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1.  Cortical Processing of Respiratory Occlusion Stimuli in Children with Central Hypoventilation Syndrome 
Rationale: The ability of patients with central hypoventilation syndrome (CHS) to produce and process mechanoreceptor signals is unknown.
Objectives: Children with CHS hypoventilate during sleep, although they generally breathe adequately during wakefulness. Previous studies suggest that they have compromised central integration of afferent stimuli, rather than abnormal sensors or receptors. Cortical integration of afferent mechanical stimuli caused by respiratory loading or upper airway occlusion can be tested by measuring respiratory-related evoked potentials (RREPs). We hypothesized that patients with CHS would have blunted RREP during both wakefulness and sleep.
Methods: RREPs were produced with multiple upper airway occlusions and were obtained during wakefulness, stage 2, slow-wave, and REM sleep. Ten patients with CHS and 20 control subjects participated in the study, which took place at the Children's Hospital of Philadelphia. Each patient was age- and sex-matched to two control subjects. Wakefulness data were collected from 9 patients and 18 control subjects.
Measurements and Main Results: During wakefulness, patients demonstrated reduced Nf and P300 responses compared with control subjects. During non-REM sleep, patients demonstrated a reduced N350 response. In REM sleep, patients had a later P2 response.
Conclusions: CHS patients are able to produce cortical responses to mechanical load stimulation during both wakefulness and sleep; however, central integration of the afferent signal is disrupted during wakefulness, and responses during non-REM are damped relative to control subjects. The finding of differences between patients and control subjects during REM may be due to increased intrinsic excitatory inputs to the respiratory system in this state.
doi:10.1164/rccm.200804-606OC
PMCID: PMC2556457  PMID: 18658113
central hypoventilation syndrome; respiratory-related evoked potentials; wakefulness; sleep
2.  Relapsed neuroblastomas show frequent RAS-MAPK pathway mutations 
Nature genetics  2015;47(8):864-871.
The majority of neuroblastoma patients have tumors that initially respond to chemotherapy, but a large proportion of patients will experience therapy-resistant relapses. The molecular basis of this aggressive phenotype is unknown. Whole genome sequencing of 23 paired diagnostic and relapsed neuroblastomas showed clonal evolution from the diagnostic tumor with a median of 29 somatic mutations unique to the relapse sample. Eighteen of the 23 relapse tumors (78%) showed mutations predicted to activate the RAS-MAPK signaling pathway. Seven events were detected only in the relapse tumor while the others showed clonal enrichment. In neuroblastoma cell lines we also detected a high frequency of activating mutations in the RAS-MAPK pathway (11/18, 61%) and these lesions predicted for sensitivity to MEK inhibition in vitro and in vivo. Our findings provide the rationale for genetic characterization of relapse neuroblastoma and show that RAS-MAPK pathway mutations may function as a biomarker for new therapeutic approaches to refractory disease.
doi:10.1038/ng.3333
PMCID: PMC4775079  PMID: 26121087
3.  Mitogen-activated protein kinase (MEK/ERK) inhibition sensitizes cancer cells to centromere-associated protein E inhibition 
Inhibition of centromere-associated protein-E (CENP-E) has demonstrated preclinical anti-tumor activity in a number of tumor types including neuroblastoma. A potent small molecule inhibitor of the kinesin motor activity of CENP-E has recently been developed (GSK923295). To identify an effective drug combination strategy for GSK923295 in neuroblastoma, we performed a screen of siRNAs targeting a prioritized set of genes that function in therapeutically tractable signaling pathways. We found that siRNAs targeted to extracellular signal-related kinase 1 (ERK1) significantly sensitized neuroblastoma cells to GSK923295-induced growth inhibition (p = 0.01). Inhibition of ERK1 activity using pharmacologic inhibitors of mitogen-activated ERK kinase (MEK1/2) showed significant synergistic growth inhibitory activity when combined with GSK923295 in neuroblastoma, lung, pancreatic and colon carcinoma cell lines. Synergistic growth inhibitory activity of combined MEK/ERK and CENP-E inhibition was a result of increased mitotic arrest and apoptosis. There was a significant correlation between ERK1/2 phosphorylation status in neuroblastoma cell lines and GSK923295 growth inhibitory activity (r = 0.823, p = 0.0006). Consistent with this result we found that lung cancer cell lines harboring RAS mutations, which leads to oncogenic activation of MEK/ERK signaling, were significantly more resistant than cell lines with wild-type RAS to GSK923295-induced growth inhibition (p = 0.047). Here we have identified (MEK/ERK) activity as a potential biomarker of relative GSK923295 sensitivity and have shown the synergistic effect of combinatorial MEK/ERK pathway and CENP-E inhibition across different cancer cell types including neuroblastoma.
doi:10.1002/ijc.27781
PMCID: PMC4706358  PMID: 22948716
CENP-E; GSK923295; ERK; MEK; neuroblastoma; Ras
4.  Genetic predisposition to neuroblastoma mediated by a LMO1 super-enhancer polymorphism 
Nature  2015;528(7582):418-421.
Summary
Neuroblastoma is a pediatric malignancy that typically arises in early childhood and is derived from the developing sympathetic nervous system. Clinical phenotypes range from localized tumors with excellent outcomes to widely metastatic disease where long-term survival is approximately 40% despite intensive therapy1. A previous genome-wide association study (GWAS) identified common polymorphisms at the LMO1 gene locus that are highly associated with neuroblastoma susceptibility and oncogenic addiction to LMO1 in the tumor cells2. Here we sought to discover the causal DNA variant at this locus and the mechanism by which it leads to neuroblastoma tumorigenesis. We first imputed all possible genotypes across the LMO1 locus and then mapped highly associated single nucleotide polymorphism (SNPs) to areas of chromatin accessibility, evolutionary conservation, and transcription factor binding sites. SNP rs2168101 G>T was the most highly associated variant (combined P=7.47×10-29, Odds Ratio 0.65, 95% CI: 0.60-0.70) and resided in a super-enhancer defined by extensive acetylation of histone H3 lysine 27 within the first intron of LMO1. The ancestral G-allele that is associated with tumor formation resides in a conserved GATA transcription factor binding motif. We show that the newly evolved protective TATA allele is associated with decreased total LMO1 expression (P=0.028) in neuroblastoma primary tumors and ablates GATA3 binding (P<0.0001). We demonstrate allelic imbalance favoring the G-containing strand in tumors heterozygous for this SNP as demonstrated both by RNA sequencing (P<0.0001) and reporter assays (P=0.002). These findings show that a recently evolved polymorphism within a super-enhancer element in the first intron of LMO1 influences neuroblastoma susceptibility through differential GATA transcription factor binding and direct modulation of LMO1 expression in cis, and this leads to an oncogenic dependency in tumor cells.
doi:10.1038/nature15540
PMCID: PMC4775078  PMID: 26560027
5.  Synergistic Activity of PARP Inhibition by Talazoparib (BMN 673) with Temozolomide in Pediatric Cancer Models in the Pediatric Preclinical Testing Program 
Background
Inhibitors of poly-ADP ribose polymerase (PARP), an enzyme involved in base excision repair (BER) have demonstrated single agent activity against tumors deficient in homologous repair processes. Ewing sarcoma cells are also sensitive to PARP inhibitors, although the mechanism is not understood. Here we evaluated the stereo-selective PARP inhibitor, talazoparib (BMN 673), combined with temozolomide or topotecan.
Procedures
Talazoparib was tested in vitro in combination with temozolomide (0.3–1,000 μmol/L) or topotecan (0.03-100 nmol/L) and in vivo at a dose of 0.1 mg/kg administered twice daily for 5 days combined with temozolomide (30 mg/kg/daily x 5; combination A) or 0.25 mg/kg administered twice daily for 5 days combined with temozolomide (12 mg/kg/daily x 5; combination B).
Results
In vitro talazoparib potentiated the toxicity of temozolomide up to 85-fold, with marked potentiation in Ewing sarcoma and leukemia lines (30–50-fold). There was less potentiation for topotecan. In vivo, talazoparib potentiated the toxicity of temozolomide, and Combination A and Combination B represent the maximum tolerated doses when combined with low dose or high dose talazoparib, respectively. Both combinations demonstrated significant synergism against 5 of 10 Ewing sarcoma xenografts. The combination demonstrated modest activity against most other xenograft models. Pharmacodynamic studies showed a treatment-induced complete loss of PARP only in tumor models sensitive to either talazoparib alone or talazoparib plus temozolomide.
Conclusions
The high level of activity observed for talazoparib plus temozolomide in Ewing sarcoma xenografts makes this an interesting combination to consider for pediatric evaluation.
doi:10.1158/1078-0432.CCR-14-2572
PMCID: PMC4587665  PMID: 25500058
Preclinical Testing; Developmental Therapeutics; PARP inhibitor
7.  Targeting the mTOR Complex by Everolimus in NRAS Mutant Neuroblastoma 
PLoS ONE  2016;11(1):e0147682.
High-risk neuroblastoma remains lethal in about 50% of patients despite multimodal treatment. Recent attempts to identify molecular targets for specific therapies have shown that Neuroblastoma RAS (NRAS) is significantly mutated in a small number of patients. However, few inhibitors for the potential treatment for NRAS mutant neuroblastoma have been investigated so far. In this in-vitro study, we show that MEK inhibitors AZD6244, MEK162 and PD0325901 block cell growth in NRAS mutant neuroblastoma cell lines but not in NRAS wild-type cell lines. Several studies show that mutant NRAS leads to PI3K pathway activation and combined inhibitors of PI3K/mTOR effectively block cell growth. However, we observed the combination of MEK inhibitors with PI3K or AKT inhibitors did not show synergestic effects on cell growth. Thus, we tested single mTOR inhibitors Everolimus and AZD8055. Interestingly, Everolimus and AZD8055 alone were sufficient to block cell growth in NRAS mutant cell lines but not in wild-type cell lines. We found that Everolimus alone induced apoptosis in NRAS mutant neuroblastoma. Furthermore, the combination of mTOR and MEK inhibitors resulted in synergistic growth inhibition. Taken together, our results show that NRAS mutant neuroblastoma can be targeted by clinically available Everolimus alone or in combination with MEK inhibitors which could impact future clinical studies.
doi:10.1371/journal.pone.0147682
PMCID: PMC4731059  PMID: 26821351
8.  Initial Testing (Stage 1) of the PARP Inhibitor BMN 673 by the Pediatric Preclinical Testing Program: PALB2 Mutation Predicts Exceptional in Vivo Response to BMN 673 
Pediatric blood & cancer  2014;62(1):91-98.
Introduction
BMN 673 is a potent inhibitor of poly-ADP ribose polymerase (PARP) that is in clinical testing with a primary focus on BRCA-mutated cancers. BMN 673 is active both through inhibiting PARP catalytic activity and by tightly trapping PARP to DNA at sites of single strand breaks.
Methods
BMN 673 was tested in vitro at concentrations ranging from 0.1 nM to 1 μM and in vivo at a daily dose of 0.33 mg/kg administered orally twice daily (Mon-Fri) and once daily on weekends (solid tumors) for 28 days.
Results
The median relative IC50 (rIC50) concentration against the PPTP cell lines was 25.8 nM. The median rIC50 for the Ewing cell lines was lower than for the remaining cell lines (6.4 versus 31.1 nM, respectively). In vivo BMN 673 induced statistically significant differences in EFS distribution in 17/43 (39.5%) xenograft models. Three objective regressions were observed: a complete response (CR) in a medulloblastoma line (BT-45), a maintained CR in a Wilms tumor line (KT-10), and a maintained CR in an ependymoma line (BT-41). BMN 673 maintained its high level of activity against KT-10 with a 3-fold reduction in dose. KT-10 possesses a truncating mutation in PALB2 analogous to PALB2 mutations associated with hereditary breast and ovarian cancer that abrogate homologous recombination (HR) repair.
Conclusions
The PPTP results suggest that single agent BMN 673 may have limited clinical activity against pediatric cancers. Single agent activity is more likely for patients whose tumors have defects in HR repair.
doi:10.1002/pbc.25201
PMCID: PMC4456187  PMID: 25263539
Preclinical Testing; Developmental Therapeutics; PARP inhibitor; PALB2
9.  Initial Testing (Stage 1) of the Phosphatidylinositol 3’ Kinase Inhibitor, SAR245408 (XL147) by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2012;60(5):791-798.
Background
Activation of the PI3 kinase pathway occurs frequently in many adult cancers and is implicated in tumor cell proliferation, survival, and resistance to chemotherapy and radiotherapy. However, less is known regarding the relevance of this pathway in pediatric cancers. Here we have evaluated SAR245408, a novel small molecule PI3K inhibitor, against childhood cancer cell lines and xenografts.
Procedures
SAR245408 was tested against the PPTP in vitro cell line panel at concentrations from 10 nM to 100 µM and against the PPTP in vivo xenograft panels at a dose of 100 mg/kg administered orally daily × 14.
Results
In vitro SAR245408 demonstrated cytotoxic activity, with a median relative IC50 value of 10.9 µM (range 2.7 µM to 24.5 µM). SAR245408 was well tolerated in vivo, and all 44 tested xenograft models were evaluable for efficacy. SAR245408 induced significant differences in EFS distribution compared to control in 29 of 37 (79%) of solid tumor xenografts and in 2 of 7 (29%) ALL xenografts. SAR245408 induced tumor growth inhibition meeting criteria for intermediate EFS T/C activity (EFS T/C > 2) in 4 of 37 (11%) solid tumor xenografts. Intermediate EFS T/C activity was also observed for 2 of 7 (29%) evaluable ALL xenografts. Objective responses were not observed for solid tumor or for ALL xenografts.
Conclusions
Under the conditions evaluated in this study, SAR245408 achieved modest single-agent activity against most PPTP preclinical models. Further exploration of SAR245408 in combination with standard agents or with other signaling inhibitors could be considered.
doi:10.1002/pbc.24301
PMCID: PMC4684943  PMID: 23002019
Preclinical Testing; Developmental Therapeutics; PI3K inhibitor
10.  Common genetic variants in NEFL influence gene expression and neuroblastoma risk 
Cancer research  2014;74(23):6913-6924.
The genetic etiology of sporadic neuroblastoma is still largely obscure. In a genome-wide association study, we identified single nucleotide polymorphisms (SNP) associated with neuroblastoma at the LINC00340, BARD1, LMO1, DUSP12, HSD17B12, HACE1 and LIN28B gene loci, but these explain only a small fraction of neuroblastoma heritability. Other neuroblastoma susceptibility genes are likely hidden among signals discarded by the multiple testing corrections. In this study, we evaluated 8 additional genes selected as candidates for further study based on proven involvement in neuroblastoma differentiation. SNP at these candidate genes were tested for association with disease susceptibility in 2101 cases and 4202 controls, with the associations found replicated in an independent cohort of 459 cases and 809 controls. Replicated associations were further studied for cis-effect using gene expression, transient overexpression, silencing and cellular differentiation assays. The neurofilament gene NEFL harbored three SNP associated with neuroblastoma (rs11994014; Pcombined=0.0050; OR=0.88, rs2979704; Pcombined=0.0072; OR=0.87, rs105911; Pcombined=0.0049; OR=0.86). The protective allele of rs1059111 correlated with increased NEFL expression. Biological investigations showed that ectopic overexpression of NEFL inhibited cell growth specifically in neuroblastoma cells carrying the protective allele. NEFL overexpression also enhanced differentiation and impaired the proliferation and anchorage-independent growth of cells with protective allele and basal NEFL expression, while impairing invasiveness and proliferation of cells homozygous for the risk genotype. Clinically, high levels of NEFL expression in primary neuroblastoma specimens was associated with better overall survival (P=0.03; HR=0.68). Our results show that common variants of NEFL influence neuroblastoma susceptibility and they establish that NEFL expression influences disease initiation and progression.
doi:10.1158/0008-5472.CAN-14-0431
PMCID: PMC4253722  PMID: 25312269
neuroblastoma; SNP; NEFL; genetic association; GWAS
11.  Initial Solid Tumor Testing (Stage 1) of AZD1480, an Inhibitor of Janus Kinases 1 and 2 by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2014;61(11):1972-1979.
Background
AZD1480 is an ATP competitive inhibitor of Janus kinases 1 and 2 (JAK1, 2) that has been shown to inhibit the growth of solid tumor models. This agent was selected for testing the putative role of JAK/STAT signaling in the standard PPTP solid tumor models.
Procedures
AZD1480 was tested against the PPTP in vitro cell line panel at concentrations from 1.0 nM to 10 M and against the PPTP in vivo solid tumor xenograft panels at (60 mg/kg once daily (SID) × 5) for 3 consecutive weeks. Additional studies evaluated 5 to 20 mg/kg BID × 5 with SID dosing at 7–30 mg/kg at weekends for 3 consecutive weeks.
Results
In vitro the median relative IC50 (rIC50) for the PPTP cell lines was 1.5 µM, with a range from 0.3 µM to 5.9 µM. The two cell lines with rIC50 values of 0.3 µM both had ALK activating genomic alterations. AZD1480 demonstrated statistically significant differences (p<0.05) in EFS distribution compared to control in 89% of the solid tumor xenografts. AZD1480 induced intermediate (EFS T/C > 2) or high-level growth inhibition in 15 of 30 (50%) solid tumor xenografts. Tumor regressions were observed in 3 of 6 Wilms tumor models at doses that induced inhibition of Stat3(Y705) phosphorylation.
Conclusions
AZD1480 demonstrated significant tumor growth inhibition against most PPTP solid tumor xenografts, similar to that observed for antiangiogenic agents tested by the PPTP. Tumor regressing activity was noted for Wilms tumor xenografts.
doi:10.1002/pbc.25175
PMCID: PMC4201390  PMID: 25131802
Preclinical Testing; Developmental Therapeutics; JAK1/2 inhibitor
12.  Neuroblastoma - Undifferentiated Subtype, Prognostic Significance of Prominent Nucleolar Formation and MYC/MYCN Protein Expression: A Report from the Children’s Oncology Group 
Cancer  2013;119(20):3718-3726.
Purpose
To investigate biological/clinicopathological characteristics of neuroblastoma, undifferentiated subtype (NBUD).
Patients and Methods
157 NBUD cases filed at the Children’s Oncology Group Neuroblastoma Pathology Reference Laboratory were studied, and survival rates of the patients were analyzed with known prognostic factors. Immunostainings for MYCN and MYC protein were performed on 68 tumors.
Results
NBUD cases had a poor prognosis (48.4±5.0% 3-year event-free survival [EFS]; 56.5±5.0% overall survival), and were often associated with high Mitosis-Karyorrhexis Index (MKI, 65%), prominent nucleoli (PN, 83%), ≥18months of age (75%), MYCN amplification (MYCN-A, 83%), diploid pattern (63%), and 1pLOH (loss of heterozygosity, 72%). However, these prognostic indicators, except for MYCN status, had no significant impact on survival. Surprisingly, EFS for patients with MYCN-A tumors (53.4±5.6%) was significantly better (P=0.0248) than for patients with MYCN-Non-Amplified (MYCN-NA) tumors (31.7±11.7%), with MYCN-NA and PN (+) tumors having the worst prognosis (9.3+8.8%, p=0.0045). Immunohistochemically, MYCN expression was found in 42/48 MYCN-A tumors. In contrast, MYC expression was almost exclusively found in the MYCN-NA tumors (9/20) especially when they had PN (8/11). Those patients with only MYC-positive tumors had the worst EFS (N=8, 12.5±11.7%) compared with only MYCN-positive (N=39, 49.9±17.7%) and both negative tumors (N=15, 70.0±17.1%) (P=0.0029). High MKI was often found in only MYCN-positive (30/38) but rarely in only MYC-positive (2/8) tumors.
Conclusions
NBUD represents a unique subtype of neuroblastoma associated with a poor prognosis. In this subtype, MYC protein expression may be a new prognostic factor indicating more aggressive clinical behavior than MYCN amplification and subsequent MYCN protein expression.
doi:10.1002/cncr.28251
PMCID: PMC4554323  PMID: 23901000
Neuroblastoma; undifferentiated subtype; MYCN Amplification; MYC/MYCN expression; prognostic factors; MYC gene expression
13.  Initial Testing (Stage 1) of the Investigational mTOR Kinase Inhibitor MLN0128 by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2014;61(8):1486-1489.
MLN0128 is an investigational small molecule ATP-competitive inhibitor of the serine/threonine kinase mTOR. MLN0128 was tested against the in vitro panel at concentrations ranging from 0.1 nM to 1 μM and against the PPTP in vivo panels at a dose of 1 mg/kg administered orally daily x 28. In vitro the median relative IC50 concentration was 19 nM. In vivo MLN0128 induced significant differences in EFS in 24/31 (77%) solid tumor models, but 0/7 ALL xenografts. The modest activity observed for MLN0128 against the PPTP preclinical models is similar to that previously reported for another TOR kinase inhibitor.
doi:10.1002/pbc.24989
PMCID: PMC4248662  PMID: 24623675
Preclinical Testing; Developmental Therapeutics; mTOR inhibitor
14.  Initial Testing (Stage 1) of the Notch Inhibitor PF-03084014, by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2014;61(8):1493-1496.
PF-03084014, a γ-secretase inhibitor, was tested against the PPTP in vitro cell line panel (1.0 nM to 10 μM) and against the in vivo xenograft panels (administered orally twice daily on days 1–7 and 15–21). PF-03084014 demonstrated limited in vitro activity, with no cell line achieving ≥50% inhibition. PF-03084014 induced significant differences in EFS distribution in 14 of 35 (40%) solid tumor xenografts, and 1 of 9 ALL xenografts (which lacked a NOTCH1 mutation), but objective responses were not observed. PF-03084014 demonstrated limited single agent activity in vitro and in vivo against the pediatric preclinical models studied.
doi:10.1002/pbc.25026
PMCID: PMC4225044  PMID: 24664981
Preclinical Testing; Developmental Therapeutics; Notch inhibitors
15.  Ataxia-telangiectasia mutated (ATM) silencing promotes neuroblastoma progression through a MYCN independent mechanism 
Oncotarget  2015;6(21):18558-18576.
Neuroblastoma, a childhood cancer with highly heterogeneous biology and clinical behavior, is characterized by genomic aberrations including amplification of MYCN. Hemizygous deletion of chromosome 11q is a well-established, independent marker of poor prognosis. While 11q22-q23 is the most frequently deleted region, the neuroblastoma tumor suppressor in this region remains to be identified. Chromosome bands 11q22-q23 contain ATM, a cell cycle checkpoint kinase and tumor suppressor playing a pivotal role in the DNA damage response. Here, we report that haploinsufficiency of ATM in neuroblastoma correlates with lower ATM expression, event-free survival, and overall survival. ATM loss occurs in high stage neuroblastoma without MYCN amplification. In SK-N-SH, CLB-Ga and GI-ME-N human neuroblastoma cells, stable ATM silencing promotes neuroblastoma progression in soft agar assays, and in subcutaneous xenografts in nude mice. This effect is dependent on the extent of ATM silencing and does not appear to involve MYCN. Our findings identify ATM as a potential haploinsufficient neuroblastoma tumor suppressor, whose inactivation mirrors the increased aggressiveness associated with 11q deletion in neuroblastoma.
PMCID: PMC4621910  PMID: 26053094
ataxia-telangiectasia mutated; neuroblastoma; MYCN; 11q
16.  Initial Testing of Lenalidomide by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2011;57(4):606-611.
Background
Lenalidomide, a novel immunomodulatory agent, is reported to modulate stem cell differentiation, and have direct antiproliferative activity as well as inhibit inflammation and hyperalgesia. On the basis of this varied pharmacological profile, lenalidomide is under investigation as a treatment for a range of oncologic indications.
Procedures
Lenalidomide was evaluated against the PPTP in vitro panel using 96 hour exposure at concentrations ranging from 1 nM to 10 μM. It was tested against the PPTP in vivo panels at a dose of 30 mg/kg administered orally (PO) oncedaily for a planned for 6 weeks.
Results
In vitro activity was not observed at concentrations up to 10 μM. Lenalidomide was well tolerated, and induced significant differences in EFS distribution compared to control in 7 of 37 (18.9%) of the evaluable solid tumor xenografts and in 0 of 8 (0%) of the evaluable ALL xenografts. The best response in the solid tumor panel was PD2 [progressive disease with growth delay (EFS T/C > 1.5)], observed in 4 of 37 (10.8%) solid tumor xenografts. A single ALL xenograft showed a PD2 response.
Conclusions
Direct antiproliferative effects of lenalidomide were not observed in vitro. In vivo lenalidomide demonstrated low activity against tumors in immune-deficient mice. Our results suggest that lenalidomide’s utility in the pediatric clinical setting may depend upon its ability to induce antitumor activity through effects on host immune and stromal cells rather than through direct effects on tumor cells.
doi:10.1002/pbc.22877
PMCID: PMC4505747  PMID: 21360651
Preclinical Testing; Developmental Therapeutics; Lenalidomide
17.  Initial Testing of JNJ-26854165 (Serdemetan) by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2011;59(2):329-332.
JNJ-26854165 was originally developed as an activator of p53 capable of inducing apoptosis in cancer cell lines. In vitro, JNJ-26854165 demonstrated cytotoxic activity. The ALL cell line panel had a significantly lower median IC50 (0.85 µM) than the remaining cell lines. In vivo JNJ-26854165 induced significant differences in EFS distribution compared to control in 18 of 37 solid tumors and in 5 of 7 of the evaluable ALL xenografts. Objective responses were observed in 4 of 37 solid tumor xenografts, and 2 of 7 ALL xenografts achieved PR or CR. Responses were noted in xenografts with both mutant and wild-type p53.
doi:10.1002/pbc.23319
PMCID: PMC4504194  PMID: 21922647
Preclinical Testing; Developmental Therapeutics; JNJ-26854165
18.  Initial Testing (Stage 1) of the Antibody-Maytansinoid Conjugate, IMGN901 (Lorvotuzumab Mertansine), by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2013;60(11):1860-1867.
Background
IMGN901 (lorvotuzumab mertansine) is an antibody-drug conjugate composed of a humanized antibody that specifically binds to CD56 (NCAM, neural cell adhesion molecule) and that is conjugated to the maytansinoid, DM1 (a microtubule targeting agent).
Procedures
IMGN901 and DM1-SMe (unconjugated DM1 as a mixed disulfide with thiomethane to cap its sulfhydryl group) were tested in vitro at concentrations ranging from 0.01 nM to 0.1 μM and 0.3 pM to 3 nM, respectively. IMGN901 was tested against a subset of PPTP solid tumor xenografts focusing on those with high CD56 expression.The combination of IMGN901 with topotecan was also evaluated.
Results
Neuroblastoma models expressed CD56 at or above the median expression level for all PPTP xenografts and cell lines. Neuroblastoma cell lines demonstrated relatively low sensitivity to DM1-SMe compared to other cell lines, but the sensitivity of neuroblastoma cell lines to IMGN901 was comparable to that of non-neuroblastoma cell lines. In vivo, objective responses were observed in 9 of 24 (38%) models including, 3 of 7 neuroblastoma xenografts, and 2 of 7 rhabdomyosarcoma xenografts. All xenografts with objective responses showed homogeneous high-level staining by IHC for CD56, but not all xenografts with homogenous high-level staining had objective responses. Combined with topotecan, IMGN901 demonstrated therapeutic enhancement against 2 of 4 neuroblastoma models.
Conclusions
IMGN901 has anti-tumor activity against some CD56 expressing pediatric cancer models. High expression of CD56 is a biomarker for in vivo response, but resistance mechanisms to IMGN901 in some high CD56 expressing lines need to be defined.
doi:10.1002/pbc.24647
PMCID: PMC4260400  PMID: 23798344
Preclinical Testing; Developmental Therapeutics; antibody-maytansinoid conjugate; microtubules
19.  Dual CDK4/CDK6 Inhibition Induces Cell Cycle Arrest and Senescence in Neuroblastoma 
Purpose
Neuroblastoma is a pediatric cancer that continues to exact significant morbidity and mortality. Recently, a number of cell cycle proteins, particularly those within the Cyclin D/CDK4/CDK6/RB network, have been shown to exert oncogenic roles in neuroblastoma, suggesting that their therapeutic exploitation might improve patient outcomes.
Experimental Procedures
We evaluated the effect of dual CDK4/CDK6 inhibition on neuroblastoma viability using LEE011, a highly specific CDK4/6 inhibitor.
Results
Treatment with LEE011 significantly reduced proliferation in 12 of 17 human neuroblastoma-derived cell lines by inducing cytostasis at nanomolar concentrations (mean IC50 = 307 ± 68 nM in sensitive lines). LEE011 caused cell cycle arrest and cellular senescence that was attributed to dose-dependent decreases in phosphorylated RB and FOXM1, respectively. In addition, responsiveness of neuroblastoma xenografts to LEE011 translated to the in vivo setting in that there was a direct correlation of in vitro IC50 values with degree of subcutaneous xenograft growth delay. While our data indicate that neuroblastomas sensitive to LEE011 were more likely to contain genomic amplification of MYCN (p = 0.01), the identification of additional clinically accessible biomarkers is of high importance.
Conclusions
Taken together, our data show that LEE011 is active in a large subset of neuroblastoma cell line and xenograft models, and supports the clinical development of this CDK4/6 inhibitor as a therapy for patients with this disease.
doi:10.1158/1078-0432.CCR-13-1675
PMCID: PMC3844928  PMID: 24045179
Neuroblastoma; CDK4; CDK6; LEE011; MYCN
20.  Phase II Study of Irinotecan and Temozolomide in Children With Relapsed or Refractory Neuroblastoma: A Children's Oncology Group Study 
Journal of Clinical Oncology  2010;29(2):208-213.
Purpose
This phase II study was conducted to determine the response rate associated with use of irinotecan and temozolomide for children with relapsed/refractory neuroblastoma.
Patients and Methods
Patients with relapsed/refractory neuroblastoma measurable by cross-sectional imaging (stratum 1) or assessable by bone marrow aspirate/biopsy or metaiodobenzylguanidine (MIBG) scan (stratum 2) received irinotecan (10 mg/m2/dose 5 days a week for 2 weeks) and temozolomide (100 mg/m2/dose for 5 days) every 3 weeks. Response was assessed after three and six courses using International Neuroblastoma Response Criteria. Of the first 25 evaluable patients on a given stratum, five or more patients with complete or partial responses were required to conclude that further study would be merited.
Results
Fifty-five eligible patients were enrolled. The objective response rate was 15%. Fourteen patients (50%) on stratum 1 and 15 patients (56%) on stratum 2 had stable disease. Objective responses were observed in three of the first 25 evaluable patients on stratum 1 and five of the first 25 evaluable patients on stratum 2. Less than 6% of patients experienced ≥ grade 3 diarrhea. Although neutropenia was observed, less than 10% of patients developed evidence of infection while neutropenic.
Conclusion
The combination of irinotecan and temozolomide was well tolerated. The objective response rate of 19% in stratum 2 suggests that this combination may be effective for patients with neuroblastoma detectable by MIBG or marrow analysis. Although fewer objective responses were observed in patients with disease measurable by computed tomography/magnetic resonance imaging, patients in both strata seem to have derived clinical benefit from this therapy.
doi:10.1200/JCO.2010.31.7107
PMCID: PMC3058276  PMID: 21115869
21.  Integrating Cell-Based and Clinical Genome-Wide Studies to Identify Genetic Variants Contributing to Treatment Failure in Neuroblastoma Patients 
High-risk neuroblastoma is an aggressive malignancy with high rates of treatment failure. We evaluated genetic variants associated with in vitro sensitivity to two derivatives of cyclophosphamide for association with clinical response in a separate replication cohort of neuroblastoma patients (n=2,709). Lymphoblastoid cell lines (LCLs) were exposed to increasing concentrations of 4-hydroperoxycyclophosphamide [4HC n=422] and phosphoramide mustard [PM n=428] to determine sensitivity. Genome-wide association studies (GWAS) were performed to identify single nucleotide polymorphisms (SNPs) associated with 4HC and PM sensitivity. SNPs consistently associated with LCL sensitivity were analyzed for associations with event-free survival in patients. Two linked SNPs, rs9908694 and rs1453560, were found to be associated with PM sensitivity in LCLs across populations and were associated with event-free survival in all patients (P=0.01) and within the high-risk subset (P=0.05). Our study highlights the value of cell-based models to identify candidate variants that may predict response to treatment in patients with cancer.
doi:10.1038/clpt.2014.37
PMCID: PMC4029857  PMID: 24549002
neuroblastoma; pharmacogenomics; cell-based models; IKZF3; ZPBP2; expression quantitative trait loci
22.  Rare Variants in TP53 and Susceptibility to Neuroblastoma 
TP53 is the most frequently mutated gene in human malignancies; however, de novo somatic mutations in childhood embryonal cancers such as neuroblastoma are rare. We report on the analysis of three independent case–control cohorts comprising 10290 individuals and demonstrate that rs78378222 and rs35850753, rare germline variants in linkage disequilibrium that map to the 3′ untranslated region (UTR) of TP53 and 5′ UTR of the Δ133 isoform of TP53, respectively, are robustly associated with neuroblastoma (rs35850753: odds ratio [OR] = 2.7, 95% confidence interval [CI] = 2.0 to 3.6, P combined = 3.43×10−12; rs78378222: OR = 2.3, 95% CI = 1.8 to 2.9, P combined = 2.03×10−11). All statistical tests were two-sided. These findings add neuroblastoma to the complex repertoire of human cancers influenced by the rs78378222 hypomorphic allele, which impairs proper termination and polyadenylation of TP53 transcripts. Future studies using whole-genome sequencing data are likely to reveal additional rare variants with large effect sizes contributing to neuroblastoma tumorigenesis.
doi:10.1093/jnci/dju047
PMCID: PMC3982892  PMID: 24634504
23.  Inactivation of SMC2 shows a synergistic lethal response in MYCN-amplified neuroblastoma cells 
Cell Cycle  2014;13(7):1115-1131.
The condensin complex is required for chromosome condensation during mitosis; however, the role of this complex during interphase is unclear. Neuroblastoma is the most common extracranial solid tumor of childhood, and it is often lethal. In human neuroblastoma, MYCN gene amplification is correlated with poor prognosis. This study demonstrates that the gene encoding the condensin complex subunit SMC2 is transcriptionally regulated by MYCN. SMC2 also transcriptionally regulates DNA damage response genes in cooperation with MYCN. Downregulation of SMC2 induced DNA damage and showed a synergistic lethal response in MYCN-amplified/overexpression cells, leading to apoptosis in human neuroblastoma cells. Finally, this study found that patients bearing MYCN-amplified tumors showed improved survival when SMC2 expression was low. These results identify novel functions of SMC2 in DNA damage response, and we propose that SMC2 (or the condensin complex) is a novel molecular target for the treatment of MYCN-amplified neuroblastoma.
doi:10.4161/cc.27983
PMCID: PMC4013162  PMID: 24553121
condensin complex; DNA damage response; MYCN; neuroblastoma; synergistic lethal response
24.  Age-Dependent Prognostic Effect by Mitosis-Karyorrhexis Index in Neuroblastoma: A Report from the Children’s Oncology Group 
Prognostic effects of Mitosis-Karyorrhexis Index (MKI) used in the International Neuroblastoma Pathology Classification (INPC) are age-dependent. A total of 4,282 neuroblastomas reviewed at the Children’s Oncology Group Neuroblastoma Pathology Reference Laboratory (8/1/2001–3/31/2012) included 2,365 low-MKI (L-MKI), 1,068 intermediate-MKI (I-MKI), and 849 high-MKI (H-MKI) tumors. Cox proportional hazards models were fit to determine age cut-offs at which the relative risk of event/death was maximized in each MKI class. Backward-selected Cox models were fit to determine the prognostic strength of the age cut-offs for survival in the presence of other prognostic factors. The age cut-offs used in the INPC for L-MKI tumors (<60 months, n = 2,710, 84.0% ± 1.0% event-free survival [EFS], 93.8 ± 0.7% overall survival [OS] vs ≥60 months, n = 195, 49.8% ± 4.6% EFS, 71.7% ± 4.1% OS; P < 0.0001) and I-MKI tumors (<18 months, n = 568, 83.8% ± 2% EFS, 93.7% ± 1.3% OS vs ≥18 months, n = 500, 51.4% ± 2.9% EFS, 66.7% ± 2.7% OS; P < 0.0001) were within the effective range for distinguishing prognostic groups. As for H-MKI tumors (no cut-off age in the INPC, 51.0% ± 2.2% EFS, 64.4% ± 2.1% OS), a new cut-off of 3–4 months was suggested (<4 months, n = 38, 82.3% ± 8.4% EFS, 81.8% ± 8.5% OS vs ≥4 months, n = 811, 49.6% ± 2.2% EFS, 63.7% ± 2.1% OS, P = 0.0034 and 0.0437, respectively). Multivariate analyses revealed that cut-offs of 60 and 18 months for L-MKI and I-MKI tumors, respectively, were independently prognostic. However, the cut-off of 4 months for H-MKI tumors did not reach statistical significance in the presence of other factors. The age cut-offs for MKI classes (60 months for L-MKI, 18 months for I-MKI, no cut-off for H-MKI) in the current INPC are reasonable and effective for distinguishing prognostic groups with increased risk of event/death for older patients.
doi:10.2350/14-06-1505-OA.1
PMCID: PMC4340697  PMID: 25207821
age cut-off; International Neuroblastoma Pathology Classification; mitosis-karyorrhexis index; neuroblastoma; prognosis
25.  Initial Testing (Stage 1) of the histone deacetylase inhibitor, quisinostat (JNJ-26481585), by the Pediatric Preclinical Testing Program 
Pediatric blood & cancer  2013;61(2):245-252.
Background
Quisinostat (JNJ-26481585) is a second generation pyrimidyl-hydroxamic acid histone deacetylase (HDAC) inhibitor with high cellular potency towards class I and II HDACs. Quisinostat was selected for clinical development as it showed prolonged pharmacodynamic effects in vivo and demonstrated improved single agent antitumoral efficacy compared to other analogs.
Procedures
Quisinostat was tested against the PPTP in vitro panel at concentrations ranging from 1.0 nM to 10 μM and was tested against the PPTP in vivo panels at a dose of 5 mg/kg (solid tumors) or 2.5 mg/kg (ALL models) administered intraperitoneally daily x 21.
Results
In vitro quisinostat demonstrated potent cytotoxic activity, with T/C% values approaching 0% for all of the cell lines at the highest concentration tested. The median relative IC50 value for the PPTP cell lines was 2.2 nM, (range <1 nM to 19 nM). quisinostat induced significant differences in EFS distribution compared to control in 21 of 33 (64%) of the evaluable solid tumor xenografts and in 4 of 8 (50%) of the evaluable ALL xenografts. An objective response was observed in 1 of 33 solid tumor xenografts while for the ALL panel, two xenografts achieved complete response (CR) or maintained CR, and a third ALL xenograft achieved stable disease.
Conclusions
Quisinostat demonstrated broad activity in vitro, and retarded growth in the majority of solid tumor xenografts studied. The most consistent in vivo activity signals observed were for the glioblastoma xenografts and T-cell ALL xenografts.
doi:10.1002/pbc.24724
PMCID: PMC4225045  PMID: 24038993
Preclinical Testing; Developmental Therapeutics; HDAC inhibitor

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