, and the understanding of the differing biological potencies, kinetics, and isomer-specific activities of these novel PUFA metabolites.

Co-expression of COX-2 and 5-LO in primary glioblastoma is associated with poor prognosis

Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LO) are important factors in tumorigenesis and malignant progression; however, studies of their roles in glioblastoma have produced conflicting results. To define the frequencies of COX-2 and 5-LO expression and their correlation with clinicopathological features and prognosis, tumor tissues from 76 cases of newly diagnosed primary ordinary glioblastoma were examined for COX-2 and 5-LO expression by immunohistochemistry. The expression levels of COX-2 and 5-LO and the relationships between the co-expression of COX-2/5-LO and patient age and gender, edema index (EI), Karnofsky Performance Scale and overall survival (OS) were analyzed. COX-2 and 5-LO were expressed in 73.7 % (56/76) and 92.1 % (70/76) of the samples, respectively. Among the clinicopathological characteristics, only age (>60 years) exhibited a significant association with the high expression of COX-2. No statistically significant correlations were found in the 5-LO cohort. A significant positive correlation was revealed between the COX-2 and 5-LO scores (r = 0.374; p = 0.001). The elevated co-expression of COX-2 and 5-LO was observed primarily in the patients over the age of 60 years. Patients with a high expression of COX-2 had a significantly shorter OS (p < 0.01), whereas the immunoexpression of 5-LO was not associated with the OS of patients with glioblastoma. Survival analysis indicated that simultaneous high levels of COX-2 and 5-LO expression were significantly correlated with poor OS and, conversely, that a low/low expression pattern of these two proteins was significantly associated with better OS (p < 0.05). Moreover, the Cox multivariable proportional hazard model showed that a high expression of COX-2, high co-expression of COX-2 and 5-LO, and a high Ki-67 index were significant predictors of shorter OS in primary glioblastoma, independent of age, gender, EI, 5-LO expression and p53 status. The hazard ratios for OS were 2.347 (95 % CI 1.30-4.25, p = 0.005), 1.900 (95 % CI 1.30-2.78, p = 0.001), and 2.210 (95 % CI 1.19-4.09, p = 0.011), respectively. These results suggest that COX-2 and 5-LO play roles in tumorigenesis and the progression of primary glioblastoma and that the co-expression pattern of COX-2/5-LO may be used as an independent prognostic factor in this disease.

Activity cliffs and activity cliff generators based on chemotype-related activity landscapes

Activity cliffs have large impact in drug discovery; therefore, their detection and quantification are of major importance. This work introduces the metric activity cliff enrichment factor and expands the previously reported activity cliff generator concept by adding chemotype information to representations of the activity landscape. To exemplify these concepts, three molecular databases with multiple biological activities were characterized. Compounds in each database were grouped into chemotype classes. Then, pairwise comparisons of structure similarities and activity differences were calculated for each compound and used to construct chemotype-based structure-activity similarity (SAS) maps. Different landscape distributions among four major regions of the SAS maps were observed for different subsets of molecules grouped in chemotypes. Based on this observation, the activity cliff enrichment factor was calculated to numerically detect chemotypes enriched in activity cliffs. Several chemotype classes were detected having major proportion of activity cliffs than the entire database. In addition, some chemotype classes comprising compounds with smooth structure activity relationships (SAR) were detected. Finally, the activity cliff generator concept was applied to compounds grouped in chemotypes to extract valuable SAR information.

Anti-proliferative and pro-apoptotic effects of lichen-derived compound protolichesterinic acid are not mediated by its lipoxygenase-inhibitory activity

Lipoxygenases (LOXs) and their products are involved in several biological functions and have been associated with carcinogenesis. Protolichesterinic acid (PA), a lichen metabolite, inhibits 5- and 12-LOX and has anti-proliferative effects on various cancer cell lines. Here, PA was shown to inhibit proliferation of multiple myeloma cells, RPMI 8226 and U266, and pancreatic cancer cells AsPC-1. Apoptosis was induced only in multiple myeloma cells. Cell-cycle associated changes in expression and sub-cellular localization of 5- and 12-LOX were not affected by PA but increased cytoplasmic localisation was found to accompany morphological changes at later stages. Assessment by mass spectrometry showed that PA entered the pancreatic cancer cells. However, effects on LOX metabolites were only evident after treatment with concentrations exceeding those having anti-proliferative effects and no effects were measurable in the myeloma cells. We conclude that the anti-proliferative and pro-apoptotic effects of PA are not mediated directly through inhibition of LOX activity.

Hydroxyoctadecadienoic acids: Oxidised derivatives of linoleic acid and their role in inflammation associated with metabolic syndrome and cancer

Linoleic acid (LA) is a major constituent of low-density lipoproteins. An essential fatty acid, LA is a polyunsaturated fatty acid, which is oxidised by endogenous enzymes and reactive oxygen species in the circulation. Increased levels of low-density lipoproteins coupled with oxidative stress and lack of antioxidants drive the oxidative processes. This results in synthesis of a range of oxidised derivatives, which play a vital role in regulation of inflammatory processes. The derivatives of LA include, hydroxyoctadecadienoic acids, oxo-​octadecadienoic acids, epoxy octadecadecenoic acid and epoxy-keto-octadecenoic acids. In this review, we examine the role of LA derivatives and their actions on regulation of inflammation relevant to metabolic processes associated with atherogenesis and cancer. The processes affected by LA derivatives include, alteration of airway smooth muscles and vascular wall, affecting sensitivity to pain, and regulating endogenous steroid hormones associated with metabolic syndrome. LA derivatives alter cell adhesion molecules, this initial step, is pivotal in regulating inflammatory processes involving transcription factor peroxisome proliferator-activated receptor pathways, thus, leading to alteration of metabolic processes. The derivatives are known to elicit pleiotropic effects that are either beneficial or detrimental in nature hence making it difficult to determine the exact role of these derivatives in the progress of an assumed target disorder. The key may lie in understanding the role of these derivatives at various stages of development of a disorder. Novel pharmacological approaches in altering the synthesis or introduction of synthesised LA derivatives could possibly help drive processes that could regulate inflammation in a beneficial manner. Chemical Compounds: Linoleic acid (PubChem CID: 5280450), 9- hydroxyoctadecadienoic acid (PubChem CID: 5312830), 13- hydroxyoctadecadienoic acid (PubChem CID: 6443013), 9-oxo-​octadecadienoic acid (PubChem CID: 3083831), 13-oxo-​octadecadienoic acid (PubChem CID: 4163990), 9,10-epoxy-12-octadecenoate (PubChem CID: 5283018), 12,13-epoxy-9-keto-10- trans -octadecenoic acid (PubChem CID: 53394018), Pioglitazone (PubChem CID: 4829).

Comparative proteomic analysis of hypertrophic chondrocytes in osteoarthritis

Background

Osteoarthritis (OA) is a multi-factorial disease leading progressively to loss of articular cartilage and subsequently to loss of joint function. While hypertrophy of chondrocytes is a physiological process implicated in the longitudinal growth of long bones, hypertrophy-like alterations in chondrocytes play a major role in OA. We performed a quantitative proteomic analysis in osteoarthritic and normal chondrocytes followed by functional analyses to investigate proteome changes and molecular pathways involved in OA pathogenesis.

Methods

Chondrocytes were isolated from articular cartilage of ten patients with primary OA undergoing knee replacement surgery and six normal donors undergoing fracture repair surgery without history of joint disease and no OA clinical manifestations. We analyzed the proteome of chondrocytes using high resolution mass spectrometry and quantified it by label-free quantification and western blot analysis. We also used WebGestalt, a web-based enrichment tool for the functional annotation and pathway analysis of the differentially synthesized proteins, using the Wikipathways database. ClueGO, a Cytoscape plug-in, is also used to compare groups of proteins and to visualize the functionally organized Gene Ontology (GO) terms and pathways in the form of dynamical network structures.

Results

The proteomic analysis led to the identification of a total of ~2400 proteins. 269 of them showed differential synthesis levels between the two groups. Using functional annotation, we found that proteins belonging to pathways associated with regulation of the actin cytoskeleton, EGF/EGFR, TGF-β, MAPK signaling, integrin-mediated cell adhesion, and lipid metabolism were significantly enriched in the OA samples (p ≤10⁻⁵). We also observed that the proteins GSTP1, PLS3, MYOF, HSD17B12, PRDX2, APCS, PLA2G2A SERPINH1/HSP47 and MVP, show distinct synthesis levels, characteristic for OA or control chondrocytes.

Conclusion

In this study we compared the quantitative changes in proteins synthesized in osteoarthritic compared to normal chondrocytes. We identified several pathways and proteins to be associated with OA chondrocytes. This study provides evidence for further testing on the molecular mechanism of the disease and also propose proteins as candidate markers of OA chondrocyte phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-015-9085-6) contains supplementary material, which is available to authorized users.

Biosynthesis, biological effects, and receptors of hydroxyeicosatetraenoic acids (HETEs) and oxoeicosatetraenoic acids (oxo-ETEs) derived from arachidonic acid

Arachidonic acid can be oxygenated by a variety of different enzymes, including lipoxygenases, cyclooxygenases, and cytochrome P450s, and can be converted to a complex mixture of oxygenated products as a result of lipid peroxidation. The initial products in these reactions are hydroperoxyeicosatetraenoic acids (HpETEs) and hydroxyeicosatetraenoic acids (HETEs). Oxoeicosatetraenoic acids (oxo-ETEs) can be formed by the actions of various dehydrogenases on HETEs or by dehydration of HpETEs. Although a large number of different HETEs and oxo-ETEs have been identified, this review will focus principally on 5-oxo-ETE, 5S-HETE, 12S-HETE, and 15S-HETE. Other related arachidonic acid metabolites will also be discussed in less detail. 5-Oxo-ETE is synthesized by oxidation of the 5-lipoxygenase product 5S-HETE by the selective enzyme, 5-hydroxyeicosanoid dehydrogenase. It actions are mediated by the selective OXE receptor, which is highly expressed on eosinophils, suggesting that it may be important in eosinophilic diseases such as asthma. 5-Oxo-ETE also appears to stimulate tumor cell proliferation and may also be involved in cancer. Highly selective and potent OXE receptor antagonists have recently become available and could help to clarify its pathophysiological role. The 12-lipoxygenase product 12S-HETE acts by the GPR31 receptor and promotes tumor cell proliferation and metastasis and could therefore be a promising target in cancer therapy. It may also be involved as a proinflammatory mediator in diabetes. In contrast, 15S-HETE may have a protective effect in cancer. In addition to GPCRs, higher concentration of HETEs and oxo-ETEs can activate peroxisome proliferator-activated receptors (PPARs) and could potentially regulate a variety of processes by this mechanism. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Mammalian lipoxygenases and their biological relevance

Lipoxygenases (LOXs) form a heterogeneous class of lipid peroxidizing enzymes, which have been implicated not only in cell proliferation and differentiation but also in the pathogenesis of various diseases with major public health relevance. As other fatty acid dioxygenases LOXs oxidize polyunsaturated fatty acids to their corresponding hydroperoxy derivatives, which are further transformed to bioactive lipid mediators (eicosanoids and related substances). On the other hand, lipoxygenases are key players in the regulation of the cellular redox homeostasis, which is an important element in gene expression regulation. Although the first mammalian lipoxygenases were discovered 40 years ago and although the enzymes have been well characterized with respect to their structural and functional properties the biological roles of the different lipoxygenase isoforms are not completely understood. This review is aimed at summarizing the current knowledge on the physiological roles of different mammalian LOX-isoforms and their patho-physiological function in inflammatory, metabolic, hyperproliferative, neurodegenerative and infectious disorders. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Differential cell growth/apoptosis behavior of 13-hydroxyoctadecadienoic acid enantiomers in a colorectal cancer cell line

Cyclooxygenases (COXs) and lipoxygenases (LOXs) are important enzymes that metabolize arachidonic and linoleic acids. Various metabolites generated by the arachidonic acid cascade regulate cell proliferation, apoptosis, differentiation, and senescence. Hydroxyoctadecadienoic acids (HODEs) are synthesized from linoleic acid, giving two enantiomeric forms for each metabolite. The aim was to investigate the effect of 13-HODE enantiomers on nondifferentiated Caco-2 cell growth/apoptosis. Our results indicate that 13(S)-HODE decreases cell growth and DNA synthesis of nondifferentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS). Moreover, 13(S)-HODE showed an apoptotic effect that was reduced in the presence of a specific peroxisome proliferator-activated receptor-γ (PPARγ) antagonist. In addition, we observed that 13(S)-HODE but not 13(R)-HODE is a ligand to PPARγ, confirming the implication of this nuclear receptor in 13(S)-HODE actions. In contrast, 13(R)-HODE increases cell growth and DNA synthesis in the absence of FBS. 13(R)-HODE interaction with BLT receptors activates ERK and CREB signaling pathways, as well as PGE2 synthesis. These results suggest that the proliferative effect of 13(R)-HODE could be due, at least in part, to COX pathway activation. Thus both enantiomers use different receptors and have contrary effects. We also found these differential effects of 9-HODE enantiomers on cell growth/apoptosis. Therefore, the balance between (R)-HODEs and (S)-HODEs in the intestinal epithelium could be important to its cell growth/apoptosis homeostasis.

Pomegranate and its components as alternative treatment for prostate cancer

Prostate cancer is the second leading cause of cancer deaths in men in the United States. There is a major need for less toxic but yet effective therapies to treat prostate cancer. Pomegranate fruit from the tree Punica granatum has been used for centuries for medicinal purposes and is described as “nature’s power fruit”. Recent research has shown that pomegranate juice (PJ) and/or pomegranate extracts (PE) significantly inhibit the growth of prostate cancer cells in culture. In preclinical murine models, PJ and/or PE inhibit growth and angiogenesis of prostate tumors. More recently, we have shown that three components of PJ, luteolin, ellagic acid and punicic acid together, have similar inhibitory effects on prostate cancer growth, angiogenesis and metastasis. Results from clinical trials are also promising. PJ and/or PE significantly prolonged the prostate specific antigen (PSA) doubling time in patients with prostate cancer. In this review we discuss data on the effects of PJ and PE on prostate cancer. We also discuss the effects of specific components of the pomegranate fruit and how they have been used to study the mechanisms involved in prostate cancer progression and their potential to be used in deterring prostate cancer metastasis.

Downregulation of COX-2 and CYP 4A signaling by isoliquiritigenin inhibits human breast cancer metastasis through preventing anoikis resistance, migration and invasion

Flavonoids exert extensive in vitro anti-invasive and in vivo anti-metastatic activities. Anoikis resistance occurs at multiple key stages of the metastatic cascade. Here, we demonstrate that isoliquiritigenin (ISL), a flavonoid from Glycyrrhiza glabra, inhibits human breast cancer metastasis by preventing anoikis resistance, migration and invasion through downregulating cyclooxygenase (COX)-2 and cytochrome P450 (CYP) 4A signaling. ISL induced anoikis in MDA-MB-231 and BT-549 human breast cancer cells as evidenced by flow cytometry and the detection of caspase cleavage. Moreover, ISL inhibited the mRNA expression of phospholipase A2, COX-2 and CYP 4A and decreased the secretion of prostaglandin E2 (PGE2) and 20-hydroxyeicosatetraenoic acid (20-HETE) in detached MDA-MB-231 cells. In addition, it decreased the levels of phospho-PI3K (Tyr(458)), phospho-PDK (Ser(241)) and phospho-Akt (Thr(308)). Conversely, the exogenous addition of PGE2, WIT003 (a 20-HETE analog) and an EP4 agonist (CAY10580) or overexpression of constitutively active Akt reversed ISL-induced anoikis. ISL exerted the in vitro anti-migratory and anti-invasive activities, whereas the addition of PGE2, WIT003 and CAY10580 or overexpression of constitutively active Akt reversed the in vitro anti-migratory and anti-invasive activities of ISL in MDA-MB-231 cells. Notably, ISL inhibited the in vivo lung metastasis of MDA-MB-231 cells, together with decreased intratumoral levels of PGE2, 20-HETE and phospho-Akt (Thr(308)). In conclusion, ISL inhibits breast cancer metastasis by preventing anoikis resistance, migration and invasion via downregulating COX-2 and CYP 4A signaling. It suggests that ISL could be a promising multi-target agent for preventing breast cancer metastasis, and anoikis could represent a novel mechanism through which flavonoids may exert the anti-metastatic activities.

p50-associated COX-2 extragenic RNA (PACER) activates COX-2 gene expression by occluding repressive NF-κB complexes

Deregulated expression of COX-2 has been causally linked to development, progression, and outcome of several types of human cancer. We describe a novel fundamental level of transcriptional control of COX-2 expression. Using primary human mammary epithelial cells and monocyte/macrophage cell lines, we show that the chromatin boundary/insulator factor CTCF establishes an open chromatin domain and induces expression of a long non-coding RNA within the upstream promoter region of COX-2. Upon induction of COX-2 expression, the lncRNA associates with p50, a repressive subunit of NF-κB, and occludes it from the COX-2 promoter, potentially facilitating interaction with activation-competent NF-κB p65/p50 dimers. This enables recruitment of the p300 histone acetyltransferase, a domain-wide increase in histone acetylation and assembly of RNA Polymerase II initiation complexes. Our findings reveal an unexpected mechanism of gene control by lncRNA-mediated repressor occlusion and identify the COX-2-lncRNA, PACER, as a new potential target for COX-2-modulation in inflammation and cancer.

DOI:http://dx.doi.org/10.7554/eLife.01776.001

To produce a protein a cell must first transcribe the DNA in a gene to make a messenger RNA molecule, which is then translated to make the protein. However, cells also produce other types of RNA molecules which do not become proteins. MicroRNAs, for example, regulate the expression of genes as proteins, while the role of other RNA molecules called long non-coding RNAs (lncRNAs) is not well understood.

Now Krawczyk and Emerson have found an lncRNA that controls a gene called COX-2 that is often implicated in breast, colon, prostate, and lung cancer. This RNA molecule, which is called PACER, originates near the start of the COX-2 gene, but it cannot be messenger RNA because it does not contain the instructions to make the COX-2 protein, and it is too long to be a microRNA. Further experiments showed that the newly discovered lncRNA activates the expression of the COX-2 gene.

Krawczyk and Emerson found that PACER attracts enzymes that spotlight genes that need to be activated, thus increasing the transcription of these genes to make messenger RNA. Genes can also be switched on and off by various molecules binding to nearby DNA, and PACER encourages the activation of COX-2 by keeping away the molecules that might switch it off.

In addition to shedding new light on the role of lncRNAs, these results suggest that PACER could be a suitable therapeutic target in cancers that involve the COX-2 gene.

DOI:http://dx.doi.org/10.7554/eLife.01776.002

Photodynamic therapeutic role of indocyanine green in tumor-associated inflammation in skin cancer

BACKGROUND

Indocyanine green (ICG) is a promising water-soluble photosensitizer for photodynamic therapy (PDT) of tumors. It was reported to have promising phototoxic effect on different cell lines. This study aimed to evaluate the efficacy of ICG as an efficient PS agent for skin cancer induced in mice.

METHODS

Skin squamous cell carcinoma was induced in female CD-1 mice by 7,12-dimethylbenzanthracene and 12-O-tetradecanoyl-phorbol-13-acetate followed by an ICG/PDT treatment. The laser irradiation for PDT was adjusted to cover the whole body of the mice to make sure that the treatment protocol will be delivered to multiple tumors.

RESULTS

The treatment of skin cancer by ICG/PDT using intravenously injected ICG initiated tumor cell death and significantly decreased cell proliferation as indicated by the reduction in proliferating cell nuclear antigen positivity. A significant reduction in the inflammatory mediators; tumor necrosis factor-α, nitric oxide and 5-lipoxygenase was reported, however the level of cyclooxygenase-2 (COX-2) was significantly elevated after ICG/PDT treatment.

CONCLUSION

The proposed ICG/PDT treatment modality showed a significant anti-tumor and anti-inflammatory activity against skin cancer accompanied with COX-2 elevation.

Inactivation of lipoxygenase and cyclooxygenase by natural betalains and semi-synthetic analogues

Betalains are natural pigments characteristic of plants of the order Caryophyllales. In this work, the role of betalains in the anti-inflammatory activity described for plant extracts is analysed in terms of the inactivation of the enzymes involved in the biochemical response (lipoxygenase and cyclooxygenase). Pure natural betalains and semi-synthetic analogues are demonstrated to promote a significant reduction of the enzymes activity. Reactions were followed spectrophotometrically and by HPLC-DAD. Phenethylamine-betaxanthin was the most potent in the inactivation of cyclooxygenase, with a reduction of 32% of the control activity at 125μM, while the natural pigment betanidin and a betalain analogue derived from indoline resulted as the most potent inactivators of lipoxygenase, with IC50 values of 41.4 and 40.1μM, respectively. Molecular docking studies revealed that betalains interact with the lipoxygenase amino acids involved in substrate binding and with Tyr-385 and Ser-530 close to the cyclooxygenase active site, interfering in enzyme catalysis.

Eicosanoid profiling in an orthotopic model of lung cancer progression by mass spectrometry demonstrates selective production of leukotrienes by inflammatory cells of the microenvironment

Eicosanoids are bioactive lipid mediators derived from arachidonic acid¹ (AA), which is released by cytosolic phospholipase A₂ (cPLA₂). AA is metabolized through three major pathways, cyclooxygenase (COX), lipoxygenase (LO) and cytochrome P450, to produce a family of eicosanoids, which individually have been shown to have pro- or anti-tumorigenic activities in cancer. However, cancer progression likely depends on complex changes in multiple eicosanoids produced by cancer cells and by tumor microenvironment and a systematic examination of the spectrum of eicosanoids in cancer has not been performed. We used liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) to quantitate eicosanoids produced during lung tumor progression in an orthotopic immunocompetent mouse model of lung cancer, in which Lewis lung carcinoma (LLC) cells are injected into lungs of syngeneic mice. The presence of tumor increased products of both the cyclooxygenase and the lipoxygenase pathways in a time-dependent fashion. Comparing tumors grown in cPLA₂ knockout vs wild-type mice, we demonstrated that prostaglandins (PGE₂, PGD₂ and PGF_2a) were produced by both cancer cells and the tumor microenvironment (TME), but leukotriene (LTB₄, LTC₄, LTD₄, LTE₄) production required cPLA₂ expression in the TME. Using flow cytometry, we recovered tumor-associated neutrophils and 2 types of tumor-associated macrophages from tumor-bearing lungs and we defined their distinct eicosanoid profiles by LC/MS/MS. The combination of flow cytometry and LC/MS/MS unravels the complexity of eicosanoid production in lung cancer and provides a rationale to develop therapeutic strategies that target select cell populations to inhibit specific classes of eicosanoids.

The antiangiogenic activity of Kushecarpin D, a novel flavonoid isolated from Sophora flavescens Ait

AIMS

Kushecarpin D (KD) is a novel flavonoid isolated from the traditional Chinese herbal medicine Kushen (the dried root of Sophora flavescens Ait). As part of our continuous effort to explore Chinese traditional medicinal herbs and to identify novel natural anticancer products, the antiangiogenic properties of KD were examined in vitro using a human umbilical vein endothelial cell line (ECV304).

MAIN METHODS

The SRB and Trypan Blue exclusion assays were used to evaluate the effect of KD on cell proliferation. The antiangiogenic activities of KD were evaluated through studies of cell migration, cell adhesion, and tube formation. DCFH-DA and DHE fluorescent assays were used to detect the reactive oxygen species (ROS) levels. Catalase activity was detected using the colorimetric ammonium molybdate method. Cell cycle and apoptosis were measured using flow cytometry and the Hoechst 33258 staining assay.

KEY FINDINGS

The results indicated that KD showed antiangiogenic activity via inhibitory effects on cell proliferation, cell migration, cell adhesion, and tube formation. ROS levels were down-regulated and catalase activity was up-regulated after treatment with KD. The cell cycle was arrested at the G2/M phase, while no apoptosis was observed using the Hoechst 33258 staining assay or following the flow cytometric analysis of the sub-G1 proportion.

SIGNIFICANCE

The antiangiogenic properties of KD, in combination with its anti-proliferative effect and ability to induce cell cycle arrest without inducing apoptosis, make it a good candidate for development as antitumor agent. However, further studies are essential to elucidate its mechanism of action.

Activation of the leukotriene B4 receptor 2-reactive oxygen species (BLT2-ROS) cascade following detachment confers anoikis resistance in prostate cancer cells

The majority of prostate cancer-related deaths are associated with advanced and metastatic malignancies. Although anoikis resistance has been recognized as one of the hallmarks of metastatic prostate malignancies, the molecular events that cause anoikis resistance are poorly understood. In this study, we found that the detachment of PC-3 prostate cancer cells caused a time-dependent increase in the expression level of the leukotriene B4 receptor-2 (BLT2) and that BLT2 played a critical role in establishing anoikis resistance in these cells. Blocking BLT2 with the pharmacological inhibitor LY255283 or with RNAi knockdown clearly abolished anoikis resistance and resulted in severe apoptotic death. Additionally, we demonstrated that the activation of NADPH oxidase (NOX) and subsequent generation of reactive oxygen species (ROS) were downstream of BLT2 signaling and led to the activation of NF-κB, thus establishing anoikis resistance during cell detachment. Furthermore, we observed that the ectopic expression of BLT2 in normal prostate PWR-1E cells rendered the cells resistant to anoikis and apparently diminished apoptotic cell death following detachment. Taken together, our results suggest that BLT2-NOX-ROS-NF-κB cascade induction during detachment confers a novel mechanism of anoikis resistance in prostate cancer cells and potentially contributes to prostate cancer progression.