Immunotherapy for neuroblastoma: turning promise into reality

Targeting of heme oxygenase-1 as a novel immune regulator of neuroblastoma

Heme oxygenase (HO)-1 catalyzes the degradation of cytotoxic heme into biliverdin and blocks antitumor immune responses, thus protecting cancer against host defense. Whether this scenario also applies to neuroblastoma (NB), the most common extracranial solid childhood tumor, is not known. Here, we demonstrate for the first time a prognostic relevance of HO-1 expression in samples from NB patients and show that targeting of HO-1 prevents both cancer resistance against cellular stress and immune escape in the syngeneic NXS2 A/J mouse model of NB. High HO-1 RNA expression in NB tissues emerged as unfavorable prognostic marker, in particular for patients older than 18 months as indicated by univariate as well as multivariate survival probability analyses including disease stage and MYCN status. On the basis of this observation we aimed to target HO-1 by systemic as well as tumor-specific zinc protoporphyrin-mediated HO-1 suppression in a syngeneic immunocompetent NB mouse model. This resulted in 50% reduction of primary tumor growth and a suppression of spontaneous liver metastases. Importantly, HO-1 inhibition abrogated immune cell paralysis affecting CD4 and CD8 T-effector cells. This in turn reverted HO-1-dependent immune escape mechanisms in NB by increasing NB apoptosis and improved DC maturation. In summary, HO-1 emerges as a novel immune regulator in NB and emerges as a promising target for the development of therapeutic approaches.

Well-defined single polymer nanoparticles for the antibody-targeted delivery of chemotherapeutic agents

Aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization was employed to prepare a series of linear copolymers of N,N-dimethylacrylamide (DMA) and 2-hydroxyethylacrylamide (HEAm) with narrow Đ values over a molecular weight range spanning three orders of magnitude (103 to 106 Da). Trithiocarbonate-based RAFT chain transfer agents (CTAs) were grafted onto these scaffolds using carbodiimide chemistry catalyzed with DMAP. The resultant graft chain transfer agent (gCTA) was subsequently employed to synthesize polymeric brushes with a number of important vinyl monomer classes including acrylamido, methacrylamido, and methacrylate. Brush polymerization kinetics were evaluated for the aqueous RAFT polymerization of DMA from a 10 arm gCTA. Polymeric brushes containing hydroxyl functionality were further functionalized in order to prepare 2nd generation gCTAs which were subsequently employed to prepare polymers with a brushed-brush architecture with molecular weights in excess of 106 Da. These resultant single particle nanoparticles (SNPs) were employed as drug delivery vehicles for the anthracycline-based drug doxorubicin via copolymerization of DMA with a protected carbazate monomer (bocSMA). Cell-specific targeting functionality was also introduced via copolymerization with a biotin-functional monomer (bioHEMA). Drug release of the hydrazone linked doxorubicin was evaluated as function of pH and serum and chemotherapeutic activity was evaluated in SKOV3 ovarian cancer cells.

Immunomodulatory monoclonal antibodies combined with peptide vaccination provide potent immunotherapy in an aggressive murine neuroblastoma model

PURPOSE

Neuroblastoma is one of the commonest extracranial tumors of childhood. The majority of patients present with metastatic disease for which outcome remains poor. Immunotherapy is an attractive therapeutic approach for this disease, and a number of neuroblastoma tumor antigens have been identified. Here, we examine the therapeutic potential of combining immunomodulatory monoclonal antibodies (mAb) with peptide vaccination in murine neuroblastoma models.

EXPERIMENTAL DESIGN

Neuroblastoma-bearing mice were treated with mAb targeting 4-1BB, CD40, and CTLA-4 alone, or in combination with a peptide derived from the tumor antigen survivin (GWEDPPNDI). Survivin-specific immune response and therapeutic efficacy were assessed.

RESULTS

In the Neuro2a model, treatment of established tumor with anti-4-1BB, anti-CD40, or anti-CTLA-4 mAb results in tumor regression and long-term survival in 40% to 60% of mice. This is dependent on natural killer (NK) and CD8(+) T cells and is associated with tumor CD8(+) lymphocyte infiltrate. Successful therapy is achieved only if mAb is given to mice once tumors are established, suggesting dependence on sufficient tumor to provide antigen. In the more aggressive AgN2a and NXS2 models, single-agent mAb therapy provides ineffective therapy. However, if mAb (anti-CTLA-4) is given in conjunction with survivin peptide vaccination, then 60% long-term survival is achieved. This is associated with the generation of survivin-specific T-cell immunity, which again is only shown in the presence of tumor antigen.

CONCLUSIONS

These data suggest that the combination of antigen and costimulatory mAb may provide effective immunotherapy against neuroblastoma and may be of particular use in the minimal residual disease setting.

Immune response to racotumomab in a child with relapsed neuroblastoma

Immunotherapy targeting ganglioside antigens is a powerful tool for the treatment of high risk neuroblastoma. However, only treatment with anti-GD2 antibodies has been used in clinical practice and other options may be pursued. We report the use of racotumomab, an anti-idiotype vaccine against N-glycolyl neuraminic acid (NeuGc)- containing gangliosides, eliciting an immune response in a child with relapsed neuroblastoma expressing the NeuGcGM3 ganglioside.

NK cells engineered to express a GD2 -specific antigen receptor display built-in ADCC-like activity against tumour cells of neuroectodermal origin

Treatment of high-risk neuroblastoma (NB) represents a major challenge in paediatric oncology. Alternative therapeutic strategies include antibodies targeting the disialoganglioside GD₂, which is expressed at high levels on NB cells, and infusion of donor-derived natural killer (NK) cells. To combine specific antibody-mediated recognition of NB cells with the potent cytotoxic activity of NK cells, here we generated clonal derivatives of the clinically applicable human NK cell line NK-92 that stably express a GD₂-specific chimeric antigen receptor (CAR) comprising an anti-GD₂ ch14.18 single chain Fv antibody fusion protein with CD3-ζ chain as a signalling moiety. CAR expression by gene-modified NK cells facilitated effective recognition and elimination of established GD₂ expressing NB cells, which were resistant to parental NK-92. In the case of intrinsically NK-sensitive NB cell lines, we observed markedly increased cell killing activity of retargeted NK-92 cells. Enhanced cell killing was strictly dependent on specific recognition of the target antigen and could be blocked by GD₂-specific antibody or anti-idiotypic antibody occupying the CAR’s cell recognition domain. Importantly, strongly enhanced cytotoxicity of the GD₂-specific NK cells was also found against primary NB cells and GD₂ expressing tumour cells of other origins, demonstrating the potential clinical utility of the retargeted effector cells.

Neuroblastoma progress on many fronts: the Neuroblastoma Research Symposium

Neuroblastoma (NBL) is a pediatric tumor of infancy derived from precursor cells of the sympathetic nervous system. Clinicians and researchers in developmental biology and genetics recently met to facilitate meaningful crosstalk and to discuss considerable progress made in the clinical treatment and basic biology of NBL. For instance, discoveries in familial NBL have identified genetic aberrations in Phox2b and Alk that predispose to NBL, while advances in epigenetics and MYCN regulation have also offered insight into NBL pathogenesis and future treatment. Moreover, novel therapeutic avenues are also being explored, including targeted immunotherapies, and innovative radiotherapeutic and chemotherapeutic approaches. This multi-disciplinary meeting was convened to aid the transfer of new biological findings into the clinic and to use clinical advances to inform the basic biological understanding of this devastating disease.

A vector design that allows fast and convenient production of differently tagged proteins

Recombinant-tagged proteins have a widespread use in experimental research as well as in clinical diagnostic and therapeutic approaches. Well-stocked sets of differently tagged variants of a same protein would be of great help. However, the construction of differently tagging vectors is a demanding task since cloning procedures need several tailored DNA inserts. In this study, we describe a novel vector system that allows a cost- and time-effective production of differently tagged variants of a same protein by using the same DNA fragment and a set of vectors each carrying a different tag. The design of these expression vectors is based on an intronic region that becomes functional upon cloning the insert sequence, splicing of which attaches a certain tag to the protein termini. This strategy allows for the cloning of the fragment that codes for the protein of interest, without any further modification, into different vectors, previously built and ready-to-use, each carrying a tag that will be joined to the protein. Proof of principle for our expression system, presented here, is shown through the production of a functional anti-GD2 Fab fragment tagged with biotin or polyhistidine, or a combination of both, followed by the demonstration of the functional competencies of both the protein and the tags.