Inhibition In Neuroblastoma Research Articles

Preclinical Therapeutic Efficacy of RAF/MEK/ERK and IGF1R/AKT/mTOR Inhibition in Neuroblastoma.

Activating mutations in the RAS/MAPK pathway are observed in relapsed neuroblastoma. Preclinical studies indicate that these tumors have an increased sensitivity to inhibitors of the RAS/MAPK pathway, such as MEK inhibitors. MEK inhibitors do not induce durable responses as single agents, indicating a need to identify synergistic combinations of targeted agents to provide therapeutic benefit. We previously showed preclinical therapeutic synergy between a MEK inhibitor, trametinib, and a monoclonal antibody specific for IGF1R, ganitumab in RAS-mutated rhabdomyosarcoma. Neuroblastoma cells, like rhabdomyosarcoma cells, are sensitive to the inhibition of the RAS/MAPK and IGF1R/AKT/mTOR pathways. We hypothesized that the combination of trametinib and ganitumab would be effective in RAS-mutated neuroblastoma. In this study, trametinib and ganitumab synergistically suppressed neuroblastoma cell proliferation and induced apoptosis in cell culture. We also observed a delay in tumor initiation and prolongation of survival in heterotopic and orthotopic xenograft models treated with trametinib and ganitumab. However, the growth of both primary and metastatic tumors was observed in animals receiving the combination of trametinib and ganitumab. Therefore, more preclinical work is necessary before testing this combination in patients with relapsed or refractory RAS-mutated neuroblastoma.

Abstract 5122: Modulating anti-GD2 immunotherapy via dual DFMO and TGF-β inhibition in neuroblastoma

Abstract Neuroblastoma (NB) is an often-lethal childhood solid tumor. Anti-GD2 immunotherapy improves survival but not all responses are durable. Transforming growth factor-beta (TGFβ) has been implicated in solid tumor immunoresistance. High-risk NBs harbor activated MYC or MYCN to coordinately expand intratumoral polyamines (PA), oncometabolites with immunomodulatory roles, to support tumor progression. Difluoromethylornithine (DFMO) is an inhibitor of ornithine decarboxylase, the rate-limiting enzyme in PA synthesis, and has shown activity in preclinical NB models, including TH-MYCN+/+ transgenic mice, and is in clinical trials in children. We sought to augment anti-GD2 therapy using DFMO and the small molecule TGFβ-receptor inhibitor, galunisertib. We randomized TH-MYCN+/+ mice in two experiments (10 therapy arms; n=6-10 mice/arm) to receive combinations of DFMO, galunisertib, and anti-GD2 antibody m14G2a and to assess impact on survival. We measured 770 genes using nCounter Immuno-Oncology 360 (Nanostring), 36 cytokines using xMap bead-arrays (Luminex), and tumor-infiltrating leukocytes using flow cytometry in harvested tumors. Cell line TGFβ signaling was evaluated in tissue culture. In vitro, galunisertib consistently suppressed the upregulated TGFβ-Smad2/3 signaling cascade in MYCN-amplified neuroblastoma cell lines. In vivo, DFMO alone extends mouse survival and increases intra-tumoral neutrophils and natural killer (NK) cells. These NK cells increased surface expression of activation receptors like NKG2D (p<0.05), while tumor cells increased surface expression of NK-ligands. Tumor cells also expressed increased latency-associated peptide (LAP; p<0.05), a TGFβ precursor, suggesting NK cells were poised to kill but restrained by TGFβ. Cytotoxicity assays showed reversal of this inhibition with TGFβR1 inhibitor galunisertib in vitro. In a proof-of-concept trial, DFMO and galunisertib (DFMO/gal) demonstrated a clinical anti-tumor synergistic effect. DFMO/gal treated tumors had upregulated NK cell activity genes and downregulated TGFβ signaling genes. Cytokine analysis confirmed DFMO induced upregulation of TGFβ1 and TGFβ2 (p<0.01) that was modulated by galunisertib. IL6, GCSF, and GMCSF were markedly downregulated in tumors treated with both DFMO and galunisertib (p<0.05). An expanded trial showed DFMO/gal added to m14G2a showed no significant survival benefit over the DFMO and m14G2a combination. Ultimately, DFMO creates a pro-inflammatory cellular and cytokine milieu in TH-MYCN+/+ NBs. DFMO and TGFβR1 inhibition via galunisertib activate NK cells further and decrease the anti-inflammatory cytokine IL6. Ongoing studies are further characterizing the gene expression and cytokine levels of the NB TME under these treatment conditions. Citation Format: Om H. Gandhi, Christina S. Turn, Kangning Liu, Annette T. Vu, Hamid Bassiri, Michael D. Hogarty. Modulating anti-GD2 immunotherapy via dual DFMO and TGF-β inhibition in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5122.

PIM Kinase Inhibition Sensitizes Neuroblastoma to Doxorubicin

BackgroundChemoresistance contributes to relapse in high-risk neuroblastoma. Cancer cells acquire resistance through multiple mechanisms, including drug efflux pumps. In neuroblastoma, multidrug resistance-associated protein-1 (MRP1/ABCC1) efflux pump expression correlates with worse outcomes. These pumps are regulated by PIM kinases, a family of serine–threonine kinases, overexpressed in neuroblastoma. We hypothesized PIM kinase inhibition would sensitize neuroblastoma cells by modulating MRP1. MethodsKocak database query evaluated ABCC1, PIM1, PIM2, and PIM3 expression in neuroblastoma patients. SK-N-AS and SK-N-BE(2) cells were treated with doxorubicin or the pan-PIM kinase inhibitor, AZD1208. Flow cytometry assessed intracellular doxorubicin accumulation. AlamarBlue assay measured viability. The lethal dose 50% (LD50) of each drug and combination indices (CI) were calculated and isobolograms constructed to determine synergy. ResultsKocak database query demonstrated positive correlation between PIM genes and ABCC1. PIM kinase inhibition increased intracellular doxorubicin accumulation in both cell lines, suggesting PIM kinase regulation of MRP1. Isobolograms showed synergy between AZD1208 and doxorubicin. ConclusionsThe correlation between PIM and ABCC1 gene expression suggests PIM kinases may contribute to neuroblastoma chemotherapeutic resistance. PIM kinase inhibition increased intracellular doxorubicin accumulation. Combination treatment with AZD1208 and doxorubicin decreased neuroblastoma cell viability in a synergistic fashion. These findings support further investigations of PIM kinase inhibition in neuroblastoma. Type of StudyBasic Science Research. Level of EvidenceNA.

Abstract B002: ALK signaling primes the DNA damage response sensitizing ALK-driven neuroblastoma to therapeutic ATR inhibition

Abstract High-risk neuroblastoma (NB) currently presents significant clinical challenges. MYCN and ALK, which are often involved in high-risk NB, lead to increased replication stress in cancer cells, providing options for therapeutic exploitation. We previously identified an ATR/ALK inhibitor combination as an effective therapeutic approach in two independent genetically modified mouse NB models. Here, we identify an underlying molecular mechanism, in which ALK signaling leads to phosphorylation of ATR and CHK1, supporting an effective DNA damage response. The importance of ALK inhibition is supported by mouse data, in which monotreatment with ATRi resulted in a robust initial response, but subsequent relapse, in contrast to a 14-day ALKi/ATRi combination treatment that resulted in robust and sustained responses. Finally, we show that the remarkable response to the 14-day combined ATR/ALK inhibition protocol reflects a robust differentiation response in the tumor, reprogramming tumor cells to a neuronal/Schwann cell lineage identity. Our results identify a unique ability of ATR inhibition to trigger neuroblastoma differentiation and underscore the importance of further exploring combined ALK/ATR inhibition in NB, particularly in high-risk patient groups with oncogene-induced replication stress. Citation Format: Ruth H. Palmer, Bengt Hallberg, Marcus Borenäs, Ganesh Umapathy, Dan E. Lind, Wei-Yun Lai, Jikui Guan, Joel Johansson, Agata Aniszewska. ALK signaling primes the DNA damage response sensitizing ALK-driven neuroblastoma to therapeutic ATR inhibition [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr B002.

ALK signaling primes the DNA damage response sensitizing ALK-driven neuroblastoma to therapeutic ATR inhibition.

High-risk neuroblastoma (NB) is a significant clinical challenge. MYCN and Anaplastic Lymphoma Kinase (ALK), which are often involved in high-risk NB, lead to increased replication stress in cancer cells, suggesting therapeutic strategies. We previously identified an ATR (ataxia telangiectasia and Rad3-related)/ALK inhibitor (ATRi/ALKi) combination as such a strategy in two independent genetically modified mouse NB models. Here, we identify an underlying molecular mechanism, in which ALK signaling leads to phosphorylation of ATR and CHK1, supporting an effective DNA damage response. The importance of ALK inhibition is supported by mouse data, in which ATRi monotreatment resulted in a robust initial response, but subsequent relapse, in contrast to a 14-d ALKi/ATRi combination treatment that resulted in a robust and sustained response. Finally, we show that the remarkable response to the 14-d combined ATR/ALK inhibition protocol reflects a robust differentiation response, reprogramming tumor cells to a neuronal/Schwann cell lineage identity. Our results identify an ability of ATR inhibition to promote NB differentiation and underscore the importance of further exploring combined ALK/ATR inhibition in NB, particularly in high-risk patient groups with oncogene-induced replication stress.

Abstract C159: ALK signaling primes the DNA damage response allowing exploitation of ATR inhibition in ALK-driven Neuroblastoma

Abstract High-risk neuroblastoma currently presents significant clinical challenges. Oncogenes such as MYCN and ALK, which are often involved in high-risk neuroblastoma, result in increased replication stress in cancer cells, offering therapeutically exploitable options. We previously identified an ATR/ALK inhibitor combination as an effective therapeutic approach in two independent genetically modified mouse neuroblastoma models. Here we show that ALK signaling leads to phosphorylation of ATR and CHK1, supporting an effective DNA damage response. Remarkably, the importance of ALK inhibition is supported by mouse data, in which ATRi monotreatment resulted in a robust initial response, but subsequent relapse, in contrast to ALKi/ATRi combination treatment that resulted in robust and sustained responses. Here, we describe the mechanism underlying the remarkable tumor response to combined ATR/ALK inhibition. Our results identify a unique ability of ATR inhibition to trigger tumor regression in neuroblastoma and underscore the importance of further exploring combined ALK/ATR inhibition in neuroblastoma, particularly in high-risk patient groups with oncogene-induced replication stress. Citation Format: Marcus Borenäs, Ganesh Umapathy, Dan E. Lind, Wei-Yun Lai, Jikui Guan, Joel Johansson, Eva Jennische, Alexander Schmidt, Jonatan Gabre, Mats Bemark, Michael N. Hall, Jimmy Van den Eynden, Bengt Hallberg, Ruth H. Palmer. ALK signaling primes the DNA damage response allowing exploitation of ATR inhibition in ALK-driven Neuroblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C159.

Correction: MYCN expression induces replication stress and sensitivity to PARP inhibition in neuroblastoma

Correction: MYCN expression induces replication stress and sensitivity to PARP inhibition in neuroblastoma

Chromosome 11q loss and MYCN amplification demonstrate synthetic lethality with checkpoint kinase 1 inhibition in neuroblastoma.

Neuroblastoma is the most common extracranial solid tumor found in children and despite intense multi-modal therapeutic approaches, low overall survival rates of high-risk patients persist. Tumors with heterozygous loss of chromosome 11q and MYCN amplification are two genetically distinct subsets of neuroblastoma that are associated with poor patient outcome. Using an isogenic 11q deleted model system and high-throughput drug screening, we identify checkpoint kinase 1 (CHK1) as a potential therapeutic target for 11q deleted neuroblastoma. Further investigation reveals MYCN amplification as a possible additional biomarker for CHK1 inhibition, independent of 11q loss. Overall, our study highlights the potential power of studying chromosomal aberrations to guide preclinical development of novel drug targets and combinations. Additionally, our study builds on the growing evidence that DNA damage repair and replication stress response pathways offer therapeutic vulnerabilities for the treatment of neuroblastoma.

Abstract 2018: Therapeutic benefit of dual ALK and FAK inhibition in neuroblastoma

Abstract Neuroblastoma (NB) is the most common extracranial pediatric tumor, and accounts for approximately 12% of cancer-related deaths in children. Though several genomic drivers have been identified, the development of targeted therapy for treating this aggressive pediatric malignancy has yet to be realized. Thus, there exists an urgent need to develop alternative therapeutic strategies for treating aggressive and metastatic NB. One novel approach is to therapeutically target anaplastic lymphoma kinase (ALK) and focal adhesion kinase (FAK), which are multi-functional tyrosine kinases implicated in neural development and play an important role in growth and metastasis of several cancers. Genomic aberrations of ALK such as overexpression, amplifications, and mutations, have been reported in NB. The role of FAK has also been delineated in NB as well as associated with disease metastasis. Using in silico analysis of sequencing data from NB patients procured from Pediatric MI-ONCOSEQ (precision oncology program), we found a cohort of patients that express high ALK and FAK expression. Given the potential roles of ALK and FAK in NB, we evaluated the efficacy of a novel compound ESK440, which is a dual ALK and FAK inhibitor. ESK440 has passed Phase 1 clinical trials in adult patients with solid tumors. It is capable of crossing the blood brain barrier and binds to several mutated forms of ALK, thus making ESK440 an attractive therapeutic candidate for treating NB. A wide panel of NB cancer cell lines were screened with ESK440, and a CellTiter-Glo® Luminescent Cell Viability Assay was used to determine the IC-50s. Our results revealed that NB cells with ALK genomic aberrations (mutations and amplifications) showed low IC-50 values. Further, treatment with ESK440 inhibited ALK and FAK associated signaling pathways. We also observed decreased expression of MYCN. Intriguingly, ESK440 studies in NB xenograft model (NB-1) resulted in tumor regression in treated animals. Altogether, our study has discovered the therapeutic potential of dual ALK and FAK inhibitor in NB, and our findings may provide the foundation for initiating clinical trials targeting this disease in pediatric patients. Citation Format: Seema Chugh, Jean C. Tien, Jennifer Hon, Pushpinder Singh Bawa, Carson Kenum, Chi Chiang Li, Yunhui Cheng, Andrew D. Delekta, Jae Eun Choi, Rahul Mannan, Yuanyuan Qiao, Rajen Mody, Arul Chinnaiyan. Therapeutic benefit of dual ALK and FAK inhibition in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2018.

Abstract 2006: Preclinical evaluation of dual AURKA (LY3295668) and BCL2 (venetoclax) inhibition in neuroblastoma (NB)

Abstract Introduction: Deregulated expression of the MYCN oncogene is associated with the development of many neural-derived pediatric cancers including NB, medulloblastoma and atypical teratoid rhabdoid tumors. Amplification of the MYCN oncogene is present in over 40% of high-risk NBs that remain lethal in most patients, thus developing better therapies for these patients is essential. While direct therapeutic targeting of MYCN protein remains challenging, we previously demonstrated synergistic activity of dual targeting of BCL-2 (venetoclax) and AURKA (MLN8237) in MYCN-amplified NB (Ham Cancer Cell, 2016). With MLN8237 no longer being developed due to toxicities related to AURKB inhibition, testing of a highly selective AURKA inhibitor, LY3295668, is warranted. Methods: LY3295668 (Chemie Tek) and venetoclax (Selleck Chem) were tested alone and in combination in six NB PDX models using 2-3 mice/arm. Five Patient Derived Xenograft (PDX) models tested (COG-N-424x, COG-N-453x, NB-1643, Obelix-Rx and Obelix-2x) were MYCN-amplified and one xenograft model (SK-N-AS) was MYCN-non-amplified. First, a comprehensive toxicity study, testing LY3295668 at 30mg/kg with venetoclax at 100mg/kg, 75mg/kg, 50mg/kg, and 25mkg/kg, was performed. Based on tolerability of combination, an optimal dose of 30mg/kg for LY3295668 and 50mg/kg for venetoclax was selected and administered once daily, seven days a week, via oral gavage for 60 days. These were the maximum tolerated doses when tested in combination, that did not result in weight loss greater than 15% or other overt signs of toxicity. Results: LY3295668 (30mg/kg) and venetoclax (50mg/kg) were well tolerated as monotherapy, and when administered in combination showed a maximum weight loss of 13%. Single agent therapy resulted in minimal if any growth delay. Four of five MYCN-amplified PDX models demonstrated maintained complete responses and one showed significant tumor growth delay. No effect was observed in the MYCN-non-amplified model with single agent or combination treatment compared to vehicle. Conclusions: Dual targeting of AURKA and BCL2 with LY3295668 and venetoclax is tolerable and demonstrates compelling anti-tumor activity in MYCN-amplified NB PDX models, validating our earlier findings (Ham et al). These preclinical results provisionally support clinical development of this combination for NB patients with MYCN amplification. Assessment of additional PDX models is currently ongoing and will be reported. Citation Format: David Groff, Colleen Casey, Kateryna krytska, Matthew Tsang, Christina Acholla, John M. Maris, Yael P. Mosse. Preclinical evaluation of dual AURKA (LY3295668) and BCL2 (venetoclax) inhibition in neuroblastoma (NB) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2006.

Synergistic Anti-Tumor Effect of Combining Selective CDK7 and BRD4 Inhibition in Neuroblastoma.

PurposeCyclin-dependent kinases (CDKs) that have critical roles in RNA polymerase II (Pol II)-mediated gene transcription are emerging as therapeutic targets in cancer. We have previously shown that THZ1, a covalent inhibitor of CDKs 7/12/13, leads to cytotoxicity in MYCN-amplified neuroblastoma through the downregulation of super-enhancer-associated transcriptional upregulation. Here we determined the effects of YKL-5-124, a novel covalent inhibitor with greater selectivity for CDK7 in neuroblastoma cells.Experimental DesignWe tested YKL-5-124 in MYCN-amplified and nonamplified neuroblastoma cells individually and in combination with other inhibitors in cell line and animal models. Cell viability, target validation, effects on cell cycle and transcription were analyzed.ResultsCDK7 inhibition with YKL-5-124 did not lead to significant cell death, but resulted in aberrant cell cycle progression especially in MYCN-amplified cells. Unlike THZ1, YKL-5-124 had minimal effects on Pol II C-terminal domain phosphorylation, but significantly inhibited that of the CDK1 and CDK2 cell cycle kinases. Combining YKL-5-124 with the BRD4 inhibitor JQ1 resulted in synergistic cytotoxicity. A distinct MYCN-gene expression signature associated with resistance to BRD4 inhibition was suppressed with the combination. The synergy between YKL-5-124 and JQ1 translated into significant tumor regression in cell line and patient-derived xenograft mouse models of neuroblastoma.ConclusionsThe combination of CDK7 and BRD4 inhibition provides a therapeutic option for neuroblastoma and suggests that the addition of YKL-5-124 could improve the therapeutic efficacy of JQ1 and delay resistance to BRD4 inhibition.

Abstract P118: Analysis of macrophage function and histone deacetylase inhibition in neuroblastoma

Abstract Background: Neuroblastoma is the third most common childhood cancer and accounts for 12% of cancer-associated deaths in children under the age of 15. Treatment of neuroblastoma with the histone deacetylase inhibitor (HDACi) vorinostat induces increased infiltration of macrophages with upregulated immune cell-surface receptors. Neuroblastoma cells release VEGF and M-CSF, which may alter intratumoral macrophage populations. VEGF has also been implicated in alteration of amyloid precursor protein family processing. Our lab demonstrated that amyloid precursor protein 2 (APLP2), a member of the amyloid precursor protein family, plays an important role in the migration of tumor cells. APLP2 is known to be expressed by macrophages, but no studies have previously examined macrophage functions that are impacted by APLP2 in the context of neuroblastoma disease and its treatment by HDACi drugs. Because of the high morbidity and mortality associated with neuroblastoma, studies such as this one that are designed to comprehend the interaction of immunity and treatment in neuroblastoma are clinically significant. Methods: We treated neuroblastoma tumor cells (Neuro-2a) in vitro with M344, an HDACi with structural similarity to vorinostat, and assessed viability through MTT assay. In addition, we generated mice with APLP2 knockout in cells expressing the Csf-1 receptor (a protein characteristically expressed by macrophages and dendritic cells). Polarization of macrophages isolated from the macrophage-targeted APLP2-knockout mice was achieved through treatment with IFN-γ and LPS (M1) or IL-4 (M2). Macrophages were then analyzed through western blotting and flow cytometry for APLP2 expression and polarization markers. Results: Following polarization, macrophages collected from the bone marrow of macrophage-targeted APLP2-knockout mice have an altered distribution of M1 and M2 sub-populations, which are macrophage sub-populations that differ in their migratory capabilities, as well as in their abilities to stimulate or suppress anti-tumor immunity. Furthermore, we showed that M1 and M2 subpopulations of bone marrow-derived macrophages from normal mice differ in their expression of APLP2. We also demonstrated that M344 decreased neuroblastoma cell growth. Thus, APLP2 is influential in macrophage biology, and we have created a novel mouse model for defining its specific contributions in mice treated with HDACi drugs that influence macrophage biology. Conclusions: We have made progress in understanding the impact of the HDACi drug M344 on neuroblastoma cells and are ready to analyze its impact on macrophage/dendritic cell populations in a syngeneic neuroblastoma mouse model, as well as to define the role of APLP2 in the function of these cell populations in the context of neuroblastoma. In addition to their potential contribution to the development of new neuroblastoma therapies, the results from this study are expected to expand our comprehension of macrophage function and regulation, and thus will be of broad value in the immunology and oncology fields. Citation Format: Gabrielle L. Brumfield, Shelby M. Knoche, Alaina C. Larson, Brittany J. Poelaert, Benjamin T. Goetz, Poomy Pandey, Donald W. Coulter, Joyce C. Solheim. Analysis of macrophage function and histone deacetylase inhibition in neuroblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P118.

Translational Strategies for Repotrectinib in Neuroblastoma.

Limited clinical data are available regarding the utility of multikinase inhibition in neuroblastoma. Repotrectinib (TPX-0005) is a multikinase inhibitor that targets ALK, TRK, JAK2/STAT, and Src/FAK, which have all been implicated in the pathogenesis of neuroblastoma. We evaluated the preclinical activity of repotrectinib monotherapy and in combination with chemotherapy as a potential therapeutic approach for relapsed/refractory neuroblastoma. In vitro sensitivity to repotrectinib, ensartinib, and cytotoxic chemotherapy was evaluated in neuroblastoma cell lines. In vivo antitumor effect of repotrectinib monotherapy, and in combination with chemotherapy, was evaluated using a genotypically diverse cohort of patient-derived xenograft (PDX) models of neuroblastoma. Repotrectinib had comparable cytotoxic activity across cell lines irrespective of ALK mutational status. Combination with chemotherapy demonstrated increased antiproliferative activity across several cell lines. Repotrectinib monotherapy had notable antitumor activity and prolonged event-free survival compared with vehicle and ensartinib in PDX models (P < 0.05). Repotrectinib plus chemotherapy was superior to chemotherapy alone in ALK-mutant and ALK wild-type PDX models. These results demonstrate that repotrectinib has antitumor activity in genotypically diverse neuroblastoma models, and that combination of a multikinase inhibitor with chemotherapy may be a promising treatment paradigm for translation to the clinic.

Proteomics identify nuclear export as a targetable pathway in neuroblastoma: Comment on “XPO1 inhibition with selinexor synergizes with proteasome inhibition in neuroblastoma by targeting nuclear export of IκB”

Neuroblastoma (NBL) is an embryonal malignancy of childhood with poor outcomes for patient with high-risk disease. Multimodal treatment approaches have improved outcomes but at the cost of significant toxicity, and there is no durable therapeutic approach for relapsed disease. As NBL has no singular oncogenic driver, targeted therapeutic options have been limited. Galinski et al report the results of a proteomic screen of neuroblastomas and identify the nuclear export protein XPO1 as a protein that is preferentially expressed and located in neuroblast nuclei. XPO1 overexpression is associated with nuclear export of IκB and increased NF-κB activity, both of which can be abrogated in NBL cell lines with the XPO1 inhibitor Selinexor with or without the proteasome inhibitor bortezomib. This work highlights new strategies for therapeutic target identification and the novel identification of nuclear export as a targetable oncogenic pathway across malignancies.

XPO1 inhibition with selinexor synergizes with proteasome inhibition in neuroblastoma by targeting nuclear export of IkB

Across many cancer types in adults, upregulation of the nuclear-to-cytoplasmic transport protein Exportin-1 (XPO1) correlates with poor outcome and responsiveness to selinexor, an FDA-approved XPO1 inhibitor. Similar data are emerging in childhood cancers, for which selinexor is being evaluated in early phase clinical studies. Using proteomic profiling of primary tumor material from patients with high-risk neuroblastoma, as well as gene expression profiling from independent cohorts, we have demonstrated that XPO1 overexpression correlates with poor patient prognosis. Neuroblastoma cell lines are also sensitive to selinexor in the low nanomolar range. Based on these findings and knowledge that bortezomib, a proteasome inhibitor, blocks degradation of XPO1 cargo proteins, we hypothesized that combination treatment with selinexor and bortezomib would synergistically inhibit neuroblastoma cellular proliferation. We observed that selinexor promoted nuclear retention of IkB and that bortezomib augmented the ability of selinexor to induce cell-cycle arrest and cell death by apoptosis. This synergy was abrogated through siRNA knockdown of IkB. The synergistic effect of combining selinexor and bortezomib in vitro provides rationale for further investigation of this combination treatment for patients with high-risk neuroblastoma.

Formulation of magnetic nanocomposites for intracellular delivery of micro-RNA for MYCN inhibition in neuroblastoma

Neuroblastoma, which accounts for almost 6% of all cancers in infants, originates from the sympathoadrenal progenitor cells within the neural crest. Approximately 25 % of neuroblastoma cases result from the amplification of the MYC-related oncogene MYCN, thus leading to high disease risk and poor prognosis; hence, studies focusing on the inhibition of MYCN are indispensable. Interestingly, microRNA-34 (miR-34) is a prospective candidate for cancer therapy because of its oncogenic and tumor-suppressing ability. This study presents the synthesis, characterization, and application of cationic magnetic nanocomposites (MNCs) comprising branched polyethylenimine (PEI)-coated iron oxide nanoparticles (IONPs). These positively charged MNCs possess the ability to penetrate the negatively charged cell wall for the delivery of miR-34a molecules into cancerous cells. The characteristic peaks at 3380, 1620, 2900, and 2840 cm−1 corresponding to −NH− and −CH2− groups suggest successful coating of PEI on the surface of IONPs. The X-ray powder diffraction (XRPD) peak of the prepared MNCs at 2θ = 35.44° resembled that of magnetite (Fe3O4, (311)). The transfection efficiency was enhanced through a magnetic field that enabled a very rapid concentration of the completely delivered vector dose onto cells. Additionally, the results of small-angle neutron scattering (SANS) revealed that core heat was generated and subsequently led to shell softening, which was activated by an alternative magnetic field (AMF). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that MNCs did not exhibit any significant toxicity against the tested cells. The increased amplification of miR-34a led to the suppression of the MYCN protein, which consequently inhibited the growth of neuroblastoma cells.

NRAS Status Determines Sensitivity to SHP2 Inhibitor Combination Therapies Targeting the RAS-MAPK Pathway in Neuroblastoma.

Survival for high-risk neuroblastoma remains poor and treatment for relapsed disease rarely leads to long-term cures. Large sequencing studies of neuroblastoma tumors from diagnosis have not identified common targetable driver mutations other than the 10% of tumors that harbor mutations in the anaplastic lymphoma kinase (ALK) gene. However, at neuroblastoma recurrence, more frequent mutations in genes in the RAS-MAPK pathway have been detected. The PTPN11-encoded tyrosine phosphatase SHP2 is an activator of the RAS pathway, and we and others have shown that pharmacologic inhibition of SHP2 suppresses the growth of various tumor types harboring KRAS mutations such as pancreatic and lung cancers. Here we report inhibition of growth and downstream RAS-MAPK signaling in neuroblastoma cells in response to treatment with the SHP2 inhibitors SHP099, II-B08, and RMC-4550. However, neuroblastoma cell lines harboring endogenous NRAS Q61K mutation (which is commonly detected at relapse) or isogenic neuroblastoma cells engineered to overexpress NRASQ61K were distinctly resistant to SHP2 inhibitors. Combinations of SHP2 inhibitors with other RAS pathway inhibitors such as trametinib, vemurafenib, and ulixertinib were synergistic and reversed resistance to SHP2 inhibition in neuroblastoma in vitro and in vivo. These results suggest for the first time that combination therapies targeting SHP2 and other components of the RAS-MAPK pathway may be effective against conventional therapy-resistant relapsed neuroblastoma, including those that have acquired NRAS mutations. SIGNIFICANCE: These findings suggest that conventional therapy-resistant, relapsed neuroblastoma may be effectively treated via combined inhibition of SHP2 and MEK or ERK of the RAS-MAPK pathway.

MYCN expression induces replication stress and sensitivity to PARP inhibition in neuroblastoma.

This study investigates the influence expression of the MYCN oncogene has on the DNA damage response, replication fork progression and sensitivity to PARP inhibition in neuroblastoma. In a panel of neuroblastoma cell lines, MYCN amplification or MYCN expression resulted in increased cell death in response to a range of PARP inhibitors (niraparib, veliparib, talazoparib and olaparib) compared to the response seen in non-expressing/amplified cells. MYCN expression slowed replication fork speed and increased replication fork stalling, an effect that was amplified by PARP inhibition or PARP1 depletion. Increased DNA damage seen was specifically induced in S-phase cells. Importantly, PARP inhibition caused a significant increase in the survival of mice bearing MYCN expressing tumours in a transgenic murine model of MYCN expressing neuroblastoma. Olaparib also sensitized MYCN expressing cells to camptothecin- and temozolomide-induced cell death to a greater degree than non-expressing cells. In summary, MYCN expression leads to increased replication stress in neuroblastoma cells. This effect is exaggerated by inhibition of PARP, resulting in S-phase specific DNA damage and ultimately increased tumour cell death. PARP inhibition alone or in combination with classical chemotherapeutics is therefore a potential therapeutic strategy for neuroblastoma and may be more effective in MYCN expressing tumours.

Increased Efficacy of Histone Methyltransferase G9a Inhibitors Against MYCN-Amplified Neuroblastoma.

Targeted inhibition of proteins modulating epigenetic changes is an increasingly important priority in cancer therapeutics, and many small molecule inhibitors are currently being developed. In the case of neuroblastoma (NB), a pediatric solid tumor with a paucity of intragenic mutations, epigenetic deregulation may be especially important. In this study we validate the histone methyltransferase G9a/EHMT2 as being associated with indicators of poor prognosis in NB. Immunological analysis of G9a protein shows it to be more highly expressed in NB cell-lines with MYCN amplification, which is a primary determinant of dismal outcome in NB patients. Furthermore, G9a protein in primary tumors is expressed at higher levels in poorly differentiated/undifferentiated NB, and correlates with high EZH2 expression, a known co-operative oncoprotein in NB. Our functional analyses demonstrate that siRNA-mediated G9a depletion inhibits cell growth in all NB cell lines, but, strikingly, only triggers apoptosis in NB cells with MYCN amplification, suggesting a synthetic lethal relationship between G9a and MYCN. This pattern of sensitivity is also evident when using small molecule inhibitors of G9a, UNC0638, and UNC0642. The increased efficacy of G9a inhibition in the presence of MYCN-overexpression is also demonstrated in the SHEP-21N isogenic model with tet-regulatable MYCN. Finally, using RNA sequencing, we identify several potential tumor suppressor genes that are reactivated by G9a inhibition in NB, including the CLU, FLCN, AMHR2, and AKR1C1-3. Together, our study underlines the under-appreciated role of G9a in NB, especially in MYCN-amplified tumors.

Limited antitumor activity of combined BET and MEK inhibition in neuroblastoma.

The treatment of high-risk neuroblastoma continues to present a formidable challenge to pediatric oncology. Previous studies have shown that Bromodomain and extraterminal (BET) inhibitors can inhibit MYCN expression and suppress MYCN-amplified neuroblastoma in vivo. Furthermore, alterations within RAS-MAPK (mitogen-activated protein kinase) signaling play significant roles in neuroblastoma initiation, maintenance, and relapse, and mitogen-activated extracellular signal-regulated kinase (MEK)inhibitors demonstrate efficacy in subsets of neuroblastoma preclinical models. Finally, hyperactivation of RAS-MAPK signaling has been shown to promote resistance to BET inhibitors. Therefore, we examined the antitumor efficacy of combined BET/MEK inhibition utilizing I-BET726 or I-BET762 and trametinib in high-risk neuroblastoma. Utilizing a panel of genomically annotated neuroblastoma cell line models, we investigated the in vitro effects of combined BET/MEK inhibition on cell proliferation and apoptosis. Furthermore, we evaluated the effects of combined inhibition in neuroblastoma xenograft models. Combined BET and MEK inhibition demonstrated synergistic effects on the growth and survival of a large panel of neuroblastoma cell lines through augmentation of apoptosis. A combination therapy slowed tumor growth in a non-MYCN-amplified, NRAS-mutated neuroblastoma xenograft model, but had no efficacy in an MYCN-amplified model harboring a loss-of-function mutation in NF1. Combinatorial BET and MEK inhibition was synergistic in the vast majority of neuroblastoma cell lines in the in vitro setting but showed limited antitumor activity in vivo. Collectively, these data do not support clinical development of this combination in high-risk neuroblastoma.