BackgroundNeuroblastoma (NB) is the most common cancer in infancy and most frequent cause of death from extracranial solid tumors in children. Ornithine decarboxylase (ODC) expression is an independent indicator of poor prognosis in NB patients. This study investigated safety, response, pharmacokinetics, genetic and metabolic factors associated with ODC in a clinical trial of the ODC inhibitor difluoromethylornithine (DFMO) ± etoposide for patients with relapsed or refractory NB.Methods and FindingsTwenty-one patients participated in a phase I study of daily oral DFMO alone for three weeks, followed by additional three-week cycles of DFMO plus daily oral etoposide. No dose limiting toxicities (DLTs) were identified in patients taking doses of DFMO between 500-1500 mg/m2 orally twice a day. DFMO pharmacokinetics, single nucleotide polymorphisms (SNPs) in the ODC gene and urinary levels of substrates for the tissue polyamine exporter were measured. Urinary polyamine levels varied among patients at baseline. Patients with the minor T-allele at rs2302616 of the ODC gene had higher baseline levels (p=0.02) of, and larger decreases in, total urinary polyamines during the first cycle of DFMO therapy (p=0.003) and had median progression free survival (PFS) that was over three times longer, compared to patients with the major G allele at this locus although this last result was not statistically significant (p=0.07). Six of 18 evaluable patients were progression free during the trial period with three patients continuing progression free at 663, 1559 and 1573 days after initiating treatment. Median progression-free survival was less among patients having increased urinary polyamines, especially diacetylspermine, although this result was not statistically significant (p=0.056).ConclusionsDFMO doses of 500-1500mg/m2/day are safe and well tolerated in children with relapsed NB. Children with the minor T allele at rs2302616 of the ODC gene with relapsed or refractory NB had higher levels of urinary polyamine markers and responded better to therapy containing DFMO, compared to those with the major G allele at this locus. These findings suggest that this patient subset may display dependence on polyamines and be uniquely susceptible to therapies targeting this pathway.Trial RegistrationClinicaltrials.gov NCT#01059071

High risk neuroblastoma (HRNB) accounts for 15% of all pediatric cancer deaths. Despite aggressive therapy approximately half of patients will relapse, typically with only transient responses to second-line therapy. This study evaluated the ornithine decarboxylase inhibitor difluoromethylornithine (DFMO) as maintenance therapy to prevent relapse following completion of standard therapy (Stratum 1) or after salvage therapy for relapsed/refractory disease (Stratum 2). This Phase II single agent, single arm multicenter study enrolled from June 2012 to February 2016. Subjects received 2 years of oral DFMO (750 ± 250 mg/m2 twice daily). Event free survival (EFS) and overall survival (OS) were determined on an intention-to-treat (ITT) basis. 101 subjects enrolled on Stratum 1 and 100 were eligible for ITT analysis; two-year EFS was 84% (±4%) and OS 97% (±2%). 39 subjects enrolled on Stratum 2, with a two-year EFS of 54% (±8%) and OS 84% (±6%). DFMO was well tolerated. The median survival time is not yet defined for either stratum. DFMO maintenance therapy for HRNB in remission is safe and associated with high EFS and OS. Targeting ODC represents a novel therapeutic mechanism that may provide a new strategy for preventing relapse in children with HRNB.

Neuroblastoma (NB) is associated with MYCN oncogene amplification occurring in approximately 30% of NBs and is associated with poor prognosis. MYCN is linked to a number of genes including ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. ODC expression is elevated in many forms of cancer including NB. Alpha-difluoromethylornithine (DFMO), an ODC inhibitor, is currently being used in a Phase I clinical trial for treatment of NB. However, cancer cells treated with DFMO may overcome their polyamine depletion by the uptake of polyamines from extracellular sources. A novel polyamine transport inhibitor, AMXT-1501, has not yet been tested in NB. We propose that inhibiting ODC with DFMO, coupled with polyamine transport inhibition by AMXT-1501 will result in enhanced NB growth inhibition. Single and combination drug treatments were conducted on three NB cell lines. DFMO IC 50 values ranged from 20.76 to 33.3 mM, and AMXT-1501 IC 50 values ranged from 14.13 to 17.72 mM in NB. The combination treatment resulted in hypophosphorylation of retinoblastoma protein (Rb), suggesting growth inhibition via G 1 cell cycle arrest. Increased expression of cleaved PARP and cleaved caspase 3 in combination-treated cells starting at 48 hr suggested apoptosis. The combination treatment depleted intracellular polyamine pools and decreased intracellular ATP, further verifying growth inhibition. Given the current lack of effective therapies for patients with relapsed/refractory NB and the preclinical effectiveness of DFMO with AMXT-1501, this combination treatment provides promising preclinical results. DFMO and AMXT-1501 may be a potential new therapy for children with NB.Neuroblastoma (NB) is the most common extracranial solid pediatric tumor, accounting 8-10% of all pediatric cancers and for 15% of cancer-related deaths in children. 1 Approximately 650 new cases of NB arise in the United States each year. Of the children diagnosed, roughly 70% have disease that has already metastasized to other parts of the body. Children with high-risk NB have a long-term survival of less than 50%, despite the use of intensive multimodality therapy. 2 Of the children with relapsed or refractory disease, there are no known curative measures and the 5-year survival is less than 10%. Biomarkers are powerful tools for determining diagnosis and prognosis for different cancers, including NB. The oncogenic transcription factor MYCN is amplified in roughly 30% of all NBs and is generally associated with high-risk disease and poor survival. 3,4 As a transcription factor, MYCN induces and represses a large number of genes involved in multiple biological processes including cell growth and differentiation. However, the genes necessary or sufficient to initiate neuroblastoma tumorigenesis downstream of MYCN remain to be established. 5 Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis in mammalian cells, is directly activated by c-MYC and MYCN 6-8 and is overexpressed in NB. 9-11 ODC decarboxylates t...

The primary aim of this phase 1 study was to determine the maximum tolerated dose (MTD) and evaluate the safety of nifurtimox alone and in combination with cyclophosphamide and topotecan in multiple relapsed/refractory neuroblastoma pediatric patients. The secondary aim was to evaluate the pharmacokinetics of nifurtimox and the treatment response. To these ends, we performed a phase 1 dose escalation trial of daily oral nifurtimox with toxicity monitoring to determine the MTD, followed by 3 cycles of nifurtimox in combination with cyclophosphamide and topotecan. Samples were collected to determine the pharmacokinetic parameters maximum concentration, time at which maximum concentration is reached, and area under the curve between 0 and 8 hours. Treatment response was evaluated by radiographic and radionuclide (I-metaiodobenzylguanidine) imaging, measurement of urinary catecholamines, and clearance of bone marrow disease. We determined the MTD of nifurtimox to be 30 mg/kg/d. The non-dose-limiting toxicities were mainly nausea and neuropathy. The dose-limiting toxicities of 2 patients at 40 mg/kg/d were a grade 3 pulmonary hemorrhage and a grade 3 neuropathy (reversible). Overall, nifurtimox was well tolerated by pediatric patients at a dose of 30 mg/kg/d, and tumor responses were seen both as a single agent and in combination with chemotherapy. A Phase 2 study to determine the antitumor efficacy of nifurtimox is currently underway.

LIN28 has emerged as an oncogenic driver in a number of cancers, including neuroblastoma (NB). Overexpression of LIN28 correlates with poor outcome in NB, therefore drugs that impact the LIN28/Let-7 pathway could be beneficial in treating NB patients. The LIN28/Let-7 pathway affects many cellular processes including the regulation of cancer stem cells and glycolytic metabolism. Polyamines, regulated by ornithine decarboxylase (ODC) modulate eIF-5A which is a direct regulator of the LIN28/Let-7 axis. We propose that therapy inhibiting ODC will restore balance to the LIN28/Let-7 axis, suppress glycolytic metabolism, and decrease MYCN protein expression in NB. Difluoromethylornithine (DFMO) is an inhibitor of ODC in clinical trials for children with NB. In vitro experiments using NB cell lines, BE(2)-C, SMS-KCNR, and CHLA90 show that DFMO treatment reduced LIN28B and MYCN protein levels and increased Let-7 miRNA and decreased neurosphere formation. Glycolytic metabolic activity decreased with DFMO treatment in vivo. Additionally, sensitivity to DFMO treatment correlated with LIN28B overexpression (BE(2)-C>SMS-KCNR>CHLA90). This is the first study to demonstrate that DFMO treatment restores balance to the LIN28/Let-7 axis and inhibits glycolytic metabolism and neurosphere formation in NB and that PET scans may be a meaningful imaging tool to evaluate the therapeutic effects of DFMO treatment.

Neuroblastoma is the most common extracranial solid tumor in children and, when disseminated, carries a poor prognosis. Even with aggressive combinations of chemotherapy, surgery, autologous bone marrow transplant and radiation, long-term survival remains at 30% and new therapies are needed. Recently, a patient with neuroblastoma who acquired Chagas disease was treated with nifurtimox with subsequent reduction in tumor size. The effect of nifurtimox on the neuroblastoma cell lines CHLA-90, LA1-55n, LA-N2, SMS-KCNR, and SY5Y was examined. Nifurtimox decreased cell viability in a concentration-dependent manner. Cell morphology, TUNEL assay, and caspase-3 activation indicate that cell death was primarily due to apoptosis. Nifurtimox also suppressed basal and TrkB-mediated Akt phosphorylation, and the cytotoxicity of nifurtimox was attenuated by a tyrosine hydroxylase inhibitor (alpha methyl tyrosine). Nifurtimox killed catecholaminergic, but not cholinergic, autonomic neurons in culture. In vivo xenograft models showed inhibition of tumor growth with a histologic decrease in proliferation and increase in apoptosis. These results suggest that nifurtimox induces cell death in neuroblastoma. Therefore, further studies are warranted to develop nifurtimox as a promising new treatment for neuroblastoma.

The cytotoxic, anti-proliferative and apoptotic effects of 3-Bromoacetoxy Calcidiol (B3CD), a derivative of vitamin D 3 precursor calcidiol, on human neuroblastoma (NB) cells were examined. NB, predominantly a tumor of early childhood, is the most common extracranial solid tumor. Despite aggressive treatments, survival for advanced stages remains low and novel treatment strategies are needed. B3CD-induced apoptosis in various neuroblastic cells via caspases-3 and -9 activation. B3CD upregulated mitochondrial pro-apoptotic Bax and anti-apoptotic Bcl-2 expression, caused cytochrome c release, downregulated N-Myc expression and activated pro-survival marker Akt. Accordingly, B3CD treatment dose dependently reduced the viability of NB cells with IC 50 values between 1 and 3 μM. The cytotoxicity of B3CD was significantly higher than for the calcemic parentcompound vitamin D 3 (IC 50 between 10 and 30 μM). Further studies revealed that B3CD treatment inhibits the proliferation of NB cells at low concentrations (IC 50 between 30 and 100 nM). Cell cycle analysis showed a dramatic increase in the apoptotic sub-diploidal population along with a cell cycle block. In summary, the present study shows that B3CD is toxic to NB cells via suppression of cell proliferation and cell viability by caspase activation and regulation of survival signals. These results suggest that B3CD could be developed as a treatment for NB. Keywords chemical biology; drug design; kinases; signal transductionNeuroblastoma (NB), predominantly a tumor of early childhood, is the most common extracranial solid tumor. Two-thirds of the cases occur in children below the age of five. NB account for 7-10% of all childhood cancers; in the majority of patients older than 1 year of age, the disease is fatal (1). There are approximately 500-1000 new cases of NB in the USA each year (2). Treatment methods currently available include surgery, radiation therapy, chemotherapy, and autologous stem cell transplantation (3-5) either alone or in combination, depending on the location and biological characteristics of the cancer cells, stage and the risk group to which the patient belongs. However, despite intensive multimodality treatment, more than 50% of children with high-risk disease relapse, because of drug-resistant residual disease *Corresponding author: Laurent Brard, lbrard@wihri.org; Laurent_Brard_MD@Brown.edu Thilo S. Lange and Rakesh K. Singh contributed equally to the manuscript. [6][7][8]. Eradication of refractory microscopic disease remains one of the most significant challenges in the treatment of the high-risk NB and innovative treatments need to be designed. NIH Public AccessCalcitriol/vitamin D 3 (1,25-dihydroxy-vitamin D 3 ) (Figure 1), an endocrine hormone responsible for calcium and mineral homeostasis, inhibits cell proliferation and induces differentiation, via binding to the vitamin D receptor (VDR) (9). Its clinical use in cancer therapy is limited by its hypercalcemic side-effects (10-12). Synthetic analogs of calcitriol/ vitamin D ...

Neuroblastoma is a sympathetic nervous system tumor, primarily presenting in children under 6 years of age. The long-term prognosis for patients with high-risk neuroblastoma (HRNB) remains poor despite aggressive multimodal therapy. This report provides an update to a phase II trial evaluating DFMO as maintenance therapy in HRNB. Event-free survival (EFS) and overall survival (OS) of 81 subjects with HRNB treated with standard COG induction, consolidation and immunotherapy followed by 2 years of DFMO on the NMTRC003/003b Phase II trial were compared to a historical cohort of 76 HRNB patients treated at Beat Childhood Cancer Research Consortium (BCC) hospitals who were disease-free after completion of standard upfront therapy and did not receive DFMO. The 2-and 5-year EFS were 86.4%