Antibodies to Costimulatory Receptor 4-1BB Enhance Anti-tumor Immunity via T Regulatory Cell Depletion and Promotion of CD8 T Cell Effector Function.

The costimulatory receptor 4-1BB is expressed on activated immune cells, including activated T cells. Antibodies targeting 4-1BB enhance the proliferation and survival of antigen-stimulated T cells in vitro and promote CD8 T cell-dependent anti-tumor immunity in pre-clinical cancer models. We found that T regulatory (Treg) cells infiltrating human or murine tumors expressed high amounts of 4-1BB. Intra-tumoral Treg cells were preferentially depleted by anti-4-1BB mAbs in vivo. Anti-4-1BB mAbs also promoted effector T cell agonism to promote tumor rejection. These distinct mechanisms were competitive and dependent on antibody isotype and FcγR availability. Administration of anti-4-1BB IgG2a, which preferentially depletes Treg cells, followed by either agonistic anti-4-1BB IgG1 or anti-PD-1 mAb augmented anti-tumor responses in multiple solid tumor models. An antibody engineered to optimize both FcγR-dependent Treg cell depleting capacity and FcγR-independent agonism delivered enhanced anti-tumor therapy. These insights into the effector mechanisms of anti-4-1BB mAbs lay the groundwork for translation into the clinic.

A single bout of vigorous intensity exercise enhances the efficacy of rituximab against human chronic lymphocytic leukaemia B-cells ex vivo.

Chronic lymphocytic leukaemia (CLL) is characterised by the clonal proliferation and accumulation of mature B-cells and is often treated with rituximab, an anti-CD20 monoclonal antibody immunotherapy. Rituximab often fails to induce stringent disease eradication, due in part to failure of antibody-dependent cellular cytotoxicity (ADCC) which relies on natural killer (NK)-cells binding to rituximab-bound CD20 on B-cells. CLL cells are diffusely spread across lymphoid and other bodily tissues, and ADCC resistance in survival niches may be due to several factors including low NK-cell frequency and a suppressive stromal environment that promotes CLL cell survival. It is well established that exercise bouts induce a transient relocation of NK-cells and B-cells into peripheral blood, which could be harnessed to enhance the efficacy of rituximab in CLL by relocating both target and effector cells together with rituximab in blood. In this pilot study, n = 20 patients with treatment-naïve CLL completed a bout of cycling 15 % above anaerobic threshold for âˆ¼ 30-minutes, with blood samples collected pre-, immediately post-, and 1-hour post-exercise. Flow cytometry revealed that exercise evoked a 254 % increase in effector (CD3-CD56+CD16+) NK-cells in blood, and a 67 % increase in CD5+CD19+CD20+ CLL cells in blood (all p < 0.005). NK-cells were isolated from blood samples pre-, and immediately post-exercise and incubated with primary isolated CLL cells with or without the presence of rituximab to determine specific lysis using a calcein-release assay. Rituximab-mediated cell lysis increased by 129 % following exercise (p < 0.001). Direct NK-cell lysis of CLL cells - independent of rituximab - was unchanged following exercise (p = 0.25). We conclude that exercise improved the efficacy of rituximab-mediated ADCC against autologous CLL cells ex vivo and propose that exercise should be explored as a means of enhancing clinical responses in patients receiving anti-CD20 immunotherapy.

National advisory panels for childhood cancer in the United Kingdom: An evaluation of current practice and a best practice statement for the future.

BACKGROUND: National advisory panels (NAPs) have been established for the care of children and young people (CYP) with cancer in the United Kingdom since 2011, with an increase in panel number in recent years. Their practice has not previously been reviewed; therefore, we sought to evaluate the role, practice and impact of six selected NAPs offering expertise in ependymoma, histiocytosis, leukaemia, neuroblastoma, renal tumours and sarcoma. PROCEDURE: This service evaluation used mixed methodology, including review of NAP documentation, semi-structured interviews with the NAP chairs and an analysis of the cases referred for discussion. RESULTS: Total 1110 referrals were analysed. Results demonstrated the significant scope and amount of work undertaken by the NAPs, largely testament to the commitment of the panel members. Specific roles fulfilled have been highlighted, and NAP recommendations have been shown to influence clinical decision-making and be implemented in the majority of cases. Despite widespread good practice, areas to address have been identified; these include clarity regarding NAP membership, consistency in recommendations, the consideration of holistic information to promote personalised management and the exploration of wider multidisciplinary team roles. CONCLUSIONS: In the context of increasing demand and the escalating number of NAPs, it is timely to consider how service improvement can be facilitated. Best practice guidelines have been formulated as a product of this study, to promote a sustainable and effective model for NAPs. Review and benchmarking national panel performance against these guidelines will drive high standards of care going forward and they should be embedded as standard practice.

Tri-Lineage Differentiation Potential of Osteosarcoma Cell Lines and Human Bone Marrow Stromal Cells from Different Anatomical Locations.

The bone cancer osteosarcoma, found mainly in adolescents, routinely forms around the growth plate/metaphysis of long bones. Bone marrow composition changes with age, shifting from a more hematopoietic to an adipocyte-rich tissue. This conversion occurs in the metaphysis during adolescence, implicating a link between bone marrow conversion and osteosarcoma initiation. To assess this, the tri-lineage differentiation potential of human bone marrow stromal cells (HBMSCs) isolated from the femoral diaphysis/metaphysis (FD) and epiphysis (FE) was characterized and compared to two osteosarcoma cell lines, Saos-2 and MG63. Compared to FE-cells, FD-cells showed an increase in tri-lineage differentiation. Additionally, differences were found between the Saos-2 cells exhibiting higher levels of osteogenic differentiation, lower adipogenic differentiation, and a more developed chondrogenic phenotype than MG63, with the Saos-2 being more comparable to FD-derived HBMSCs. The differences found between the FD and FE derived cells are consistent with the FD region containing more hematopoietic tissue compared to the FE. This may be related to the similarities between FD-derived cells and Saos-2 cells during osteogenic and chondrogenic differentiation. These studies reveal distinct differences in the tri-lineage differentiations of 'hematopoietic' and 'adipocyte rich' bone marrow, which correlate with specific characteristics of the two osteosarcoma cell lines.

Thirteen-Valent Pneumococcal Conjugate Vaccine in Children With Acute Lymphoblastic Leukemia: Protective Immunity Can Be Achieved on Completion of Treatment.

BACKGROUND: Children with acute lymphoblastic leukemia (ALL) are at increased risk of developing invasive pneumococcal disease. This study describes the immunogenicity of 13-valent pneumococcal conjugate vaccine (PCV13) during and after chemotherapy. METHODS: Children with ALL were allocated to study groups and received a single dose of PCV13: group 1, maintenance chemotherapy; group 2, end of chemotherapy; group 3, 6 months after chemotherapy. A protective vaccine response was defined as at least 10 of 12 serotypes (or >83% of serotypes with data) achieving postvaccination serotype-specific immunoglobulin G ≥0.35 µg/mL and ≥4-fold rise, compared to prevaccination at 1 and 12 months. RESULTS: One hundred eighteen children were recruited. Only 12.8% (5/39; 95% confidence interval [CI], 4.3%-27.4%) of patients vaccinated during maintenance (group 1) achieved a protective response at 1 month postvaccination and none had a protective response at 12 months. For group 2 patients, 59.5% (22/37; 95% CI, 42.1%-75.3%) achieved a response at 1 month and 37.9% (11/29; 95% CI, 20.7%-57.7%) maintained immunity at 12 months. For group 3 patients, 56.8% (21/37; 95% CI, 39.5%-72.9%) achieved a protective response at 1 month and 43.3% (13/30; 95% CI, 25.5%-62.6%) maintained immunity at 12 months. CONCLUSIONS: This study demonstrated that the earliest time point at which protective immunity can be achieved in children with ALL is on completion of chemotherapy. This is earlier than current recommendations and may improve protection during a period when children are most susceptible to infection. CLINICAL TRIALS REGISTRATION: EudraCT 2009-011587-11.

The Role of Pre-Clinical 3-Dimensional Models of Osteosarcoma.

Treatment for osteosarcoma (OS) has been largely unchanged for several decades, with typical therapies being a mixture of chemotherapy and surgery. Although therapeutic targets and products against cancer are being continually developed, only a limited number have proved therapeutically active in OS. Thus, the understanding of the OS microenvironment and its interactions are becoming more important in developing new therapies. Three-dimensional (3D) models are important tools in increasing our understanding of complex mechanisms and interactions, such as in OS. In this review, in vivo animal models, in vitro 3D models and in ovo chorioallantoic membrane (CAM) models, are evaluated and discussed as to their contribution in understanding the progressive nature of OS, and cancer research. We aim to provide insight and prospective future directions into the potential translation of 3D models in OS.

Hypercalcaemia secondary to ectopic parathyroid hormone expression in an adolescent with metastatic alveolar rhabdomyosarcoma.

We report the case of a 14-year-old male with metastatic alveolar rhabdomyosarcoma, presenting with hypercalcaemia (3.89 mmol/l) and elevated parathyroid hormone (PTH) level (10.2 pmol/l). Imaging demonstrated extensive bony lytic damage, with "floating teeth" in the mandible. Normalisation of calcium levels and bony reformation of the mandible occurred following chemotherapy; PTH levels decreased initially but remained above normal levels. Imaging did not demonstrate any evidence of parathyroid abnormality. Tumour ectopic PTH secretion is a very rare cause of hypercalcaemia of malignancy in children. Hypercalcaemia with an elevated PTH, in the absence of parathyroid-related cause, should prompt investigation for underlying malignancy.

Development of immunomonitoring of antibody­dependent cellular cytotoxicity against neuroblastoma cells using whole blood.

Neuroblastoma, a childhood tumour of neuroectodermal origin, accounts for 15 % of paediatric cancer deaths, which is often metastatic at diagnosis and despite aggressive therapies, it has poor long-term prognosis with high risk of recurrence. Monoclonal antibody (mAb) therapy targeting GD2, a disialoganglioside expressed on neuroblastoma, has shown promise in recent trials with natural killer cell (NK)-mediated antibody-dependent cellular cytotoxicity (ADCC) thought to be central to efficacy, although other immune effectors may be important. To further enhance therapy, immunomonitoring of patients is essential to elucidate the in vivo mechanisms of action and provides surrogate end points of efficacy for future clinical trials. Our aim was to establish a 'real-time' ex vivo wholeblood (WB) immunomonitoring strategy to perform within the logistical constraints such as limited sample volumes, anticoagulant effects, sample stability and shipping time. A fluorescent dye release assay measuring target cell lysis was coupled with flow cytometry to monitor specific effector response. Significant target cell lysis with anti-GD2 antibody (p < 0.05) was abrogated following NK depletion. NK up-regulation of CD107a and CD69 positively correlated with target cell lysis (r > 0.6). The ADCC activity of WB correlated with peripheral blood mononuclear cells (r > 0.95), although WB showed overall greater target cell lysis attributed to the combination of NK-mediated ADCC, CD16+ granulocyte degranulation and complement- dependent cytotoxicity. Response was maintained in heparinised samples stored for 24 h at room temperature, but not 4 °C. Critically, the assay showed good reproducibility (mean % CV < 6.4) and was successfully applied to primary neuroblastoma samples. As such, WB provides a resourceful analysis of multiple mechanisms for efficient end point monitoring to correlate immune modulation with clinical outcome.

Integrative analysis of neuroblastoma by single-cell RNA sequencing identifies the NECTIN2-TIGIT axis as a target for immunotherapy.

Pediatric patients with high-risk neuroblastoma have poor survival rates and urgently need more effective treatment options with less side effects. Since novel and improved immunotherapies may fill this need, we dissect the immunoregulatory interactions in neuroblastoma by single-cell RNA-sequencing of 24 tumors (10 pre- and 14 post-chemotherapy, including 5 pairs) to identify strategies for optimizing immunotherapy efficacy. Neuroblastomas are infiltrated by natural killer (NK), T and B cells, and immunosuppressive myeloid populations. NK cells show reduced cytotoxicity and T cells have a dysfunctional profile. Interaction analysis reveals a vast immunoregulatory network and identifies NECTIN2-TIGIT as a crucial immune checkpoint. Combined blockade of TIGIT and PD-L1 significantly reduces neuroblastoma growth, with complete responses (CR) in vivo. Moreover, addition of TIGIT+PD-L1 blockade to standard relapse treatment in a chemotherapy-resistant Th-ALKF1174L/MYCN 129/SvJ syngeneic model induces CR. In conclusion, our integrative analysis provides promising targets and a rationale for immunotherapeutic combination strategies.

Review: Targeting EZH2 in neuroblastoma.

Neuroblastoma is one of the commonest extra-cranial pediatric tumors, and accounts for over 15% of all childhood cancer mortality. Risk stratification for children with neuroblastoma is based on age, stage, histology, and tumor cytogenetics. The majority of patients are considered to have high-risk neuroblastoma, for which the long-term survival is less than 50%. Current treatments combine surgical resection, chemotherapy, stem cell transplantation, radiotherapy, anti-GD2 based immunotherapy as well as the differentiating agent isotretinoin. Despite the intensive multimodal therapies applied, there are high relapse rates, and recurrent disease is often resistant to further therapy. Enhancer of Zeste Homolog 2 (EZH2), a catalytic subunit of Polycomb Repressive Complex 2 (PRC2), is a histone methyltransferase that represses transcription through trimethylation of lysine residue K27 on histone H3 (H3K27me3). It is responsible for epigenetic repression of transcription, making EZH2 an essential regulator for cell differentiation. Overexpression of EZH2 has been shown to promote tumorigenesis, cancer cell proliferation and prevent tumor cells from differentiating in a number of cancers. Therefore, research has been ongoing for the past decade, developing treatments that target EZH2 in neuroblastoma. This review summarises the role of EZH2 in neuroblastoma and evaluates the latest research findings on the therapeutic potential of targeting EZH2 in the treatment of neuroblastoma.

Methodological advances in the discovery of novel neuroblastoma therapeutics.

INTRODUCTION: Neuroblastoma is a cancer of the sympathetic nervous system that causes up to 15% of cancer-related deaths among children. Among the ~1,000 newly diagnosed cases per year in Europe, more than half are classified as high-risk, with a 5-year survival rate <50%. Current multimodal treatments have improved survival among these patients, but relapsed and refractory tumors remain a major therapeutic challenge. A number of new methodologies are paving the way for the development of more effective and safer therapies to ultimately improve outcomes for high-risk patients. AREAS COVERED: The authors provide a critical review on methodological advances aimed at providing new therapeutic opportunities for neuroblastoma patients, including preclinical models of human disease, generation of omics data to discover new therapeutic targets, and artificial intelligence-based technologies to implement personalized treatments. EXPERT OPINION: While survival of childhood cancer has improved over the past decades, progress has been uneven. Still, survival is dismal for some cancers, including high-risk neuroblastoma. Embracing new technologies (e.g. molecular profiling of tumors, 3D in vitro models, etc.), international collaborative efforts and the incorporation of new therapies (e.g. RNA-based therapies, epigenetic therapies, immunotherapy) will ultimately lead to more effective and safer therapies for these subgroups of neuroblastoma patients.

Cyclophosphamide depletes tumor infiltrating T regulatory cells and combined with anti-PD-1 therapy improves survival in murine neuroblastoma.

The outcome for children with high-risk neuroblastoma is poor despite intensive multi-modal treatment protocols. Toxicity from current treatments is significant, and novel approaches are needed to improve outcome. Cyclophosphamide (CPM) is a key component of current chemotherapy regimens and is known to have immunomodulatory effects. However, this has not been investigated in the context of tumor infiltrating lymphocytes in neuroblastoma. Using murine models of neuroblastoma, the immunomodulatory effects of low-dose CPM were investigated using detailed immunophenotyping. We demonstrated that CPM resulted in a specific depletion of intratumoral T regulatory cells by apoptosis, and when combined with anti-PD-1 antibody therapy, this resulted in improved therapeutic efficacy. CPM combined with anti-PD-1 therapy was demonstrated to be an effective combinational therapy, with metronomic CPM found to be more effective than single dosing in more resistant tumor models. Overall, this pre-clinical data strongly support clinical evaluation of such combination strategies in neuroblastoma.

Fc-null anti-PD-1 monoclonal antibodies deliver optimal checkpoint blockade in diverse immune environments.

BACKGROUND: Despite extensive clinical use, the mechanisms that lead to therapeutic resistance to anti-programmed cell-death (PD)-1 monoclonal antibodies (mAbs) remain elusive. Here, we sought to determine how interactions between the Fc region of anti-PD-1 mAbs and Fcγ receptors (FcγRs) affect therapeutic activity and how these are impacted by the immune environment. METHODS: Mouse and human anti-PD-1 mAbs with different Fc binding profiles were generated and characterized in vitro. The ability of these mAbs to elicit T-cell responses in vivo was first assessed in a vaccination setting using the model antigen ovalbumin. The antitumor activity of anti-PD-1 mAbs was investigated in the context of immune 'hot' MC38 versus 'cold' neuroblastoma tumor models, and flow cytometry performed to assess immune infiltration. RESULTS: Engagement of activating FcγRs by anti-PD-1 mAbs led to depletion of activated CD8 T cells in vitro and in vivo, abrogating therapeutic activity. Importantly, the extent of this Fc-mediated modulation was determined by the surrounding immune environment. Low FcγR-engaging mouse anti-PD-1 isotypes, which are frequently used as surrogates for human mAbs, were unable to expand ovalbumin-reactive CD8 T cells, in contrast to Fc-null mAbs. These results were recapitulated in mice expressing human FcγRs, in which clinically relevant hIgG4 anti-PD-1 led to reduced endogenous expansion of CD8 T cells compared with its engineered Fc-null counterpart. In the context of an immunologically 'hot' tumor however, both low-engaging and Fc-null mAbs induced long-term antitumor immunity in MC38-bearing mice. Finally, a similar anti-PD-1 isotype hierarchy was demonstrated in the less responsive 'cold' 9464D neuroblastoma model, where the most effective mAbs were able to delay tumor growth but could not induce long-term protection. CONCLUSIONS: Our data collectively support a critical role for Fc:FcγR interactions in inhibiting immune responses to both mouse and human anti-PD-1 mAbs, and highlight the context-dependent effect that anti-PD-1 mAb isotypes can have on T-cell responses. We propose that engineering of Fc-null anti-PD-1 mAbs would prevent FcγR-mediated resistance in vivo and allow maximal T-cell stimulation independent of the immunological environment.

DIPG Harbors Alterations Targetable by MEK Inhibitors, with Acquired Resistance Mechanisms Overcome by Combinatorial Inhibition.

The survival of children with diffuse intrinsic pontine glioma (DIPG) remains dismal, with new treatments desperately needed. In a prospective biopsy-stratified clinical trial, we combined detailed molecular profiling and drug screening in newly established patient-derived models in vitro and in vivo. We identified in vitro sensitivity to MEK inhibitors in DIPGs harboring MAPK pathway alterations, but treatment of patient-derived xenograft models and a patient at relapse failed to elicit a significant response. We generated trametinib-resistant clones in a BRAFG469V model through continuous drug exposure and identified acquired mutations in MEK1/2 with sustained pathway upregulation. These cells showed hallmarks of mesenchymal transition and expression signatures overlapping with inherently trametinib-insensitive patient-derived cells, predicting sensitivity to dasatinib. Combined trametinib and dasatinib showed highly synergistic effects in vitro and on ex vivo brain slices. We highlight the MAPK pathway as a therapeutic target in DIPG and show the importance of parallel resistance modeling and combinatorial treatments for meaningful clinical translation. SIGNIFICANCE: We report alterations in the MAPK pathway in DIPGs to confer initial sensitivity to targeted MEK inhibition. We further identify for the first time the mechanism of resistance to single-agent targeted therapy in these tumors and suggest a novel combinatorial treatment strategy to overcome it in the clinic. This article is highlighted in the In This Issue feature, p. 587.

Immune characterization of pre-clinical murine models of neuroblastoma.

Immunotherapy offers a potentially less toxic, more tumor-specific treatment for neuroblastoma than conventional cytotoxic therapies. Accurate and reproducible immune competent preclinical models are key to understanding mechanisms of action, interactions with other therapies and mechanisms of resistance to immunotherapy. Here we characterized the tumor and splenic microenvironment of two syngeneic subcutaneous (NXS2 and 9464D), and a spontaneous transgenic (TH-MYCN) murine model of neuroblastoma, comparing histological features and immune infiltrates to previously published data on human neuroblastoma. Histological sections of frozen tissues were stained by immunohistochemistry and immunofluorescence for immune cell markers and tumor architecture. Tissues were dissociated by enzymatic digestion, stained with panels of antibodies to detect and quantify cancer cells, along with lymphocytic and myeloid infiltration by flow cytometry. Finally, we tested TH-MYCN mice as a feasible model for immunotherapy, using prior treatment with cyclophosphamide to create a therapeutic window of minimal residual disease to favor host immune development. Immune infiltration differed significantly between all the models. TH-MYCN tumors were found to resemble immune infiltration in human tumors more closely than the subcutaneous models, alongside similar GD2 and MHC class I expression. Finally, TH-MYCN transgenic mice were administered cyclophosphamide alone or in combination with an anti-GD2 or anti-4-1BB monoclonal antibody, which resulted in increase in survival in both combination therapies. The TH-MYCN transgenic mouse is a promising in vivo model for testing immunotherapy compounds and combination therapy in a preclinical setting.

Immune reconstitution in children following chemotherapy for acute leukemia.

Although survival rates for pediatric acute lymphoblastic leukemia are now excellent, this is at the expense of prolonged chemotherapy regimens. We report the long-term immune effects in children treated according to the UK Medical Research Council UKALL 2003 protocol. Peripheral blood lymphocyte subsets and immunoglobulin levels were studied in 116 participants, at six time points, during and for 18-month following treatment, with 30-39 patients analyzed at each time point. Total lymphocytes were reduced during maintenance chemotherapy and remained low 18 months following treatment completion. CD4 T cells remained significantly reduced 18 months after treatment, but CD8 cells and natural killer cells recovered to normal values. The fall in naïve B-cell numbers during maintenance was most marked, but numbers recovered rapidly after cessation of treatment. Memory B cells, particularly nonclass-switched memory B cells, remained below normal levels 18 months following treatment. All immunoglobulin subclasses were reduced during treatment compared to normal values, with IgM levels most affected. This study demonstrates that immune reconstitution differs between lymphocyte compartments. Although total B-cell numbers recover rapidly, disruption of memory/naïve balance persists and T-cell compartment persist at 18 months. This highlights the impact of modern chemotherapy regimens on immunity, and thus, infectious susceptibility and response to immunization.

Immunotherapy for neuroblastoma: turning promise into reality.

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

PD-1/PD-L1 blockade in paediatric cancers: What does the future hold?

Checkpoint blockade (CPB) immunotherapy has shown unprecedented success in a wide range of adult malignancies, and is increasingly being employed in the treatment of advanced cancers. However, the experience in the paediatric population remains limited and the small number of single agent studies reported have shown disappointing response rates. Paediatric cancers offer unique challenges that can hinder the translation of CPB into the paediatric clinic, and combinational therapies are likely to be needed to achieve therapeutic success. As the number of paediatric trials using CPB rapidly increases, understanding the challenges that these agents may encounter in this population is of special significance to allow the design of optimal combinatorial strategies for each tumour type. Here, we offer an overview of the unique biological and immunological features of paediatric cancers as compared to adult malignancies, and how these might impact the overall success of CPB in the paediatric population. We review the growing body of pre-clinical and clinical experiences to date, and discuss future strategies involving the combination of CPB with traditionally used therapies (chemotherapy and radiotherapy) or with other newly developed immunotherapies.

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.

Hepatoblastoma in a child with a paternally-inherited ABCC8 mutation and mosaic paternal uniparental disomy 11p causing focal congenital hyperinsulinism.

Hepatoblastoma is a tumour of early childhood occurring in association with genetic syndromes including Beckwith-Wiedemann Syndrome (BWS) which results from dominance of paternally-inherited genes on chromosome 11p15. We report a child without clinical BWS, neonatally diagnosed with focal congenital hyperinsulinism resulting from a paternally-inherited recessively-acting mutation of ABCC8 and pancreatic paternal uniparental disomy (UPD) for chromosome 11p15, who subsequently developed hepatoblastoma. Genetic testing showed UPD 11p15 in the pancreas and liver but not systemically, allowing the expression of mutated ABCC8 in both tissues. Infants with large or multifocal forms of focal congenital hyperinsulinism may be at risk of BWS-like tumours due to mosaic UPD despite negative whole-blood and buccal DNA testing and tumour surveillance should be considered for this minority.