5-Lipoxygenase: Its involvement in gastrointestinal malignancies

Arachidonic acid metabolism as a novel pathogenic factor in gastrointestinal cancers

Gastrointestinal (GI) cancers are a major global health burden, representing 20% of all cancer diagnoses and 22.5% of global cancer-related deaths. Their aggressive nature and resistance to treatment pose a significant challenge, with late-stage survival rates below 15% at five years. Therefore, there is an urgent need to delve deeper into the mechanisms of gastrointestinal cancer progression and optimize treatment strategies. Increasing evidence highlights the active involvement of abnormal arachidonic acid (AA) metabolism in various cancers. AA is a fatty acid mainly metabolized into diverse bioactive compounds by three enzymes: cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes. Abnormal AA metabolism and altered levels of its metabolites may play a pivotal role in the development of GI cancers. However, the underlying mechanisms remain unclear. This review highlights a unique perspective by focusing on the abnormal metabolism of AA and its involvement in GI cancers. We summarize the latest advancements in understanding AA metabolism in GI cancers, outlining changes in AA levels and their potential role in liver, colorectal, pancreatic, esophageal, gastric, and gallbladder cancers. Moreover, we also explore the potential of targeting abnormal AA metabolism for future therapies, considering the current need to explore AA metabolism in GI cancers and outlining promising avenues for further research. Ultimately, such investigations aim to improve treatment options for patients with GI cancers and pave the way for better cancer management in this area.

Novel Multi-Target Agents Based on the Privileged Structure of 4-Hydroxy-2-quinolinone

In this work, the privileged scaffold of 4-hydroxy-2quinolinone is investigated through the synthesis of carboxamides and hybrid derivatives, as well as through their bioactivity evaluation, focusing on the ability of the molecules to inhibit the soybean LOX, as an indication of their anti-inflammatory activity. Twenty-one quinolinone carboxamides, seven novel hybrid compounds consisting of the quinolinone moiety and selected cinnamic or benzoic acid derivatives, as well as three reverse amides are synthesized and classified as multi-target agents according to their LOX inhibitory and antioxidant activity. Among all the synthesized analogues, quinolinone-carboxamide compounds 3h and 3s, which are introduced for the first time in the literature, exhibited the best LOX inhibitory activity (IC50 = 10 μM). Furthermore, carboxamide 3g and quinolinone hybrid with acetylated ferulic acid 11e emerged as multi-target agents, revealing combined antioxidant and LOX inhibitory activity (3g: IC50 = 27.5 μM for LOX inhibition, 100% inhibition of lipid peroxidation, 67.7% ability to scavenge hydroxyl radicals and 72.4% in the ABTS radical cation decolorization assay; 11e: IC50 = 52 μM for LOX inhibition and 97% inhibition of lipid peroxidation). The in silico docking results revealed that the synthetic carboxamide analogues 3h and 3s and NDGA (the reference compound) bind at the same alternative binding site in a similar binding mode.

Structure and ligand based design for identification of highly potent molecules against 5-LOX

We report here small molecules consisting of dichlorophenyl substituted oxindole that is further tagged with pyrrole/indole moieties. These molecules were designed on the basis of the analysis of binding mode of 5-LOX with arachidonic acid and zileuton. The molecules traverse the active site pocket of the enzyme that otherwise hosts AA and zileuton. Moreover, with a provision of derivatization at pyrrole/indole-N, the physico-chemical properties of the molecules can be adjusted. Appreciable 5-LOX inhibitory activities of the compounds in sub-micromolar range were observed and their aqueous solubility, binding with human serum albumin and stability in blood plasma and liver microsomes were checked. The Michaelis-Menten constants obtained during the binding of the compounds with 5-LOX indicated competitive binding of the compounds with the enzyme. Overall, the combination of molecular modelling and experimental studies identified promising molecules against inflammatory diseases.

The ALOX5 inhibitor Zileuton regulates tumor-associated macrophage M2 polarization by JAK/STAT and inhibits pancreatic cancer invasion and metastasis

5-lipoxygenase (encoded by ALOX5) plays an important role in immune regulation. Zileuton is currently the only approved ALOX5 inhibitor. However, the mechanisms of ALOX5 and Zileuton in progression of pancreatic cancer remain unclear. Therefore, we investigated the effects of Zileuton on tumor-associated macrophage M2 polarization and pancreatic cancer invasion and metastasis, both in vivo and in vitro. In bulk RNA sequencing (RNA-seq) and single-cell RNA sequencing (scRNA-seq) analyses, we found a significant association between elevated levels of ALOX5 and poor survival, adverse stages, M2 macrophage infiltration, and the activation of JAK/STAT pathways in macrophages. In clinical samples, immunofluorescence, quantitative real-time PCR and immunohistochemical results verified the high expression of ALOX5 in pancreatic cancer, primarily in macrophages. We constructed PANC-1 human pancreatic cancer cells and macrophages overexpressing ALOX5 using lentivirus. In PANC-1 pancreatic cancer cells, low-dose Zileuton inhibited PANC-1 cell invasion and migration by blocking ALOX5. In macrophages, ALOX5 induced the M2-like phenotype through the JAK/STAT pathway and promoted the chemotaxis of macrophages towards PANC-1 cells, while Zileuton can inhibit these effects. We constructed the nude mouse model of in situ transplantation tumor of pancreatic cancer. After treatment with Zileuton, the mice showed increased survival rates and reduced liver metastasis. These findings indicate that ALOX5 regulates tumor-associated macrophage M2 polarization via the JAK/STAT pathway and promotes invasion and metastasis in pancreatic cancer. Zileuton can inhibit these effects by inhibiting ALOX5. These results provide a theoretical basis for the potential use of Zileuton in the treatment of pancreatic cancer.

Membrane Lipid Derivatives: Roles of Arachidonic Acid and Its Metabolites in Pancreatic Physiology and Pathophysiology

One of the most important constituents of the cell membrane is arachidonic acid. Lipids forming part of the cellular membrane can be metabolized in a variety of cellular types of the body by a family of enzymes termed phospholipases: phospholipase A2, phospholipase C and phospholipase D. Phospholipase A2 is considered the most important enzyme type for the release of arachidonic acid. The latter is subsequently subjected to metabolization via different enzymes. Three enzymatic pathways, involving the enzymes cyclooxygenase, lipoxygenase and cytochrome P450, transform the lipid derivative into several bioactive compounds. Arachidonic acid itself plays a role as an intracellular signaling molecule. Additionally, its derivatives play critical roles in cell physiology and, moreover, are involved in the development of disease. Its metabolites comprise, predominantly, prostaglandins, thromboxanes, leukotrienes and hydroxyeicosatetraenoic acids. Their involvement in cellular responses leading to inflammation and/or cancer development is subject to intense study. This manuscript reviews the findings on the involvement of the membrane lipid derivative arachidonic acid and its metabolites in the development of pancreatitis, diabetes and/or pancreatic cancer.

The activities and mechanisms of intestinal microbiota metabolites of TCM herbal ingredients could be illustrated by a strategy integrating spectrum-effects, network pharmacology, metabolomics and molecular docking analysis: Platycodin D as an example

BACKGROUND

The intestinal microbiota plays a key role in understanding the mechanism of traditional Chinese medicine (TCM), as it could transform the herbal ingredients to metabolites with higher bioavailability and activity comparing to their prototypes. Nevertheless, the study of the activity and mechanism of microbiota metabolites reported by the published literature still lacks viable ways. Hence a new strategy is proposed to solve this issue.

PURPOSE

A new strategy to study the activity and mechanism of intestinal microbiota metabolites of TCM herbal ingredients by integrating spectrum-effect relationship, network pharmacology, metabolomics analysis and molecular docking together was developed and proposed.

METHOD

Platycodin D (PD) and its microbiota metabolites with antitussive and expectorant effect were selected as an example for demonstration. First, the PD and its microbiota metabolites with important contribution to antitussive and/or expectorant effects were screened through spectrum-effect relationship analysis. Second, network pharmacology and metabolomics analysis were integrated to identify the upstream key targets of PD and its microbiota metabolites as well as the downstream endogenous metabolites. Finally, the active forms of PD were further confirmed by molecular docking.

RESULTS

Results showed that PD was an active ingredient with antitussive and/or expectorant effects, and the active forms of PD were its microbiota metabolites: 3-O-β-d-glucopyranosyl platycodigenin, 3-O-β-d-glucopyranosyl isoplatycodigenin, 7‑hydroxyl-3-O-β-d-glucopyranosyl platycodigenin, platycodigenin and isoplatycodigenin. In addition, those microbiota metabolites could bind the key targets of PAH, PLA2G2A, ALOX5, CYP2C9 and CYP2D6 to exert antitussive effects by regulating four metabolic pathways of phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism, glycerophospholipid metabolism and linoleic acid metabolism. Similarly, they could also bind the key targets of PLA2G1B, ALOX5, CYP2C9 and CYP2D6 to exert expectorant effect by regulating two pathways of glycerophospholipid metabolism and linoleic acid metabolism.

CONCLUSION

The proposed strategy paves a new way for the illustration of the activities and mechanisms of TCM herbal ingredients, which is very important to reconcile the conundrums of TCM herbal ingredients with low oral bioavailability but high activity.

Arachidonate lipoxygenases 5 is a novel prognostic biomarker and correlates with high tumor immune infiltration in low-grade glioma

Objective: To investigate the prognostic value of arachidonate lipoxygenases 5 (ALOX5) expression and methylation, and explore the immune functions of arachidonate lipoxygenases 5 expression in low-grade glioma (LGG). Materials and Methods: Using efficient bioinformatics approaches, the differential expression of arachidonate lipoxygenases 5 and the association of its expression with clinicopathological characteristics were evaluated. Then, we analyzed the prognostic significance of arachidonate lipoxygenases 5 expression and its methylation level followed by immune cell infiltration analysis. The functional enrichment analysis was conducted to determine the possible regulatory pathways of arachidonate lipoxygenases 5 in low-grade glioma. Finally, the drug sensitivity analysis was performed to explore the correlation between arachidonate lipoxygenases 5 expression and chemotherapeutic drugs. Results: arachidonate lipoxygenases 5 mRNA expression was increased in low-grade glioma and its expression had a notable relation with age and subtype (p < 0.05). The elevated mRNA level of arachidonate lipoxygenases 5 could independently predict the disease-specific survival (DSS), overall survival (OS), and progression-free interval (PFI) (p < 0.05). Besides, arachidonate lipoxygenases 5 expression was negatively correlated with its methylation level and the arachidonate lipoxygenases 5 hypomethylation led to a worse prognosis (p < 0.05). The arachidonate lipoxygenases 5 expression also showed a positive connection with immune cells, while low-grade glioma patients with higher immune cell infiltration had poor survival probability (p < 0.05). Further, arachidonate lipoxygenases 5 might be involved in immune- and inflammation-related pathways. Importantly, arachidonate lipoxygenases 5 expression was negatively related to drug sensitivity. Conclusion: arachidonate lipoxygenases 5 might be a promising biomarker, and it probably occupies a vital role in immune cell infiltration in low-grade glioma.

BML-111, the agonist of lipoxin A4, suppresses epithelial-mesenchymal transition and migration of MCF-7 cells via regulating the lipoxygenase pathway

Introduction: Aberrant epithelial-mesenchymal transition (EMT) and migration frequently occur during tumour progression. BML-111, an analogue of lipoxin A4, has been implicated in inflammation in cancer research. Methods: 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, western blot, Reverse Transcription Polymerase Chain Reaction (RT-PCR), transwell assay, immunofluorescence, and immunohistochemistry were conducted in this study. Results: In vitro experiments revealed that BML-111 inhibited EMT and migration in CoCl2-stimulated MCF-7 cells. These effects were achieved by inhibiting MMP-2 and MMP-9, which are downregulated by 5-lipoxygenase (5-LOX). Moreover, BML-111 inhibited EMT and migration of breast cancer cells in BALB/c nude mice inoculated with MCF-7 cells. Conclusion: Our results suggest that BML-111 may be a potential therapeutic drug for breast cancer and that blocking the 5-LOX pathway could be a possible approach for mining effective drug targets.

Chemical Composition and Antioxidant, Antimicrobial, and Anti-Inflammatory Properties of Origanum compactum Benth Essential Oils from Two Regions: In Vitro and In Vivo Evidence and In Silico Molecular Investigations

The purposes of this investigatory study were to determine the chemical composition of the essential oils (EOs) of Origanum compactum from two Moroccan regions (Boulemane and Taounate), as well as the evaluation of their biological effects. Determining EOs' chemical composition was performed by a gas chromatography-mass spectrophotometer (GC-MS). The antioxidant activity of EOs was evaluated using free radical scavenging ability (DPPH method), fluorescence recovery after photobleaching (FRAP), and lipid peroxidation inhibition assays. The anti-inflammatory effect was assessed in vitro using the 5-lipoxygenase (5-LOX) inhibition test and in vivo using the carrageenan-induced paw edema model. Finally, the antibacterial effect was evaluated against several strains using the disk-diffusion assay and the micro-dilution method. The chemical constituent of O. compactum EO (OCEO) from the Boulemane zone is dominated by carvacrol (45.80%), thymol (18.86%), and α-pinene (13.43%). However, OCEO from the Taounate zone is rich in 3-carene (19.56%), thymol (12.98%), and o-cymene (11.16%). OCEO from Taounate showed higher antioxidant activity than EO from Boulemane. Nevertheless, EO from Boulemane considerably inhibited 5-LOX (IC50 = 0.68 ± 0.02 µg/mL) compared to EO from Taounate (IC50 = 1.33 ± 0.01 µg/mL). A similar result was obtained for tyrosinase inhibition with Boulemane EO and Taounate EO, which gave IC50s of 27.51 ± 0.03 μg/mL and 41.83 ± 0.01 μg/mL, respectively. The in vivo anti-inflammatory test showed promising effects; both EOs inhibit and reduce inflammation in mice. For antibacterial activity, both EOs were found to be significantly active against all strains tested in the disk-diffusion test, but O. compactum EO from the Boulemane region showed the highest activity. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) for O. compactum EO from the Boulemane region ranged from 0.06 to 0.25% (v/v) and from 0.15 to 0.21% (v/v) for O. compactum from the Taounate region. The MBC/MIC index revealed that both EOs exhibited remarkable bactericidal effects.

A novel melanoma prognostic model based on the ferroptosis-related long non-coding RNA

Ferroptosis is an iron-dependent programmed cell death related to the biological process of many kinds of tumors. Long noncoding RNAs (LncRNA) have been found to play essential roles in the tumor, and their functions in the ferroptosis of tumor cells have been partially discovered. However, there is no summary of ferroptosis-related LncRNA and its functions in melanoma. In the present study, we aim to explore the expression profile of ferroptosis-related LncRNA genes and their value in melanoma prognosis by bioinformatics analysis. The expression of ferroptosis-related gene (FRG) from melanoma clinical data was extracted based on the Cancer Genome Atlas (TCGA) database. By screening the RNA expression data of 472 cases of melanoma and 810 cases of normal skin, eighteen ferroptosis-related differential genes were found to be related to the overall survival rate. Furthermore, 384 ferroptosis-related LncRNAs were discovered through constructing the mRNA-LncRNA co-expression network, and ten of them were found with prognostic significance in melanoma by multivariate Cox analysis. Risk assessment showed that the high expression of LncRNA00520 is associated with poor prognosis, while the increased expression of the other LncRNA is beneficial to the prognosis of patients with melanoma. From univariate and multivariate Cox regression analysis, there were ten ferroptosis-related LncRNA risk models towards to be significant independent prognostic factors for patients with melanoma and valuable predictive factors for overall survival (OS)(P<0.05). The ROC curve further suggested that the risk score has relatively reliable predictive ability (AUC=0.718). The protein level of ferroptosis-related genes was verified by the HPA database and IHC test, leading to the discovery that the expressions of ALOX5, PEBP1, ACSL4, and ZEB1 proteins up-regulated in tumor tissues, and existed differences between tumor tissues and normal tissues. In conclusion, we identified ten ferroptosis-related LncRNA and constructed a prognosis model base.

Development and validation of a novel 3-gene prognostic model for pancreatic adenocarcinoma based on ferroptosis-related genes

Background

Molecular markers play an important role in predicting clinical outcomes in pancreatic adenocarcinoma (PAAD) patients. Analysis of the ferroptosis-related genes may provide novel potential targets for the prognosis and treatment of PAAD.

Methods

RNA-sequence and clinical data of PAAD was downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) public databases. The PAAD samples were clustered by a non-negative matrix factorization (NMF) algorithm. The differentially expressed genes (DEGs) between different subtypes were used by “limma_3.42.2” package. The R software package clusterProfiler was used for functional enrichment analysis. Then, a multivariate Cox proportional and LASSO regression were used to develop a ferroptosis-related gene signature for pancreatic adenocarcinoma. A nomogram and corrected curves were constructed. Finally, the expression and function of these signature genes were explored by qRT-PCR, immunohistochemistry (IHC) and proliferation, migration and invasion assays.

Results

The 173 samples were divided into 3 categories (C1, C2, and C3) and a 3-gene signature model (ALOX5, ALOX12, and CISD1) was constructed. The prognostic model showed good independent prognostic ability in PAAD. In the GSE62452 external validation set, the molecular model also showed good risk prediction. KM-curve analysis showed that there were significant differences between the high and low-risk groups, samples with a high-risk score had a worse prognosis. The predictive efficiency of the 3-gene signature-based nomogram was significantly better than that of traditional clinical features. For comparison with other models, that our model, with a reasonable number of genes, yields a more effective result. The results obtained with qPCR and IHC assays showed that ALOX5 was highly expressed, whether ALOX12 and CISD1 were expressed at low levels in tissue samples. Finally, function assays results suggested that ALOX5 may be an oncogene and ALOX12 and CISD1 may be tumor suppressor genes.

Conclusions

We present a novel prognostic molecular model for PAAD based on ferroptosis-related genes, which serves as a potentially effective tool for prognostic differentiation in pancreatic cancer patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02431-8.

Zileuton inhibits arachidonate-5-lipoxygenase to exert antitumor effects in preclinical cervical cancer models

BACKGROUND

Inhibitors of arachidonate lipoxygenase 5 (ALOX5) exhibit anticancer activity. Zileuton is an FDA-approved drug for treating asthma and an ALOX5 inhibitor. This study evaluated the efficacy of zileuton in cervical cancer, determined the molecular mechanism of action, and assessed ALOX5 expression in cervical cancer patients.

METHODS

The effects of zileuton were evaluated using cervical cancer cell lines and xenograft mouse models. Loss-of-function analysis of ALOX5 was performed using siRNA. The levels of ALOX5 and 5-HETE were determined using immunohistochemistry and ELISA.

RESULTS

Zileuton resulted in cell proliferation inhibition and apoptosis induction in a dose-dependent manner, regardless of cellular origin or HPV infection. In two independent cervical cancer xenograft mouse models, zileuton at nontoxic doses significantly prevented tumor formation and decreased tumor growth. Zileuton acts on cervical cancer cells by inhibiting the ALOX5-5-HETE axis. Of note, ALOX5-5-HETE was significantly upregulated in cervical cancer compared with normal tissue. Inhibition of ALOX5 via the siRNA approach mimics the inhibitory effects of zileuton and confirms the roles of ALOX5 in cervical cancer.

CONCLUSIONS

Our work demonstrates that the ALOX5-5-HETE axis is activated in cervical cancer, with important roles in growth and survival, and this can be therapeutically targeted by zileuton. Our findings also provide preclinical evidence to assess the efficacy of zileuton in cervical cancer in clinical settings.

Fatty acids and evolving roles of their proteins in neurological, cardiovascular disorders and cancers

The dysregulation of fat metabolism is involved in various disorders, including neurodegenerative, cardiovascular, and cancers. The uptake of long-chain fatty acids (LCFAs) with 14 or more carbons plays a pivotal role in cellular metabolic homeostasis. Therefore, the uptake and metabolism of LCFAs must constantly be in tune with the cellular, metabolic, and structural requirements of cells. Many metabolic diseases are thought to be driven by the abnormal flow of fatty acids either from the dietary origin and/or released from adipose stores. Cellular uptake and intracellular trafficking of fatty acids are facilitated ubiquitously with unique combinations of fatty acid transport proteins and cytoplasmic fatty acid-binding proteins in every tissue. Extensive data are emerging on the defective transporters and metabolism of LCFAs and their clinical implications. Uptake and metabolism of LCFAs are crucial for the brain's functional development and cardiovascular health and maintenance. In addition, data suggest fatty acid metabolic transporter can normalize activated inflammatory response by reprogramming lipid metabolism in cancers. Here we review the current understanding of how LCFAs and their proteins contribute to the pathophysiology of three crucial diseases and the mechanisms involved in the processes.

ALOX5-5-HETE promotes gastric cancer growth and alleviates chemotherapy toxicity via MEK/ERK activation

Background

Recent studies highlight the regulatory role of arachidonate lipoxygenase5 (Alox5) and its metabolite 5‐hydroxyeicosatetraenoic acid (5‐HETE) in cancer tumorigenesis and progression. In this study, we analyzed the expression, biological function and the downstream signaling of Alox5 in gastric cancer.

Methods

Alox5 protein levels were measured using IHC and ELISA. Growth, migration and survival assays were performed. Phosphorylation of molecules involved in growth and survival signaling were analyzed by WB. Analysis of variance and t‐test were used for statistic analysis.

Results

Alox5 and 5‐HETE levels were upregulated in gastric cancer patients. ALOX5 overexpression or 5‐HETE addition activates gastric cancer cells and reduces chemotherapy’s efficacy. In contrast, ALOX5 inhibition via genetic and pharmacological approaches suppresses gastric cancer cells and enhances chemotherapy’s efficacy. In addition, Alox5 inhibition led to suppression of ERK‐mediated signaling pathways whereas ALOX5‐5‐HETE activates ERK‐mediated signaling in gastric cancer cells.

Conclusions

Our work demonstrates the critical role of ALOX5‐5‐HETE in gastric cancer and provides pre‐clinical evidence to initialize clinical trial using zileuton in combination with chemotherapy for treating gastric cancer.

Novel quinolinone-pyrazoline hybrids: synthesis and evaluation of antioxidant and lipoxygenase inhibitory activity

The present project deals with the investigation of structure-activity relationship of several quinolinone-chalcone and quinolinone-pyrazoline hybrids, in an effort to discover promising antioxidant and anti-inflammatory agents. In order to accomplish this goal, four bioactive hybrid quinolinone-chalcone compounds (8a-8d) were synthesized via an aldol condensation reaction, which were then chemically modified, forming fifteen new pyrazoline analogues (9a-9o). All the synthesized analogues were in vitro evaluated in terms of their antioxidant and soybean lipoxygenase (LOX) inhibitory activity. Among all the pyrazoline derivatives, compounds 9b and 9m were found to possess the best combined activity, whereas 9b analogue exhibited the most potent LOX inhibitory activity, with IC50 value 10 μM. The in silico docking results revealed that the synthetic pyrazoline analogue 9b showed high AutoDock Vina score (- 10.3 kcal/mol), while all the tested derivatives presented allosteric interactions with the enzyme.

Screening and isolation of potential lipoxidase and superoxide dismutase inhibitors from Scutellaria baicalensis Georgi using high-speed countercurrent chromatography target-guided by ultrafiltration-liquid chromatography-mass spectrometry

We present a simple and efficient method based on ultrafiltration high-performance liquid chromatography coupled with a photodiode array detector and electrospray ionization mass spectrometry for the rapid screening and identification of ligands obtainable from the extract of Scutellaria baicalensis. Five major compounds (chrysin-6-C-arabinosyl-8-C-glucoside, chrysin-6-C-glucosyl-8-C-arabinoside, baicalin, oroxylin A-7-O-glucuronide, and wogonoside) were identified as potentially effective inhibitors of lipoxidase and superoxide dismutase. Subsequently, specific binding ligands were separated by high-speed countercurrent chromatography, using ethyl acetate/ethyl alcohol/water acetate (0.1%) (1.0:0.1:1.0, v/v/v) as the solvent system. To the best of our knowledge, this is the first report of S. baicalensis extracts containing potent lipoxidase and superoxide dismutase inhibitors. Our results demonstrate that the systematic isolation of bioactive components from the n-butyl alcohol layer of S. baicalensis guided by ultrafiltration high-performance liquid chromatography coupled with photodiode array detection and electrospray ionization mass spectrometry represents a feasible and efficient technique that could also be employed for the identification and isolation of other enzyme inhibitors.

Targeting of the Alox12-12-HETE in Blast Crisis Chronic Myeloid Leukemia Inhibits Leukemia Stem/Progenitor Cell Function

Introduction

Chronic myeloid leukemia (CML) is a myeloid malignancy characterized by the oncogene BCR-ABL. CML responds well to therapy targeting BCR-ABL in the chronic phase but is resistant to treatment when it progresses to the blast phase (BP). This study attempted to address whether arachidonate 12-lipoxygenase (Alox12) confers to CML drug resistance.

Materials and Methods

We analyzed the expression of Alox12 using Western blotting, ELISA, and RT-PCR methods. Loss of functional analysis was performed using cellular activity assays on CML and normal hematopoietic stem/progenitor cells (HSPCs).

Results

Alox12 and 12-Hydroxyeicosatetraenoic acid (12-HETE) are overexpressed in BP-CML but not HSPCs, and that Alox12-12-HETE axis is regulated by BCR-ABL. The Alox12-12-HETE axis is required for CML. Specific Alox12 inhibitor inhibits colony formation, survival, and self-renewal capacity in BP-CML HSPCs, and to a significantly greater extent than in normal HSPCs. Of note, the Alox12 inhibitor significantly augments dasatinib’s efficacy in BP-CML HSPCs. Mechanism studies show that Alox12 inhibition does not affect activities of essential signaling pathways involved in maintaining stem cell function, such as Wnt, p53, and bone morphogenetic protein (BMP). In contrast, we show that Alox12 inhibition disrupts nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis and induces oxidative stress and damage in CML HSPCs and committed cells.

Conclusion

Alox12-12-HETE axis is a specific and critical regulator of BP-CML HSPCs functions. Pharmacological inhibition of Alox12 may be useful in BP-CML.

Eicosanoids in Cancer: New Roles in Immunoregulation

Eicosanoids represent a family of active biolipids derived from arachidonic acid primarily through the action of cytosolic phospholipase A2-α. Three major downstream pathways have been defined: the cyclooxygenase (COX) pathway which produces prostaglandins and thromboxanes; the 5-lipoxygenase pathway (5-LO), which produces leukotrienes, lipoxins and hydroxyeicosatetraenoic acids, and the cytochrome P450 pathway which produces epoxygenated fatty acids. In general, these lipid mediators are released and act in an autocrine or paracrine fashion through binding to cell surface receptors. The pattern of eicosanoid production is cell specific, and is determined by cell-specific expression of downstream synthases. Increased eicosanoid production is associated with inflammation and a panel of specific inhibitors have been developed designated non-steroidal anti-inflammatory drugs. In cancer, eicosanoids are produced both by tumor cells as well as cells of the tumor microenvironment. Earlier studies demonstrated that prostaglandin E2, produced through the action of COX-2, promoted cancer cell proliferation and metastasis in multiple cancers. This resulted in the development of COX-2 inhibitors as potential therapeutic agents. However, cardiac toxicities associated with these agents limited their use as therapeutic agents. The advent of immunotherapy, especially the use of immune checkpoint inhibitors has revolutionized cancer treatment in multiple malignancies. However, the majority of patients do not respond to these agents as monotherapy, leading to intense investigation of other pathways mediating immunosuppression in order to develop rational combination therapies. Recent data have indicated that PGE2 has immunosuppressive activity, leading to renewed interest in targeting this pathway. However, little is known regarding the role of other eicosanoids in modulating the tumor microenvironment, and regulating anti-tumor immunity. This article reviews the role of eicosanoids in cancer, with a focus on their role in modulating the tumor microenvironment. While the role of PGE2 will be discussed, data implicating other eicosanoids, especially products produced through the lipoxygenase and cytochrome P450 pathway will be examined. The existence of small molecular inhibitors and activators of eicosanoid pathways such as specific receptor blockers make them attractive candidates for therapeutic trials, especially in combination with novel immunotherapies such as immune checkpoint inhibitors.

Fabrication of curcumin-zein-ethyl cellulose composite nanoparticles using antisolvent co-precipitation method

The stable colloidal nano-dispersion of curcumin (CU) loaded zein-ethyl cellulose (ZN-EC) as three hydrophobic agent in water was prepared using two step antisolvent co-precipitation method. The EC coated NPs were prepared by adding EC in ethyl acetate to the ZN-CU NPs at a concentration ratio of 1: 3.5 w/v. The prepared colloidal suspension of ZN-EC showed high physical stability during storage time. The particle diameters and zeta potential values of ZN-CU and ZN-CU-EC colloidal suspensions were 140 ± 12 nm, 38 ± 2 mV and 179 ± 12 nm, 12 ± 2 mV, respectively. Based on Scanning electron microscopy (SEM) images, participation of EC on the surface of ZN-CU particles could reduce the sticky appearance of particles. Encapsulation efficiency of CU in NPs did not improve after precipitation of EC, but the stability of NPs against pH changes, increased and release rate of CU from NPs at different pH values (3-8) were significantly reduced in comparison of ZN-CU NPs. The EC coated NPs showed the excessive protection for CU antioxidant activity during storage. In conclusion, the prepared NPs, with high physical stability, have good potential for encapsulation and delivery of CU to colon region.

Aberrant ALOX5 Activation Correlates with HER2 Status and Mediates Breast Cancer Biological Activities through Multiple Mechanisms

Arachidonate lipoxygenases (ALOX) have been implicated in playing a critical role in tumorigenesis, development, and metastasis. We previously reported that ALOX12 is involved in breast cancer chemoresistance. In this study, we demonstrate that the ALOX5 activation correlates with the HER2 expression and mediates breast cancer growth and migration. We found that the ALOX5 expression and activity were upregulated in breast cancer patients, particularly in those tissues with HER2-positive. ALOX5 upregulation was also observed in HER2-positive breast cancer cells. In contrast, HER2 inhibition led to decreased expression and activity of ALOX5 but not ALOX5AP, suggesting that HER2 specifically regulates the ALOX5 expression and activity in breast cancer cells. We further demonstrated that ALOX5 is important for breast cancer biological activities with the predominant roles in growth and migration, likely through RhoA, focal adhesion, and PI3K/Akt/mTOR signaling but not epithelial mesenchymal transition (EMT). Our work is the first to report a correlation between the ALOX5 activity and HER2 overexpression in breast cancer. Our findings also highlight the therapeutic value of inhibiting ALOX5 in breast cancer, particularly those patients with the HER2 overexpression.

Diversity of Chromanol and Chromenol Structures and Functions: An Emerging Class of Anti-Inflammatory and Anti-Carcinogenic Agents

Natural chromanols and chromenols comprise a family of molecules with enormous structural diversity and biological activities of pharmacological interest. A recently published systematic review described more than 230 structures that are derived from a chromanol ortpd chromenol core. For many of these compounds structure-activity relationships have been described with mostly anti-inflammatory as well as anti-carcinogenic activities. To extend the knowledge on the biological activity and the therapeutic potential of these promising class of natural compounds, we here present a report on selected chromanols and chromenols based on the availability of data on signaling pathways involved in inflammation, apoptosis, cell proliferation, and carcinogenesis. The chromanol and chromenol derivatives seem to bind or to interfere with several molecular targets and pathways, including 5-lipoxygenase, nuclear receptors, and the nuclear-factor "kappa-light-chain-enhancer" of activated B-cells (NFκB) pathway. Interestingly, available data suggest that the chromanols and chromenols are promiscuitively acting molecules that inhibit enzyme activities, bind to cellular receptors, and modulate mitochondrial function as well as gene expression. It is also noteworthy that the molecular modes of actions by which the chromanols and chromenols exert their effects strongly depend on the concentrations of the compounds. Thereby, low- and high-affinity molecular targets can be classified. This review summarizes the available knowledge on the biological activity of selected chromanols and chromenols which may represent interesting lead structures for the development of therapeutic anti-inflammatory and chemopreventive approaches.

α-Conotoxins Enhance both the In Vivo Suppression of Ehrlich carcinoma Growth and In Vitro Reduction in Cell Viability Elicited by Cyclooxygenase and Lipoxygenase Inhibitors

Several biochemical mechanisms, including the arachidonic acid cascade and activation of nicotinic acetylcholine receptors (nAChRs), are involved in increased tumor survival. Combined application of inhibitors acting on these two pathways may result in a more pronounced antitumor effect. Here, we show that baicalein (selective 12-lipoxygenase inhibitor), nordihydroguaiaretic acid (non-selective lipoxygenase inhibitor), and indomethacin (non-selective cyclooxygenase inhibitor) are cytotoxic to Ehrlich carcinoma cells in vitro. Marine snail α-conotoxins PnIA, RgIA and ArIB11L16D, blockers of α3β2/α6β2, α9α10 and α7 nAChR subtypes, respectively, as well as α-cobratoxin, a blocker of α7 and muscle subtype nAChRs, exhibit low cytotoxicity, but enhance the antitumor effect of baicalein 1.4-fold after 24 h and that of nordihydroguaiaretic acid 1.8-3.9-fold after 48 h of cell cultivation. α-Conotoxin MII, a blocker of α6-containing and α3β2 nAChR subtypes, increases the cytotoxic effect of indomethacin 1.9-fold after 48 h of cultivation. In vivo, baicalein, α-conotoxins MII and PnIA inhibit Ehrlich carcinoma growth and increase mouse survival; these effects are greatly enhanced by the combined application of α-conotoxin MII with indomethacin or conotoxin PnIA with baicalein. Thus, we show, for the first time, antitumor synergism of α-conotoxins and arachidonic acid cascade inhibitors.

Inhibition of arachidonate lipoxygenase12 targets lung cancer through inhibiting EMT and suppressing RhoA and NF-κB activity

The carcinogenic function of arachidonate lipoxygenase12 (Alox12) has been reported in various cancers. However, little is known on the role of Alox12 in lung cancer. Here, we demonstrate that Alox12 is upregulated and contributes to biological activities of lung cancer through multiple mechanisms. We found that Alox12 mRNA and protein levels were increased by 2.5-fold in a panel of lung cancer cell lines compared to normal lung cells. The expression of Alox12 varied among lung cancer cell lines. The immunohistochemistry analysis on paired normal and tumor lung tissues from twenty patients showed that Alox12 protein level is higher in lung cancer than normal lung tissues from the majority of patients. We further observed the upregulation of Alox12-12-HETE signaling axis in lung cancer tissues. Overexpression of Alox12 promoted growth and migration in normal lung cells and lung cancer cells. In contrast, Alox12 inhibition via genetic and pharmacological approaches suppressed growth and migration, induced apoptosis, and sensitized lung cancer cells to chemotherapy. This is through suppressing RhoA signaling, inhibiting epithelial-to-mesenchymal transition (EMT) and NF-κB activity. Our work reveals the therapeutic value of inhibiting Alox12 in overcoming chemoresistance in lung cancer.

ALOX12 inhibition sensitizes breast cancer to chemotherapy via AMPK activation and inhibition of lipid synthesis

Arachidonate lipoxygenase12 (Alox12) and its metabolites 12S-hydroxyeicosatetraenoic acid (12S-HETE) have been implicated in influencing tumor transformation and progression. In this study, we have systematically evaluated the expression, function and the downstream effectors of Alox12 in breast cancer using loss- and gain-of-function approaches. We demonstrated that both mRNA and protein levels of Alox12 were significantly increased in multiple breast cancer cell lines compared to normal breast cells. The upregulation of Alox12 expression was also observed in breast cancer tissues and their matched normal breast tissues obtained from patients. Functionally, we demonstrated that Alox12 overexpression was sufficient to stimulate growth in normal breast cells but not breast cancer cells. This also protects breast cancer cell from chemotherapy-induced growth arrest and apoptosis. In contrast, Alox12 depletion inhibited breast cancer growth and survival, and significantly enhanced the chemotherapeutic agents' efficacy. Mechanism studies showed that Alox12 depletion activated AMP-activated protein kinase (AMPK), leading to the inhibition of acetyl-CoA carboxylase1 (ACC1) enzyme activity and lipid synthesis. The recuse of the effects of Alox12 depletion using Alox12 metabolites 12S-HETE further confirmed that AMPK and its subsequent inhibition of ACC1 activity and lipid synthesis were the downstream signaling of Alox12 inhibition. Our findings highlighted the important role of Alox12 in breast cancer, particularly in response to chemotherapy. Our work also demonstrate that inhibiting Alox12 is a possible alternative therapeutic strategy to overcome chemoresistance in breast cancer.