Cysteinyl leukotriene receptor expression pattern affects migration of breast cancer cells and survival of breast cancer patients

The role of signaling pathways mediated by the GPCRs CysLTR1/2 in melanocyte proliferation and senescence

In contrast with sun exposure-induced melanoma, rarer melanocytic tumors and neoplasms with low mutational burden present opportunities to study isolated signaling mechanisms. These include uveal melanoma and blue nevi, which are often driven by mutations within the G protein-coupled signaling cascade downstream of cysteinyl leukotriene receptor 2. Here, we review how the same mutations within this pathway drive the growth of melanocytes in one tissue but can inhibit the growth of those in another, exemplifying the role of the tissue environment in the delicate balance between uncontrolled cell growth and senescence.

Potential of Anti-Leukotriene Drugs as New Therapeutic Agents for Inhibiting Cholangiocarcinoma Progression

Cholangiocarcinoma (CCA) is a cancer with a poor prognosis due to difficulties in diagnosis and limited treatment options, highlighting the urgent need for new targeted therapies. In a clinical setting, we found that leukotriene levels in bile were higher than in serum. Immunohistochemical analysis of surgically resected samples also revealed that CysLT receptor 1 (CysLTR1) was more highly expressed in CCA than in normal bile duct tissue, prompting us to investigate leukotriene as a potential therapeutic target in CCA. In vitro studies using CCA cell lines expressing CysLTR1 showed that leukotriene D4, a major ligand of CysLTR1, promoted cell proliferation, with increased phosphorylation of AKT and extracellular signal-regulated kinase 1/2 (ERK1/2). Additionally, treatment with two clinically available anti-allergic drugs-zileuton, an inhibitor of CysLT formation, and montelukast, a CysLTR1 inhibitor-had inhibitory effects on cell proliferation and migratory capacity, accompanied by the reduced phosphorylation of AKT and ERK1/2. Furthermore, the simultaneous administration of both drugs synergistically enhanced the inhibitory effect on cell proliferation. Our study suggests that use of these drugs may represent a novel approach to treat CCA through drug repositioning.

Chemoprevention of esophageal adenocarcinoma in a rat surgical model by a cysteinyl leukotriene receptor‑1 antagonist

Reflux of gastroduodenal contents into the esophagus leads to the development of esophagitis and inflammation-associated pathologies, such as Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). The role of the lipoxygenase (LOX) pathway in carcinogenesis has been recently reported; however, its involvement in esophageal carcinogenesis remains unclear. To address this, the present study investigated the potential of pranlukast, a cysteinyl leukotriene receptor-1 antagonist, to suppress the progression of BE and EAC in a rat duodenogastroesophageal reflux (DGER) model. Male Wistar rats that underwent DGER were divided into two groups. One group was fed commercial chow (control group), and the other was fed experimental chow containing pranlukast (pranlukast group). The rats were sacrificed at 10, 20, 30 and 40 weeks after surgery, and their esophagi were examined. Expression levels of 5-LOX, CD68, IL-8, VEGF and Ki-67 were investigated using immunohistochemistry, and apoptosis was analyzed using the TUNEL method. In the pranlukast group, esophagitis was milder, and the incidence of BE and EAC was significantly lower (P<0.05) compared with that in the control group at 40 weeks after surgery. The number of cells positive for IL-8 and VEGF were significantly lower in the pranlukast group compared with the control group. Proliferative activity was also lower in the pranlukast group compared with the control group (P<0.05). Pranlukast treatment increased apoptosis (P<0.05). Overall, Pranlukast suppressed esophageal carcinogenesis in a rat DGER model, decreasing inflammatory cytokines such as IL-8 and VEGF.

1,4-dihydroxy quininib activates ferroptosis pathways in metastatic uveal melanoma and reveals a novel prognostic biomarker signature

Uveal melanoma (UM) is an ocular cancer, with propensity for lethal liver metastases. When metastatic UM (MUM) occurs, as few as 8% of patients survive beyond two years. Efficacious treatments for MUM are urgently needed. 1,4-dihydroxy quininib, a cysteinyl leukotriene receptor 1 (CysLT1) antagonist, alters UM cancer hallmarks in vitro, ex vivo and in vivo. Here, we investigated the 1,4-dihydroxy quininib mechanism of action and its translational potential in MUM. Proteomic profiling of OMM2.5 cells identified proteins differentially expressed after 1,4-dihydroxy quininib treatment. Glutathione peroxidase 4 (GPX4), glutamate-cysteine ligase modifier subunit (GCLM), heme oxygenase 1 (HO-1) and 4 hydroxynonenal (4-HNE) expression were assessed by immunoblots. Biliverdin, glutathione and lipid hydroperoxide were measured biochemically. Association between the expression of a specific ferroptosis signature and UM patient survival was performed using public databases. Our data revealed that 1,4-dihydroxy quininib modulates the expression of ferroptosis markers in OMM2.5 cells. Biochemical assays validated that GPX4, biliverdin, GCLM, glutathione and lipid hydroperoxide were significantly altered. HO-1 and 4-HNE levels were significantly increased in MUM tumor explants from orthotopic patient-derived xenografts (OPDX). Expression of genes inhibiting ferroptosis is significantly increased in UM patients with chromosome 3 monosomy. We identified IFerr, a novel ferroptosis signature correlating with UM patient survival. Altogether, we demontrated that in MUM cells and tissues, 1,4-dihydroxy quininib modulates key markers that induce ferroptosis, a relatively new type of cell death driven by iron-dependent peroxidation of phospholipids. Furthermore, we showed that high expression of specific genes inhibiting ferroptosis is associated with a worse UM prognosis, thus, the IFerr signature is a potential prognosticator for which patients develop MUM. All in all, ferroptosis has potential as a clinical biomarker and therapeutic target for MUM.

The tumor promoter cysteinyl leukotriene receptor 1 regulates PD-L1 expression in colon cancer cells via the Wnt/β-catenin signaling axis

Immunotherapy targeting programmed death-ligand 1 (PD-L1) or PD-1 in solid tumors has been shown to be clinically beneficial. However, in colorectal cancer (CRC), only a subset of patients benefit from PD-1/PD-L1 treatment. Previously, we showed that high cysteinyl leukotriene receptor 1 (CysLT₁R) levels are associated with poor prognosis in CRC patients. Recently, we have revealed the role of the tumor promoter CysLT₁R in drug resistance and stemness in colon cancer (CC) cells. Here, we show the role of the CysLT₁R/Wnt/β-catenin signaling axis in the regulation of PD-L1 using both in vitro and in vivo preclinical model systems. Interestingly, we found that both endogenous and IFNγ-induced PD-L1 expression in CC cells is mediated through upregulation of CysLT₁R, which enhances Wnt/β-catenin signaling. Therapeutic targeting of CysLT₁R with its antagonist montelukast (Mo), as well as CRISPR/Cas9-mediated or doxycycline-inducible functional absence of CysLT₁R, negatively regulated PD-L1 expression in CC cells. Interestingly, an anti-PD-L1 neutralizing antibody exhibited stronger effects together with the CysLT₁R antagonist in cells (Apc^mut or CTNNB1^mut) with either endogenous or IFNγ-induced PD-L1 expression. Additionally, mice treated with Mo showed depletion of PD-L1 mRNA and protein. Moreover, in CC cells with combined treatment of a Wnt inhibitor and an anti-PD-L1 antibody was effective only in β-catenin-dependent (APC^mut) context. Finally, analysis of public dataset showed positive correlations between the PD-L1 and CysLT₁R mRNA levels. These results elucidate a previously underappreciated CysLT₁R/Wnt/β-catenin signaling pathway in the context of PD-L1 inhibition in CC, which might be considered for improving the efficacy of anti-PD-L1 therapy in CC patients. Video Abstract.

DNA Methylation and Gene Expression of the Cysteinyl Leukotriene Receptors as a Prognostic and Metastatic Factor for Colorectal Cancer Patients

Colorectal cancer (CRC), one of the leading causes of cancer-related deaths in the western world, is the third most common cancer for both men and women. As a heterogeneous disease, colon cancer (CC) is caused by both genetic and epigenetic changes. The prognosis for CRC is affected by a variety of features, including late diagnosis, lymph node and distant metastasis. The cysteinyl leukotrienes (CysLT), as leukotriene D₄ and C₄ (LTD₄ and LTC₄), are synthesized from arachidonic acid via the 5-lipoxygenase pathway, and play an important role in several types of diseases such as inflammation and cancer. Their effects are mediated via the two main G-protein-coupled receptors, CysLT₁R and CysLT₂R. Multiple studies from our group observed a significant increase in CysLT₁R expression in the poor prognosis group, whereas CysLT₂R expression was higher in the good prognosis group of CRC patients. Here, we systematically explored and established the role of the CysLTRs, cysteinyl leukotriene receptor 1(CYSLTR1) and cysteinyl leukotriene receptor 2 (CYSLTR2) gene expression and methylation in the progression and metastasis of CRC using three unique in silico cohorts and one clinical CRC cohort. Primary tumor tissues showed significant CYSLTR1 upregulation compared with matched normal tissues, whereas it was the opposite for the CYSLTR2. Univariate Cox proportional-hazards (CoxPH) analysis yielded a high expression of CYSLTR1 and accurately predicted high-risk patients in terms of overall survival (OS; hazard ratio (HR) = 1.87, p = 0.03) and disease-free survival [DFS] Hazard ratio [HR] = 1.54, p = 0.05). Hypomethylation of the CYSLTR1 gene and hypermethylation of the CYSLTR2 gene were found in CRC patients. The M values of the CpG probes for CYSLTR1 are significantly lower in primary tumor and metastasis samples than in matched normal samples, but those for CYSLTR2 are significantly higher. The differentially upregulated genes between tumor and metastatic samples were uniformly expressed in the high-CYSLTR1 group. Two epithelial-mesenchymal transition (EMT) markers, E-cadherin (CDH1) and vimentin (VIM) were significantly downregulated and upregulated in the high-CYSLTR1 group, respectively, but the result was opposite to that of CYSLTR2 expression in CRC. CDH1 expression was high in patients with less methylated CYSLTR1 but low in those with more methylated CYSLTR2. The EMT-associated observations were also validated in CC SW620 cell-derived colonospheres, which showed decreased E-cadherin expression in the LTD₄ stimulated cells, but not in the CysLT₁R knockdown SW620 cells. The methylation profiles of the CpG probes for CysLTRs significantly predicted lymph node (area under the curve [AUC] = 0.76, p < 0.0001) and distant (AUC = 0.83, p < 0.0001) metastasis. Intriguingly, the CpG probes cg26848126 (HR = 1.51, p = 0.03) for CYSLTR1, and cg16299590 (HR = 2.14, p = 0.03) for CYSLTR2 significantly predicted poor prognosis in terms of OS, whereas the CpG probe cg16886259 for CYSLTR2 significantly predicts a poor prognosis group in terms of DFS (HR = 2.88, p = 0.03). The CYSLTR1 and CYSLTR2 gene expression and methylation results were successfully validated in a CC patient cohort. In this study, we have demonstrated that CysLTRs' methylation and gene expression profile are associated with the progression, prognosis, and metastasis of CRC, which might be used for the assessment of high-risk CRC patients after validating the result in a larger CRC cohort.

Blockade of Platelet CysLT1R Receptor with Zafirlukast Counteracts Platelet Protumoral Action and Prevents Breast Cancer Metastasis to Bone and Lung

Metastases are the main cause of death in cancer patients, and platelets are largely known for their contribution in cancer progression. However, targeting platelets is highly challenging given their paramount function in hemostasis. Using a high-throughput screening and platelet-induced breast tumor cell survival (PITCS) assay as endpoint, we identified the widely used anti-asthmatic drugs and cysteinyl leukotriene receptor 1 (CysLT1R) antagonists, zafirlukast and montelukast, as new specific blockers of platelet protumoral action. Here, we show that human MDA-B02 breast cancer cells produce CysLT through mechanisms involving microsomal glutathione-S-transferase 1/2/3 (MGST1/2/3) and that can modulate cancer cell–platelet interactions via platelet–CysLT1R. CysLT1R blockade with zafirlukast decreased platelet aggregation and adhesion on cancer cells and inhibited PITCS, migration, and invasion in vitro. Zafirlukast significantly reduced, by 90%, MDA-B02 cell dissemination to bone in nude mice and reduced by 88% 4T1 spontaneous lung metastasis formation without affecting primary tumor growth. Combined treatment of zafirlukast plus paclitaxel totally inhibited metastasis of 4T1 cells to the lungs. Altogether, our results reveal a novel pathway mediating the crosstalk between cancer cells and platelets and indicate that platelet CysLT1R represents a novel therapeutic target to prevent metastasis without affecting hemostasis.

Five-lipoxygenase-activating protein-mediated CYLD attenuation is a candidate driver in hepatic malignant lesion

Hepatocellular carcinoma (HCC) is an inflammation-associated cancer. However, the lipid pro-inflammatory mediators have only been seldom investigated in HCC pathogenesis. Cylindromatosis (CYLD) attenuation is involved in hepatocarcinogenesis. Here, we aimed to evaluate the significance of hepatic lipid pro-inflammatory metabolites of arachidonate-affected CYLD expression via the 5-lipoxygenase (5-LO) pathway. Resection liver tissues from HCC patients or donors were evaluated for the correlation of 5-LO/cysteinyl leukotrienes (CysLTs) signaling to the expression of CYLD. The impact of functional components in 5-LO/CysLTs cascade on survival of HCC patients was subsequently assessed. Both livers from canines, a preponderant animal for cancer research, and genetic-modified human HCC cells treated with hepatocarcinogen aristolochic acid I (AAI) were further used to reveal the possible relevance between 5-LO pathway activation and CYLD suppression. Five-LO-activating protein (FLAP), an essential partner of 5-LO, was significantly overexpressed and was parallel to CYLD depression, CD34 neovascular localization, and high Ki-67 expression in the resection tissues from HCC patients. Importantly, high hepatic FLAP transcription markedly shortened the median survival time of HCC patients after surgical resection. In the livers of AAI-treated canines, FLAP overexpression was parallel to enhanced CysLTs contents and the simultaneous attenuation of CYLD. Moreover, knock-in FLAP significantly diminished the expression of CYLD in AAI-treated human HCC cells. In summary, the hepatic FLAP/CysLTs axis is a crucial suppressor of CYLD in HCC pathogenesis, which highlights a novel mechanism in hepatocarcinogenesis and progression. FLAP therefore can be explored for the early HCC detection and a target of anti-HCC therapy.

Cysteinyl Leukotriene Receptor Antagonists Associated With a Decreased Incidence of Cancer: A Retrospective Cohort Study

Aim

Cysteinyl leukotrienes receptor antagonists (LTRAs) are promising chemoprevention options to target cysteinyl leukotriene signaling in cancer. However, only a number of randomized clinical trials (RCTs) or observational studies have been conducted to date; thus, the effect of LTRAs on patients is yet to be elucidated. Using insurance claim data, we aimed to evaluate whether LTRAs have cancer preventive effects by observing patients who took LTRAs.

Method

Patients diagnosed with asthma, allergic rhinitis, chronic cough, and have no history of cancer were followed-up from 2005 to 2017. Cox proportional hazard regression analysis was conducted to estimate the hazard ratios (HRs) for cancer risk of LTRA users.

Result

We followed-up (median: 5.6 years) 188,906 matched patients (94,453 LTRA users and 94,453 non-users). LTRA use was associated with a decreased risk of cancer (adjusted HR [aHR] = 0.85, 95% confidence interval [CI] = 0.83–0.87). The cancer risk showed a tendency to decrease rapidly when LTRAs were used in high dose (aHR = 0.56, 95% CI = 0.40–0.79) or for longer durations of more than 3 years (aHR = 0.68, 95% CI = 0.60–0.76) and 5 years (aHR = 0.33, 95% CI = 0.26–0.42). The greater preventive effects of LTRAs were also observed in patients with specific risk factors related to sex, age, smoking, and the presence of comorbidities.

Conclusion

In this study, we found that LTRA use was associated with a decreased risk of cancer. The high dose and long duration of the use of LTRAs correlated with a lower cancer risk. Since LTRAs are not yet used for the prevention or treatment of cancer, our findings could be used for developing a new chemo-regimen or designing feasible RCTs.

Cysteinyl Leukotriene Pathway and Cancer

Cancer remains a leading cause of death worldwide, despite many advances being made in recent decades. Changes in the tumor microenvironment, including dysregulated immunity, may contribute to carcinogenesis and cancer progression. The cysteinyl leukotriene (CysLT) pathway is involved in several signal pathways, having various functions in different tissues. We summarized major findings of studies about the roles of the CysLT pathway in cancer. Many in vitro studies suggested the roles of CysLTs in cell survival/proliferation via CysLT₁ receptor (CysLT₁R). CysLT₁R antagonism decreased cell vitality and induced cell death in several types of cancer cells, such as colorectal, urological, breast, lung and neurological malignancies. CysLTs were also associated with multidrug resistance of cancer, and CysLT₁R antagonism might reverse chemoresistance. Some animal studies demonstrated the beneficial effects of CysLT₁R antagonist in inhibiting tumorigenesis and progression of some cancer types, particularly colorectal cancer and lung cancer. The expression of CysLT₁R was shown in various cancer tissues, particularly colorectal cancer and urological malignancies, and higher expression was associated with a poorer prognosis. The chemo-preventive effects of CysLT₁R antagonists were demonstrated in two large retrospective cohort studies. In summary, the roles of the CysLT pathway in cancer have been delineated, whereas further studies are still warranted.

Anti-Allergic Drug Suppressed Pancreatic Carcinogenesis via Down-Regulation of Cellular Proliferation

Pancreatic cancer is a fatal disease, and thus its chemoprevention is an important issue. Based on the recent report that patients with allergic diseases have a low risk for pancreatic cancer, we examined the potential chemopreventive effect of anti-allergic agents using a hamster pancreatic carcinogenesis model. Among the three anti-allergic drugs administered, montelukast showed a tendency to suppress the incidence of pancreatic cancer. Further animal study revealed a significantly decreased incidence of pancreatic cancer in the high-dose montelukast group compared with controls. The development of the pancreatic intraepithelial neoplasia lesions was also significantly suppressed. The Ki-67 labeling index was significantly lower in pancreatic carcinomas in the high-dose montelukast group than in controls. In vitro experiments revealed that montelukast suppressed proliferation of pancreatic cancer cells in a dose-dependent manner with decreased expression of phospho-ERK1/2. Montelukast induced G1 phase arrest. Conversely, leukotriene D₄ (LTD₄), an agonist of CYSLTR1, increased cellular proliferation of pancreatic cancer cells with an accumulation of phospho-ERK1/2. In our cohort, pancreatic ductal adenocarcinoma patients with high CYSLTR1 expression showed a significantly unfavorable clinical outcome compared with those with low expression. Our results indicate that montelukast exerts a chemopreventive effect on pancreatic cancer via the LTD₄–CYSLTR1 axis and has potential for treatment of pancreatic carcinogenesis.

Emerging role of cysteinyl LTs in cancer

Cysteinyl leukotrienes (CysLTs) are inflammatory lipid mediators that play a central role in the pathophysiology of several inflammatory diseases. Recently, there has been an increased interest in determining how these lipid mediators orchestrate tumour development and metastasis through promoting a pro-tumour micro-environment. Up-regulation of CysLTs receptors and CysLTs production is found in a number of cancers and has been associated with increased tumorigenesis. Understanding the molecular mechanisms underlying the role of CysLTs and their receptors in cancer progression will help investigate the potential of targeting CysLTs signalling for anti-cancer therapy. This review gives an overview of the biological effects of CysLTs and their receptors, along with current knowledge of their regulation and expression. It also provides a recent update on the molecular mechanisms that have been postulated to explain their role in tumorigenesis and on the potential of anti-CysLTs in the treatment of cancer.

Small-wedge synchrotron and serial XFEL datasets for Cysteinyl leukotriene GPCRs

Structural studies of challenging targets such as G protein-coupled receptors (GPCRs) have accelerated during the last several years due to the development of new approaches, including small-wedge and serial crystallography. Here, we describe the deposition of seven datasets consisting of X-ray diffraction images acquired from lipidic cubic phase (LCP) grown microcrystals of two human GPCRs, Cysteinyl leukotriene receptors 1 and 2 (CysLT₁R and CysLT₂R), in complex with various antagonists. Five datasets were collected using small-wedge synchrotron crystallography (SWSX) at the European Synchrotron Radiation Facility with multiple crystals under cryo-conditions. Two datasets were collected using X-ray free electron laser (XFEL) serial femtosecond crystallography (SFX) at the Linac Coherent Light Source, with microcrystals delivered at room temperature into the beam within LCP matrix by a viscous media microextrusion injector. All seven datasets have been deposited in the open-access databases Zenodo and CXIDB. Here, we describe sample preparation and annotate crystallization conditions for each partial and full datasets. We also document full processing pipelines and provide wrapper scripts for SWSX and SFX data processing.

Measurement(s)	X-ray diffraction data • protein complex • protein structure data • protein crystallization
Technology Type(s)	small-wedge synchrotron crystallography • x-ray crystallography assay • X-ray free electron laser serial femtosecond crystallography
Factor Type(s)	type of G-protein-coupled receptor • type of antagonist

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.13128758

High Cysteinyl Leukotriene Receptor 1 Expression Correlates with Poor Survival of Uveal Melanoma Patients and Cognate Antagonist Drugs Modulate the Growth, Cancer Secretome, and Metabolism of Uveal Melanoma Cells

Metastatic uveal melanoma (UM) is a rare, but often lethal, form of ocular cancer arising from melanocytes within the uveal tract. UM has a high propensity to spread hematogenously to the liver, with up to 50% of patients developing liver metastases. Unfortunately, once liver metastasis occurs, patient prognosis is extremely poor with as few as 8% of patients surviving beyond two years. There are no standard-of-care therapies available for the treatment of metastatic UM, hence it is a clinical area of urgent unmet need. Here, the clinical relevance and therapeutic potential of cysteinyl leukotriene receptors (CysLT1 and CysLT2) in UM was evaluated. High expression of CYSLTR1 or CYSLTR2 transcripts is significantly associated with poor disease-free survival and poor overall survival in UM patients. Digital pathology analysis identified that high expression of CysLT1 in primary UM is associated with reduced disease-specific survival (p = 0.012; HR 2.76; 95% CI 1.21-6.3) and overall survival (p = 0.011; HR 1.46; 95% CI 0.67-3.17). High CysLT1 expression shows a statistically significant (p = 0.041) correlation with ciliary body involvement, a poor prognostic indicator in UM. Small molecule drugs targeting CysLT1 were vastly superior at exerting anti-cancer phenotypes in UM cell lines and zebrafish xenografts than drugs targeting CysLT2. Quininib, a selective CysLT1 antagonist, significantly inhibits survival (p < 0.0001), long-term proliferation (p < 0.0001), and oxidative phosphorylation (p < 0.001), but not glycolysis, in primary and metastatic UM cell lines. Quininib exerts opposing effects on the secretion of inflammatory markers in primary versus metastatic UM cell lines. Quininib significantly downregulated IL-2 and IL-6 in Mel285 cells (p < 0.05) but significantly upregulated IL-10, IL-1β, IL-2 (p < 0.0001), IL-13, IL-8 (p < 0.001), IL-12p70 and IL-6 (p < 0.05) in OMM2.5 cells. Finally, quininib significantly inhibits tumour growth in orthotopic zebrafish xenograft models of UM. These preclinical data suggest that antagonism of CysLT1, but not CysLT2, may be of therapeutic interest in the treatment of UM.

Leukotriene receptor antagonists enhance HCC treatment efficacy by inhibiting ADAMs and suppressing MICA shedding

In our previous genome-wide association study, we demonstrated the association between MHC class I-related chain A (MICA) and hepatocellular carcinoma (HCC) development in patients with chronic hepatitis C. Increasing membrane-bound MICA (mMICA) in cancer cells by reducing MICA sheddases facilitates natural killer (NK) cell-mediated cytotoxicity. Our recent study clarified that A disintegrin and metalloproteases (ADAM), including ADAM9, are MICA sheddases in HCC, and that the suppression of ADAMs increases mMICA, demonstrating the rationality of mMICA-NK targeted therapy. Furthermore, we showed that regorafenib suppresses ADAM9 transcriptionally and translationally. A library of FDA-approved drugs was screened for more efficient inhibitors of ADAM9. Flow cytometry evaluation of the expression of mMICA after treatment with various candidate drugs identified leukotriene receptor antagonists as potential ADAM9 inhibitors. Furthermore, leukotriene receptor antagonists alone or in combination with regorafenib upregulated mMICA, which was in turn downregulated by leukotriene C4 and D4 via ADAM9 function. Our study demonstrates that leukotriene receptor antagonists could be developed as novel drugs for immunological control and suppression of ADAM9 in HCC. Further, leukotriene receptor antagonists should be explored as combination therapy partners with conventional multi-kinase inhibitors for developing therapeutic strategies with enhanced efficacies for HCC management and treatment.

Cysteinyl leukotriene receptor 1 promotes 5-fluorouracil resistance and resistance-derived stemness in colon cancer cells

Colon cancer is a therapy-resistant cancer with a low 5-year survival frequency. The drug 5-fluorouracil (5-FU) has been used as a first-line therapy in metastatic colon cancer in combination with leucovorin or oxaliplatin with a >40% resistance rate. High CysLT₁R expression in tumors is associated with poor survival of colon cancer patients. We sought to examine the role of CysLT₁R in 5-FU resistance and established 5-FU-resistant (5-FU-R) colon cancer cells. These 5-FU-R-cells expressed increased levels of CysLT₁R and showed increased survival and migration compared to nonresistant cells. Increases in thymidylate synthase and active β-catenin were also observed in the 5-FU-R-cells. LTD₄/CysLT₁R signaling was further increased and abolished after CYSLTR1 CRISPR-Cas9-knockdown and reduced in CysLT₁R-doxycycline-knockdown experiments and CysLT₁R-antagonist montelukast/5-FU-treated cells. Montelukast and 5-FU resulted in synergistic effects by reducing HT-29 cell and 5-FU-R-HT-29 cell migration and zebrafish xenograft metastasis. An increase in the stem cell markers in 5-FU-R-cells and 5-FU-R-cell-derived colonospheres and in CysLT₁R-Dox-knockdown cells increased colonosphere formation and stem cell markers was noticed after 5-FU treatment. IL-4-mediated stemness in both HT-29-colonospheres and 5-FU-R-cell derived colonospheres was abolished by montelukast or montelukast + 5-FU-treatment. Targeting CysLT₁R signaling by montelukast might reverse drug resistance and decrease resistance-derived stemness in colon cancer patients.

Network pharmacology identification of mechanisms of cerebral ischemia injury amelioration by Baicalin and Geniposide

Cerebral ischemia is one of the main causes of human neurological dysfunction. Baicalin (BC) and Geniposide (GP) and their combination (BC/GP) have an ameliorative effect on cerebral ischemia. Here, we use network pharmacology to predict the targets of BC, GP and BC/GP, then explored the protective mechanisms of the drugs on cerebral ischemia injury caused by abnormal activation of microglia cells in vitro. The results indicate that 45 targets related to cerebral ischemic injury were predicted by network pharmacology, and 26 cerebral ischemia related pathways were extracted by the KEGG database. In vitro lipopolysaccharide (LPS) stimulated BV-2 cells to establish a model of inflammatory injury induced by microglia. The effects of BC, GP and BC/GP on the expression of TNF-α, IL-1β and IL-10, TGF-β and TNF-α were verified. Network pharmacology predicts the regulation of the 5-LOX/CysLTs inflammatory pathway. Finally, we found that GP and BC/GP exert anti-inflammatory and neuroprotective effects by regulating the polarization state of microglia and down-regulating 5-LOX/CysLTs, and has certain protective effects on nerve damage following cerebral ischemia.

The anticancer properties and mechanism of action of tablysin-15, the RGD-containing disintegrin, in breast cancer cells

α_vβ₃ integrin expressed on cancer cell surfaces is associated with important cancer hallmarks including survival and metastasis and is thus a potential anticancer drug target. Tablysin-15 contains the RGD motif and is a high-affinity α_vβ₃ integrin antagonist. The aim of this study was to investigate the antitumor effect and mechanism of action of tablysin-15 against α_vβ₃ integrin high-expressing breast cancer cell lines in vitro and in vivo. Tablysin-15 dose-dependently inhibited the proliferation, migration, and invasion of two breast cancer cell lines via the α_vβ₃ integrin in vitro. Proliferation inhibition was attributable to G0/G1 phase cell cycle arrest rather than apoptosis or necrosis. Furthermore, tablysin-15 downregulated the activity and mRNA expression of MMP-2/-9, VEGF, and COX-2 but upregulated TIMP-1/-2 mRNA in both cell lines. Further, tablysin-15 suppressed the expression of CDK2, CDK6, cyclin D1, and cyclin E, the phosphorylation of FAK, Akt, GSK-3β, and ERK, and the nuclear translocation of NF-κB while increasing the expression of the CDK inhibitor p21^waf1/C1. Lastly, tablysin-15 provided effective antitumor protection in vivo. Thus, tablysin-15 inhibits the metastasis and proliferation of breast cancer cells through binding α_vβ₃ integrin and blocking FAK-associated signaling pathways as well as nuclear translocation of NF-κB.

Cysteinyl leukotriene receptor 1 facilitates tumorigenesis in a mouse model of colitis-associated colon cancer

Cysteinyl leukotriene receptor 1 (CysLT1R) has been shown to be up-regulated in the adenocarcinomas of colorectal cancer patients, which is associated with a poor prognosis. In a spontaneous model of colon cancer, CysLT1R disruption was associated with a reduced tumor burden in double-mutant female mice (ApcMin/+/Cysltr1-/-) compared to ApcMin/+ littermates. In the current study, we utilized a genetic approach to investigate the effect of CysLT1R in the induced azoxymethane/dextran sulfate sodium (AOM/DSS) model of colitis-associated colon cancer. We found that AOM/DSS female mice with a global disruption of the Cysltr1 gene (Cysltr1-/-) had a higher relative body weight, a more normal weight/length colon ratio and smaller-sized colonic polyps compared to AOM/DSS wild-type counterparts. The Cysltr1-/- colonic polyps exhibited low-grade dysplasia, while wild-type polyps had an adenoma-like phenotype. The Cysltr1-/- colonic polyps exhibited significant decreases in nuclear β-catenin and COX-2 protein expression, while the normal crypts surrounding the polyps exhibited increased Mucin 2 expression. Furthermore, Cysltr1-/- mice exhibited an overall reduction in inflammation, with a significant decrease in proinflammatory cytokines, polyp 5-LOX expression and infiltration of CD45 leukocytes and F4/80 macrophages. In conclusion, the present genetic approach in an AOM/DSS model further supports an important role for CysLT1R in colon tumorigenesis.

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

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

Montelukast Induces Apoptosis-Inducing Factor-Mediated Cell Death of Lung Cancer Cells

Developing novel chemo-prevention techniques and advancing treatment are key elements to beating lung cancer, the most common cause of cancer mortality worldwide. Our previous cohort study showed that cysteinyl leukotriene receptor antagonists, mainly montelukast, decreased the lung cancer risk in asthma patients. In the current study, we conducted in vivo and in vitro experiments to demonstrate the inhibiting effect of montelukast on lung cancer and to investigate the underlying mechanisms. Using Lewis lung carcinoma-bearing mice, we showed that feeding montelukast significantly delayed the tumor growth in mice (p < 0.0001). Montelukast inhibited cell proliferation and colony formation and induced the cell death of lung cancer cells. Further investigation showed the down-regulation of B-cell lymphoma 2 (Bcl-2), up-regulation of Bcl-2 homologous antagonist/killer (Bak), and nuclear translocation of apoptosis-inducing factor (AIF) in montelukast-treated lung cancer cells. Montelukast also markedly decreased the phosphorylation of several proteins, such as with no lysine 1 (WNK1), protein kinase B (Akt), extracellular signal-regulated kinase 1/2 (Erk1/2), MAPK/Erk kinase (MEK), and proline-rich Akt substrate of 40-kDa (PRAS40), which might contribute to cell death. In conclusion, montelukast induced lung cancer cell death via the nuclear translocation of AIF. This study confirmed the chemo-preventive effect of montelukast shown in our previous cohort study. The utility of montelukast in cancer prevention and treatment thus deserves further studies.

Cross-Talk between Cancer Cells and the Tumour Microenvironment: The Role of the 5-Lipoxygenase Pathway

5-lipoxygenase is an enzyme responsible for the synthesis of a range of bioactive lipids signalling molecules known collectively as eicosanoids. 5-lipoxygenase metabolites such as 5-hydroxyeicosatetraenoic acid (5-HETE) and a number of leukotrienes are mostly derived from arachidonic acid and have been shown to be lipid mediators of inflammation in different pathological states including cancer. Upregulated 5-lipoxygenase expression and metabolite production is found in a number of cancer types and has been shown to be associated with increased tumorigenesis. 5-lipoxygenase activity is present in a number of diverse cell types of the immune system and connective tissue. In this review, we discuss potential routes through which cancer cells may utilise the 5-lipoxygenase pathway to interact with the tumour microenvironment during the development and progression of a tumour. Furthermore, immune-derived 5-lipoxygenase signalling can drive both pro- and anti-tumour effects depending on the immune cell subtype and an overview of evidence for these opposing effects is presented.

Evaluation of Cysteinyl Leukotriene Signaling as a Therapeutic Target for Colorectal Cancer

Colorectal cancer is the third most common cancer worldwide and is associated with significant morbidity and mortality. Current pharmacotherapy options include cytotoxic chemotherapy, anti-VEGF, and anti-EGFR targeting drugs, but these are limited by toxic side effects, limited responses and ultimately resistance. Cysteinyl leukotriene (CysLT) signaling regulates intestinal homeostasis with mounting evidence suggesting that CysLT signaling also plays a role in the pathogenesis of colorectal cancer. Therefore, CysLT signaling represents a novel target for this malignancy. This review evaluates reported links between CysLT signaling and established hallmarks of cancer in addition to its pharmacological potential as a new therapeutic target.

A new correlation clustering method for cancer mutation analysis

MOTIVATION

Cancer genomes exhibit a large number of different alterations that affect many genes in a diverse manner. An improved understanding of the generative mechanisms behind the mutation rules and their influence on gene community behavior is of great importance for the study of cancer.

RESULTS

To expand our capability to analyze combinatorial patterns of cancer alterations, we developed a rigorous methodology for cancer mutation pattern discovery based on a new, constrained form of correlation clustering. Our new algorithm, named C³ (Cancer Correlation Clustering), leverages mutual exclusivity of mutations, patient coverage and driver network concentration principles. To test C³, we performed a detailed analysis on TCGA breast cancer and glioblastoma data and showed that our algorithm outperforms the state-of-the-art CoMEt method in terms of discovering mutually exclusive gene modules and identifying biologically relevant driver genes. The proposed agnostic clustering method represents a unique tool for efficient and reliable identification of mutation patterns and driver pathways in large-scale cancer genomics studies, and it may also be used for other clustering problems on biological graphs.

AVAILABILITY AND IMPLEMENTATION

The source code for the C³ method can be found at https://github.com/jackhou2/C3 CONTACTS: jianma@cs.cmu.edu or milenkov@illinois.eduSupplementary information: Supplementary data are available at Bioinformatics online.

Leukotriene receptor expression in esophageal squamous cell cancer and non-transformed esophageal epithelium: a matched case control study

BACKGROUND

Leukotriene B4 (LTB4R and LTB4R2) and cysteinyl leukotriene receptors (CYSLTR1 and CYSLTR2) contribute to malignant cell transformation. We aimed to investigate the expression of LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 in esophageal squamous cell carcinoma and adjacent non-transformed squamous epithelium of the esophagus, as well as in control biopsy samples from esophageal squamous epithelium of patients with functional dyspepsia.

METHODS

Expression of LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 was analyzed by immunohistochemistry (IHC) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in biopsy samples of 19 patients with esophageal squamous cell cancer and 9 sex- and age-matched patients with functional dyspepsia.

RESULTS

LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 were expressed in all biopsy samples. Major findings were: 1) protein levels of all leukotriene receptors were significantly increased in esophageal squamous cell cancer compared to control mucosa (p < 0.05); 2) CYSLTR1 and CYSLTR2 gene expression was decreased in cancer tissue compared to control at 0.26-fold and 0.23-fold respectively; 3) an up-regulation of LTB4R (mRNA and protein expression) and a down-regulation of CYSLTR2 (mRNA expression) in non-transformed epithelium of cancer patients compared to control (p < 0.05) was observed.

CONCLUSIONS

The expression of leukotriene receptors was deregulated in esophageal squamous cell cancer. Up-regulation of LTB4R and down-regulation of CYSLTR2 gene expression may occur already in normal squamous esophageal epithelium of patients with esophageal cancer suggesting a potential role of these receptors in early steps of esophageal carcinogenesis. Larger studies are warranted to confirm these observations.

The eicosanoids leukotriene D4 and prostaglandin E2 promote the tumorigenicity of colon cancer-initiating cells in a xenograft mouse model

Background

Colorectal cancer is one of the most common types of cancers worldwide. Recent studies have identified cancer-initiating cells (CICs) as a subgroup of replication-competent cells in the development of colorectal cancer. Although it is understood that an inflammation-rich tumor microenvironment presumably supports CIC functions, the contributory factors are not very well defined. The present study advances our understanding of the role of the eicosanoids leukotriene D₄ (LTD₄) and prostaglandin E₂ (PGE₂) in the tumorigenic ability of CICs and investigates the consequential changes occurring in the tumor environment that might support tumor growth.

Methods

In this study we used human HCT-116 colon cancer ALDH⁺ cells in a nude mouse xenograft model. Protein expression and immune cell was determined in tumor-dispersed cells by flow cytometry and in tumor sections by immunohistochemistry. mRNA expressions were quantified using RT-q-PCR and plasma cytokine levels by Multiplex ELISA.

Results

We observed that LTD₄ and PGE₂ treatment augmented CIC-induced tumor growth. LTD₄-and PGE₂-treated xenograft tumors revealed a robust increase in ALDH and Dclk1 protein expression, coupled with activated β-catenin signaling and COX-2 up-regulation. Furthermore, LTD₄ or PGE₂ accentuated the accumulation of CD45 expressing cells within xenograft tumors. Further analysis revealed that these infiltrating immune cells consisted of neutrophils (LY6G) and M2 type macrophages (CD206⁺). In addition, LTD₄ and PGE₂ treatment significantly elevated the plasma levels of cysteinyl leukotrienes and PGE₂, as well as levels of IL-1β, IL-2, IL-6, TNF-α and CXCL1/KC/GRO. In addition, increased mRNA expression of IL-1β, IL-6 and IL-10 were detected in tumors from mice that had been treated with LTD₄ or PGE₂.

Conclusion

Our data suggest that both LTD₄ and PGE₂ promote CICs in initiating tumor growth by allowing modifications in the tumor environment. Our data indicate that new therapeutic strategies targeting eicosanoids, specifically LTD₄ and PGE₂, could be tested for better therapeutic management of colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2466-z) contains supplementary material, which is available to authorized users.

Transcriptome analysis of G protein-coupled receptors in distinct genetic subgroups of acute myeloid leukemia: identification of potential disease-specific targets

Acute myeloid leukemia (AML) is associated with poor clinical outcome and the development of more effective therapies is urgently needed. G protein-coupled receptors (GPCRs) represent attractive therapeutic targets, accounting for approximately 30% of all targets of marketed drugs. Using next-generation sequencing, we studied the expression of 772 GPCRs in 148 genetically diverse AML specimens, normal blood and bone marrow cell populations as well as cord blood-derived CD34-positive cells. Among these receptors, 30 are overexpressed and 19 are downregulated in AML samples compared with normal CD34-positive cells. Upregulated GPCRs are enriched in chemokine (CCR1, CXCR4, CCR2, CX3CR1, CCR7 and CCRL2), adhesion (CD97, EMR1, EMR2 and GPR114) and purine (including P2RY2 and P2RY13) receptor subfamilies. The downregulated receptors include adhesion GPCRs, such as LPHN1, GPR125, GPR56, CELSR3 and GPR126, protease-activated receptors (F2R and F2RL1) and the Frizzled family receptors SMO and FZD6. Interestingly, specific deregulation was observed in genetically distinct subgroups of AML, thereby identifying different potential therapeutic targets in these frequent AML subgroups.

Expression of cysteinyl leukotriene receptor 1 and 2 (CysLTR1 and CysLTR2) in the lymphocytes of hyperplastic tonsils: comparison between allergic and nonallergic snoring children

BACKGROUND

Cysteinyl leukotriene receptor 1 and 2 (CysLTR1 and CysLTR2) are involved in allergic processes and play a role in adenotonsillar hyperplasia (AH). Clinically, only CysLTR1 may be blocked by montelukast. Our objective was to compare the expression of CysLTR1 and CysLTR2 in the B and T cells of hyperplasic tonsils of sensitized (SE) and control (NS) snoring children.

METHODS

Sixty children, 5 to 10 years of age, referred for adenotonsillectomy, were divided into SE and NS groups, according to their responses to the skin-prick test. Cells from the removed tissues were stained for CysLTR1, CysLTR2, CD19, and CD3 and counted via flow cytometry. messenger RNA (mRNA) expression of the CysLTRs genes was measured real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR).

RESULTS

The SE group showed reduced expression of the small CD3+/CysLTR1+ lymphocytes (4.6 ± 2.2 vs 6.5 ± 5.0; p = 0.04). Regarding the large lymphocytes, the SE group showed lower expression of CD3+/CysLTR1+ (40.9 ± 14.5 vs 47.6 ± 11.7; p = 0.05), CD19+/CysLTR1+ (44.6 ± 16.9 vs 54.1 ± 12.4; p = 0.01), and CD19+/CysLTR2+ (55.3 ± 11.3 vs 61.5 ± 12.6; p = 0.05) lymphocytes. Considering the total number of lymphocytes, the SE group had fewer CD3+/CysLTR1+ lymphocytes (11.1 ± 5.5 vs 13.7 ± 6.2; p = 0.04). All other cell populations exhibited reduced expression in the SE group without statistical significance. The expression of CysLTR2 was significantly higher (p < 0.05) than CysLTR1 in most studied cell populations. The mRNA expression did not show significant differences between the groups.

CONCLUSION

The expression of CysLTR is higher in the lymphocytes of the NS children, and CysLTR2 shows greater expression than CysLTR1 Respiratory allergies do not appear to be a stimulus for AH occurrence. Newer drugs capable of blocking both CysLTRs warrant further study.

Cysteinyl Leukotriene Receptor Antagonists Decrease Cancer Risk in Asthma Patients

Previous in vitro and in vivo studies have demonstrated the potential of using cysteinyl leukotriene receptor antagonists (LTRAs) for chemoprevention, but this has not been investigated in any clinical setting. We therefore investigated the chemopreventive effect of LTRAs in a nationwide population-based study. From the Taiwan National Health Insurance Research Database, we enrolled adults with newly-diagnosed asthma between 2001 and 2011. Among these patients, each LTRA user was matched with five randomly-selected LTRA non-users by sex, age, asthma diagnostic year and modified Charlson Comorbidity Index score. We considered the development of cancer as the outcome. Totally, 4185 LTRA users and 20925 LTRA non-users were identified. LTRA users had a significantly lower cancer incidence rate than LTRA non-users did. Multivariable Cox regression analyses adjusting for baseline characteristics and comorbidities showed LTRA use was an independent protecting factor (hazard ratio = 0.31 [95% CI: 0.24–0.39]), and cancer risk decreased progressively with higher cumulative dose of LTRAs. In conclusion, this study revealed that the LTRA use decreased cancer risk in a dose-dependent manner in asthma patients. The chemopreventive effect of LTRAs deserves further study.

Structure and putative signaling mechanism of Protease activated receptor 2 (PAR2) - a promising target for breast cancer

Experimental evidences have observed enhanced expression of protease activated receptor 2 (PAR2) in breast cancer consistently. However, it is not yet recognized as an important therapeutic target for breast cancer as the primary molecular mechanisms of its activation are not yet well-defined. Nevertheless, recent reports on the mechanism of GPCR activation and signaling have given new insights to GPCR functioning. In the light of these details, we attempted to understand PAR2 structure & function using molecular modeling techniques. In this work, we generated averaged representative stable models of PAR2, using protease activated receptor 1 (PAR1) as a template and selected conformation based on their binding affinity with PAR2 specific agonist, GB110. Further, the selected model was used for studying the binding affinity of putative ligands. The selected ligands were based on a recent publication on phylogenetic analysis of Class A rhodopsin family of GPCRs. This study reports putative ligands, their interacting residues, binding affinity and molecular dynamics simulation studies on PAR2-ligand complexes. The results reported from this study would be useful for researchers and academicians to investigate PAR2 function as its physiological role is still hypothetical. Further, this information may provide a novel therapeutic scheme to manage breast cancer.

Update on leukotriene, lipoxin and oxoeicosanoid receptors: IUPHAR Review 7

The endogenous ligands for the LT, lipoxin (LX) and oxoeicosanoid receptors are bioactive products produced by the action of the lipoxygenase family of enzymes. The LT receptors BLT1 and BLT2 , are activated by LTB4 and the CysLT1 and CysLT2 receptors are activated by the cysteinyl-LTs, whereas oxoeicosanoids exert their action through the OXE receptor. In contrast to these pro-inflammatory mediators, LXA4 transduces responses associated with the resolution of inflammation through the receptor FPR2/ALX (ALX/FPR2). The aim of the present review is to give a state of the field on these receptors, with focus on recent important findings. For example, BLT1 receptor signalling in cancer and the dual role of the BLT2 receptor in pro- and anti-inflammatory actions have added more complexity to lipid mediator signalling. Furthermore, a cross-talk between the CysLT and P2Y receptor systems has been described, and also the presence of novel receptors for cysteinyl-LTs, such as GPR17 and GPR99. Finally, lipoxygenase metabolites derived from ω-3 essential polyunsaturated acids, the resolvins, activate the receptors GPR32 and ChemR23. In conclusion, the receptors for the lipoxygenase products make up a sophisticated and tightly controlled system of endogenous pro- and anti-inflammatory signalling in physiology and pathology.

Cysteinyl leukotrienes and their receptors: Bridging inflammation and colorectal cancer

Long-standing inflammation has emerged as a hallmark of neoplastic transformation of epithelial cells and may be a limiting factor of successful conventional tumor therapies. A complex milieu composed of distinct stromal and immune cells, soluble factors and inflammatory mediators plays a crucial role in supporting and promoting various types of cancers. An augmented inflammatory response can predispose a patient to colorectal cancer (CRC). Common risk factors associated with CRC development include diet and lifestyle, altered intestinal microbiota and commensals, and chronic inflammatory bowel diseases. Cysteinyl leukotrienes are potent inflammatory metabolites synthesized from arachidonic acid and have a broad range of functions involved in the etiology of various pathologies. This review discusses the important role of cysteinyl leukotriene signaling in linking inflammation and CRC.

5-Lipoxygenase and cysteinyl leukotriene receptor 1 regulate epidermal growth factor-induced cell migration through Tiam1 upregulation and Rac1 activation

Cell migration is an essential step for tumor metastasis. The small GTPase Rac1 plays an important role in cell migration. Previously, we reported that epidermal growth factor (EGF) induced two waves of Rac1 activation; namely, at 5 min and 12 h after stimulation. A second wave of EGF-induced Rac1 activation was required for EGF-induced cell migration, however, the spatiotemporal regulation of the second wave of EGF-induced Rac1 activation remains largely unclear. In this study, we found that 5-lipoxygenase (5-LOX) is activated in the process of EGF-induced cell migration, and that leukotriene C₄ (LTC₄) produced by 5-LOX mediated the second wave of Rac1 activation, as well as cell migration. Furthermore, these effects caused by LTC₄ were found to be blocked in the presence of the antagonist of cysteinyl leukotriene receptor 1 (CysLT1). This blockage indicates that LTC₄-mediated CysLT1 signaling regulates the second EGF-induced wave of Rac1 activation. We also found that 5-LOX inhibitors, CysLT1 antagonists and the knockdown of CysLT1 inhibited EGF-induced T cell lymphoma invasion and metastasis-inducing protein 1 (Tiam1) expression. Tiam1 expression is required for the second wave of EGF-induced Rac1 activation in A431 cells. Therefore, our results indicate that the 5-LOX/LTC₄/CysLT1 signaling pathway regulates EGF-induced cell migration by increasing Tiam1 expression, leading to a second wave of Rac1 activation. Thus, CysLT1 may serve as a new molecular target for antimetastatic therapy. In addition, the CysLT1 antagonist, montelukast, which is used clinically for allergy treatment, might have great potential as a novel type of antimetastatic agent.

CysLT(1)R antagonists inhibit tumor growth in a xenograft model of colon cancer

The expression of the inflammatory G-protein coupled receptor CysLT₁R has been shown to be upregulated in colon cancer patients and associated with poor prognosis. The present study investigated the correlation between CysLT₁R and colon cancer development in vivo using CysLT₁R antagonists (ZM198,615 or Montelukast) and the nude mouse xenograft model. Two drug administration regimens were established. The first regimen was established to investigate the importance of CysLT₁R in tumor initiation. Nude mice were inoculated with 50 µM CysLT₁R antagonist-pretreated HCT-116 colon cancer cells and received continued treatment (5 mg/kg/day, intraperitoneally). The second regimen aimed to address the role of CysLT₁R in tumor progression. Nude mice were inoculated with non-pretreated HCT-116 cells and did not receive CysLT₁R antagonist treatment until recordable tumor appearance. Both regimens resulted in significantly reduced tumor size, attributed to changes in proliferation and apoptosis as determined by reduced Ki-67 levels and increased levels of p21^WAF/Cip1 (P<0.01), cleaved caspase 3, and the caspase-cleaved product of cytokeratin 18. Decreased levels of VEGF (P<0.01) and reduced vessel size (P<0.05) were also observed, the latter only in the ZM198,615-pretreatment group. Furthermore, we performed a series of in vitro studies using the colon cancer cell line HCT-116 and CysLT₁R antagonists. In addition to significant reductions in cell proliferation, adhesion and colony formation, we observed induction of cell cycle arrest and apoptosis in a dose-dependent manner. The ability of Montelukast to inhibit growth of human colon cancer xenograft was further validated by using two additional colon cancer cell lines, SW-480 and HT-29. Our results demonstrate that CysLT₁R antagonists inhibit growth of colon cancer xenografts primarily by reducing proliferation and inducing apoptosis of the tumor cells.

Regulation of cysteinyl leukotriene receptor 2 expression--a potential anti-tumor mechanism

Background

The cysteinyl leukotrienes receptors (CysLTRs) are implicated in many different pathological conditions, such as inflammation and cancer. We have previously shown that colon cancer patients with high CysLT₁R and low CysLT₂R expression demonstrate poor prognosis. Therefore, we wanted to investigate ways for the transcriptional regulation of CysLT₂R, which still remains to be poorly understood.

Methodology/Principal Findings

We investigated the potential role of the anti-tumorigenic interferon α (IFN-α) and the mitogenic epidermal growth factor (EGF) on CysLT₂R regulation using non-transformed intestinal epithelial cell lines and colon cancer cells to elucidate the effects on the CysLT₂R expression and regulation. This was done using Western blot, qPCR, luciferase reporter assay and a colon cancer patient array. We found a binding site for the transcription factor IRF-7 in the putative promoter region of CysLT₂R. This site was involved in the IFN-α induced activity of the CysLT₂R luciferase reporter assay. In addition, IFN-α induced the activity of the differentiation marker alkaline phosphatase along with the expression of mucin-2, which protects the epithelial layer from damage. Interestingly, EGF suppressed both the expression and promoter activity of the CysLT₂R. E-boxes present in the CysLT₂R putative promoter region were involved in the suppressing effect. CysLT₂R signaling was able to suppress cell migration that was induced by EGF signaling.

Conclusions/Significance

The patient array showed that aggressive tumors generally expressed less IFN-α receptor and more EGFR. Interestingly, there was a negative correlation between CysLT₂R and EGFR expression. Our data strengthens the idea that there is a protective role against tumor progression for CysLT₂R and that it highlights new possibilities to regulate the CysLT₂R.

Upregulation of leukotriene receptors in gastric cancer

Background

Leukotrienes (LT) mediate allergic and inflammatory processes. Previously, we identified significant changes in the expression pattern of LT receptors in the gastric mucosa after eradication of Helicobacter pylori infection. The aim of the present study was to evaluate the expression of 5-lipoxygenase (5-LOX) and LT receptors in gastric cancer (GC).

Methods

The expression of 5-LOX and receptors for LTB4 (BLT-1, BLT-2) and cysteinyl-LT (CysLT-1, CysLT-2) were analyzed by immunohistochemistry (IHC) in GC samples of 35 consecutive patients who underwent gastrectomy and in 29 tumor-free tissue specimens from gastric mucosa.

Results

Male-to-female ratio was 24:11. The median age was 70 years (range 34–91). Twenty-two patients had GC of intestinal, six of diffuse, six of mixed and one of undifferentiated type. The IHC analysis showed a nearly ubiquitous expression of studied proteins in GC (88–97%) and in tumor-free specimens as well (89–100%). An increase in the immunoreactive score of both BLT receptors and CysLT-1 was observed in GC compared to tumor-free gastric mucosa (p < 0.001 for BLT-1; p < 0.01 for BLT-2 and CysLT-1, Mann-Whitney U-test). No differences in the IHC expression of 5-LOX and CsyLT-2 were observed between GC and tumor-free mucosa. The expression of BLT-2, CysLT-1 and CysLT-2 was increased in GC of intestinal type when compared to the diffuse type (p < 0.05; Mann-Whitney U-test).

Conclusions

LTB4 receptors and CysLT-1 are up-regulated in GC tissue implying a role in gastric carcinogenesis.