Lactate dehydrogenase inhibition synergizes with IL-21 to promote CD8+ T cell stemness and antitumor immunity.

Interleukin (IL)-2 and IL-21 dichotomously shape CD8+ T cell differentiation. IL-2 drives terminal differentiation, generating cells that are poorly effective against tumors, whereas IL-21 promotes stem cell memory T cells (TSCM) and antitumor responses. Here we investigated the role of metabolic programming in the developmental differences induced by these cytokines. IL-2 promoted effector-like metabolism and aerobic glycolysis, robustly inducing lactate dehydrogenase (LDH) and lactate production, whereas IL-21 maintained a metabolically quiescent state dependent on oxidative phosphorylation. LDH inhibition rewired IL-2-induced effects, promoting pyruvate entry into the tricarboxylic acid cycle and inhibiting terminal effector and exhaustion programs, including mRNA expression of members of the NR4A family of nuclear receptors, as well as Prdm1 and Xbp1 While deletion of Ldha prevented development of cells with antitumor effector function, transient LDH inhibition enhanced the generation of memory cells capable of triggering robust antitumor responses after adoptive transfer. LDH inhibition did not significantly affect IL-21-induced metabolism but caused major transcriptomic changes, including the suppression of IL-21-induced exhaustion markers LAG3, PD1, 2B4, and TIM3. LDH inhibition combined with IL-21 increased the formation of TSCM cells, resulting in more profound antitumor responses and prolonged host survival. These findings indicate a pivotal role for LDH in modulating cytokine-mediated T cell differentiation and underscore the therapeutic potential of transiently inhibiting LDH during adoptive T cell-based immunotherapy, with an unanticipated cooperative antitumor effect of LDH inhibition and IL-21.

Next-generation humanized patient-derived xenograft mouse model for pre-clinical antibody studies in neuroblastoma.

Faithful tumor mouse models are fundamental research tools to advance the field of immuno-oncology (IO). This is particularly relevant in diseases with low incidence, as in the case of pediatric malignancies, that rely on pre-clinical therapeutic development. However, conventional syngeneic and genetically engineered mouse models fail to recapitulate the tumor heterogeneity and microenvironmental complexity of human pathology that are essential determinants of cancer-directed immunity. Here, we characterize a novel mouse model that supports human natural killer (NK) cell development and engraftment of neuroblastoma orthotopic patient-derived xenograft (O-PDX) for pre-clinical antibody and cytokine testing. Using cytotoxicity assays, single-cell RNA-sequencing, and multi-color flow cytometry, we demonstrate that NK cells that develop in the humanized mice are fully licensed to execute NK cell cytotoxicity, permit human tumor engraftment, but can be therapeutically redirected to induce antibody-dependent cell-mediated cytotoxicity (ADCC). Although these cells share phenotypic and molecular features with healthy controls, we noted that they lacked an NK cell subset, termed activated NK cells, that is characterized by differentially expressed genes that are induced by cytokine activation. Because this subset of genes is also downregulated in patients with neuroblastoma compared to healthy controls, we hypothesize that this finding could be due to tumor-mediated suppressive effects. Thus, despite its technical complexity, this humanized patient-derived xenograft mouse model could serve as a faithful system for future testing of IO applications and studies of underlying immunologic processes.

Immunotherapy approaches targeting neuroblastoma.

PURPOSE OF REVIEW: In the era of immune-oncology, a breakthrough in the field of pediatric solid tumor research has been the demonstration that immunotherapy for patients with high-risk neuroblastoma improves the event-free and overall survival. Immunotherapeutic approaches including a monoclonal antibody targeting the cell surface glycosphingolipid disialoganglioside and cytokines successfully eliminate minimal residual disease. RECENT FINDINGS: Since this seminal discovery, clinical trials evaluating immunotherapy in combination with chemotherapy and cellular therapies have begun to demonstrate effectiveness in treatment of bulky disease. Broader knowledge has also been gained regarding immunotherapy-limiting side-effects. Furthermore, biologic studies in actively treated patients have contributed to our growing understanding of the underlying immunologic processes and mechanisms of tumor response and immune evasion. SUMMARY: The example of neuroblastoma is beginning to demonstrate that various immunotherapies combined with more conventional anticancer treatments can be synergistic. These advancements pose new challenges to both clinical researchers and medical provider and herald a new era in pediatric cancer therapy.

The role of interleukin-2, all-trans retinoic acid, and natural killer cells: surveillance mechanisms in anti-GD2 antibody therapy in neuroblastoma.

Although anti-disialoganglioside (GD2) antibodies are successfully used for neuroblastoma therapy, a third of patients with neuroblastoma experience treatment failure or serious toxicity. Various strategies have been employed in the clinic to improve antibody-dependent cell-mediated cytotoxicity (ADCC), such as the addition of interleukin (IL)-2 to enhance natural killer (NK) cell function, adoptive transfer of allogeneic NK cells to exploit immune surveillance, and retinoid-induced differentiation therapy. Nevertheless, these mechanisms are not fully understood. We developed a quantitative assay to test ADCC induced by the anti-GD2 antibody Hu14.18K322A in nine neuroblastoma cell lines and dissociated cells from orthotopic patient-derived xenografts (O-PDXs) in culture. IL-2 improved ADCC against neuroblastoma cells, and differentiation with all-trans retinoic acid stabilized GD2 expression on tumor cells and enhanced ADCC as well. Degranulation was highest in licensed NK cells that expressed CD158b (P < 0.001) and harbored a killer-cell immunoglobulin-like receptor (KIR) mismatch against the tumor-specific human leukocyte antigen (HLA; P = 0.016). In conclusion, IL-2 is an important component of immunotherapy because it can improve the cytolytic function of NK cells against neuroblastoma cells and could lower the antibody dose required for efficacy, thereby reducing toxicity. The effect of IL-2 may vary among individuals and a biomarker would be useful to predict ADCC following IL-2 activation. Sub-populations of NK cells may have different levels of activity dependent on their licensing status, KIR expression, and HLA-KIR interaction. Better understanding of HLA-KIR interactions and the molecular changes following retinoid-induced differentiation is necessary to delineate their role in ADCC.

Rapid decrease of serum alpha-fetoprotein and tumor volume predicts outcome in children with hepatoblastoma treated with neoadjuvant chemotherapy.

BACKGROUND: Neoadjuvant chemotherapy is given to children with unresectable hepatoblastoma to increase the rate and safety of curative complete surgical resection. Elevated levels of serum alpha-fetoprotein (sAFP) decline with tumor shrinkage. In this single-institution retrospective study, we determined early dynamic changes of sAFP levels and tumor volume in children during therapy for unresectable hepatoblastoma. METHODS: We correlated early dynamic changes of sAFP levels and tumor volume and the sum of the longest primary tumor and measurable metastatic disease diameters as per RECIST 1.1 criteria with patient outcome. RESULTS: There were 34 patients, 7 of whom died of disease. Patients with ≥ 90% (≥ 1 log10) decrease in sAFP levels after two chemotherapy courses had a better event-free survival (P = 0.039) and overall survival (OS; P = 0.045) than those with < 90% decrease. During this treatment interval, average tumor volume decreased from 481 mL (± 254 mL) to 268 mL (± 258 mL; P < 0.001) which was associated with OS (P = 0.029). Relative change in sAFP levels or tumor volume in between course 2 and pre-surgery or response as per RECIST 1.1 was not associated with OS. CONCLUSION: Early decline of sAFP levels and tumor volume, but not response as per RECIST 1.1 may predict survival in children with unresectable hepatoblastoma. This finding could be useful to identify therapy non-responders for whom alternative interventions may be required for cure. Confirmation of the finding using larger patient cohorts will be necessary before this strategy is incorporated into prospective trials.

Multifocal nerve lesions and LZTR1 germline mutations in segmental schwannomatosis.

Schwannomatosis is a genetic disorder characterized by the occurrence of multiple peripheral schwannomas. Segmental schwannomatosis is diagnosed when schwannomas are restricted to 1 extremity and is thought to be caused by genetic mosaicism. We studied 5 patients with segmental schwannomatosis through microstructural magnetic resonance neurography and mutation analysis of NF2, SMARCB1, and LZTR1. In 4 of 5 patients, subtle fascicular nerve lesions were detected in clinically unaffected extremities. Two patients exhibited LZTR1 germline mutations. This appears contrary to a simple concept of genetic mosaicism and suggests more complex and heterogeneous mechanisms underlying the phenotype of segmental schwannomatosis than previously thought. Ann Neurol 2016;80:625-628.

The Role of Leukapheresis in the Current Management of Hyperleukocytosis in Newly Diagnosed Childhood Acute Lymphoblastic Leukemia.

BACKGROUND: Hyperleukocytosis in children with acute lymphoblastic leukemia (ALL) has been associated with early morbidity and mortality. The use of leukapheresis in these children treated with contemporary therapy remains controversial. PROCEDURE: We analyzed clinical data from patients enrolled onto frontline protocols for ALL (Total Therapy XV and XVI) between 2003 and 2014. We documented adverse events within the first 14 days in patients with a white blood cell (WBC) count ≥200 × 10(9) /l and reviewed their management. RESULTS: Fifty-three (7.8%) of 678 consecutive pediatric patients with newly diagnosed ALL presented with hyperleukocytosis (median WBC count 393 × 10(9) /l; range 200-1,014). Two deaths in patients without initial hyperleukocytosis occurred within the first 2 weeks from diagnosis secondary to bacterial sepsis. A total of 21 (40%) patients with ALL and hyperleukocytosis developed grade 3 or 4 adverse events regardless of the use of leukapheresis (P > 0.99 and P = 0.19). Sixteen of 53 (30%) patients with ALL received low-dose chemotherapy for leukocytoreduction initially. One-third of patients received urate oxidase, and none of the patients with hyperleukocytosis required hemodialysis. CONCLUSIONS: The early morbidity and mortality commonly associated with hyperleukocytosis in children with newly diagnosed ALL can be avoided with contemporary supportive care and conservative management possibly obviating the need for costly and potentially dangerous leukapheresis.

Quantitative associations of scalp and body subcutaneous neurofibromas with internal plexiform tumors in neurofibromatosis 1.

Internal plexiform neurofibromas are a major cause of adverse outcomes in patients with neurofibromatosis 1 (NF1). We investigated the relationship of the numbers of subcutaneous neurofibromas of the scalp or body to internal plexiform tumor volume in 120 NF1 patients who had undergone whole body magnetic resonance imaging (MRI). We identified internal plexiform neurofibromas in 55% of patients, subcutaneous neurofibromas of the body in 75%, and subcutaneous neurofibromas of the scalp in 45%. The number of subcutaneous neurofibromas of the body and scalp were associated with each other (Spearman's Rho = 0.36; P < 0.001). The presence of internal tumors was associated with the presence (odds ratio [OR] = 4.38, 95% confidence interval [CI] 2.04-9.86, P < 0.001) and number (OR = 1.06 per neurofibroma, 95% CI 1.02-1.13, P < 0.001) of subcutaneous neurofibromas of the scalp. The total internal tumor volume was associated with the number of subcutaneous neurofibromas of the body (OR = 1.00086 per neurofibroma, 1.000089-1.0016, P = 0.029) and of the scalp (OR = 1.056 per neurofibroma, 1.029-1.083, P < 0.0001). Numbers of subcutaneous neurofibromas of the scalp and body are associated with internal plexiform tumor burden in NF1. Recognition of these associations may improve clinical management by helping to identify patients who will benefit most from whole body MRI and more intense clinical surveillance.

Characterization of spinal findings in children and adults with neurofibromatosis type 1 enrolled in a natural history study using magnetic resonance imaging.

To characterize spinal abnormalities in patients with neurofibromatosis type 1 (NF1) using magnetic resonance imaging (MRI). NF1 patients with at least one spine MRI were selected from participants prospectively enrolled in the National Cancer Institute NF1 Natural History Study. Data were analyzed retrospectively. Ninety-seven patients (38 females, median age 14.2 years, standard deviation [SD] 7.6) had baseline imaging of the spine, and 26 patients (27 %) had one follow-up spine MRI (follow up time 2.5 years, SD 1.1, range 0.7-4.7). Seventy-eight patients (80 %) had spinal neurofibromas, with rising frequency from 70 % in patients younger than 10 years to 80 % in patients aged 10-18 years to 89 % in individuals older than 18 years of age. At baseline, 33/97 patients (34 %) had MRI changes consistent with spinal cord compression that was most prevalent at the cervical (43 %) and lumbar spine region (40 %). Seven of nine patients with progression of their spinal neurofibromas developed cord compression. Paraspinal plexiform neurofibromas (PNs) were present in 77/97 patients (79 %), of which 68 patients (88 %) had concomitant spinal neurofibromas. Spinal curvature abnormality was present in 50/97 patients (51 %, 20 females, median age 14.6 years, SD 7.6). Patients with paraspinal PNs had six-fold higher odds of developing spinal curvature abnormalities compared to patients without PN (OR = 5.9, 95 % CI 1.81 to 19.44, p = 0.0033). A total of 58/97 patients (60 %, median age 16.1 years, SD 7.8, range 4.8-48.2 years) presented with neurologic abnormalities that progressed in 12/26 patients (46 %). Substantial spinal neurofibroma and paraspinal PN burden was observed in our study population, which represents a selective group of patients with specifically more severe tumor involvement than the general NF1 population. Occurrence and progression of spinal neurofibromas on repeat evaluations highlight the need for longitudinal clinical monitoring in patients with known spinal disease.

Relationship between whole-body tumor burden, clinical phenotype, and quality of life in patients with neurofibromatosis.

Patients with neurofibromatosis 1 (NF1), NF2, and schwannomatosis share a predisposition to develop multiple nerve sheath tumors. Previous studies have demonstrated that patients with NF1 and NF2 have reduced quality of life (QOL), but no studies have examined the relationship between whole-body tumor burden and QOL in these patients. We administered a QOL questionnaire (the SF-36) and a visual analog pain scale (VAS) to a previously described cohort of adult neurofibromatosis patients undergoing whole-body MRI. One-sample t-tests were used to compare norm-based SF-36 scores to weighted population means. Spearman correlation coefficients and multiple linear regression analyses controlling for demographic and disease-specific clinical variable were used to relate whole-body tumor volume to QOL scales. Two hundred forty-five patients (142 NF1, 53 NF2, 50 schwannomatosis) completed the study. Subjects showed deficits in selected subscales of the SF-36 compared to adjusted general population means. In bivariate analysis, increased tumor volume was significantly associated with pain in schwannomatosis patients, as measured by the SF-36 bodily pain subscale (rho = -0.287, P = 0.04) and VAS (rho = 0.34, P = 0.02). Regression models for NF2 patients showed a positive relationship between tumor burden and increased pain, as measured by the SF-36 (P = 0.008). Patients with NF1, NF2, and schwannomatosis suffer from reduced QOL, although only pain shows a clear relationship to patient's overall tumor burden. These findings suggest that internal tumor volume is not a primary contributor to QOL and emphasize the need for comprehensive treatment approaches that go beyond tumor-focused therapies such as surgery by including psychosocial interventions.

Benign whole body tumor volume is a risk factor for malignant peripheral nerve sheath tumors in neurofibromatosis type 1.

The purpose of this study is to determine whether benign whole body tumor volume of plexiform neurofibromas (PNs) is a risk factor for malignant peripheral nerve sheath tumors (MPNST) in individuals with neurofibromatosis type 1 (NF1). Thirty-one NF1 patients with MPNSTs and 62 age- and sex-matched NF1 patients without MPNSTs, who had undergone whole body magnetic resonance imaging (MRI) were analyzed for benign whole body tumor volume. Mann-Whitney U test, Wilcoxon signed ranks test, Fisher's exact test (two-tailed), and logistic regression analysis were used for statistical analysis. Sixteen percent of all patients with MPNST did not have internal PN. The median whole body benign tumor volume in patients with PN was 352.0 mL among the MPNST group and 3.8 mL in the comparison group (p < 0.001). When the patients were stratified by age as younger or older than 30 years (median age of MPNST diagnosis), the median benign whole body tumor volume was 693.0 mL in MPNST patients and 0.0 mL in control patients younger than 30 years (p < 0.001). The mean number of PNs in MPNST patients was 2.8 (range 0-13, median 2.0) and 1.4 (range 0-13, median 1.0) in patients without MPNST (p = 0.001). The risk of MPNST development increased 0.2 % with each additional mL of benign PN volume (adjusted odds ratio [OR] = 1.002, 95 % confidence interval [CI] 1.001-1.003, p = 0.005) and was higher in patients younger than 30 years (adjusted OR = 1.007, 95 % CI 1.002-1.012, p = 0.003). Higher numbers of PNs, larger whole body benign tumor volume, and younger age are important risk factors for MPNST. We identified a subgroup of patients with MPNST without internal PN on MRI and the lack of correlation of MPNST development with tumor burden in older patients. These findings may alter our belief that all MPNSTs arise from pre-existing PNs and suggest that surveillance MRI based on clinical suspicion may be warranted in older patients, respectively.

INSPIRED Symposium Part 5: Expanding the Use of CAR T Cells in Children and Young Adults.

Chimeric antigen receptor (CAR) T cell therapy has demonstrated remarkable efficacy in relapsed/refractory (r/r) B cell malignancies, including in pediatric patients with acute lymphoblastic leukemia (ALL). Expanding this success to other hematologic and solid malignancies is an area of active research and, although challenges remain, novel solutions have led to significant progress over the past decade. Ongoing clinical trials for CAR T cell therapy for T cell malignancies and acute myeloid leukemia (AML) have highlighted challenges, including antigen specificity with off-tumor toxicity and persistence concerns. In T cell malignancies, notable challenges include CAR T cell fratricide and prolonged T cell aplasia, which are being addressed with strategies such as gene editing and suicide switch technologies. In AML, antigen identification remains a significant barrier, due to shared antigens across healthy hematopoietic progenitor cells and myeloid blasts. Strategies to limit persistence and circumvent the immunosuppressive tumor microenvironment (TME) created by AML are also being explored. CAR T cell therapies for central nervous system and solid tumors have several challenges, including tumor antigen heterogeneity, immunosuppressive and hypoxic TME, and potential for off-target toxicity. Numerous CAR T cell products have been designed to overcome these challenges, including "armored" CARs and CAR/T cell receptor (TCR) hybrids. Strategies to enhance CAR T cell delivery, augment CAR T cell performance in the TME, and ensure the safety of these products have shown promising results. In this manuscript, we will review the available evidence for CAR T cell use in T cell malignancies, AML, central nervous system (CNS), and non-CNS solid tumor malignancies, and recommend areas for future research.

Cooperative Armoring of CAR and TCR T Cells by T Cell-Restricted IL15 and IL21 Universally Enhances Solid Tumor Efficacy.

PURPOSE: Chimeric antigen receptor (CAR) and T-cell receptor (TCR) T-cell therapies are effective in a subset of patients with solid tumors, but new approaches are needed to universally improve patient outcomes. Here, we developed a technology to leverage the cooperative effects of IL15 and IL21, two common cytokine-receptor gamma chain family members with distinct, pleiotropic effects on T cells and other lymphocytes, to enhance the efficacy of adoptive T cells. EXPERIMENTAL DESIGN: We designed vectors that induce the constitutive expression of either membrane-tethered IL15, IL21, or IL15/IL21. We used clinically relevant preclinical models of transgenic CARs and TCRs against pediatric and adult solid tumors to determine the effect of the membrane-tethered cytokines on engineered T cells for human administration. RESULTS: We found that self-delivery of these cytokines by CAR or TCR T cells prevents functional exhaustion by repeated stimulation and limits the emergence of dysfunctional natural killer (NK)-like T cells. Across different preclinical murine solid tumor models, we observed enhanced regression with each individual cytokine but the greatest antitumor efficacy when T cells were armored with both. CONCLUSIONS: The coexpression of membrane-tethered IL15 and IL21 represents a technology to enhance the resilience and function of engineered T cells against solid tumors and could be applicable to multiple therapy platforms and diseases. See related commentary by Ruffin et al., p. 1431.

Growth behavior of plexiform neurofibromas after surgery.

PURPOSE: The aim of this study was to analyze growth rate and identify prognostic factors for progression of postoperative plexiform neurofibromas in patients with neurofibromatosis type 1. METHODS: We measured postoperative tumor volume change per year on magnetic resonance imaging. Linear regression models were applied to identify risk factors for tumor progression. RESULTS: Fifty-two patients (mean age: 25.4 years (3.2-64.2 years)) with 56 plexiform neurofibromas were analyzed. Initial median tumor volume was 40.3 ml (SD: 1,552 (0-10,800)). Surgical indications included disfigurement (n = 21), pain (n = 20), and functional deficits (n = 16). Sixteen percent of all cases experienced acute surgical complication, and 13% showed late complication. Eight patients (19%; 6 children and 2 adults) with residual tumor had repeat surgery for tumor progression. Median tumor progression was 0.6% change per year (SD ± 27.4; range: -59.2 to 88.1) and 2.9% from baseline (SD ± 163.9; range -1,001.3 to 81.8). Patients aged 21 years and younger had the highest progression rate (P < 0.01). For every year of age, the mean growth rate decreased by -0.463 mean percent (P = 0.03). With age as a continuous variable, age, the site of the tumor, and depth were the only factors associated with tumor progression. Fourteen plexiform neurofibromas (10 nodular and 4 diffuse) in 13 patients (5 children and 8 adults) were completely resected (by visualization) and did not relapse during observation (mean: 2.9 years; range: 1.1-5.8 years). CONCLUSION: Age, tumor type, location, and depth are helpful to estimate the progression of plexiform neurofibromas after surgery. Patients benefit from elective surgery of small and completely removable plexiform neurofibromas.

Watchful waiting for some children with a mediastinal mass: the potential role for ¹8F-fluorodeoxyglucose positron emission tomography: a case report and review of the literature.

BACKGROUND: Benign hyperplastic thymus is a rare but important differential diagnosis of anterior mediastinal lesions. Histological and radiological criteria are used to distinguish this benign condition from other malignant diseases but have their limitations, and biopsy of mediastinal masses can be risky. We report for the first time the diagnostic value of fluorodeoxyglucose 18F positron emission tomography for patients with incidentally identified anterior mediastinal masses to avoid biopsy in some cases. CASE PRESENTATION: A 2 year old girl presented with new onset of emesis and constipation leading to the incidental discovery of an anterior mediastinal mass on radiograph. Chest computed tomography revealed cystic components within the mass concerning for a malignancy. Biopsy of the lesion and bone marrow aspiration and biopsy were negative but there was concern that the mediastinal biopsy may have missed the malignant component of the lesion. Hence, a positron emission tomography scan was obtained that showed mild homogeneous fluorodeoxyglucose 18F avidity within the mass similar to that of normal thymus. The diagnosis of benign hyperplastic thymus was made. CONCLUSION: The differential diagnosis of an incidentally found anterior mediastinal mass includes malignancy, but benign lesions such as benign hyperplastic thymus must also be considered, particularly when the complete blood count and biochemical profile are normal. Fluorodeoxyglucose 18F positron emission tomography can help guide a clinician's decision for further interventions and treatment.

Internal tumor burden in neurofibromatosis Type I patients with large NF1 deletions.

Neurofibromatosis Type 1 (NF1) is a frequent tumor suppressor gene disorder characterized by multiple benign tumors and high risk of malignancy. Internal tumor burden is a major disease-associated manifestation and can be most adequately assessed by magnetic resonance imaging of the whole body. Approximately 5% of NF1 patients have constitutional large NF1-deletions that are generally associated with more severe clinical manifestations. Here, we investigated whether these deletion patients also have more and/or larger internal tumors by assessing internal tumors and their total volume (exclusive of cutaneous and subcutaneous) in 38 NF1 deletion patients (including eight mosaic cases) and 114 age- and gender-matched NF1 patients without deletions. The incidence of internal tumors was significantly lower in mosaic deletion patients (1/8 = 13%) but did not differ between the 30 nonmosaic deletion patients and the 90 age- and gender-matched NF1 patients without large deletions used as controls. Neither the number nor the total volume of tumors per patient differed significantly between the latter two groups. However, extremely high tumor burden (>3,000 ml) was significantly more frequent among nonmosaic NF1 deletion patients than among NF1 patients without large deletions (13% vs. 1%, P = 0.014). Thus, as a group, patients with NF1 deletions do not exhibit a significantly higher internal tumor burden than NF1 patients without such deletions. However, deletion patients can frequently have extremely large internal tumors and thus demand special attention.

HAND2 Assists MYCN Enhancer Invasion to Regulate a Noradrenergic Neuroblastoma Phenotype.

Noradrenergic neuroblastoma is characterized by a core transcriptional regulatory circuitry (CRC) comprised of transcription factors (TF) such as PHOX2B, HAND2, and GATA3, which form a network with MYCN. At normal physiologic levels, MYCN mainly binds to promoters but when aberrantly upregulated as in neuroblastoma, MYCN also binds to enhancers. Here, we investigated how MYCN invades enhancers and whether CRC TFs play a role in this process. HAND2 was found to regulate chromatin accessibility and to assist MYCN binding to enhancers. Moreover, HAND2 cooperated with MYCN to compete with nucleosomes to regulate global gene transcription. The cooperative interaction between MYCN and HAND2 could be targeted with an Aurora A kinase inhibitor plus a histone deacetylase inhibitor, resulting in potent downregulation of both MYCN and the CRC TFs and suppression of MYCN-amplified neuroblastoma tumor growth. This study identifies cooperation between MYCN and HAND2 in neuroblastoma and demonstrates that simultaneously targeting MYCN and CRC TFs is an effective way to treat this aggressive pediatric tumor. SIGNIFICANCE: HAND2 and MYCN compete with nucleosomes to regulate global gene transcription and to drive a malignant neuroblastoma phenotype.

Preclinical optimization of a GPC2-targeting CAR T-cell therapy for neuroblastoma.

BACKGROUND: Although most patients with newly diagnosed high-risk neuroblastoma (NB) achieve remission after initial therapy, more than 50% experience late relapses caused by minimal residual disease (MRD) and succumb to their cancer. Therapeutic strategies to target MRD may benefit these children. We developed a new chimeric antigen receptor (CAR) targeting glypican-2 (GPC2) and conducted iterative preclinical engineering of the CAR structure to maximize its anti-tumor efficacy before clinical translation. METHODS: We evaluated different GPC2-CAR constructs by measuring the CAR activity in vitro. NOD-SCID mice engrafted orthotopically with human NB cell lines or patient-derived xenografts and treated with human CAR T cells served as in vivo models. Mechanistic studies were performed using single-cell RNA-sequencing. RESULTS: Applying stringent in vitro assays and orthotopic in vivo NB models, we demonstrated that our single-chain variable fragment, CT3, integrated into a CAR vector with a CD28 hinge, CD28 transmembrane, and 4-1BB co-stimulatory domain (CT3.28H.BBζ) elicits the best preclinical anti-NB activity compared with other tested CAR constructs. This enhanced activity was associated with an enrichment of CD8+ effector T cells in the tumor-microenvironment and upregulation of several effector molecules such as GNLY, GZMB, ZNF683, and HMGN2. Finally, we also showed that the CT3.28H.BBζ CAR we developed was more potent than a recently clinically tested GD2-targeted CAR to control NB growth in vivo. CONCLUSION: Given the robust preclinical activity of CT3.28H.BBζ, these results form a promising basis for further clinical testing in children with NB.

Non-coding RNA ANRIL and the number of plexiform neurofibromas in patients with NF1 microdeletions.

BACKGROUND: Neurofibromatosis type-1 (NF1) is caused by mutations of the NF1 gene at 17q11.2. In 95% of non-founder NF1 patients, NF1 mutations are identifiable by means of a comprehensive mutation analysis. 5-10% of these patients harbour microdeletions encompassing the NF1 gene and its flanking regions. NF1 is characterised by tumours of the peripheral nerve sheaths, the pathognomonic neurofibromas. Considerable inter- and intra-familial variation in expressivity of the disease has been observed which is influenced by genetic modifiers unrelated to the constitutional NF1 mutation. The number of plexiform neurofibromas (PNF) in NF1 patients is a highly heritable genetic trait. Recently, SNP rs2151280 located within the non-coding RNA gene ANRIL at 9p21.3, was identified as being strongly associated with PNF number in a family-based association study. The T-allele of rs2151280, which correlates with reduced ANRIL expression, appears to be associated with higher PNF number. ANRIL directly binds to the SUZ12 protein, an essential component of polycomb repressive complex 2, and is required for SUZ12 occupancy of the CDKN2A/CDKN2B tumour suppressor genes as well as for their epigenetic silencing. METHODS: Here, we explored a potential association of PNF number and PNF volume with SNP rs2151280 in 29 patients with constitutional NF1 microdeletions using the exact Cochran-Armitage test for trends and the exact Mann-Whitney-Wilcoxon test. Both the PNF number and total tumour volume in these 29 NF1 patients were assessed by whole-body MRI. The NF1 microdeletions observed in these 29 patients encompassed the NF1 gene as well as its flanking regions, including the SUZ12 gene. RESULTS: In the 29 microdeletion patients investigated, neither the PNF number nor PNF volume was found to be associated with the T-allele of rs2151280. CONCLUSION: Our findings imply that, at least in patients with NF1 microdeletions, PNF susceptibility is not associated with rs2151280. Although somatic inactivation of the NF1 wild-type allele is considered to be the PNF-initiating event in NF1 patients with intragenic mutations and patients with NF1 microdeletions, both patient groups may differ with regard to tumour progression because of the heterozygous constitutional deletion of SUZ12 present only in patients with NF1 microdeletions.

Combining selinexor with alisertib to target the p53 pathway in neuroblastoma.

Neuroblastoma accounts for 15% of cancer-related deaths in children, highlighting an unmet need for novel therapies. Selinexor is a small molecule inhibitor of XPO1. XPO1 shuffles cargo proteins with a nuclear export sequence from the nucleus to the cytosol, many of which are essential for cancer growth and cell maintenance. We systematically tested the effect of selinexor against neuroblastoma cells in vitro and in vivo and used an advanced proteomic and phosphoproteomic screening approach to interrogate unknown mechanisms of action. We found that selinexor induced its cytotoxic effects in neuroblastoma through the predominantly nuclear accumulation of p53 and global activation of apoptosis pathways. Selinexor also induced p53 phosphorylation at site S315, which is one initiating step for p53 degradation. Since this phosphorylation step is undertaken mostly by aurora kinase A (AURKA), we used the clinically available AURKA inhibitor, alisertib, and found p53-mediated lethality could be further augmented in three orthotopic xenograft mouse models. These findings suggest a potential therapeutic benefit using selinexor and alisertib to synergistically increase p53-mediated cytotoxicity of high-risk neuroblastoma.