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Neuroblastoma is treated with aggressive multimodal therapy, yet more than 50% of patients experience relapse. We recently showed that relapsed neuroblastomas frequently harbor mutations leading to hyperactivated ERK signaling and sensitivity to MEK inhibition therapy. Here we sought to define a synergistic therapeutic partner to potentiate MEK inhibition. We first surveyed 22 genetically annotated human neuroblastoma-derived cell lines (from 20 unique patients) for sensitivity to the MEK inhibitor binimetinib. After noting an inverse correlation with sensitivity to ribociclib (CDK4/6 inhibitor), we studied the combinatorial effect of these two agents using proliferation assays, cell-cycle analysis, Ki67 immunostaining, time-lapse microscopy, and xenograft studies. Sensitivity to binimetinib and ribociclib was inversely related ( = -0.58, = 0.009). amplification status and expression were associated with ribociclib sensitivity and binimetinib resistance, whereas increased MAPK signaling was the main determinant of binimetinib sensitivity and ribociclib resistance. Treatment with both compounds resulted in synergistic or additive cellular growth inhibition in all lines tested and significant inhibition of tumor growth in three of four xenograft models of neuroblastoma. The augmented growth inhibition was attributed to diminished cell-cycle progression that was reversible upon removal of drugs. Here we demonstrate that combined binimetinib and ribociclib treatment shows therapeutic synergy across a broad panel of high-risk neuroblastoma preclinical models. These data support testing this combination therapy in relapsed high-risk neuroblastoma patients, with focus on cases with hyperactivated RAS-MAPK signaling. .

Purpose. 123I-metaiodobenzylguanidine (MIBG) is used for the diagnostic evaluation of neuroblastoma. We evaluated the relationship between norepinephrine transporter (NET) expression and clinical MIBG uptake. Methods. Quantitative reverse transcription PCR (N = 82) and immunohistochemistry (IHC; N = 61) were performed for neuroblastoma NET mRNA and protein expression and correlated with MIBG avidity on diagnostic scans. The correlation of NET expression with clinical features was also performed. Results. Median NET mRNA expression level for the 19 MIBG avid patients was 12.9% (range 1.6–73.7%) versus 5.9% (range 0.6–110.0%) for the 8 nonavid patients (P = 0.31). Median percent NET protein expression was 50% (range 0–100%) in MIBG avid patients compared to 10% (range 0–80%) in nonavid patients (P = 0.027). MYCN amplified tumors had lower NET protein expression compared to nonamplified tumors (10% versus 50%; P = 0.0002). Conclusions. NET protein expression in neuroblastoma correlates with MIBG avidity. MYCN amplified tumors have lower NET protein expression.

Adenosine, an important signaling molecule in asthma, produces bronchoconstriction in asthmatics. Adenosine produces bronchoconstriction in allergic rabbits, primates, and humans by activating A 1 adenosine receptors (ARs). Effects of L-97-1 [3-[2-(4-aminophenyl)-ethyl]-8-benzyl-7-{2-ethyl-(2-hydroxyethyl)-amino]-ethyl}-1-propyl-3,7-dihydro-purine-2,6-dione] a water-soluble, small molecule A 1 AR antagonist were investigated on early and late phase allergic responses (EAR and LAR) in a hyper-responsive rabbit model of asthma. Rabbits were made allergic by intraperitoneal injections of house dust mite [HDM; 312 allergen units (AU)] extract within 24 h of their birth. Booster HDM injections were given weekly for 1 month, biweekly for 4 months, and continued monthly thereafter. Hyperresponsiveness was monitored by measuring lung dynamic compliance (Cdyn), after histamine or adenosine aerosol challenge in allergic rabbits. Hyper-responsive rabbits were subjected to aerosol of HDM (2500 AU), 1 h after intragastric administration of L-97-1 (10 mg/kg) solution or an equivalent volume of saline. Cdyn was significantly higher after treatment with L-97-1 compared with untreated controls (p Ͻ 0.05 n ϭ 5). Histamine PC 30 was significantly higher (p Ͻ 0.05; n ϭ 5) after L-97-1 at 24 h compared with histamine PC 30 at 24 h after HDM. Adenosine PC 30 was significantly higher at 15 min and 6 h after L-97-1 compared with control (p Ͻ 0.05; n ϭ 5). L-97-1 showed strong affinity for human A 1 ARs in radioligand binding studies and no inhibition toward human phosphodiesterase II, III, IV, and V enzymes. These data suggest that L-97-1 produces a significant reduction of histamine or adenosineinduced hyper-responsiveness and HDM-induced EAR and LAR in allergic rabbits by blocking A1 ARs and may be beneficial as an oral therapy for human asthma.Adenosine is an endogenous nucleoside-signaling molecule and acts on adenosine receptors (ARs) to produce a number of physiological effects in humans, including bronchoconstriction and lung inflammation. Moreover, it is becoming increasingly apparent that adenosine is an important signaling molecule in human asthma. When administered by inhalation, adenosine produces concentration-dependent bronchoconstriction in patients with asthma, but not in normal subjects (Cushley et al., 1983;Polosa, 2002;Rorke and Holgate, 2002). Adenosine levels are increased in the bronchoalveolar fluid of asthmatics and also in the plasma of patients with exercise-induced asthma (Driver et al., 1993;Vizi et al., 2002). There is also an association between allergen exposure and adenosine monophosphate (AMP) responsiveness in asthmatics (Currie et al., 2003). In asthma, the airway re-

The currently available therapeutic radiopharmaceutical for highrisk neuroblastoma, 131 I-metaiodobenzylguanidine, is ineffective at targeting micrometastases because of the low-linear-energy-transfer (LET) properties of high-energy β-particles. In contrast, Auger radiation has high-LET properties with nanometer ranges in tissue, efficiently causing DNA damage when emitted near DNA. The aim of this study was to evaluate the cytotoxicity of targeted Auger therapy in preclinical models of high-risk neuroblastoma. Methods: We used a radiolabled poly(adenosine diphosphate ribose) polymerase (PARP) inhibitor called 125 I-KX1 to deliver Auger radiation to PARP-1, a chromatin-binding enzyme overexpressed in neuroblastoma. The in vitro cytotoxicity of 125 I-KX1 was assessed in 19 neuroblastoma cell lines, followed by in-depth pharmacologic analysis in a sensitive and resistant pair of cell lines. Immunofluorescence microscopy was used to characterize 125 I-KX1-induced DNA damage. Finally, in vitro and in vivo microdosimetry was modeled from experimentally derived pharmacologic variables. Results: 125 I-KX1 was highly cytotoxic in vitro across a panel of neuroblastoma cell lines, directly causing double-strand DNA breaks. On the basis of subcellular dosimetry, 125 I-KX1 was approximately twice as effective as 131 I-KX1, whereas cytoplasmic 125 I-metaiodobenzylguanidine demonstrated low biological effectiveness. Despite the ability to deliver a focused radiation dose to the cell nuclei, 125 I-KX1 remained less effective than its α-emitting analog 211 At-MM4 and required significantly higher activity for equivalent in vivo efficacy based on tumor microdosimetry. Conclusion: Chromatin-targeted Auger therapy is lethal to high-risk neuroblastoma cells and has the potential to be used in micrometastatic disease. This study provides the first evidence for cellular lethality from a PARP-1-targeted Auger emitter, calling for further investigation into targeted Auger therapy.

Alternative radiolabeled targeted agents are being investigated for children with relapsed neuroblastoma who do not respond to I 131-metaiodobenzylguanidine (MIBG) therapy. DOTATATE targets somatostatin receptors (SSTR), particularly SSTR2, which are expressed on neuroblastoma cells. We investigated SSTR2 expression in neuroblastoma tumors (36 high risk; 33 non-high risk patients) and correlated SSTR2 levels with clinical features, norepinephrine transporter (NET) expression and MIBG avidity. SSTR2 and NET immunohistochemistry scores (0-3) were calculated on biopsies using digital image analysis based on staining intensity and distribution. Clinical data were correlated with SSTR2 expression. Median SSTR2 score for 69 patients was 1.31 (0.26-2.55). Non-high risk neuroblastoma was associated with higher SSTR2 score (p=0.032). SSTR2 expression did not correlate with age, INSS stage, MYCN amplification and histology. Higher SSTR2 scores were observed in MIBG-avid versus non-avid NB. SSTR2 score were not significantly associated with NET score (r=−0.062, p=0.62). Twenty-six patients who relapsed or progressed had a median SSTR2 score of 1.33 (0.26-2.55). Patients with neuroblastoma including relapsed or progressive disease showed SSTR2 expression at diagnosis, suggesting they could be candidates for radiolabeled DOTA-conjugated peptide imaging or therapy.

Background Prior studies suggest that neuroblastomas that do not accumulate metaiodobenzyl-guanidine (MIBG) on diagnostic imaging (MIBG non-avid) may have more favorable features compared with MIBG avid tumors. We compared clinical features, biologic features, and clinical outcomes between patients with MIBG nonavid and MIBG avid neuroblastoma. Procedure Patients had metastatic high- or intermediate-risk neuroblastoma and were treated on Children’s Oncology Group protocols A3973 or A3961. Comparisons of clinical and biologic features according to MIBG avidity were made with chi-squared or Fisher exact tests. Event-free (EFS) and overall (OS) survival compared using log–rank tests and modeled using Cox models. Results Thirty of 343 patients (8.7%) had MIBG nonavid disease. Patients with nonavid tumors were less likely to have adrenal primary tumors (34.5 vs. 57.2%; P = 0.019), bone metastases (36.7 vs. 61.7%; P = 0.008), or positive urine catecholamines (66.7 vs. 91.0%; P < 0.001) compared with patients with MIBG avid tumors. Nonavid tumors were more likely to be MYCN amplified (53.8 vs. 32.6%; P =0.030) and had lower norepinephrine transporter expression. Patients with MIBG non-avid disease had a 5-year EFS of 50.0% compared with 38.7% for patients with MIBG avid disease (P = 0.028). On multivariate testing in high-risk patients, MIBG avidity was the sole adverse prognostic factor for EFS identified (hazard ratio 1.77; 95% confidence interval 1.04–2.99; P = 0.034). Conclusions Patients with MIBG nonavid neuroblastoma have lower rates of adrenal primary tumors, bone metastasis, and catecholamine secretion. Despite being more likely to have MYCN-amplified tumors, these patients have superior outcomes compared with patients with MIBG avid disease.

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