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SummaryLaboratory diagnosis of lupus anticoagulant (LA) is based on prolongation in at least one coagulation assay (diluted Russell’s viper venom time – dRVVT or activated partial thromboplastin time – aPTT), which normalises after addition of phospholipids. Both assays may be influenced by anticoagulants and therefore LA should not be tested during warfarin or heparin treatment. It has been shown (primarily in vitro) that direct oral anticoagulants (DOACs – dabigatran [DAB], rivaroxaban [RIV] and apixaban [API]) may also influence LA testing. We tested the effects of DOACs on assays routinely used for the diagnosis of LA in patients treated with these drugs in a real-life setting. Plasma from patients with atrial fibrillation treated with DAB (n=30), RIV (n=20) and API (n=17) and not known to have LA were tested using dRVVT (LA-screen and LA-confirm, Life Diagnostics) and aPTT (PTT-LA, Diagnostica Stago and aPTT Actin FS, Siemens Healthcare Diagnostics) assays. According to the diagnostics algorithm, dRVVT and aPTT ratios of 1.4 positive, while if the ratios were 1.2–1.4 LA could not be ruled out. Plasma concentrations varied between 8–172 µg/l for DAB, 8–437 µg/l for RIV and 36–178 µg/l for API. LA diagnosis was negative in only eight (27 %) plasma samples from patients treated with DAB, and in five (25 %) and four samples (24 %) from patients treated with RIV and API, respectively. LA Positivity (dRVVT and aPTT ratios >1.4) was found in 5 cases (17 %) among patients treated with DAB, in 10 cases (50 %) treated with RIV and in 7 cases (41 %) treated with API. A concentration-dependent effect of DOACs on dRVVT-based parameters was observed, particularly as regards DAB. At lower concentrations, RIV and API had only minor effects on the confirmatory tests (below 100 µg/l and 70 µg/l, respectively). Our results suggest that a risk of overestimation of LA detection is present in samples from patients treated with DOACs. Therefore, LA testing should not be performed during treatment with DOACs. Prolongation in confirmatory assays may be helpful for the recognition of false positivity, especially as regards DAB.

Embryonic neural tumors are responsible for a disproportionate number of cancer deaths in children. Although dramatic improvements in survival for pediatric malignancy has been achieved in previous years advancements seem to be slowing down. For the development of new enhanced therapy and an increased understanding of the disease, pre-clinical models better capturing the neoplastic niche are essential. Tumors of early childhood present in this respect a particular challenge. Here, we explore how components of the embryonic process in stem‑cell induced mature teratoma can function as an experimental in vivo microenvironment instigating the growth of injected childhood neuroblastoma (NB) cell lines. Three human NB cell lines, IMR-32, Kelly and SK-N-BE(2), were injected into mature pluripotent stem cell‑induced teratoma (PSCT) and compared to xenografts of the same cell lines. Proliferative NB cells from all lines were readily detected in both models with a typical histology of a poorly differentiated NB tumor with a variable amount of fibrovascular stroma. Uniquely in the PSCT microenvironment, NB cells were found integrated in a non‑random fashion. Neuroblastoma cells were never observed in areas with well-differentiated somatic tissue i.e. bone, muscle, gut or areas of other easily identifiable tissue types. Instead, the three cell lines all showed initial growth exclusively occurring in the embryonic loose mesenchymal stroma, resulting in a histology recapitulating NB native presentation in vivo. Whether this reflects the 'open' nature of loose mesenchyme more easily giving space to new cells compared to other more dense tissues, the rigidity of matrix providing physical cues modulating NB characteristics, or if embryonic loose mesenchyme may supply developmental cues that attracted or promoted the integration of NB, remains to be tested. We tentatively hypothesize that mature PSCT provide an embryonic niche well suited for in vivo studies on NB.

Tumor-associated inflammation is a driving force in several adult cancers and intake of low-dose aspirin has proven to reduce cancer incidence. Little is known about tumor-associated inflammation in pediatric neoplasms and no in vivo data exists on the effectiveness of low-dose aspirin on established tumors. The present study employs the transgenic TH-MYCN mouse model for neuroblastoma (NB) to evaluate inflammatory patterns paralleling tumor growth in vivo and low-dose aspirin as a therapeutic option for high-risk NB. Spontaneously arising abdominal tumors were monitored for tumor-associated inflammation ex vivo at various stages of disease and homozygous mice received daily low-dose aspirin (10 mg/kg) using oral ga vage or no treatment, from 4.5 to 6 weeks of age. Using flow cytometry, a transition from an adaptive immune response predominated by CD8 + T cell in early neoplastic lesions, towards enrichment in immature cells of the innate immune system, including myeloid-derived suppressor cells, dendritic cells and tumor-associated macrophages, was detected during tumor progression. An M1 to M2 transition of tumor-associated macrophages was demonstrated, paralleled by a deterioration of dendritic cell status. Treatment with low-dose aspirin to mice homozygous for the TH-MYCN transgene significantly reduced the tumor burden (P < 0.01), the presence of tumorassociated cells of the innate immune system (P < 0.01), as well as the intratumoral expression of transforming growth factor-β, thromboxane A2 (P < 0.05) and prostaglandin D2 (P < 0.01). In conclusion, tumor-associated inflammation appears as a potential therapeutic target in NB and low-dose aspirin reduces tumor burden in the TH-MYCN transgenic mouse model of NB, hence warranting further studies on aspirin in high-risk NB.

The metabolism of arachidonic acid by the cyclooxygenase (COX) or lipoxygenase (LO) pathways generates eicosanoids that have been implicated in the pathogenesis of a variety of human diseases, including cancer. In this study, we examined the expression and significance of components within the 5-LO pathway in human neuroblastoma, an embryonal tumor of the sympathetic nervous system. High expression of 5-LO, 5-LO-activating protein (FLAP), leukotriene A(4) hydrolase, leukotriene C(4) synthase, and leukotriene receptors was detected in a majority of primary neuroblastoma tumors and all cell lines investigated. Expression of 5-LO and FLAP was evident in tumor cells but not in nonmalignant adrenal medulla where neuroblastomas typically arise. Moreover, neuroblastoma cells produce leukotrienes, and stimulation of neuroblastoma cells with leukotrienes increased neuroblastoma cell viability. Inhibitors of 5-LO (AA-861), FLAP (MK-886), or the leukotriene receptor antagonist montelukast inhibited neuroblastoma cell growth by induction of G(1)-cell cycle arrest and apoptosis. Similarly, specific 5-LO and leukotriene receptor silencing by small interfering RNA decreased neuroblastoma cell growth. These findings provide new insights into the pathobiology of neuroblastoma, and the use of leukotriene pathway inhibitors as a novel adjuvant therapy for children with neuroblastoma warrants further consideration.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumor necrosis factor (TNF) family of cytokines, acts on responsive cells via binding to a cell surface receptor called Fn14. TWEAK binding to an Fn14 receptor or constitutive Fn14 overexpression has been shown to activate nuclear factor κB signaling which is important in tumorigenesis and cancer therapy resistance. In the present study, we demonstrate that TWEAK and Fn14 are expressed in neuroblastoma cell lines and primary tumors, and both are observed at increased levels in high-stage tumors. The treatment of neuroblastoma cell lines with recombinant TWEAK in vitro causes increased survival, and this effect is partially due to the activation of NF-κB signaling. Moreover, TWEAK induces the release of matrix metalloprotease-9 (MMP-9) in neuroblastoma cells, suggesting that TWEAK may play a role in the invasive phase of neuroblastoma tumorigenesis. TWEAK-induced cell survival was significantly reduced by silencing the TWEAK and Fn14 gene functions by siRNA. Thus, the expression of TWEAK and Fn14 in neuroblastoma suggests that TWEAK functions as an important regulator of primary neuroblastoma growth, invasion and survival and that the therapeutic intervention of the TWEAK/Fn14 pathway may be an important clinical strategy in neuroblastoma therapy.

Background Prostaglandin E(2) (PGE(2)) is an important mediator in tumor-promoting inflammation. High expression of cyclooxygenase-2 (COX-2) has been detected in the embryonic childhood tumor neuroblastoma, and treatment with COX inhibitors significantly reduces tumor growth. Here, we have investigated the significance of a high COX-2 expression in neuroblastoma by analysis of PGE(2) production, the expression pattern and localization of PGE(2) receptors and intracellular signal transduction pathways activated by PGE(2). Principal findings A high expression of the PGE(2) receptors, EP1, EP2, EP3 and EP4 in primary neuroblastomas, independent of biological and clinical characteristics, was detected using immunohistochemistry. In addition, mRNA and protein corresponding to each of the receptors were detected in neuroblastoma cell lines. Immunofluorescent staining revealed localization of the receptors to the cellular membrane, in the cytoplasm, and in the nuclear compartment. Neuroblastoma cells produced PGE(2) and stimulation of serum-starved neuroblastoma cells with PGE(2) increased the intracellular concentration of calcium and cyclic AMP with subsequent phosphorylation of Akt. Addition of 16,16-dimethyl PGE(2) (dmPGE(2)) increased cell viability in a time, dose- and cell line-dependent manner. Treatment of neuroblastoma cells with a COX-2 inhibitor resulted in a diminished cell growth and viability that was reversed by the addition of dmPGE(2). Similarly, PGE(2) receptor antagonists caused a decrease in neuroblastoma cell viability in a dose-dependent manner. Conclusions These findings demonstrate that PGE(2) acts as an autocrine and/or paracrine survival factor for neuroblastoma cells. Hence, specific targeting of PGE(2) signaling provides a novel strategy for the treatment of childhood neuroblastoma through the inhibition of important mediators of tumor-promoting inflammation.

There is strong evidence for a role of prostaglandin E 2 (PGE 2 ) in cancer cell proliferation and tumor development. In PGE 2 biosynthesis, cyclooxygenases (COX-1/COX-2) convert arachidonic acid to PGH 2 , which can be isomerized to PGE 2 by microsomal PGE-synthase-1 (MPGES-1). The human prostate cancer cell line DU145 expressed high amounts of MPGES-1 in a constitutive manner. MPGES-1 expression also was detectable in human prostate cancer tissues, where it appeared more abundant compared with benign hyperplasia. By using shRNA, we established stable and practically complete knockdown of MPGES-1, both in DU145 cells with high constitutive expression and in the non-small cell lung cancer cell line A549, where MPGES-1 is inducible. For microsomes prepared from knockdown clones, conversion of PGH 2 to PGE 2 was reduced by 85–90%. This resulted in clear phenotypic changes: MPGES-1 knockdown conferred decreased clonogenic capacity and slower growth of xenograft tumors (with disintegrated tissue structure) in nude mice. For DU145 cells, MPGES-1 knockdown gave increased apoptosis in response to genotoxic stress (adriamycin), which could be rescued by exogenous PGE 2 . The results suggest that MPGES-1 is an alternative therapeutic target in cancer cells expressing this enzyme.

Background: Neuroblastoma (NB) cells are enriched in the omega-6 fatty acid arachidonic acid, the substrate for the cyclooxygenase (COX) enzymes and prostaglandin biosynthesis. The inducible isoform, COX-2 is overexpressed in NB and NB cells produce prostaglandin E2 (PGE2) that acts as an autocrine and/or paracrine survival and proliferation factor. Downstream of the COX enzymes, specific synthases are responsible for the production of the respective prostaglandins. Microsomal prostaglandin E2 synthase-1 (mPGES-1) specifically converts PGH2 to PGE2 and is thought to primarily couple to COX-2. The aim of this study was to investigate if inhibition of mPGES-1 could represent an alternative therapeutic approach to COX- inhibition in NB. Methods: Western blot and immunohistochemistry were used for protein detection. Cell viability of seven NB cell-lines treated with the mPGES-1 inhibitor CAY1052 was determined by MTT-assay. Stable mPGES-1 knockdown SK-N-BE2 clones were established using shRNA and the clonogenic capacity was analysed by clonogenic assay. To study the in vivo effect of COX inhibition, four week old homozygous TH-MYCN mice were treated with 10mg/L diclofenac for two weeks. Ex vivo analyses of COX-metabolites in tumors were performed by LC-MS/MS. Results: Expression of mPGES-1 in human NB tumors and in NB cell lines could be detected. Inhibition of mPGES-1 reduced NB cell growth in vitro and knockdown of mPGES-1 significantly reduced the clonogenic capacity. Expression of COX-1, COX-2 and mPGES-1 in TH-MYCN tumors could be detected and treatment with the dual COX-inhibitor diclofenac significantly reduced tumour weight, compared to untreated animals. Ex vivo analysis of tumor tissues from treated animals revealed a significantly decreased level of COX metabolites compared to controls. The expression of mPGES-1was not affected by the treatment. Furthermore, cells staining positive for cleaved caspase-3 were more prevalent in treated tumors indicating apoptosis Induction. Conclusion: We found that mPGES-1 is expressed in NB, with a potential role for PGE2 synthesis and tumor growth. mPGES-1 represents an alternative therapeutic target for inhibiting NB growth through specific PGE2 inhibition and the TH-MYCN model is well suited for in vivo studies with this purpose. Citation Format: Anna Kock, Agnes Rasmuson, Marina Korotkova, Helena Idborg, John Inge Johnsen, Per-Johan Jakobsson, Per Kogner. Microsomal prostaglandin E2 synthase-1 may provide a novel specific therapeutic target in neuroblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2746. doi:10.1158/1538-7445.AM2013-2746

Neuroblastoma (NB) is an embryonic tumor of the sympathetic nervous system and it is the most common extracranial tumor affecting young children. Despite a very intensive treatment regimen high-risk neuroblastoma patients still have a poor prognosis. Neuroblastoma cells are enriched in arachidonic acid, over express COX-2 and produce prostaglandin E2 (PGE2) that acts as an autocrine or paracrine survival and proliferation factor by induction of Akt signaling. Downstream of the COX enzymes, specific synthases converts PGH2 into the different prostaglandins. Microsomal prostaglandin E2 synthase-1 (mPGES-1) specifically converts PGH2 to PGE2 and is thought to primarily couple to COX-2. The aim of this study is to investigate if inhibition of mPGES-1 could represent an alternative therapeutic approach to COX- inhibition in neuroblastoma. We could detect expression of mPGES-1 in a panel of seven human neuroblastoma cell lines. Stable knock down of mPGES-1 expression using shRNA significantly reduced the clonogenic capacity and treatment with the mPGES-1 inhibitor CAY1052 inhibited neuroblastoma cell growth in vitro. By immunohistochemistry and western blot we could also detect expression of COX-1, COX-2 and mPGES-1 in tumors from the transgenic TH-MYCN mouse model of neuroblastoma. Treatment of homozygous TH-MYCN mice with 10 mg/L diclofenac for two weeks, starting at the age of four weeks, significantly reduced tumour weight compared to untreated animals. Ex vivo analysis with LC-MS/MS of tumor tissues from diclofenac treated animals revealed a significant decreased level of COX metabolites compared to control. The expression of mPGES-1was not affected by the treatment. Furthermore the number of cells staining positive for cleaved caspase-3 were higher in the treated tumors indicating induced apoptosis. In conclusion, our results show that mPGES-1 is expressed in neuroblastoma therefore mPGES-1 might represent an alternative way of reducing NB growth through specific PGE2 inhibition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1420. doi:1538-7445.AM2012-1420

ABSTRACT Tumor-associated inflammation is a driving force in several adult cancers, and low doses of non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin have proven to reduce cancer incidence. Little is known about tumor-associated inflammation in pediatric neoplasms and no in vivo data exists on the effectiveness of low-dose aspirin on established tumors. Our study evaluates inflammatory patterns paralleling neuroblastoma (NB) tumor growth in vivo and low-dose aspirin as a therapeutic option for high-risk NB. Using the TH-MYCN mouse model of NB, this study demonstrates the presence and progression of tumor-associated inflammation during NB tumor growth. Ex vivo analysis of tumors revealed a transition from an adaptive immune response predominated by CD8+ T-cells in neoplastic lesions from 5 week old homozygous mice, towards an enrichment in immature cells of the innate immune system, including myeloid-derived suppressor cells (MDSCs), immature dendritic cells (DCs) and M2 tumor-associated macrophages (TAMs) during tumor progression. An ongoing M1 to M2 transition of TAMs was demonstrated, which was paralleled by a gradual deterioration of DC status. Ten days of consecutive anti-inflammatory treatment with low-dose aspirin significantly reduced tumor burden (p Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-496. doi:1538-7445.AM2012-LB-496