NBL Cells Research Articles

TIM-3 blockade enhances ex vivo stimulated allogeneic NK cell therapy for relapsed murine neuroblastoma after hematopoietic cell transplant.

High-risk neuroblastoma (HR-NBL) is an aggressive tumor of the sympathetic nervous system with high risk of relapse and poor overall survival. Allogeneic hematopoietic cell transplant (allo-HCT) has been used previously in HR-NBL patients; however, graft-versus-host-disease (GVHD) and disease progression have limited clinical application. Ex-vivo stimulated allogeneic natural killer (NK) cells represent a potential approach to enhance the graft-versus-tumor (GVT) effect without exacerbation of GVHD but have not shown efficacy in NBL. Ex-vivo stimulated NK cells from C57BL/6NCr (B6) mice were expanded with soluble IL-15/IL-15Rα alone or with irradiated CD137L/CD54+ AgN2a-4P (15-4P) at a 1:1 ratio for 10-12 days. Allogeneic NK cells were then analyzed for activation, proliferation, cytokine production, and cytotoxicity against two murine NBL cell lines, Neuro2a and NXS2, in the absence or presence of anti-TIM-3. Lethally irradiated B6AJF1 Mice received allo-HCT from B6 donors followed by NBL challenge after 7 days to mimic tumor relapse. Select groups received anti-TIM-3 starting on day 9 for every 4 days with/without infusions of 15-4P B6 NK cells on days 14, 21, and 28. In select experiments, T cell and NK cells were selectively depleted to establish their contribution to the GVT effect. All groups were analyzed for tumor growth, GVHD and overall survival. Co-culturing NK cells with 15-4P results in 78-fold expansion with increased expression of Ki-67 and NKG2D, NKp46, TRAIL and TIM-3. 15-4P stimulated allogeneic NK cells showed enhanced cytotoxicity against NBL compared to IL-15 NK cells alone but was limited in part due to high expression of TIM-3 ligands on Neuro-2a compared to NXS2. The addition of TIM-3 blockade further enhanced NK cytotoxicity versus Neuro-2a, with enhanced 15-4P NK cell degranulation, Eomes, TRAIL and FasL expression observed. Analysis of RNA from 15-4P NK cells exposed to TIM-3 blockade showed gene expression of chemokines, NKG2D/DAP12 signaling, non-canonical NF-κb pathway and TRAIL signaling. Blockade of NKG2D, TRAIL or FasL on 15-4P NK cells abrogated cytotoxicity. In vivo, the combination of 15-4P stimulated allogeneic NK cells and TIM-3 blockade after allo-HCT resulted in prolonged survival against NBL with decreased tumor burden compared to NK cells or anti-TIM-3 alone, without inducing GVHD. Depletion of NK cells, but not T cells, abrogated the GVT effect. Allo-HCT can be a platform for treating NBL using combination ex-vivo stimulated allogeneic NK cell therapy with TIM-3 blockade to enhance the GVT effect without inducing GVHD.

Kinases Controlling Stability of the Oncogenic MYCN Protein.

We previously identified the natural products isopomiferin and pomiferin as powerful, indirect MYCN-ablating agents. In this work, we expand on their mechanism of action and find that casein kinase 2 (CK2), phosphoinositide 3-kinase (PI3K), checkpoint kinase 1 (CHK1) and serine/threonine protein kinase 38-like (STK38L), as well as STK38, work synchronously to create a field effect that maintains MYCN stability. By systematically inhibiting these kinases, we degraded MYCN and induced cell death. Additionally, we synthesized and tested several simpler and more cost-effective pomiferin analogues, which successfully emulated the compound's MYCN ablating activity. Our work identified and characterized key kinases that can be targeted to interfere with the stability of the MYCN protein in NBL cells, demonstrating the efficacy of an indirect approach to targeting "undruggable" cancer drivers.

METTL1 promotes neuroblastoma development through m7G tRNA modification and selective oncogenic gene translation

BackgroundNeuroblastoma (NBL) is the most common extra-cranial solid tumour in childhood, with prognosis ranging from spontaneous remission to high risk for rapid and fatal progression. Despite existing therapy approaches, the 5-year event-free survival (EFS) for patients with advanced NBL remains below 30%, emphasizing urgent necessary for novel therapeutic strategies. Studies have shown that epigenetic disorders play an essential role in the pathogenesis of NBL. However, the function and mechanism of N7-methylguanosine (m7G) methyltransferase in NBL remains unknown.MethodsThe expression levels of m7G tRNA methyltransferase Methyltransferase-like 1 (METTL1) were analyzed by querying the Gene Expression Omnibus (GEO) database and further confirmed by immunohistochemistry (IHC) assay. Kaplan-Meier, univariate and multivariate cox hazard analysis were performed to reveal the prognostic role of METTL1. Cell function assays were performed to evaluate how METTL1 works in proliferation, apoptosis and migration in cell lines and xenograft mouse models. The role of METTL1 on mRNA translation activity of NBL cells was measured using puromycin intake assay and polysome profiling assay. The m7G modified tRNAs were identified by tRNA reduction and cleavage sequencing (TRAC-seq). Ribosome nascent-chain complex-bound mRNA sequencing (RNC-seq) was utilized to identify the variation of gene translation efficiency (TE). Analyzed the codon frequency decoded by m7G tRNA to clarify the translation regulation and mechanism of m7G modification in NBL.ResultsThis study found that METTL1 were significantly up-regulated in advanced NBL, which acted as an independent risk factor and predicted poor prognosis. Further in NBL cell lines and BALB/c-nu female mice, we found METTL1 played a crucial role in promoting NBL progression. Furthermore, m7G profiling and translation analysis revealed downregulation of METTL1 would inhibit puromycin intake efficiency of NBL cells, indicating that METTL1 did count crucially in regulation of NBL cell translation. With all tRNAs with m7G modification identified in NBL cells, knockdown of METTL1 would significantly reduce the levels of both m7G modification and m7G tRNAs expressions. Result of RNC-seq shew there were 339 overlapped genes with impaired translation in NBL cells upon METTL1 knockdown. Further analysis revealed these genes contained higher frequency of codons decoded by m7G-modified tRNAs and were enriched in oncogenic pathways.ConclusionThis study revealed the critical role and mechanism of METTL1-mediated tRNA m7G modification in regulating NBL progression, providing new insights for developing therapeutic approaches for NBL patients.

Extending the Applicability of In Ovo and Ex Ovo Chicken Chorioallantoic Membrane Assays to Study Cytostatic Activity in Neuroblastoma Cells.

PurposeThe chick chorioallantoic membrane (CAM) assay can provide an alternative versatile, cost-effective, and ethically less controversial in vivo model for reliable screening of drugs. In the presented work, we demonstrate that CAM assay (in ovo and ex ovo) can be simply employed to delineate the effects of cisplatin (CDDP) and ellipticine (Elli) on neuroblastoma (Nbl) cells in terms of their growth and metastatic potential.MethodsThe Nbl UKF-NB-4 cell line was established from recurrent bone marrow metastases of high-risk Nbl (stage IV, MYCN amplification, 7q21 gain). Ex ovo and in ovo CAM assays were optimized to evaluate the antimetastatic activity of CDDP and Elli. Immunohistochemistry, qRT-PCR, and DNA isolation were performed.ResultsEx ovo CAM assay was employed to study whether CDDP and Elli exhibit any inhibitory effects on growth of Nbl xenograft in ex ovo CAM assay. Under the optimal conditions, Elli and CDDP exhibited significant inhibition of the size of the primary tumor. To study the efficiency of CDDP and Elli to inhibit primary Nbl tumor growth, intravasation, and extravasation in the organs, we adapted the in ovo CAM assay protocol. In in ovo CAM assay, both studied compounds (CDDP and Elli) exhibited significant (p < 0.001) inhibitory activity against extravasation to all investigated organs including distal CAM.ConclusionsTaken together, CAM assay could be a helpful and highly efficient in vivo approach for high-throughput screening of libraries of compounds with expected anticancer activities.

IMMU-55. GD2 IS A MACROPHAGE CHECKPOINT MOLECULE AND COMBINED GD2/CD47 BLOCKADE RESULTS IN SYNERGISTIC EFFECTS AGAINST GD2 POSITIVE MALIGNANCIES

Abstract GD2 is a disialoganglioside expressed on a variety of tumors including DIPG, neuroblastoma and osteosarcoma. Anti-GD2 antibodies have demonstrated some success in neuroblastoma and they have either not proven to be effective or have not been evaluated in other GD2 positive malignancies. CD47 is the dominant “Don’t Eat Me” signal expressed by cancer cells to inhibit macrophages and blocking CD47 leads to phagocytosis of tumor cells. We hypothesized that CD47 blockade synergizes with anti-GD2. We measured in vitro phagocytosis of DIPG and NBL cells and observed a synergy of anti-GD2/CD47 compared to the single agents. In vivo, this combination led to the complete clearance of both orthotopic and metastatic models of NBL. Additionally, the combination significantly enhanced survival of OS xenografts. Finally, in a murine model of metastatic pulmonary OS, the combination led to a near elimination of all metastatic burden. To understand the underlying biologic basis, we studied the effects of GD2 crosslinking on tumor cells and the effects of GD2 blockade on macrophages. A portion of DIPG or NBL cells die when treated with dinutuximab, and those that survive upregulate surface calreticulin, an important pro-phagocytic (“Eat Me”) signal. Additionally, we have identified the ligand for GD2, a molecule expressed on macrophages known to inhibit phagocytosis. In summary, we have identified a novel combination of anti-GD2 and anti-CD47 antibodies that is highly effective in preclinical models and will soon be tested in children. Furthermore, we have shown that GD2 itself is a macrophage checkpoint or “Don’t Eat Me” signal.

Long noncoding RNA LINC01410 promotes the tumorigenesis of neuroblastoma cells by sponging microRNA-506-3p and modulating WEE1.

ObjectiveNeuroblastoma (NBL) is an extra‐cranial solid tumor in children. This study was attempted to investigate the regulatory mechanism of long noncoding RNA LINC01410 (LINC01410) on NBL.MethodsThe expression of LINC01410, miR‐506‐3p, and WEE1 in NBL was evaluated by quantitative real time polymerase chain reaction. The proliferation and colony formation ability of NBL cells were analyzed by MTT and colony formation assay. Flow cytometry assay was executed to measure the apoptosis and cell cycle. Dual‐luciferase reporter assay was used to detect the targeted relationships among LINC01410, miR‐506‐3p, and WEE1. Additionally, the role of LINC01410 on NBL in vivo was evaluated according to a tumor xenograft model.ResultsThe expression of LINC01410 and WEE1 was enhanced and miR‐506‐3p was inhibited in NBL. LINC01410 knockdown attenuated the cell proliferation, colony formation ability, and inhibited tumor growth. Moreover, LINC01410 silencing facilitated the apoptosis and arrested the cell cycle. LINC01410 interacted with miR‐506‐3p to elevate the WEE1 expression in NBL. Additionally, miR‐506‐3p inhibition or WEE1 overexpression weakened the reduction effects of sh‐LINC01410 on cell proliferation, colony formation ability, apoptosis, and cell cycle.ConclusionsKnockdown of LINC01410 inhibited the development of NBL by miR‐506‐3p/WEE1 axis in vitro, which could serve as a potential therapeutic target for NBL therapy.

Profound analgesia is associated with a truncated peptide resulting from tissue specific alternative splicing of DRG CA8-204 regulated by an exon-level cis-eQTL.

Carbonic anhydrase-8 (CA8) is an intracellular protein that functions as an allosteric inhibitor of inositol trisphosphate receptor-1 (ITPR1) critical to intracellular Ca++ release, synaptic functions and neuronal excitability. We showed previously that murine nociception and analgesic responses are regulated by the expression of this gene in dorsal root ganglion (DRG) associated with a cis-eQTL. In this report, we identify an exon-level cis-eQTL (rs6471859) that regulates human DRG CA8 alternative splicing, producing a truncated 1,697bp transcript (e.g., CA8-204). Our functional genomic studies show the “G” allele at rs6471859 produces a cryptic 3’UTR splice site regulating expression of CA8-204. We developed constructs to study the expression and function of the naturally occurring CA8-204G transcript (G allele at rs6471859), CA8-204C (C allele at rs6471859 reversion mutation) and CA8-201 (full length transcript). CA8-204G transcript expression occurred predominantly in non-neuronal cells (HEK293), while CA8-204C expression was restricted to neuronal derived cells (NBL) in vitro. CA8-204G produced a stable truncated transcript in HEK293 cells that was barely detectable in NBL cells. We also show CA8-204 produces a stable peptide that inhibits pITPR1 and Ca++ release in HEK293 cells. These results imply homozygous G/G individuals at rs6471859, which are common in the general population, produce exclusively CA8-204G that is barely detectable in neuronal cells. CA8 null mutations that greatly impact neuronal functions are associated with severe forms of spinal cerebellar ataxia, and our data suggest G/G homozygotes should display a similar phenotype. To address this question, we show in vivo using AAV8-FLAG-CA8-204G and AAV8-V5-CA8-201 gene transfer delivered via intra-neural sciatic nerve injection (SN), that these viral constructs are able to transduce DRG cells and produce similar analgesic and anti-hyperalgesic responses to inflammatory pain. Immunohistochemistry (IHC) examinations of DRG tissues further show CA8-204G peptide is expressed in advillin expressing neuronal cells, but to a lesser extent compared to glial cells. These findings explain why G/G homozygotes that exclusively produce this truncated functional peptide in DRG evade a severe phenotype. These genomic studies significantly advance the literature regarding structure-function studies on CA8-ITPR1 critical to calcium signaling pathways, synaptic functioning, neuronal excitability and analgesic responses.

Prediction of neuroblastoma cell response to treatment with natural or synthetic retinoids using selected protein biomarkers.

Although the administration of retinoids represents an important part of treatment for children suffering from high-risk neuroblastomas, approximately 50% of these patients do not respond to this therapy or develop resistance to retinoids during treatment. Our study focused on the comparative analysis of the expression of five genes and corresponding proteins (DDX39A, HMGA1, HMGA2, HOXC9 and PBX1) that have recently been discussed as possible predictive biomarkers of clinical response to retinoid differentiation therapy. Expression of these five candidate biomarkers was evaluated at both the mRNA and protein level in the same subset of 8 neuroblastoma cell lines after treatment with natural or synthetic retinoids. We found that the cell lines that were HMGA2-positive and/or HOXC9-negative have a reduced sensitivity to retinoids. Furthermore, the experiments revealed that the retinoid-sensitive cell lines showed a uniform pattern of change after treatment with both natural and sensitive retinoids: increased DDX39A and decreased PBX1 protein levels. Our results showed that in NBL cells, these putative protein biomarkers are associated with sensitivity or resistance to retinoids, and their endogenous or induced expression can distinguish between these two phenotypes.

Abstract 2666: Subtype-selective lethal molecules disrupt the regulatory module that drives high-risk neuroblastoma

Abstract Neuroblastoma (NBL) is a tumor that is derived from the developing neural crest, resulting in approximately 15% of pediatric cancer deaths. This cancer is characterized by multiple tumor subtypes that vary in their aggressiveness and clinical prognosis. Though MYCN amplification is associated with an aggressive subtype and poor prognosis, recent molecular classification identified a novel aggressive subtype driven by a mesenchymal gene signature. To understand the molecular mechanisms underpinning each subtype, network-based analysis identified key transcriptional regulators for each subtype that act in concert to drive tumor pathology. We hypothesize that chemical inhibitors disrupting this regulatory module will have greater chance of success in vivo, by targeting the specific drivers of the tumor subtype. In an effort to identify subtype-selective lethal molecules that could be developed into targeted therapies, we screened ~5500 bioactive molecules across a panel of four NBL cell lines representing either MycNAMP or the newly identified mesenchymal subtype (MESN). A number of subtype selective compounds were identified, and their effect on the regulatory module was evaluated using high-throughput transcriptome analysis (PLATE-Seq) (Bush EC et al., 2017) followed by Virtual Inference of Protein activity by Enriched Regulon (VIPER) analysis (Alvarez MJ et al., 2016). This analysis revealed 15 compounds that exhibited greater potency in MycNAMP cells, and inverted the MR signature that characterizes this subtype. Compounds that reverted the signature caused destabilization of MycN through diverse mechanisms, highlighting new therapeutic approaches to targeting the MycNAMP subtype. This screening strategy also identified MESN-selective compounds, including multiple statin drugs that inhibit mevalonate biosynthesis in cells. The subtype-selectivity of these well-studied drugs is being used to define their lethal mechanisms in the MESN subtype, and to understand how MycNAMP cells evade their inhibitory effects. Our multifaceted approach, including cell line-selective chemical screening coupled with high-throughput transcriptome and network analysis, can serve as a framework for future drug discovery in a variety of cancers. Citation Format: Michael E. Stokes, Alessandro Vasciaveo, Jonnell Candice Small, Presha Rajbhandari, Gonzalo Lopez, Andrea Califano, Brent R. Stockwell. Subtype-selective lethal molecules disrupt the regulatory module that drives high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2666.

Oral Metronomic Topotecan Sensitizes Crizotinib Antitumor Activity in ALKF1174L Drug-Resistant Neuroblastoma Preclinical Models

BACKGROUND: Anaplastic lymphoma kinase (ALK) inhibitor crizotinib has proven to be effective in the treatment of ALK-mutated neuroblastoma, but crizotinib resistance was commonly observed in patients. We aimed to overcome crizotinib resistance by combining with the MEK inhibitor trametinib or low-dose metronomic (LDM) topotecan in preclinical neuroblastoma models. METHODS: We selected a panel of neuroblastoma cell lines carrying various ALK genetic aberrations to assess the therapeutic efficacy on cell proliferation in vitro. Downstream signals of ALK activation, including phosphorylation of ERK1/2, Akt as well as HIF-1α expression were evaluated under normoxic and hypoxic conditions. Tumor growth inhibition was further assessed in NOD/SCID xenograft mouse models. RESULTS: All NBL cell lines responded to crizotinib treatment but at variable ED50 levels, ranging from 0.25 to 5.58 μM. ALK-mutated cell lines SH-SY5Y, KELLY, LAN-5, and CHLA-20 are more sensitive than ALK wild-type cell lines. In addition, we demonstrated that under hypoxic conditions, all NBL cell lines showed marked decrease of ED50s when compared to normoxia except for KELLY cells. Taking into consideration the hypoxia sensitivity to crizotinib, combined treatment with crizotinib and LDM topotecan demonstrated a synergistic effect in ALKF1174L-mutated SH-SY5Y cells. In vivo, single-agent crizotinib showed limited antitumor activity in ALKF1174L-mutated SH-SY5Y and KELLY xenograft models; however, when combined with topotecan, significantly delayed tumor development was achieved in both SH-SY5Y and KELLY tumor models. CONCLUSIONS: Oral metronomic topotecan reversed crizotinib drug resistance in the ALKF1174L-mutated neuroblastoma preclinical model.

Car8 dorsal root ganglion expression and genetic regulation of analgesic responses are associated with a cis-eQTL in mice.

Carbonic anhydrase-8 (Car8 mouse gene symbol) is devoid of enzymatic activity, but instead functions as an allosteric inhibitor of inositol trisphosphate receptor-1 (ITPR1) to regulate this intracellular calcium release channel important in synaptic functions and neuronal excitability. Causative mutations in ITPR1 and carbonic anhydrase-8 in mice and humans are associated with certain subtypes of spinal cerebellar ataxia (SCA). SCA mice are genetically deficient in dorsal root ganglia (DRG) Car8 expression and display mechanical and thermal hypersensitivity and susceptibility to subacute and chronic inflammatory pain behaviors. In this report, we show that DRG Car8 expression is variable across 25 naïve-inbred strains of mice, and this cis-regulated eQTL (association between rs27660559, rs27706398, and rs27688767 and DRG Car8 expression; P < 1 × 10-11) is correlated with nociceptive responses in mice. Next, we hypothesized that increasing DRG Car8 gene expression would inhibit intracellular calcium release required for morphine antinociception and might correlate with antinociceptive sensitivity of morphine and perhaps other analgesic agents. We show that mean DRG Car8 gene expression is directly related to the dose of morphine or clonidine needed to provide a half-maximal analgesic response (r = 0.93, P < 0.00002; r = 0.83, P < 0.0008, respectively), suggesting that greater DRG Car8 expression increases analgesic requirements. Finally, we show that morphine induces intracellular free calcium release using Fura 2 calcium imaging in a dose-dependent manner; V5-Car8 WT overexpression in NBL cells inhibits morphine-induced calcium increase. These findings highlight the 'morphine paradox' whereby morphine provides antinociception by increasing intracellular free calcium, while Car8 and other antinociceptive agents work by decreasing intracellular free calcium. This is the first study demonstrating that biologic variability associated with this cis-eQTL may contribute to differing analgesic responses through altered regulation of ITPR1-dependent calcium release in mice.

Abstract LB-245: Preclinical study of epigenetic drug-based differentiation therapy for neuroblastoma

Abstract Neuroblastoma (NBL) is the most common extracranial solid tumor in children. We previously reported that the CpG island methylator phenotype (CIMP) of NBL was strongly associated with poor prognosis, and also suggested that CIMP may be a possible target for DNA demethylation therapy. Differentiation therapy with 13-cis-retinoic acid has already been established as the standard for high-risk NBLs in the USA. In this study, we aimed to establish an “epigenetic drug-based differentiation therapy” using a combination of a DNA demethylating agent (5-aza-2’-deoxycytidine: 5-Aza-CdR) and a differentiation agent (tamibarotene: TBT), a new synthetic retinoid. Treatment with 5-Aza-CdR suppressed the growth of 12 NBL cell lines by increasing the number of cells in the S-phase. Genome-wide DNA methylation analysis revealed that 5-Aza-CdR treatment induced global DNA hypomethylation, and that genes related to cell death and neurological processes were enriched as hypomethylated genes, suggesting that DNA demethylation therapy might assist the differentiation agent in inducing neuron differentiation. TBT induced differentiation of five NBL cell lines along with induction of neural extension and upregulation of differentiation markers, such as HOXD4, NGFR, and NTRK1. Pretreatment with 5-Aza-CdR increased the expression levels of differentiation markers, indicating that 5-Aza-CdR enhanced TBT-induced differentiation in vitro. Finally, the tumor suppression effect of 5-Aza-CdR and TBT in vivo was investigated using a mouse xenograft model of KELLY and NB-1 cell lines. Although a synergistic effect of 5-Aza-CdR and TBT was not apparent, they could induce significant tumor regression without severe side-effects. From these data, we concluded that 5-Aza-CdR and TBT had antitumor activity in vitro and in vivo, and that epigenetic drug-based differentiation therapy is a promising therapeutic strategy for NBL. Citation Format: Naoko Hattori, Akiko Mori, Kana Kimura, Emi Kubo, Kiyoshi Asada, Hiroshi Kawamoto, Toshikazu Ushijima. Preclinical study of epigenetic drug-based differentiation therapy for neuroblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-245.

Anti-GD2 mAb and Vorinostat synergize in the treatment of neuroblastoma

ABSTRACTNeuroblastoma (NBL) is a childhood malignancy of the sympathetic nervous system. For high-risk NBL patients, the mortality rate is still over 50%, despite intensive multimodal treatment. Anti-GD2 monoclonal antibody (mAB) in combination with systemic cytokine immunotherapy has shown clinical efficacy in high-risk NBL patients. Targeted therapy using histone deacetylase inhibitors (HDACi) is currently being explored in cancer treatment and already shows promising results. Using our recently developed transplantable TH-MYCN NBL model, we here report that the HDAC inhibitor Vorinostat synergizes with anti-GD2 mAb therapy in reducing NBL tumor growth. Further mechanistic studies uncovered multiple mechanisms for the observed synergy, including Vorinostat-induced specific NBL cell death and upregulation of the tumor antigen GD2 on the cell surface of surviving NBL cells. Moreover, Vorinostat created a permissive tumor microenvironment (TME) for tumor-directed mAb therapy by increasing macrophage effector cells expressing high levels of Fc-receptors (FcR) and decreasing the number and function of myeloid-derived suppressor cells (MDSC). Collectively, these data imply further testing of other epigenetic modulators with immunotherapy and provide a strong basis for clinical testing of anti-GD2 plus Vorinostat combination therapy in NBL patients.

In vitro and in vivo efficacy of non-psychoactive cannabidiol in neuroblastoma.

Neuroblastoma (nbl) is one of the most common solid cancers in children. Prognosis in advanced nbl is still poor despite aggressive multimodality therapy. Furthermore, survivors experience severe long-term multi-organ sequelae. Hence, the identification of new therapeutic strategies is of utmost importance. Cannabinoids and their derivatives have been used for years in folk medicine and later in the field of palliative care. Recently, they were found to show pharmacologic activity in cancer, including cytostatic, apoptotic, and antiangiogenic effects. We investigated, in vitro and in vivo, the anti-nbl effect of the most active compounds in Cannabis, Δ(9)-tetrahydrocannabinol (thc) and cannabidiol (cbd). We set out to experimentally determine the effects of those compounds on viability, invasiveness, cell cycle distribution, and programmed cell death in human nbl SK-N-SH cells. Both compounds have antitumourigenic activity in vitro and impeded the growth of tumour xenografts in vivo. Of the two cannabinoids tested, cbd was the more active. Treatment with cbd reduced the viability and invasiveness of treated tumour cells in vitro and induced apoptosis (as demonstrated by morphology changes, sub-G1 cell accumulation, and annexin V assay). Moreover, cbd elicited an increase in activated caspase 3 in treated cells and tumour xenografts. Our results demonstrate the antitumourigenic action of cbd on nbl cells. Because cbd is a nonpsychoactive cannabinoid that appears to be devoid of side effects, our results support its exploitation as an effective anticancer drug in the management of nbl.

Inhibition of hypoxia inducible factors combined with all-trans retinoic acid treatment enhances glial transdifferentiation of neuroblastoma cells.

Neuroblastoma (NBL) is a heterogeneous tumor characterized by a wide range of clinical manifestations. A high tumor cell differentiation grade correlates to a favorable stage and positive outcome. Expression of the hypoxia inducible factors HIF1-α (HIF1A gene) and HIF2-α (EPAS1 gene) and/or hypoxia-regulated pathways has been shown to promote the undifferentiated phenotype of NBL cells. Our hypothesis is that HIF1A and EPAS1 expression represent one of the mechanisms responsible for the lack of responsiveness of NBL to differentiation therapy. Clinically, high levels of HIF1A and EPAS1 expression were associated with inferior survival in two NBL microarray datasets, and patient subgroups with lower expression of HIF1A and EPAS1 showed significant enrichment of pathways related to neuronal differentiation. In NBL cell lines, the combination of all-trans retinoic acid (ATRA) with HIF1A or EPAS1 silencing led to an acquired glial-cell phenotype and enhanced expression of glial-cell differentiation markers. Furthermore, HIF1A or EPAS1 silencing might promote cell senescence independent of ATRA treatment. Taken together, our data suggest that HIF inhibition coupled with ATRA treatment promotes differentiation into a more benign phenotype and cell senescence in vitro. These findings open the way for additional lines of attack in the treatment of NBL minimal residue disease.

Abstract 4380: The miR-15 family members are therapeutic candidates to treat chemoresistant neuroblastomas

Abstract Neuroblastoma (NBL) is the most common solid tumor in infants and accounts for approximately 15% of cancer deaths in children. Neuroblastomas are very heterogeneous, with prognosis ranging from spontaneous regression to aggressive clinical course, and often become refractory to all current forms of treatment. While low and intermediate-risk patients have good prognosis, high-risk patients have poor prognosis and need intense chemotherapy. Despite the aggressive treatment, 60-70% of patients will die, mainly due to resistance to therapy and metastasis. Owing to the multiple different mechanisms that confer NBL resistance to therapy, targeting single components of a pathway may not suffice to restore chemosensitivity. In this respect, it is desirable to find molecules that can regulate multiple cellular processes or different component of the same pathways, thereby overcoming MDR and improving the therapeutic response. Our strategy is aimed to use microRNAs (miRNAs) to target the oncogenic properties of MDR neuroblastomas and render them vulnerable to treatment. The mRNA expression of genes related to multidrug resistance was analyzed in multiple neuroblastoma data sets. The 3′UTR of the genes differentially expressed in the highest-risk neuroblastoma group (Stage 4, MYCN amplified) was scanned with miRNA-binding sites prediction algorithms (TargetScan, PicTar, miRANDA). MicroRNAs predicted to regulate the expression of 2 or more overexpressed genes were selected for functional validation. Thirty-six miRNAs mimetics were transfected in two different chemoresistant neuroblastoma cell lines and effects on cell proliferation were evaluated. We have found a substantial number of genes implicated in the DNA damage response deregulated in high-risk NBL. MicroRNA-binding prediction algorithms revealed that most of them could potentially be regulated by microRNAs. Functional analysis in chemoresistant NBL cell lines identified several microRNAs that regulate proliferation, the best of which were the miR-15 family members. The overexpression of miR-497 reduces de proliferation of chemoresistant NBL cell lines and induces apoptotic cell death only in MYCN-amplified cell lines. Moreover, conditional overexpression of miR-497 in neuroblastoma xenografts led to a reduction in tumor growth. CONCLUSIONS: A substantial number of genes implicated in the MDR phenotype are deregulated in high-risk NBL and can be simultaneously targeted with miRNAs, providing a new therapeutic approach for chemoresistant neuroblastomas. This work is supported by Instituto de Salud Carlos III (CP11/00052, RD12/0036/0016 and PI11/00740) cofinanced by the European Regional Development Fund (ERDF) and Asociación Española Contra el Cáncer-Junta de Barcelona. Citation Format: Aroa Soriano, Laia Paris-Coderch, Luz Jubierre, Ana Almazán-Moga, Carla Molist, Josep Roma, Soledad Gallego, José Sánchez de Toledo, Miguel F. Segura. The miR-15 family members are therapeutic candidates to treat chemoresistant neuroblastomas. [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 4380. doi:10.1158/1538-7445.AM2014-4380

Abstract 4107: Targeted re-sequencing of neuroblastoma tumors reveals chromosomal rearrangements that involve the Anaplastic Lymphoma Kinase (ALK) gene.

Abstract Neuroblastoma (NBL) is a cancer of early childhood arising from the developing sympathetic nervous system. NBL tumors display a broad clinical and biological heterogeneity, ranging from highly aggressive tumors with fatal outcome to tumors with spontaneous regression. Recurrent mutations are mainly only observed in Anaplastic Lymphoma Kinase (ALK), which is involved in the pathogenesis of both familiar and sporadic NBL. ALK encodes a tyrosine kinase receptor with importance in neuronal development and was initially characterized in anaplastic large cell lymphoma from a translocation leading to the NPM-ALK fusion protein. Subsequent studies show that additional ALK chimeras have been generated with different fusion partners in various cancers. To date no ALK-containing rearrangement has been reported in primary NBL tumors although one study has described a NBL cell line with an ALK intragenic deletion leading to constitutive ALK kinase activity. This led us to screen for and further investigate possible ALK containing translocations in our NBL material. Genomic profiling of 350 NBL samples though SNP microarrays indicated ALK-rearrangement in four primary tumors and two cell lines (IMR32 and CLB-BAR) which were further analyzed through targeted re-sequencing of the common MYCN amplicon region (Chr2;14-18Mb) and the entire ALK gene. Briefly, detection of rearrangements was performed through solution-based enrichment followed pair-end sequencing of 400-500bp libraries. Junction sites were identified by manual sequence viewing on IGV and validated through PCR followed by Sanger sequencing. With this strategy we were able to determine translocation sites for all but one sample. In one tumor ALK was found to be translocated to GAB2 (chr11q14) causing loss of the first exon of respective gene. However, ALK and GAB2 were placed head-to-head with respect to transcription direction and this novel translocation is therefore unlikely to cause a chimeric protein. Another tumor showed translocation between ALK intron 4 and chr 4 subtelomeric region without known genes. Two NBL cell lines and one tumor had both MYCN and ALK amplification and sequencing revealed high level complexity of respective amplicon with multiple rearrangements. IMR32 show involvement of at least six different 2p-regions including MYCN and ALK exon 3-4. CLB-BAR has also multiple rearrangements including an ALK intragenic translocation causing loss of exon 4-11, ultimately resulting in an ALK protein with truncated extracellular domain. Here we show that ALK translocation sites could be deduced from targeted re-sequencing without previous knowledge about fusion partner. However, no translocations resulting in chimeric protein were detected. We were also able to detect MYCN amplicon junctions, which are highly unique for each patient and could be used for detection of minimal residual disease. Citation Format: Susanne M. Fransson, Anna Djos, Niloufar Javanmardi, Rosa Noguera, Ana Berbegall, Magnus Hansson, Per Kogner, Kristina Ruuth, Ruth Palmer, Bengt Hallberg, Tommy Martinsson. Targeted re-sequencing of neuroblastoma tumors reveals chromosomal rearrangements that involve the Anaplastic Lymphoma Kinase (ALK) gene. [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 4107. doi:10.1158/1538-7445.AM2013-4107

Abstract 2963: ALK is a MYCN target gene and contributes to cell growth, migration and invasion in neuroblastoma

Abstract Neuroblastoma (NBL), the most common solid tumor of childhood, is an embryonal malignancy of the developing sympathetic nervous system. Human Anaplastic lymphoma kinase (ALK) has been identified as an oncogene mutated or amplified in NBLs. However, the role of wild-type ALK in NBL is still largely unknown. For better understanding a molecular event associated with ALK in the pathogenesis of NBL, it is necessary to clarify how ALK gene contributes to NBL progression. Previously in the analysis of NBL clinical samples, we have found that ALK expression is significantly high in MYCN amplified group. Consistent with this evidence, the developing tumors with NBL characteristics in MYCN-transgenic mice possess a high expression of ALK. In the present study, we have found that overexpression of MYCN induced ALK expression and siRNA-mediated knockdown of MYCN resulted in the downregulation of ALK expression in NBL and non-NBL cell lines. We have identified the promoter region of ALK, to which MYCN binds, in the upstream of the first exon from +30 to −350 bp and Luciferase reporter assay showed that MYCN overexpression enhanced the promoter activity of ALK. The site-specific deletion at MYCN binding site of ALK promoter region downregulated its promoter activity and chromatin immunoprecipitation (ChIP) assay indicated that MYCN can be recruited to the ALK promoter region, suggesting that ALK is directly regulated by MYCN. In general, high expression of MYCN is a well-known prognostic marker for aggressive progression and increases growth rate of NBL cells. However, the role of MYCN in enhancing cell migration and invasion has not yet been fully understood. We have further examined an effect of ALK expression in MYCN-induced cell migration. Functional assay revealed that overexpression of ALK enhanced NBL cell growth, migration as well as invasion. Moreover, these activities were suppressed by siRNA-mediated knockdown of ALK, indicating that ALK might be involved in the metastatic phenotype of NBLs. On the other hand, the forced expression of MYCN enhanced cell migration in MYCN-single copy cell line, SK-N-AS cells. Of interest, the increased migration by MYCN expression was suppressed by siRNA-mediated knockdown of ALK, suggesting that the cell migration induced by MYCN is at least partly regulated by ALK expression. Our present findings explore the fundamental understanding of ALK and help a future development of novel therapeutic tools by targeting ALK for aggressive NBLs. 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 2963. doi:1538-7445.AM2012-2963

Neuroblastoma stem cells – mechanisms of chemoresistance and histonedeacetylase inhibitors

Cancer stem cells (CSCs) form a small proportion of tumor cells that have stem cell properties: self-renewal capacity, the ability to develop into different lineages and proliferative potential. The interest in CSCs emerged from their expected role in initiation, progression and recurrence of many tumors. They are generally resistant to conventional chemotherapy and radiotherapy. There are two hypotheses about their origin: The first assumes that CSCs may arise from normal stem cells, and the second supposes that differentiated cells acquire the properties of CSCs. Both hypotheses are not mutually exclusive, as it is possible that CSCs have a diverse origin in different tumors. CD133+ cells (CD133 is marker of CSC in some tumors) isolated from NBL, osteosarcoma and Ewing sarcoma cell lines are resistant to cisplatin, carboplatin, etoposide and doxorubicin than the CD133- ones. Being resistant to chemotherapy, there were many attempts to target CSCs epigenetically including the use of histone deacetylase inhibitors. The diverse influence of valproic acid (histone deacetylase inhibitor) on normal and cancer stem cells was proved in different experiments. We have found an increase percentage of CD133+ NBL cells after their incubation with VPA in a dose that does not induce apoptosis. Further researches on CSCs and clinical application for their detection are necessary: (i) to define the CSC function in carcinogenesis, cancer development and their role in metastasis; (ii) to find a specific marker for CSCs in different tumors; (iii) to explain the role of different pathways that determine their behavior and (iv) to explain mechanisms of chemoresistance of CSCs.

Identification of Genes Targeted by CpG Island Methylator Phenotype in Neuroblastomas, and Their Possible Integrative Involvement in Poor Prognosis

Background/Aims: CpG island (CGI) methylator phenotype (CIMP) is strongly associated with poor prognosis in neuroblastomas (NBLs; hazard ratios 7–22). Methylation of nonpromoter CGIs is useful to detect the presence of the CIMP, while the poor prognosis is considered to be caused by gene silencing due to promoter methylation. Here, promoter CGIs targeted by the CIMP were searched for. Methods: A genome-wide screening was performed by methylation-sensitive representational difference analysis of CIMP(+) and CIMP(–) NBLs. Results: Promoter CGIs of 9 genes were methylated in CIMP(+) NBL cell lines and caused silencing of their downstream genes. On analysis of 90 clinical specimens, CYP26C1,FERD3L (N-TWIST), CRYBA2 and PCDHGC4 were methylated at significantly higher incidences in CIMP(+) NBLs than CIMP(–) NBLs, while the difference was unclear for NPY, SPAG6, DDIT4L, CHR3SYT and C6Orf141. Methylation of CYP26C1 and FERD3L was significantly associated with poor prognosis, but weaker than the presence of the CIMP. Treatment of an NBL cell line with a demethylating agent caused demethylation of multiple promoter CGIs, and enhanced 13-cis-retinoic acid-induced neuronal differentiation. Conclusion: Our results indicate that the CIMP causes poor prognosis of NBLs by inducing methylation of multiple promoter CGIs with various incidences.