Detection of GD2-positive cells in bone marrow samples and survival of patients with localised neuroblastoma

Biology of GD2 ganglioside: implications for cancer immunotherapy

Part of the broader glycosphingolipid family, gangliosides are composed of a ceramide bound to a sialic acid-containing glycan chain, and locate at the plasma membrane. Gangliosides are produced through sequential steps of glycosylation and sialylation. This diversity of composition is reflected in differences in expression patterns and functions of the various gangliosides. Ganglioside GD2 designates different subspecies following a basic structure containing three carbohydrate residues and two sialic acids. GD2 expression, usually restrained to limited tissues, is frequently altered in various neuroectoderm-derived cancers. While GD2 is of evident interest, its glycolipid nature has rendered research challenging. Physiological GD2 expression has been linked to developmental processes. Passing this stage, varying levels of GD2, physiologically expressed mainly in the central nervous system, affect composition and formation of membrane microdomains involved in surface receptor signaling. Overexpressed in cancer, GD2 has been shown to enhance cell survival and invasion. Furthermore, binding of antibodies leads to immune-independent cell death mechanisms. In addition, GD2 contributes to T-cell dysfunction, and functions as an immune checkpoint. Given the cancer-associated functions, GD2 has been a source of interest for immunotherapy. As a potential biomarker, methods are being developed to quantify GD2 from patients' samples. In addition, various therapeutic strategies are tested. Based on initial success with antibodies, derivates such as bispecific antibodies and immunocytokines have been developed, engaging patient immune system. Cytotoxic effectors or payloads may be redirected based on anti-GD2 antibodies. Finally, vaccines can be used to mount an immune response in patients. We review here the pertinent biological information on GD2 which may be of use for optimizing current immunotherapeutic strategies.

Combined use of multiparametric flow cytometry and cytomorphology to enhance detection of neuroblastoma metastatic cells in bone marrow

INTRODUCTION

In the context of neuroblastoma (NB), the screening for bone marrow (BM) metastasis is a recurrent issue for hematology laboratory routine practice. Detection of low tumor burden using light microscopy is often difficult. In this regard, our objective was to evaluate the performance of multiparametric flow cytometry (FC) for detecting NB metastatic cells in BM.

METHODS

We applied a new FC multiparametric panel allowing the analysis of the co-expression of 5 surface markers: GD2 (disialoganglioside 2), CD9, CD56, CD81, and CD90, on CD45-negative BM cell populations, and compared results with BM biopsy immunohistochemistry, which is the reference method.

RESULTS

In spike-in tests, the multiparametric FC successfully detected NB cells mixed in peripheral blood mononuclear cells to a level of 0.01%. FC analysis was performed on 45 sets of BM aspirates sampled from 21 children, either at diagnosis or during follow-up. Combining multiparametric FC with light microscopy improved NB metastasis detection, with a higher sensitivity (76.9% vs 61.5%) and a higher specificity (94.4% vs 77.8%) as compared to light microscopy alone. At the time of diagnosis, multiparametric FC detected NB metastatic cells in all cases.

CONCLUSION

These results illustrate the performance of multiparametric FC analysis to detect metastatic BM infiltration of NB. This is of particular interest in an emergency context, since when combined with light microscopy, it enhances the detection of metastatic invasion within a short timeframe, allowing an adapted and rapid clinical management.

Positron Emission Tomography Detects In Vivo Expression of Disialoganglioside GD2 in Mouse Models of Primary and Metastatic Osteosarcoma

The cell membrane glycolipid GD2 is expressed by multiple solid tumors, including 88% of osteosarcomas and 98% of neuroblastomas. However, osteosarcomas are highly heterogeneous, with many tumors exhibiting GD2 expression on <50% of the individual cells, while some tumors are essentially GD2-negative. Anti-GD2 immunotherapy is the current standard of care for high-risk neuroblastoma, but its application to recurrent osteosarcomas, for which no effective therapies exist, has been extremely limited. This is, in part, because the standard assays to measure GD2 expression in these heterogeneous tumors are not quantitative and are subject to tissue availability and sampling bias. To address these limitations, we evaluated a novel, sensitive radiotracer [⁶⁴Cu]Cu-Bn-NOTA-hu14.18K322A to detect GD2 expression in osteosarcomas (six patient-derived xenografts and one cell line) in vivo using positron emission tomography (PET). Tumor uptake of the radiolabeled, humanized anti-GD2 antibody [⁶⁴Cu]Cu-Bn-NOTA-hu14.18K322A was 7-fold higher in modestly GD2-expressing osteosarcomas (32% GD2-positive cells) than in a GD2-negative tumor (9.8% vs. 1.3% of the injected dose per cc, respectively). This radiotracer also identified lesions as small as 29 mm³ in a 34% GD2-positive model of metastatic osteosarcoma of the lung. Radiolabeled antibody accumulation in patient-derived xenografts correlated with GD2 expression as measured by flow cytometry (Pearson r = 0.88, P = 0.01), distinguishing moderately GD2-expressing osteosarcomas (32%-69% GD2-positive cells) from high GD2 expressors (>99%, P < 0.05). These results support the utility of GD2 imaging with PET to measure GD2 expression in osteosarcoma and thus maximize the clinical impact of anti-GD2 immunotherapy. SIGNIFICANCE: In situ assessment of all GD2-positive osteosarcoma sites with a novel PET radiotracer could significantly impact anti-GD2 immunotherapy patient selection and enable noninvasive probing of correlations between target expression and therapeutic response.

Prognostic value of initial bone marrow disease detection by multiparameter flow cytometry in children with neuroblastoma

PURPOSE

Multicolor flow cytometry (MFC) is widely available, fast and has an easy-to perform approach for finding neuroblastoma (NB) cells among normal bone marrow (BM) hematopoietic cells. Aim of the study was to investigate prognostic significance of initial MFC tumor cells' detection in BM of children with NB.

METHODS

51 patients (24 boys and 27 girls) aged from 6 days to 15 years (median age 1 year 3 months) with NB were included in the study. BM samples at the time of diagnosis were obtained from 2 to 5 aspiration sites per patient. CD45(-)CD56(+)CD81(+)GD2(+)-cells were evaluated by MFC.

RESULTS

NB cells were detected in BM by FC more frequently compared to conventional cytomorphology (49.0% and 29.4% patients, respectively, р = 0.043). Patients with NB cells detected in BM by MFC had significantly worse event-free survival and cumulative incidence of relapse/progression [0.24(0.08) and 0.60(0.10), respectively] compared to children with negative result of immunophenotyping [0.85(0.07) and 0.12(0.06), respectively, p < 0.001 in both cases]. BM involvement detection by MFC maintained its prognostic significance in various patients groups. In multivariate analysis, immunophenotyping proved to be an independent prognostic factor when analyzed jointly with other NB risk factors. In 42 patients BM involvement was also studied by RQ-PCR for PHOX2B and TH genes expression. Within groups of patients divided by RQ-PCR positivity, MFC-positivity retained prognostic significance.

CONCLUSIONS

Thus flow cytometric BM involvement detection has very strong prognostic impact even stronger than RQ-PCR. It could be used in combination with other parameters for the treatment strategy choice in patients with NB.

Prospective investigation of applicability and the prognostic significance of bone marrow involvement in patients with neuroblastoma detected by quantitative reverse transcription PCR

BACKGROUND

Detection of bone marrow (BM) involvement in patients with neuroblastoma is crucial for staging and defining prognosis. Furthermore, the persistence of residual tumor cells in the BM is associated with an unfavorable outcome.

METHODS

Expression of PHOX2B, TH, ELAVL4, and B4GALNT1 (GD2-synthase) was analyzed by quantitative polymerase chain reaction in neuroblastoma cell lines, control BM samples, and in BM samples from patients. The threshold level of expression for each gene was established through receiver operator characteristic analysis and used to determine the diagnostic test performance. The prognostic significance of BM involvement was assessed by survival rates calculations. The median of follow-up time was 36.1 months.

RESULTS

Neither PHOX2B nor TH expression was detected in control BM, while expression of ELAVL4 was found in 20 (76.9%) and GD2-synthase in 15 (57.7%) of 26 samples. The overall correct predictive value for TH, ELAVL4, and GD2-synthase, based on thresholds levels, was 0.952, 0.828, and 0.767, respectively, whereas the overall correct predictive value for PHOX2B was 0.994. The PHOX2B/TH expression in diagnostic BM of patients with neuroblastoma corresponded with a decreased survival rate (P < 0.001) in the total cohort and in different risk groups. Predominance of normalized expression of PHOX2B over TH > 1.68 in the diagnostic BM samples demonstrated an adverse prognostic effect (P = 0.006). Persistence of PHOX2B/TH expression in the BM during and after induction chemotherapy resulted in dismal outcome (P = 0.022 and P = 0.012).

CONCLUSION

PHOX2B and TH are the most optimal markers for detection of BM involvement, allowing identification of high-risk patients. Predominance of PHOX2B expression over TH has a strong adverse prognostic impact.

Modulation of the Tumor Microenvironment by CXCR4 Antagonist-Armed Viral Oncotherapy Enhances the Antitumor Efficacy of Dendritic Cell Vaccines against Neuroblastoma in Syngeneic Mice

The induction of antitumor immune responses in tumor-bearing hosts depends on efficient uptake and processing of native or modified tumors/self-antigens by dendritic cells (DCs) to activate immune effector cells, as well as the extent of the immunosuppressive network in the tumor microenvironment (TME). Because the C-X-C motif chemokine receptor 4 (CXCR4) for the C-X-C motif chemokine 12 (CXCL12) is involved in signaling interactions between tumor cells and their TME, we used oncolytic virotherapy with a CXCR4 antagonist to investigate whether targeting of the CXCL12/CXCR4 signaling axis in murine neuroblastoma cells (NXS2)-bearing syngeneic mice affects the efficacy of bone marrow (BM)-derived DCs loaded with autologous tumor cells treated with doxorubicin for induction of immunogenic cell death. Here, we show that CXCR4 antagonist expression from an oncolytic vaccinia virus delivered intravenously to mice with neuroblastoma tumors augmented efficacy of the DC vaccines compared to treatments mediated by a soluble CXCR4 antagonist or oncolysis alone. This study is the first demonstration that modulating the tumor microenvironment by an armed oncolytic virus could have a significant impact on the efficacy of DC vaccines, leading to the generation of effective protection against neuroblastoma challenge.

Neuroblastoma messenger RNA is frequently detected in bone marrow at diagnosis of localised neuroblastoma patients

INTRODUCTION

The clinical importance of the detection of neuroblastoma messenger RNA (mRNA) in bone marrow (BM) of localised neuroblastoma patients at diagnosis remains unclear. In this prospective multicentre study, BM samples of a large cohort, were studied using real-time quantitative polymerase chain reaction (qPCR).

METHODS

BM samples at diagnosis from 160 patients with localised neuroblastoma were prospectively collected at Dutch and German centres between 2009 and 2013. qPCR was performed using five neuroblastoma specific markers. The association with other biological factors and the prognostic impact of BM positivity and clinical response was assessed.

RESULTS

In 58 out of 160 patients neuroblastoma mRNA was detected in BM. In 47 of the 58 positive samples only one marker was found positive. BM positivity was significantly associated with MYCN amplification (p = 0.02) and deletion of chromosome 1p (p = 0.04). In total 31 patients had an event, of which only five patients had progression to stage IV. BM positivity was not associated with an unfavourable outcome. However, the detection of more than one marker was associated with an unfavourable outcome (systemic or local relapse) (event free survival 48% versus 85%; p = 0.03) in the whole cohort and in the observation group.

CONCLUSIONS

BM positivity was associated with unfavourable biological factors and might represent more aggressive tumours. Patients with qPCR positive BM should not be upstaged, because of very few systemic events in the cohort. However, for patients with more than one marker positive a more careful follow-up is advisable. These results need to be verified in a very large cohort of localised patients.

Evaluation of bone marrow as a metastatic site of human neuroblastoma

Arising from neural crest cells, neuroblastoma (NB) is the most common extracranial pediatric solid tumor. The clinical presentation of NB is heterogeneous, ranging from patients with asymptomatic tumor masses, who require minimal treatment, to patients with metastatic disease who are treated with multimodal therapies. Clinical outcome is also variable, with overall survival ranging from 98% to 100% in infants with stage 1 NB, to less than 30% in patients with stage 4 MYCN-amplified NB. More than 50% of patients show metastasis at diagnosis, with the involvement of different vascularized tissues, including the bone marrow (BM). In this paper, we focus on BM infiltration by NB cells, which is considered an adverse prognostic factor. In particular, we discuss the role of different biological factors that may favor the dissemination of NB cells in the BM, such as chromosomic abnormalities, gene amplification, transcription factors, cell-surface receptors, products of oncogenes, and, more importantly, cytokines and chemokines. In addition, we analyze different techniques to evaluate BM infiltration by malignant cells (i.e., flow cytometry, immunocytochemistry, and quantitative reverse transcriptase polymerase chain reaction). Finally, we review recent data regarding phenotypic and genetic characterization of BM-infiltrating malignant cells and characterization of the BM microenvironment in NB patients compared to healthy subjects.

Bone marrow of neuroblastoma patients shows downregulation of CXCL12 expression and presence of IFN signature

BACKGROUND

At diagnosis, children with neuroblastoma (NB) present with either localized or metastatic disease. Since the mechanisms responsible for BM invasion are not well known, we investigated the transcriptome of resident BM cells from NB patients as compared to healthy children.

PROCEDURE

Ninety-two and 88 children with localized and metastatic NB, respectively, and 15 healthy children were included in the study. BM resident cells recovered from BM aspirates by immunomagnetic bead manipulation were subjected to genome-wide microarray analysis. After validation in an independent set of samples, the genes significantly modulated in resident BM cells from NB patients were tested for their diagnostic/prognostic values.

RESULTS

BM resident cells, irrespective of neoplastic cell invasion, significantly overexpressed genes involved in innate immune responses, and interferon (IFN) and IFN-DRS signatures were enriched. Genes coding for metallothioneins and zinc finger proteins, and involved in histone and nucleosome/chromatin organization were also overexpressed. Resident BM cells from NB patients significantly downregulated genes involved in cell adhesion, and in erythrocyte, myeloid, and platelet differentiation pathways. Among downregulated genes, CXCL12 expression reached near complete silencing in patients with metastatic disease. The downregulation of CXCL12 expression was independent of contact between NB cell and resident BM cell.

CONCLUSIONS

We demonstrated that NB tumor growth at the primary site can alter the BM microenvironment, and the presence of BM-infiltrating NB cells makes the alterations more pronounced. Therefore, the restoration of a BM physiological state by means of IFN-α monoclonal antibody, Sifalimumab, and selective noradrenaline receptor blockers should be further studied to ameliorate patients' clinical management.

New prognostic markers in neuroblastoma

INTRODUCTION

The hallmark of neuroblastoma is its clinical and biological heterogeneity, with the likelihood of cure varying widely according to age at diagnosis, extent of disease and tumor biology. We hope this review will be useful for understanding part of the unfamiliar neuroblastoma codex.

AREAS COVERED

In the first part of this review, the authors summarize the currently used prognostic factors for risk-adapted therapy, with the focus on clinical management of neuroblastoma patients. In the second part, the authors discuss the evolving prognostic factors for future treatment schemes. A search of online medical research databases was undertaken focusing especially on literature published in the last six years.

EXPERT OPINION

Harnessing the synergy of the various forms of data, including clinical variables and biomarker profiles, would allow mathematical predictive models to be built for the individual patient, which could eventually become molecular targets of specific therapies.

Bone marrow-infiltrating human neuroblastoma cells express high levels of calprotectin and HLA-G proteins

Metastases in the bone marrow (BM) are grim prognostic factors in patients with neuroblastoma (NB). In spite of extensive analysis of primary tumor cells from high- and low-risk NB patients, a characterization of freshly isolated BM-infiltrating metastatic NB cells is still lacking. Our aim was to identify proteins specifically expressed by metastatic NB cells, that may be relevant for prognostic and therapeutic purposes. Sixty-six Italian children over 18 months of age, diagnosed with stage 4 NB, were included in the study. Metastatic NB cells were freshly isolated from patients' BM by positive immunomagnetic bead manipulation using anti-GD2 monoclonal antibody. Gene expression profiles were compared with those obtained from archived NB primary tumors from patients with 5 y-follow-up. After validation by RT-qPCR, expression/secretion of the proteins encoded by the up-regulated genes in the BM-infiltrating NB cells was evaluated by flow cytometry and ELISA. Compared to primary tumor cells, BM-infiltrating NB cells down-modulated the expression of CX3CL1, AGT, ATP1A2 mRNAs, whereas they up-regulated several genes commonly expressed by various lineages of BM resident cells. BM-infiltrating NB cells expressed indeed the proteins encoded by the top-ranked genes, S100A8 and A9 (calprotectin), CD177 and CD3, and secreted the CXCL7 chemokine. BM-infiltrating NB cells also expressed CD271 and HLA-G. We have identified proteins specifically expressed by BM-infiltrating NB cells. Among them, calprotectin, a potent inflammatory protein, and HLA-G, endowed with tolerogenic properties facilitating tumor escape from host immune response, may represent novel biomarkers and/or targets for therapeutic intervention in high-risk NB patients.

Multiple target molecular monitoring of bone marrow and peripheral blood samples from patients with localized neuroblastoma and healthy donors

BACKGROUND

Multiple target molecular monitoring of minimal residual disease in neuroblastoma (NB) patients may increase sensitivity and overcome tumor heterogeneity. However, multiple target analysis is costly and time consuming, thus improvement with respect to single target monitoring needs to be achieved.

PROCEDURES

Italian patients with localized NB were evaluated at diagnosis for TH, GD2-s, DDC, DCX, ELAV-4, STX, and Phox2b mRNA expressions. Patients with metastatic NB were tested as positive controls, together with NB primary tumors and cell lines, while healthy donors were tested as negative controls.

RESULTS

All NB-related markers but Phox2b were expressed in healthy donors, and in a high percentage of patients with localized NB without association with clinical events. The introduction of cut-off levels increased marker specificity, although the percentage of positive results was only slightly modified. While TH positivity in PB samples significantly associated with a worse prognosis, a paradox association was found for GD2-s mRNA expression. No correlation and agreement between quantitative and qualitative results obtained with the two assays were found. In the set of samples tested for all markers, no pattern of expression was found to be associated with a specific clinical situation.

CONCLUSION

These findings suggest that positive molecular results may not reflect the presence of disease, and that correlation among different markers is small in condition of low tumor burden. Thus, to reduce cost and amount of precious samples, in addition to TH, whose prognostic value was confirmed, only Phox2b warrants further evaluation in multi-center, prospective studies for high risk patients.

Identification of novel prognostic markers in relapsing localized resectable neuroblastoma

Patients with localized resectable neuroblastoma (NB) generally have an excellent prognosis and can be treated by surgery alone, but approximately 10% of them develop local recurrences or metastatic progression. The known predictive risk factors are important for the identification of localized resectable NB patients at risk of relapse and/or progression, who may benefit from early and aggressive treatment. These factors, however, identify only a subset of patients at risk, and the search for novel prognostic markers is warranted. This review focuses on the recent advances in the identification of new prognostic markers. Recently we addressed the search of novel genetic prognostic markers in a selected cohort of patients with stroma-poor localized resectable NB who underwent disease relapse or progression (group 1) or complete remission (group 2). High-resolution array-comparative genomic hybridization (CGH) DNA copy-number analysis technology was used. Chromosome 1p36.22p36.32 loss and 1q22qter gain, detected almost exclusively in group 1 patients, were significantly associated with poor event-free survival (EFS). Increasing evidence points to anaplastic lymphoma kinase (ALK) as a fundamental oncogene associated with NB. The immunohistochemical analysis of sporadic NB localized resectable primary tumors (stage 1-2) showed a correlation between aberrant ALK level of expression and tumor progression and clinical outcome. Moreover, other factors that might influence the clinical behavior of these tumors will be reviewed.

PHOX2B is a novel and specific marker for minimal residual disease testing in neuroblastoma

PURPOSE

Polymerase chain reaction (PCR)-based detection of minimal residual disease (MRD) in neuroblastoma can be used to monitor therapy response and to evaluate stem cell harvests. Commonly used PCR markers, tyrosine hydroxylase (TH) and GD2 synthase, have expression in normal tissues, thus limiting MRD detection. To identify a more specific MRD marker, we tested PHOX2B.

PATIENTS AND METHODS

To determine PHOX2B, TH, and GD2 synthase expression in normal tissues, it was measured by real-time quantitative PCR in samples of normal bone marrow (BM; n = 51), peripheral blood (PB; n = 37), and peripheral-blood stem cells (PBSCs; n = 24). Then, 289 samples of 101 Dutch patients and 47 samples of 43 German patients were tested for PHOX2B and TH; these samples included 52 tumor, 214 BM, 32 BM, and 38 PBSC harvests. Of the 214 BM samples, 167 were compared with cytology, and 47 BM samples were compared with immunocytology (IC).

RESULTS

In contrast to TH and GD2 synthase, PHOX2B was not expressed in any of the normal samples. In patient samples, PHOX2B was detected in 32% cytology-negative and in 14% IC-negative samples and in 94% of cytology-positive and in 90% of IC-positive BM samples. Overall, PHOX2B was positive in 43% compared with 31% for TH. In 24% of all samples, TH expression was inconclusive, which is similar to expression found in normal tissues. In 42% of these samples, PHOX2B expression was positive.

CONCLUSION

PHOX2B is superior to TH and GD2 synthase in specificity and sensitivity for MRD detection of neuroblastoma by using real-time quantitative PCR. We propose to include PHOX2B in additional prospective MRD studies in neuroblastoma alongside TH and other MRD markers.