Inhibition of thromboxane synthase activity modulates bladder cancer cell responses to chemotherapeutic agents

Classification models and SAR analysis on thromboxane A2 synthase inhibitors by machine learning methods

Thromboxane A2 synthase (TXS) is a promising drug target for cardiovascular diseases and cancer. In this work, we conducted a structure-activity relationship (SAR) study on 526 TXS inhibitors for bioactivity prediction. Three types of descriptors (MACCS fingerprints, ECFP4 fingerprints, and MOE descriptors) were utilized to characterize inhibitors, 24 classification models were developed by support vector machine (SVM), random forest (RF), extreme gradient boosting (XGBoost), and deep neural networks (DNN). Then we reduced the number of fingerprints according to the contribution of descriptors to the models, and constructed 16 extra models on simplified fingerprints. In general, Model_4D built by DNN algorithm and 67 bits MACCS fingerprints performs best. The prediction accuracy of the model on the test set is 0.969, and Matthews correlation coefficient (MCC) is 0.936. The distance between compound and model (dSTD-PRO) was used to characterize the application domain of the model. In the test set of Model_4D, dSTD-PRO of 91.5% compounds is lower than the corresponding training set threshold (threshold0.90 = 0.1055), and the accuracy of these compounds is 0.983. In addition, the important descriptors were summarized and further analyzed. It showed that aromatic nitrogenous heterocyclic groups were beneficial to improve the bioactivity of TXS inhibitors.

Oncopreventive and oncotherapeutic potential of licorice triterpenoid compound glycyrrhizin and its derivatives: Molecular insights

Licorice (Glycyrrhiza glabra) is a well-known natural herb used to treat different ailments since ancient times. Glycyrrhizin (GL), which is the primary triterpenoid compound of licorice extract, has been known to have broad-spectrum pharmacological effects. GL is cleaved into glucuronide and the aglycone, glycyrrhetinic acid (GA), which exists in two stereoisomeric forms: 18α- and 18β-GA. It is well documented that GL and GA have great potential as anti-inflammatory, anticancer, antiviral, anti-diabetic, antioxidant, and hepatoprotective agents. Studies undertaken during the coronavirus disease 2019 pandemic suggest that GL is effective at inhibiting the viral replication of severe acute respiratory syndrome coronavirus 2. The anticancer effects of GL and GA involve modulating various signaling pathways, such as the phosphatase and tensin homolog/phosphatidylinositol 3-kinase/protein kinase B pathway, the mitogen-activated protein kinase, and the mammalian target of rapamycin/signal transducer and activator of transcription 3, which are mainly involved in regulating cancer cell death, oxidative stress, and inflammation. The potential of GL and GA in preventing cancer development and suppressing the growth and invasion of different cancer types has been reviewed in this paper. This review also provides molecular insights on the mechanism of action for the oncopreventive and oncotherapeutic effects of GL and its derivative, GA, which could help develop more specific forms of these agents for clinical use.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Metabolomics analysis of multidrug-resistant breast cancer cellsin vitrousing methyl-tert-butyl ether method

MTBE-based cellular lipidomics to investigate the mechanisms of multidrug resistance of breast cancer.

Thromboxane A2 Receptor Inhibition Suppresses Multiple Myeloma Cell Proliferation by Inducing p38/c-Jun N-terminal Kinase (JNK) Mitogen-activated Protein Kinase (MAPK)-mediated G2/M Progression Delay and Cell Apoptosis

Multiple myeloma (MM) is a plasma cell malignancy without effective therapeutics. Thromboxane A2 (TxA2)/TxA2 receptor (T prostanoid receptor (TP)) modulates the progression of some carcinomas; however, its effects on MM cell proliferation remain unclear. In this study, we evaluated cyclooxygenase (COX) enzymes and downstream prostaglandin profiles in human myeloma cell lines RPMI-8226 and U-266 and analyzed the effects of COX-1/-2 inhibitors SC-560 and NS-398 on MM cell proliferation. Our observations implicate COX-2 as being involved in modulating cell proliferation. We further incubated MM cells with prostaglandin receptor antagonists or agonists and found that only the TP antagonist, SQ29548, suppressed MM cell proliferation. TP silencing and the TP agonist, U46619, further confirmed this finding. Moreover, SQ29548 and TP silencing promoted MM cell G2/M phase delay accompanied by reducing cyclin B1/cyclin-dependent kinase-1 (CDK1) mRNA and protein expression. Notably, cyclin B1 overexpression rescued MM cells from G2/M arrest. We also found that the TP agonist activated JNK and p38 MAPK phosphorylation, and inhibitors of JNK and p38 MAPK depressed U46619-induced proliferation and cyclin B1/CDK1 protein expression. In addition, SQ29548 and TP silencing led to the MM cell apoptotic rate increasing with improving caspase 3 activity. The knockdown of caspase 3 reversed the apoptotic rate. Taken together, our results suggest that TxA2/TP promotes MM cell proliferation by reducing cell delay at G2/M phase via elevating p38 MAPK/JNK-mediated cyclin B1/CDK1 expression and hindering cell apoptosis. The TP inhibitor has potential as a novel agent to target kinase cascades for MM therapy.

Tobacco carcinogen NNK-induced lung cancer animal models and associated carcinogenic mechanisms

Tobacco usage is a major risk factor in the development, progression, and outcomes for lung cancer. Of the carcinogens associated with lung cancer, tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is among the most potent ones. The oncogenic mechanisms of NNK are not entirely understood, hindering the development of effective strategies for preventing and treating smoking-associated lung cancers. Here, we introduce the NNK-induced lung cancer animal models in different species and its potential mechanisms. Finally, we summarize several chemopreventive agents developed from these animal models.

Anti-tumor activities of lipids and lipid analogues and their development as potential anticancer drugs

Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modulate the viability of tumor cells. In addition, many tumors over-express cyclooxygenase, lipoxygenase or cytochrome P450 enzymes that mediate the biotransformation of ω-6 polyunsaturated fatty acids (PUFAs) to potent eicosanoid regulators of tumor cell proliferation and cell death. In contrast, several analogous products from the biotransformation of ω-3 PUFAs impair particular tumorigenic pathways. For example, the ω-3 17,18-epoxide of eicosapentaenoic acid activates anti-proliferative and proapoptotic signaling cascades in tumor cells and the lipoxygenase-derived resolvins are effective inhibitors of inflammatory pathways that may drive tumor expansion. However, the development of potential anti-cancer drugs based on these molecules is complex, with in vivo stability a major issue. Nevertheless, recent successes with the antitumor alkyl phospholipids, which are synthetic analogues of naturally-occurring membrane phospholipid esters, have provided the impetus for development of further molecules. The alkyl phospholipids have been tested against a range of cancers and show considerable activity against skin cancers and certain leukemias. Very recently, it has been shown that combination strategies, in which alkyl phospholipids are used in conjunction with established anticancer agents, are promising new therapeutic approaches. In future, the evaluation of new lipid-based molecules in single-agent and combination treatments may also be assessed. This could provide a range of important treatment options in the management of advanced and metastatic cancer.

Regulation of the tumor suppressor FOXO3 by the thromboxane-A2 receptors in urothelial cancer

The transcription factor FOXO3 is a well-established tumor suppressor whose activity, stability, and localization are regulated by phosphorylation and acetylation. Previous data by our laboratory demonstrated amplified thromboxane-A₂ signaling was associated with poor prognoses in bladder cancer patients and overexpression of the thromboxane-A₂ isoform-β receptor (TPβ), but not TPα, induced malignant transformation of immortalized bladder cells in vivo. Here, we describe a mechanism of TP mediated modulation of FOXO3 activity and localization by phosphorylation and deacetylation in a bladder cancer cell model. In vitro gain and loss of function studies performed in non-transformed cell lines, UROsta and SV-HUC, revealed knockdown of FOXO3 expression by shRNA increased cell migration and invasion, while exogenously overexpressing TPβ raised basal phosphorylated (p)FOXO3-S294 levels. Conversely, overexpression of ERK-resistant, mutant FOXO3 reduced increases in UMUC3 cell migration and invasion, including that mediated by TP agonist (U46619). Additionally, stimulation of UMUC3 cells with U46619 increased pFOXO3-S294 expression, which could be attenuated by treatment with a TP antagonist (PTXA₂) or ERK inhibitor (U0126). Initially U46619 caused nuclear accumulation of pFOXO3-S294; however, prolonged stimulation increased FOXO3 cytoplasmic localization. U46619 stimulation decreased overall FOXO3 transcriptional activity, but was associated with increased expression of its pro-survival target, manganese superoxide dismutase. The data also shows that TP stimulation increased the expression of the histone deacetylase, SIRT1, and corresponded with decreased acetylated-FOXO3. Collectively, the data suggest a role for TP signaling in the regulation of FOXO3 activity, mediated in part through phosphorylation and deacetylation.

18β-Glycyrrhetinic acid suppresses cell proliferation through inhibiting thromboxane synthase in non-small cell lung cancer

18β-glycyrrhetinic acid (18β-GA) is a bioactive component of licorice. The anti-cancer activity of 18β-GA has been studied in many cancer types, whereas its effects in lung cancer remain largely unknown. We first showed that 18β-GA effectively suppressed cell proliferation and inhibited expression as well as activity of thromboxane synthase (TxAS) in non-small cell lung cancer (NSCLC) cells A549 and NCI-H460. In addition, the administration of 18β-GA did not have any additional inhibitory effect on the decrease of cell proliferation induced by transfection with TxAS small interference RNA (siRNA). Moreover, 18β-GA failed to inhibit cell proliferation in the immortalized human bronchial epithelial cells 16HBE-T and another NSCLC cell line NCI-H23, both of which expressed minimal level of TxAS as compared to A549 and NCI-H460. However, 18β-GA abolished the enhancement of cell proliferation induced by transfection of NCI-H23 with pCMV6-TxAS plasmid. Further study found that the activation of both extracellular signal-regulated kinase (ERK)1/2 and cyclic adenosine monophosphate response element binding protein (CREB) induced by TxAS cDNA transfection could be totally blocked by 18β-GA. Altogether, we have delineated that, through inhibiting TxAS and its initiated ERK/CREB signaling, 18β-GA suppresses NSCLC cell proliferation. Our study has highlighted the significance of 18β-GA with respect to prevention and treatment of NSCLC.

Genomic polymorphisms of SLC29A3 associated with overall survival in advanced non-small-cell lung cancer treated with gemcitabine

Several polymorphisms in the genes involved in drug metabolism or elimination are known to be associated with pharmacokinetic or pharmacodynamic variability, but their correlations with overall survival (OS) and response rate (RR) in lung cancer have been unknown. This prospective study was to investigate whether genetic polymorphisms could influence OS and RR in advanced or metastatic non-small-cell lung cancer (NSCLC) patients treated with third-generation cytotoxic chemotherapy. Three hundred and sixty-four patients with chemotherapy naïve stage IIIB or IV NSCLC, receiving standard first-line chemotherapy, were eligible for this study. The DNA samples were extracted from peripheral blood mononuclear cells before treatment and single nucleotide polymorphisms of solute carrier family 29 member 3 SLC29A3 (rs10999776), SULT1E1 (rs4149525), and TBXAS1 (rs2267703), a category of drug-metabolizing enzymes or transporters were analyzed. Statistical analyses were performed by the log-rank test and Cox proportional hazards model. Patients with SLC29A3 C/T+T/T genotype had longer overall survival (median OS 12.3 months, 95 % CI 11.0-13.6 months) than those with C/C genotype (median OS 11.0 months, 95 % CI 9.9-12.1 months, P = 0.030 for log-rank test). More evidently significant association was found between the SLC29A3 polymorphism and overall survival in patients treated with gemcitabine-based chemotherapy (C/T+T/T versus C/C: median OS 12.0 months, 95 % CI 10.5-13.5 months versus median OS 10.0 months, 95 % CI 9.0-11.0 months, P = 0.027 for log-rank test). No association between the other two genetic polymorphisms and OS was observed. Genes involved in the drug metabolism or elimination (SLC29A3) may be new prognostic biomarkers for patients with advanced NSCLC who receive gemcitabine as the first-line chemotherapy and may unveil an unexplored molecular pathway correlated with the drug response and further may be predictive biomarkers for these patients.

Functional analysis of human thromboxane synthase polymorphic variants

BACKGROUND

Thromboxane A synthase (TXAS) metabolizes the cyclooxygenase product prostaglandin (PG) H2 into thromboxane H2 (TXA2), a potent inducer of blood vessel constriction and platelet aggregation. Nonsynonymous polymorphisms in the TXAS gene have the potential to alter TXAS activity and affect TXA2 generation.

OBJECTIVES

The aim of this study was to assess the functional effects of genetic variants in the TXAS protein, including K258E, L357V, Q417E, E450K, and T451N.

METHODS

Wild-type TXAS and the variant proteins were expressed in a bacterial system and purified by affinity and hydroxyapatite chromatography. The two characteristic catalytic activities of TXAS were assayed in each of the purified recombinant proteins: isomerization of PGH2 to TXA2 and fragmentation of PGH2 to 12-hydroxyheptadecatrienoic acid and malondialdehyde.

RESULTS

All of the variants showed both isomerization and fragmentation activities. The Km values of the variants ranged from 27 to 52 µmol/l PGH2 (wild-type value: 32 μmol/l PGH2); the Vmax values of the variants ranged from 18 to 40 U/mg (wild-type value: 41 U/mg). The kinetic differences were largest for the L357V variant, whose Vmax/Km ratio was just 27% of the wild-type value.

CONCLUSION

The increased Km and decreased Vmax values observed with L357V suggest that this variant may generate less TXA2 at the low levels of PGH2 expected in vivo, raising the possibility of attenuated signaling through the thromboxane pathway.

Role of mitochondria in programmed cell death mediated by arachidonic acid-derived eicosanoids

Arachidonic acid-derived eicosanoids from cyclooxygenases, lipoxygenases, and cytochrome P450 are important lipid mediators involved in numerous homeostatic and pathophysiological processes. Most eicosanoids act primarily on their respective cell surface G-protein coupled receptors to elicit downstream signaling in an autocrine and paracrine fashion. Emerging evidence indicates that these hormones are also critical in apoptosis in a cell/tissue specific manner. In this review, we summarize the formation of eicosanoids and their roles as mediators in apoptosis, specifically on the roles of mitochondria in mediating these events and the signaling pathways involved. The biological relevance of eicosanoid-mediated apoptosis is also discussed.

The thromboxane synthase and receptor signaling pathway in cancer: an emerging paradigm in cancer progression and metastasis

Thromboxane A(2) (TXA(2)) is a biologically active metabolite of arachidonic acid formed by the action of the terminal synthase, thromboxane A(2) synthase (TXA(2)S), on prostaglandin endoperoxide (PGH(2)). TXA(2) is responsible for multiple biological processes through its cell surface receptor, the T-prostanoid (TP) receptor. Thromboxane A(2) synthase and TP are the two necessary components for the functioning of this potent bioactive lipid. Thromboxane A(2) is widely implicated in a range of cardiovascular diseases, owing to its acute and chronic effects in promoting platelet aggregation, vasoconstriction, and proliferation. In recent years, additional functional roles for both TXA(2)S and TP in cancer progression have been indicated. Increased cyclooxygenase (COX)-2 expression has been described in a variety of human cancers, which has focused attention on TXA(2) as a downstream metabolite of the COX-2-derived PGH(2). Several studies suggest potential involvement of TXA(2)S and TP in tumor progression, especially tumor cell proliferation, migration, and invasion that are key steps in cancer progression. In addition, the regulation of neovascularization by TP has been identified as a potent source of control during oncogenesis. There have been several recent reviews of TXA(2)S and TP but thus far none have discussed its role in cancer progression and metastasis in depth. This review will focus on some of the more recent findings and advances with a significant emphasis on understanding the functional role of TXA(2)S and TP in cancer progression and metastasis.

Thromboxane A2 modulates cisplatin-induced apoptosis through a Siva1-dependent mechanism

Thromboxane A(2) (TXA(2)) is an important lipid mediator whose function in apoptosis is the subject of conflicting reports. Here, a yeast two-hybrid screen for proteins that interact with the C-terminus of the TXA(2) receptor (TP) identified Siva1 as a new TP-interacting protein. Contradictory evidence suggests pro- and anti-apoptotic roles for Siva1. We show that a cisplatin treatment induces TXA(2) synthesis in HeLa cells. We demonstrate that endogenous TP stimulation promotes cisplatin-induced apoptosis of HeLa cells and that such modulation requires the expression of Siva1, as evidenced by inhibiting its endogenous expression using siRNAs. We reveal that, upon stimulation of TP, degradation of Siva1 is impeded, resulting in an accumulation of the protein, which translocates from the nucleus to the cytosol. Translocation of Siva1 correlates with its reduced interaction with Mdm2 (an inhibitor of p53 signalling), as well as with its increased interaction with TRAF2 and XIAP (known to enhance pro-apoptotic signalling). Our data provide a model that reconciles the pro- and anti-apoptotic roles that were reported for Siva1 and identify a new mechanism for promoting apoptosis by G protein-coupled receptors. Our findings may have implications in the use of cyclo-oxygenase inhibitors during cisplatin chemotherapy and might provide a target to reduce cisplatin toxicity on non-cancerous tissues.

Upregulation of thromboxane synthase mediates visfatin-induced interleukin-8 expression and angiogenic activity in endothelial cells

Thromboxane synthase (TXAS) is an enzyme that catalyzes the synthesis of thromboxane A(2) (TXA(2)). Overexpression of TXAS is associated with a variety of vascular diseases. Recently, we reported that visfatin, a novel adipokine, exhibits angiogenic actions. In this study, we showed that visfatin increased mRNA and protein levels of TXAS and stimulated TXA(2) biosynthesis in vascular endothelial cells. In addition, visfatin induced the expression and secretion of interleukin-8 (IL-8), which is blocked by a TXAS inhibitor and by the transfection of siRNA specific for TXAS. Furthermore, the inhibition of TXAS activity and blockade of the IL-8 receptor attenuated visfatin-induced endothelial angiogenesis. Together, these results showed that visfatin promoted IL-8 production by upregulation of TXAS, leading to angiogenic activation in endothelial cells.

Inhibition of thromboxane synthase activity improves glioblastoma response to alkylation chemotherapy

Thromboxane synthase (TXSA), an enzyme of the arachidonic acid metabolism, is upregulated in human glial tumors and is involved in glioma progression. Here, we analyzed the in vitro and in vivo effects of pharmacological inhibition of TXSA activity on human glioblastoma cells. Furegrelate, a specific inhibitor of TXSA, significantly inhibited tumor growth in an orthotopic glioblastoma model by inducing proapoptotic, antiproliferative, and antiangiogenic effects. Inhibition of TXSA induced a proapoptotic disposition of glioma cells and increased the sensitivity to the chemotherapeutic agent 1,3-bis(2-chloroethyl)-1-nitrosourea, significantly prolonging the survival time of intracerebral glioma-bearing mice. Our data demonstrate that the targeted inhibition of TXSA activity improves the efficiency of conventional alkylation chemotherapy in vivo. Our study supports the role of TXSA activity for the progression of malignant glioma and the potential utility of its therapeutic modulation for glioma treatment.

Examination of thromboxane synthase as a prognostic factor and therapeutic target in non-small cell lung cancer

Background

Thromboxane synthase (TXS) metabolises prostaglandin H2 into thromboxanes, which are biologically active on cancer cells. TXS over-expression has been reported in a range of cancers, and associated with a poor prognosis. TXS inhibition induces cell death in-vitro, providing a rationale for therapeutic intervention. We aimed to determine the expression profile of TXS in NSCLC and if it is prognostic and/or a survival factor in the disease.

Methods

TXS expression was examined in human NSCLC and matched controls by western analysis and IHC. TXS metabolite (TXB₂) levels were measured by EIA. A 204-patient NSCLC TMA was stained for COX-2 and downstream TXS expression. TXS tissue expression was correlated with clinical parameters, including overall survival. Cell proliferation/survival and invasion was examined in NSCLC cells following both selective TXS inhibition and stable TXS over-expression.

Results

TXS was over-expressed in human NSCLC samples, relative to matched normal controls. TXS and TXB₂ levels were increased in protein (p < 0.05) and plasma (p < 0.01) NSCLC samples respectively. TXS tissue expression was higher in adenocarcinoma (p < 0.001) and female patients (p < 0.05). No significant correlation with patient survival was observed. Selective TXS inhibition significantly reduced tumour cell growth and increased apoptosis, while TXS over-expression stimulated cell proliferation and invasiveness, and was protective against apoptosis.

Conclusion

TXS is over-expressed in NSCLC, particularly in the adenocarcinoma subtype. Inhibition of this enzyme inhibits proliferation and induces apoptosis. Targeting thromboxane synthase alone, or in combination with conventional chemotherapy is a potential therapeutic strategy for NSCLC.

Cigarette smoking, cyclooxygenase-2 pathway and cancer

Cigarette smoking is a major cause of mortality and morbidity worldwide. Cyclooxygenase (COX) and its derived prostanoids, mainly including prostaglandin E2 (PGE2), thromboxane A2 (TxA2) and prostacyclin (PGI2), have well-known roles in cardiovascular disease and cancer, both of which are associated with cigarette smoking. This article is focused on the role of COX-2 pathway in smoke-related pathologies and cancer. Cigarette smoke exposure can induce COX-2 expression and activity, increase PGE2 and TxA2 release, and lead to an imbalance in PGI2 and TxA2 production in favor of the latter. It exerts pro-inflammatory effects in a PGE2-dependent manner, which contributes to carcinogenesis and tumor progression. TxA2 mediates other diverse biologic effects of cigarette smoking, such as platelet activation, cell contraction and angiogenesis, which may facilitate tumor growth and metastasis in smokers. Among cigarette smoke components, nicotine and its derived nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are the most potent carcinogens. COX-2 and PGE2 have been shown to play a pivotal role in many cancers associated with cigarette smoking, including cancers of lung, gastric and bladder, while the information for the role of TxA2 and PGI2 in smoke-associated cancers is limited. Recent findings from our group have revealed how NNK influences the TxA2 to promote the tumor growth. Better understanding in the above areas may help to generate new therapeutic protocols or to optimize the existing treatment strategy.

4-Methylnitrosamino-1-3-pyridyl-1-butanone (NNK) promotes lung cancer cell survival by stimulating thromboxane A2 and its receptor

The role of thromboxane A(2) (TxA(2)) in smoking-associated lung cancer is poorly understood. This study was conducted to study the role of TxA(2) in smoking carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-promoted cell survival and growth in human lung cancer cells. We found that NNK increased TxA(2) synthase (TxAS) expression and thromboxane B(2) (TxB(2)) generation in cultured lung cancer cells, the result of which was supported by the increased level of TxAS in lung cancer tissues of smokers. Both TxAS-specific inhibitor furegrelate and TxA(2) receptor antagonist SQ29548 completely blocked NNK-mediated cell survival and growth via inducting apoptosis. TxA(2) receptor agonist U46619 reconstituted a near-full survival and growth response to NNK when TxAS was inhibited, affirming the role of TxA(2) receptor in NNK-mediated cell survival and growth. Suppression of cyclic adenosine monophosphate response element binding protein (CREB) activity by its small interference RNA blocked the effect of NNK. Phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) also had a positive role. Altogether, our results have revealed that NNK stimulates TxA(2) synthesis and activates its receptor in lung cancer cells. The increased TxA(2) may then activate CREB through PI3K/Akt and extracellular ERK pathways, thereby contributing to the NNK-promoted survival and growth of lung cancer cells.

Integrative meta-analysis of differential gene expression in acute myeloid leukemia

Background

Acute myeloid leukemia (AML) is a heterogeneous disease with an overall poor prognosis. Gene expression profiling studies of patients with AML has provided key insights into disease pathogenesis while exposing potential diagnostic and prognostic markers and therapeutic targets. A systematic comparison of the large body of gene expression profiling studies in AML has the potential to test the extensibility of conclusions based on single studies and provide further insights into AML.

Methodology/Principal Findings

In this study, we systematically compared 25 published reports of gene expression profiling in AML. There were a total of 4,918 reported genes of which one third were reported in more than one study. We found that only a minority of reported prognostically-associated genes (9.6%) were replicated in at least one other study. In a combined analysis, we comprehensively identified both gene sets and functional gene categories and pathways that exhibited significant differential regulation in distinct prognostic categories, including many previously unreported associations.

Conclusions/Significance

We developed a novel approach for granular, cross-study analysis of gene-by-gene data and their relationships with established prognostic features and patient outcome. We identified many robust novel prognostic molecular features in AML that were undetected in prior studies, and which provide insights into AML pathogenesis with potential diagnostic, prognostic, and therapeutic implications. Our database and integrative analysis are available online (http://gat.stamlab.org).

Hepatic stellate cells promote hepatocyte engraftment in rat liver after prostaglandin-endoperoxide synthase inhibition

BACKGROUND & AIMS

Hepatic inflammation occurs immediately after cells are transplanted to the liver, but the mechanisms that underlie this process are not fully defined. We examined cyclooxygenase pathways that mediate hepatic inflammation through synthesis of prostaglandins, prostacyclins, thromboxanes, and other prostanoids following transplantation of hepatocytes.

METHODS

We transplanted F344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient F344 rats. Changes in cyclooxygenase pathways were analyzed, and specific pathways were blocked pharmacologically; the effects on cell engraftment and native liver cells were determined.

RESULTS

Transplantation of hepatocytes induced hepatic expression of prostaglandin-endoperoxide synthases 1 and 2, which catalyze production of prostaglandin H2, as well as the downstream factor thromboxane synthase, which produces thromboxane A2 (a regulator of vascular and platelet responses in inflammation). Transplanted hepatocytes were in proximity with liver cells that expressed prostaglandin-endoperoxide synthases. The number of engrafted hepatocytes increased in rats given naproxen or celecoxib before transplantation but not in rats given furegrelate (an inhibitor of thromboxane synthase) or clopodigrel (an antiplatelet drug). Naproxen and celecoxib did not prevent hepatic ischemia or activation of neutrophils, Kupffer cells, or inflammatory cytokines, but they did induce hepatic stellate cells to express cytoprotective genes, vascular endothelial growth factor and hepatocyte growth factor, and matrix-type metalloproteinases and tissue inhibitor of metalloproteinase-1, which regulate hepatic remodeling.

CONCLUSIONS

Activation of cyclooxygenase pathways interferes with engraftment of transplanted hepatocytes in the liver. Pharmacologic blockade of prostaglandin-endoperoxide synthases stimulated hepatic stellate cells and improved cell engraftment.

Notch-1 regulates Akt signaling pathway and the expression of cell cycle regulatory proteins cyclin D1, CDK2 and p21 in T-ALL cell lines

Gain-of-function mutations in Notch-1 are common in T-cell lymphoblastic leukemia (T-ALL), making this receptor a promising target for drugs such as gamma-secretase inhibitors (GSIs). However, GSIs seem to be active in only a small fraction of T-ALL cell lines with constitutive Notch-1 activity and the downstream response of Notch signaling is only partially understood. To further investigate the molecular mechanisms underlying proliferation suppression and apoptosis and explore effective downstream target genes, we used RNA interference (RNAi) technology to down-regulate the expression of Notch-1 in GSIs-resistant T-ALL cell lines. Results showed that down-regulation of Notch-1 by transfection of a small interfering RNA (siRNA) could cause SupT1 cells proliferation inhibition by inducing G(0)/G(1) cell cycle arrest and apoptosis. The proliferation inhibitory and apoptotic effects resulting from down-regulation of Notch-1 may be mediated through regulating the expression of cell cycle regulatory proteins cyclin D1, CDK2 and p21 and the activity of Akt signaling. In addition, our results demonstrated that down-regulation of Notch-1 signaling could sensitize SupT1 cells to adriamycin. Taken together, cell cycle regulatory proteins and Akt signaling may be attractive targets in T-ALL.