New strategies in refractory and recurrent neuroblastoma: translational opportunities to impact patient outcome

Phase I trial of a bivalent gangliosides vaccine in combination with β-glucan for high-risk neuroblastoma in second or later remission

PURPOSE

To report on a phase I trial designed to find the maximally tolerated dose in children of the immunologic adjuvant OPT-821 in a vaccine containing neuroblastoma-associated antigens (GD2 and GD3; Clinicaltrials.gov NCT00911560). Secondary objectives were to obtain preliminary data on immune response and activity against minimal residual disease (MRD). Treatment also included the immunostimulant β-glucan.

EXPERIMENTAL DESIGN

Patients with neuroblastoma in ≥2nd complete/very good partial remission received vaccine subcutaneously (weeks 1-2-3-8-20-32-52). Vaccine contained 30 μg each of GD2 and GD3 stabilized as lactones and conjugated to the immunologic carrier protein keyhole limpet hemocyanin; and OPT-821, which was dose escalated as 50, 75, 100, and 150 μg/m(2) per injection. Oral β-glucan (40 mg/kg/day, 14 days on/14 days off) started week 6.

RESULTS

The study was completed with 15 patients because there was no dose-limiting toxicity at 150 μg/m(2) of OPT-821 (the dosing used in adults). Thirteen of fifteen patients received the entire protocol treatment, including 12 who remain relapse-free at 24+ to 39+ (median 32+) months and 1 who relapsed (single node) at 21 months. Relapse-free survival was 80% ± 10% at 24 months. Vaccine and β-glucan were well tolerated. Twelve of fifteen patients had antibody responses against GD2 and/or GD3. Disappearance of MRD was documented in 6 of 10 patients assessable for response.

CONCLUSIONS

This immunotherapy program lacks major toxicity and is transportable to any outpatient clinic. Patient outcome is encouraging but the efficacy is uncertain because of the complexity and heterogeneity of prior therapies. A larger phase II trial is underway.

Quantitative phosphoproteomic analysis identifies activation of the RET and IGF-1R/IR signaling pathways in neuroblastoma

Neuroblastoma is an embryonal tumor of childhood with a heterogenous clinical presentation that reflects differences in activation of complex biological signaling pathways. Protein phosphorylation is a key component of cellular signal transduction and plays a critical role in processes that control cancer cell growth and survival. We used shotgun LC/MS to compare phosphorylation between a human MYCN amplified neuroblastoma cell line (NB10), modeling a resistant tumor, and a human neural precursor cell line (NPC), modeling a normal baseline neural crest cell. 2181 unique phosphorylation sites representing 1171 proteins and 2598 phosphopeptides were found. Protein kinases accounted for 6% of the proteome, with a predominance of tyrosine kinases, supporting their prominent role in oncogenic signaling pathways. Highly abundant receptor tyrosine kinase (RTK) phosphopeptides in the NB10 cell line relative to the NPC cell line included RET, insulin-like growth factor 1 receptor/insulin receptor (IGF-1R/IR), and fibroblast growth factor receptor 1 (FGFR1). Multiple phosphorylated peptides from downstream mediators of the PI3K/AKT/mTOR and RAS pathways were also highly abundant in NB10 relative to NPC. Our analysis highlights the importance of RET, IGF-1R/IR and FGFR1 as RTKs in neuroblastoma and suggests a methodology that can be used to identify potential novel biological therapeutic targets. Furthermore, application of this previously unexploited technology in the clinic opens the possibility of providing a new wide-scale molecular signature to assess disease progression and prognosis.

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 (Novartis Oncology), 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 nmol/L 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. Although 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. Clin Cancer Res; 19(22); 6173-82. ©2013 AACR.

Current and future strategies for relapsed neuroblastoma: challenges on the road to precision therapy

More than half of the patients with high-risk neuroblastoma (NB) will relapse despite intensive multimodal therapy, with an additional 10% to 20% refractory to induction chemotherapy. Management of these patients is challenging, given disease heterogeneity, resistance, and organ toxicity including poor hematological reserve. This review will discuss the current treatment options and consider novel therapies on the horizon. Cytotoxic chemotherapy regimens for relapse and refractory NB typically center on the use of the camptothecins, topotecan and irinotecan, in combination with agents such as cyclophosphamide and temozolomide, with objective responses but poor long-term survival. I-meta-iodobenzylguanidine therapy is also effective for relapsed patients with meta-iodobenzylguanidine-avid disease, with objective responses in a third of cases. Immunotherapy with anti-GD2 has recently been incorporated into upfront therapy, but its role in the relapse setting remains uncertain, especially for patients with bulky disease. Future cell-based immunotherapies and other approaches may be able to overcome this limitation. Finally, many novel molecularly targeted agents are in development, some of which show specific promise for NB. Successful incorporation of these agents will require combinations with conventional cytotoxic chemotherapies, as well as the development of predictive biomarkers, to ultimately personalize approaches to patients with "targetable" molecular abnormalities.

MYCN and HDAC2 cooperate to repress miR-183 signaling in neuroblastoma

MYCN is a master regulator controlling many processes necessary for tumor cell survival. Here, we unravel a microRNA network that causes tumor suppressive effects in MYCN-amplified neuroblastoma cells. In profiling studies, histone deacetylase (HDAC) inhibitor treatment most strongly induced miR-183. Enforced miR-183 expression triggered apoptosis, and inhibited anchorage-independent colony formation in vitro and xenograft growth in mice. Furthermore, the mechanism of miR-183 induction was found to contribute to the cell death phenotype induced by HDAC inhibitors. Experiments to identify the HDAC(s) involved in miR-183 transcriptional regulation showed that HDAC2 depletion induced miR-183. HDAC2 overexpression reduced miR-183 levels and counteracted the induction caused by HDAC2 depletion or HDAC inhibitor treatment. MYCN was found to recruit HDAC2 in the same complexes to the miR-183 promoter, and HDAC2 depletion enhanced promoter-associated histone H4 pan-acetylation, suggesting epigenetic changes preceded transcriptional activation. These data reveal miR-183 tumor suppressive properties in neuroblastoma that are jointly repressed by MYCN and HDAC2, and suggest a novel way to bypass MYCN function.

Pre-Clinical Evaluation of rHDL Encapsulated Retinoids for the Treatment of Neuroblastoma

Despite major advances in pediatric cancer research, there has been only modest progress in the survival of children with high risk neuroblastoma (NB) (HRNB). The long term survival rates of HRNB in the United States are still only 30-50%. Due to resistance that often develops during therapy, development of new effective strategies is essential to improve the survival and overcome the tendency of HRNB patients to relapse subsequent to initial treatment. Current chemotherapy regimens also have a serious limitation due to off target toxicity. In the present work, we evaluated the potential application of reconstituted high density lipoprotein (rHDL) containing fenretinide (FR) nanoparticles as a novel approach to current NB therapeutics. The characterization and stability studies of rHDL-FR nanoparticles showed small size (<40 nm) and high encapsulation efficiency. The cytotoxicity studies of free FR vs. rHDL/FR toward the NB cell lines SK-N-SH and SMS-KCNR showed 2.8- and 2-fold lower IC50 values for the rHDL encapsulated FR vs. free FR. More importantly, the IC50 value for retinal pigment epithelial cells (ARPE-19), a recipient of off target toxicity during FR therapy, was over 40 times higher for the rHDL/FR as compared to that of free FR. The overall improvement in in vitro selective therapeutic efficiency was thus about 100-fold upon encapsulation of the drug into the rHDL nanoparticles. These studies support the potential value of this novel drug delivery platform for treating pediatric cancers in general, and NB in particular.

Ex vivo activation of CD56(+) immune cells that eradicate neuroblastoma

Despite the use of intensive contemporary multimodal therapy, the overall survival of patients with high-risk neuroblastoma is still less than 50%. Therefore, immunotherapy without cross-resistance and overlapping toxicity has been proposed. In this study, we report the development of a novel strategy to specifically activate and expand human CD56(+) (NCAM1) natural killer (NK) immune cells from normal donors and patients with neuroblastoma. Enriched CD56(+) cells from peripheral blood were mixed with CD56(-) fraction at 1:1 ratio and cultured in the presence of OKT3, interleukin (IL)-2, and -15 for five days and then without OKT3 for 16 more days. The final products contained more than 90% CD56(+) cells and could kill neuroblastoma cells effectively that were originally highly resistant to nonprocessed NK cells. Mechanistically, cytolysis of neuroblastoma was mediated through natural cytotoxicity receptor (NCR), DNAX accessory molecule-1 (DNAM-1; CD226), perforin, and granzyme B. Successful clinical scale-up in a good manufacturing practices (GMP)-compliant bioreactor yielded effector cells that in a neuroblastoma xenograft model slowed tumor growth and extended survival without GVHD. Investigation of CD56(+) cells from patients with neuroblastoma revealed a similar postactivation phenotype and lytic activity. Our findings establish a novel and clinically expedient strategy to generate allogeneic or autologous CD56(+) cells that are highly cytotoxic against neuroblastoma with minimal risk of GVHD.