Bjørn Helge Haug

Tumour-suppressor microRNAs let-7 and mir-101 target the proto-oncogene MYCN and inhibit cell proliferation in MYCN-amplified neuroblastoma

Background:MicroRNAs (miRNAs) regulate expression of many cancer-related genes through posttranscriptional repression of their mRNAs. In this study we investigate the proto-oncogene MYCN as a target for miRNA regulation.Methods:A luciferase reporter assay was used to investigate software-predicted miRNA target sites in the 3′-untranslated region (3′UTR) of MYCN. The miRNAs were overexpressed in cell lines by transfection of miRNA mimics or miRNA-expressing plasmids. Mutation of the target sites was used to validate MYCN 3′UTR as a direct target of several miRNAs. To measure miRNA-mediated suppression of endogenous N-myc protein, inhibition of proliferation and inhibition of clonogenic growth, miRNAs were overexpressed in a MYCN-amplified neuroblastoma cell line.Results:The results from this study show that MYCN is targeted by several miRNAs. In addition to the previously shown mir-34a/c, we experimentally validate mir-449, mir-19a/b, mir-29a/b/c, mir-101 and let-7e/mir-202 as direct MYCN-targeting miRNAs. These miRNAs were able to suppress endogenous N-myc protein in a MYCN-amplified neuroblastoma cell line. The let-7e and mir-202 were strong negative regulators of MYCN expression. The mir-101 and the let-7 family miRNAs let-7e and mir-202 inhibited proliferation and clonogenic growth when overexpressed in Kelly cells.Conclusion:The tumour-suppressor miRNAs let-7 and mir-101 target MYCN and inhibit proliferation and clonogenic growth of MYCN-amplified neuroblastoma cells.

Conditional expression of retrovirally delivered anti-MYCN shRNA as an in vitro model system to study neuronal differentiation in MYCN-amplified neuroblastoma

BackgroundNeuroblastoma is a childhood cancer derived from immature cells of the sympathetic nervous system. The disease is clinically heterogeneous, ranging from neuronal differentiated benign ganglioneuromas to aggressive metastatic tumours with poor prognosis. Amplification of the MYCN oncogene is a well established poor prognostic factor found in up to 40% of high risk neuroblastomas.Using neuroblastoma cell lines to study neuronal differentiation in vitro is now well established. Several protocols, including exposure to various agents and growth factors, will differentiate neuroblastoma cell lines into neuron-like cells. These cells are characterized by a neuronal morphology with long extensively branched neurites and expression of several neurospecific markers.ResultsIn this study we use retrovirally delivered inducible short-hairpin RNA (shRNA) modules to knock down MYCN expression in MYCN-amplified (MNA) neuroblastoma cell lines. By addition of the inducer doxycycline, we show that the Kelly and SK-N-BE(2) neuroblastoma cell lines efficiently differentiate into neuron-like cells with an extensive network of neurites. These cells are further characterized by increased expression of the neuronal differentiation markers NFL and GAP43. In addition, we show that induced expression of retrovirally delivered anti-MYCN shRNA inhibits cell proliferation by increasing the fraction of MNA neuroblastoma cells in the G1 phase of the cell cycle and that the clonogenic growth potential of these cells was also dramatically reduced.ConclusionWe have developed an efficient MYCN-knockdown in vitro model system to study neuronal differentiation in MNA neuroblastomas.

Pacemaker implantation in small hospitals: complication rates comparable to larger centres.

Aims Some countries have a demography that makes it necessary to maintain relatively small pacemaker centres. We wanted to assess the quality of pacemaker surgery in two such hospitals. Methods and results Through patient records we gathered information on ∼535 consecutive primary pacemaker implantations in two small pacemaker centres with 30 and 80 annual operations, respectively. All patients were followed for 3 years. All complications documented in the patient records were registered. Furthermore, we performed a non-systematic literature search comparing our data with reports from major centres published over the last 10 years.We found 72 complications in 64 (12.0%) of the patients, the most common being bleeding, lead failure, and pneumothorax. If minor bleedings without any consequences for the patients are excluded, the number of complications was 46 in 40 patients (7.5%). We had to reoperate on 5.2% of the patients. There was no statistically significant difference in complication rates between the two hospitals. Education candidates generated statistically significant more complications than experienced doctors (13.7 vs. 7.1%, P < 0.05). Conclusion There are no generally accepted norms of complication rates in pacemaker surgery. However, we found no indications that our centres have a rate of complications that is unacceptably high.

Inhibition of mir-21, which is up-regulated during MYCN knockdown-mediated differentiation, does not prevent differentiation of neuroblastoma cells

BACKGROUND Neuroblastoma is a malignant childhood tumour arising from precursor cells of the sympathetic nervous system. Genomic amplification of the MYCN oncogene is associated with dismal prognosis. For this group of high-risk tumours, the induction of tumour cell differentiation is part of current treatment protocols. MicroRNAs (miRNAs) are small non-coding RNA molecules that effectively reduce the translation of target mRNAs. MiRNAs play an important role in cell proliferation, apoptosis, differentiation and cancer. In this study, we investigated the role of N-myc on miRNA expression in MYCN-amplified neuroblastoma. We performed a miRNA profiling study on SK-N-BE (2) cells, and determined differentially expressed miRNAs during differentiation initiated by MYCN knockdown, using anti-MYCN short-hairpin RNA (shRNA) technology. RESULTS Microarray analyses revealed 23 miRNAs differentially expressed during the MYCN knockdown-mediated neuronal differentiation of MNA neuroblastoma cells. The expression changes were bidirectional, with 11 and 12 miRNAs being up- and down-regulated, respectively. Among the down-regulated miRNAs, we found several members of the mir-17 family of miRNAs. Mir-21, an established oncomir in a variety of cancer types, became strongly up-regulated upon MYCN knockdown and the subsequent differentiation. Neither overexpression of mir-21 in the high-MYCN neuroblastoma cells, nor repression of increased mir-21 levels during MYCN knockdown-mediated differentiation had any significant effects on cell differentiation or proliferation. CONCLUSIONS We describe a subset of miRNAs that were altered during the N-myc deprived differentiation of MYCN-amplified neuroblastoma cells. In this context, N-myc acts as both an activator and suppressor of miRNA expression. Mir-21 was up-regulated during cell differentiation, but inhibition of mir-21 did not prevent this process. We were unable to establish a role for this miRNA during differentiation and proliferation of the two neuroblastoma cell lines used in this study.

Pacemaker implantation in patients with persistent left superior vena cava

Implantation of a permanent pacemaker system is most commonly performed by puncturing the left subclavian vein and introducing the pacemaker lead(s) through the superior caval vein to the right atrium and/or ventricle. Occasionally, a persistent left superior caval vein is encountered peroperatively, complicating the procedure. This article describes three such patients and provides a review of the literature regarding one of the most common anomalies of the thoracic vessels.

Planar cell polarity gene expression correlates with tumor cell viability and prognostic outcome in neuroblastoma

BackgroundThe non-canonical Wnt/Planar cell polarity (PCP) signaling pathway is a major player in cell migration during embryonal development and has recently been implicated in tumorigenesis.MethodsTransfections with cDNA plasmids or siRNA were used to increase and suppress Prickle1 and Vangl2 expression in neuroblastoma cells and in non-tumorigenic cells. Cell viability was measured by trypan blue exclusion and protein expression was determined with western blotting. Transcriptional activity was studied with luciferase reporter assay and mRNA expression with real-time RT-PCR. Immunofluorescence stainings were used to study the effects of Vangl2 overexpression in non-tumorigenic embryonic cells. Statistical significance was tested with t-test or one-way ANOVA.ResultsHere we show that high expression of the PCP core genes Prickle1 and Vangl2 is associated with low-risk neuroblastoma, suppression of neuroblastoma cell growth and decreased Wnt/β-catenin signaling. Inhibition of Rho-associated kinases (ROCKs) that are important in mediating non-canonical Wnt signaling resulted in increased expression of Prickle1 and inhibition of β-catenin activity in neuroblastoma cells. In contrast, overexpression of Vangl2 in MYC immortalized neural stem cells induced accumulation of active β-catenin and decreased the neural differentiation marker Tuj1. Similarly, genetically modified mice with forced overexpression of Vangl2 in nestin-positive cells showed decreased Tuj1 differentiation marker during embryonal development.ConclusionsOur experimental data demonstrate that high expression of Prickle1 and Vangl2 reduce the growth of neuroblastoma cells and indicate different roles of PCP proteins in tumorigenic cells compared to normal cells. These results suggest that the activity of the non-canonical Wnt/PCP signaling pathway is important for neuroblastoma development and that manipulation of the Wnt/PCP pathway provides a possible therapy for neuroblastoma.

Abstract 3266: Inhibition of Rho-associated kinase 2 suppresses MYCN expression and induces differentiation of neuroblastoma

Background: Neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system that originates from cells within the neural crest. The non-canonical Wnt/planar cell polarity (PCP) signaling pathway regulates cytoskeletal organization, migration and maturation of neural crest cells during neuritogenesis. We and others have shown that high-risk neuroblastoma exhibit frequent mutations of genes controlling the activity of the Wnt/PCP signaling cascade leading to inhibition of Rac and activation of Rho resulting in downstream activation of the serine/threonine kinases Rho-Associated Coiled-Coil Containing Protein Kinases (ROCK1 and ROCK2) Methods: We performed whole-exome sequencing for 33 neuroblastoma samples of all clinical subgroups to search for mutations and genetic aberrations. Cytotoxic activity of ROCK inhibitors was studied in cell viability assays. Morphology and invasion were studied with microscopy. The molecular mechanisms were characterized using cell- and molecular biology techniques. In vivo studies (xenografts and the transgenic mouse model TH-MYCN) in mice were carried out to validate the therapeutic effects and toxicity. Results: Exome sequencing detected frequent mutations and gene aberrations in genes controlling the activity of PCP signalling. Analysis ofgene signatures and immunohistochemistry showed that high expression of ROCK1 and ROCK2 correlated with poor patient survival. Several mediators of Rho/Rac were differentially expressed in cell lines and patient samples. Using compounds blocking ROCK1 and ROCK2 activity revealed that the ROCK2 inhibitor HA-1077 effectively repressed proliferation and reduced cell viability in neuroblastoma. HA-1077 inhibited migration and induced differentiation through inhibition of neural outgrowth and inhibited MYCN protein expression, effects that were mimicked using siRNA against ROCK. Finally, HA-1077 reduced the growth of established neuroblastoma xenografts in nude mice and repressed tumor progression in a MYCN-driven mouse model of neuroblastoma (T-MYCN) Conclusions: Our results show the significance of the non-canonical/PCP signaling cascade in neuroblastoma development and progression. Furthermore, ROCK inhibition suppress the growth of neuroblastoma in preclinical models and provide a novel option for improved treatment of high-risk neuroblastoma. Citation Format: Cecilia Dyberg, David Forsberg, Susanne Fransson, Jessika Lannerholm Palm, Bjorn Helge Haug, Baldur Sveinbjornsson, Tommy Martinsson, Per Kogner, John Inge Johnsen, Malin Wickstrom. Inhibition of Rho-associated kinase 2 suppresses MYCN expression and induces differentiation of neuroblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3266. doi:10.1158/1538-7445.AM2015-3266

Abstract 3110: Targeting the Wnt/PCP signaling through ROCK: A new neuroblastoma drug target

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: The non-canonical Wnt/planar cell polarity (PCP) pathway regulates cytoskeletal organization, migration and neuritogenesis. Signaling is characterized by activation of the GTPases Rho and Rac, and the downstream Rho-associated protein kinases (ROCKs). Neuroblastoma is a malignant embryonal tumor of the sympathetic nervous systems, often with poor prognosis. The need for novel therapeutic approaches is great. Genetic analyses have revealed mutations and aberrations in the regulators Rho/Rac in neuroblastoma. The aim of this study was to characterize the Wnt/PCP signaling and the effects of ROCK inhibition in neuroblastoma. Methods: Cytotoxic activity of ROCK inhibitors was studied in cell viability assays. Morphology and invasion were studied with microscopy. The molecular mechanisms were characterized using cell- and molecular biology techniques. In vivo studies in mice were carried out to validate the therapeutic effects and toxicity. Results: Several mediators in the pathway were differentially expressed in cell lines and patient samples. Using compounds blocking ROCK1 and ROCK2 activity revealed that the ROCK2 inhibitor HA-1077 effectively repressed proliferation and reduced cell viability in neuroblastoma. Additionally, HA-1077 inhibited migration and induced differentiation through initiating neural outgrowth. Furthermore, HA-1077 reduced the growth of established neuroblastoma xenografts in nude mice. Conclusions: These results suggest that non-canonical Wnt signaling in general and ROCK in particular is a promising new therapeutic target for high-risk neuroblastoma. Citation Format: Cecilia Dyberg, David Forsberg, Panos Papachristou, Jessika Lannerholm-Palm, Bjorn Helge Haug, Baldur Sveinbjornsson, Hugo Lagercrantz, Per Kogner, John inge Johnsen, Malin Wickstrom. Targeting the Wnt/PCP signaling through ROCK: A new neuroblastoma drug target. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3110. doi:10.1158/1538-7445.AM2014-3110