Detection of neuroblastoma cells in bone marrow and peripheral blood at diagnosis by the reverse transcriptase-polymerase chain reaction for tyrosine hydroxylase mRNA

A comprehensive overview of liquid biopsy applications in pediatric solid tumors

Liquid biopsies are emerging as an alternative source for pediatric cancer biomarkers with potential applications during all stages of patient care, from diagnosis to long-term follow-up. While developments within this field are reported, these mainly focus on dedicated items such as a specific liquid biopsy matrix, analyte, and/or single tumor type. To the best of our knowledge, a comprehensive overview is lacking. Here, we review the current state of liquid biopsy research for the most common non-central nervous system pediatric solid tumors. These include neuroblastoma, renal tumors, germ cell tumors, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma and other soft tissue sarcomas, and liver tumors. Within this selection, we discuss the most important or recent studies involving liquid biopsy-based biomarkers, anticipated clinical applications, and the current challenges for success. Furthermore, we provide an overview of liquid biopsy-based biomarker publication output for each tumor type based on a comprehensive literature search between 1989 and 2023. Per study identified, we list the relevant liquid biopsy-based biomarkers, matrices (e.g., peripheral blood, bone marrow, or cerebrospinal fluid), analytes (e.g., circulating cell-free and tumor DNA, microRNAs, and circulating tumor cells), methods (e.g., digital droplet PCR and next-generation sequencing), the involved pediatric patient cohort, and proposed applications. As such, we identified 344 unique publications. Taken together, while the liquid biopsy field in pediatric oncology is still behind adult oncology, potentially relevant publications have increased over the last decade. Importantly, steps towards clinical implementation are rapidly gaining ground, notably through validation of liquid biopsy-based biomarkers in pediatric clinical trials.

Advances in liquid biopsy in neuroblastoma

Even with intensive treatment of high-risk neuroblastoma (NB) patients, half of high-risk NB patients still relapse. New therapies targeting the biological characteristics of NB have important clinical value for the personalized treatment of NB. However, the current biological markers for NB are mainly analyzed by tissue biopsy. In recent years, circulating biomarkers of NB based on liquid biopsy have attracted more and more attention. This review summarizes the analytes and methods for liquid biopsy of NB. We focus on the application of liquid biopsy in the diagnosis, prognosis assessment, and monitoring of NB. Finally, we discuss the prospects and challenges of liquid biopsy in NB.

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.

Label-free separation of neuroblastoma patient-derived xenograft (PDX) cells from hematopoietic progenitor cell products by acoustophoresis

Background

Graft-contaminating tumor cells correlate with inferior outcome in high-risk neuroblastoma patients undergoing hematopoietic stem cell transplantation and can contribute to relapse. Motivated by the potential therapeutic benefit of tumor cell removal as well as the high prognostic and diagnostic value of isolated circulating tumor cells from stem cell grafts, we established a label-free acoustophoresis-based microfluidic technology for neuroblastoma enrichment and removal from peripheral blood progenitor cell (PBPC) products.

Methods

Neuroblastoma patient-derived xenograft (PDX) cells were spiked into PBPC apheresis samples as a clinically relevant model system. Cells were separated by ultrasound in an acoustophoresis microchip and analyzed for recovery, purity and function using flow cytometry, quantitative real-time PCR and cell culture.

Results

PDX cells and PBPCs showed distinct size distributions, which is an important parameter for efficient acoustic separation. Acoustic cell separation did not affect neuroblastoma cell growth. Acoustophoresis allowed to effectively separate PDX cells from spiked PBPC products. When PBPCs were spiked with 10% neuroblastoma cells, recoveries of up to 98% were achieved for PDX cells while more than 90% of CD34⁺ stem and progenitor cells were retained in the graft. At clinically relevant tumor cell contamination rates (0.1 and 0.01% PDX cells in PBPCs), neuroblastoma cells were depleted by more than 2-log as indicated by RT-PCR analysis of PHOX2B, TH and DDC genes, while > 85% of CD34⁺ cells could be retained in the graft.

Conclusion

These results demonstrate the potential use of label-free acoustophoresis for PBPC processing and its potential to develop label-free, non-contact tumor cell enrichment and purging procedures for future clinical use.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02612-2.

Investigation of patient factors associated with the number of transfusions required during chemotherapy for high-risk neuroblastoma

BACKGROUND

Blood transfusion is an important supportive care for high-risk neuroblastoma. When the number of transfusions increases, transfusion-associated adverse reactions may be more problematic. However, the factors determining the degree of myelosuppression and the number of transfusions during chemotherapy for high-risk neuroblastoma remain unclear.

MATERIALS AND METHODS

We investigated patient factors determining the number of required transfusions in 15 high-risk neuroblastoma patients who received five courses of chemotherapy. Clinical data, cytokine profile and colony-forming assay with bone marrow samples at diagnosis were analysed.

RESULTS

The required number of transfusions of both platelets and erythrocytes decreased once in the second course and then increased as the course progressed. The variability among cases increased as the chemotherapy course progressed. In cases of low peripheral blood platelet count and lower fibrinogen level at diagnosis, the number of platelet transfusions was higher during chemotherapy. In contrast, there was a negative correlation between the forming ability of granulocyte-macrophage or erythroid colonies and the number of erythrocyte transfusions in the latter period.

CONCLUSION

In the early stages of chemotherapy, bone marrow infiltration in neuroblastoma and/or coagulopathy complication may cause thrombocytopenia and requirement of platelet transfusion; conversely, in the later stages, the number of erythrocyte transfusions may be defined by the patient's inherent hematopoietic ability. These factors may be useful in predicting the required number of transfusions.

Progress toward liquid biopsies in pediatric solid tumors

Pediatric solid tumors have long been known to shed tumor cells, DNA, RNA, and proteins into the blood. Recent technological advances have allowed for improved capture and analysis of these typically scant circulating materials. Efforts are ongoing to develop "liquid biopsy" assays as minimally invasive tools to address diagnostic, prognostic, and disease monitoring needs in childhood cancer care. Applying these highly sensitive technologies to serial liquid biopsies is expected to advance understanding of tumor biology, heterogeneity, and evolution over the course of therapy, thus opening new avenues for personalized therapy. In this review, we outline the latest technologies available for liquid biopsies and describe the methods, pitfalls, and benefits of the assays that are being developed for children with extracranial solid tumors. We discuss what has been learned in several of the most common pediatric solid tumors including neuroblastoma, sarcoma, Wilms tumor, and hepatoblastoma and highlight promising future directions for the field.

Label-free neuroblastoma cell separation from hematopoietic progenitor cell products using acoustophoresis - towards cell processing of complex biological samples

Processing of complex cell preparations such as blood and peripheral blood progenitor cell (PBPC) transplants using label-free technologies is challenging. Transplant-contaminating neuroblastoma cells (NBCs) can contribute to relapse, and we therefore aimed to provide proof-of-principle evidence that label-free acoustophoretic separation can be applied for diagnostic NBC enrichment and removal ("purging") from human blood and PBPC products. Neuroblastoma cells spiked into blood and PBPC preparations served as model systems. Acoustophoresis enabled to enrich NBCs from mononuclear peripheral blood cells and PBPC samples with recovery rates of up to 60-97%. When aiming at high purity, NBC purities of up to 90% were realized, however, compromising recovery. Acoustophoretic purging of PBPC products allowed substantial tumour cell depletion of 1.5-2.3 log. PBPC loss under these conditions was considerable (>43%) but could be decreased to less than 10% while still achieving NBC depletion rates of 60-80%. Proliferation of cells was not affected by acoustic separation. These results provide first evidence that NBCs can be acoustically separated from blood and stem cell preparations with high recovery and purity, thus indicating that acoustophoresis is a promising technology for the development of future label-free, non-contact cell processing of complex cell products.

Dynamics of Minimal Residual Disease in Neuroblastoma Patients

Neuroblastoma is a common extracranial solid tumor of neural crest (NC) origin that accounts for up to 15% of all pediatric cancer deaths. The disease arises from a transient population of NC cells that undergo an epithelial-mesenchymal transition (EMT) and generate diverse cell-types and tissues. Patients with neuroblastoma are characterized by their extreme heterogeneity ranging from spontaneous regression to malignant progression. More than half of newly diagnosed patients present highly metastatic tumors and are stratified into a high-risk group with dismal outcome. As many as 20% of high-risk patients have residual disease that is refractory or progressive during induction chemotherapy. Although a majority of high-risk patients achieve remission, larger part of those patients has minimal residual disease (MRD) that causes relapse even after additional consolidation therapy. MRD is composed of drug-resistant tumor cells and dynamically presented as cancer stem cells (CSCs) in residual tumors, circulating tumor cells (CTCs) in peripheral blood (PB), and disseminated tumor cells (DTCs) in bone marrow (BM) and other metastatic sites. EMT appears to be a key mechanism for cancer cells to acquire MRD phenotypes and malignant aggressiveness. Due to the restricted availability of residual tumors, PB and BM have been used to isolate and analyze CTCs and DTCs to evaluate MRD in cancer patients. In addition, recent technical advances make it possible to use circulating tumor DNA (ctDNA) shed from tumor cells into PB for MRD evaluation. Because MRD can be detected by tumor-specific antigens, genetic or epigenetic changes, and mRNAs, numerous assays using different methods and samples have been reported to detect MRD in cancer patients. In contrast to the tumor-specific gene-rearrangement-positive acute lymphoblastic leukemia (ALL) and the oncogenic fusion-gene-positive chronic myelogenous leukemia (CML) and several solid tumors, the clinical significance of MRD remains to be established in neuroblastoma. Given the extreme heterogeneity of neuroblastoma, dynamics of MRD in neuroblastoma patients will hold a key to the clinical validation. In this review, we summarize the biology and detection methods of cancer MRD in general and evaluate the available assays and clinical significance of neuroblastoma MRD to clarify its dynamics in neuroblastoma patients.

Opportunities and challenges of circulating biomarkers in neuroblastoma

Molecular analysis of nucleic acid and protein biomarkers is becoming increasingly common in paediatric oncology for diagnosis, risk stratification and molecularly targeted therapeutics. However, many current and emerging biomarkers are based on analysis of tumour tissue, which is obtained through invasive surgical procedures and in some cases may not be accessible. Over the past decade, there has been growing interest in the utility of circulating biomarkers such as cell-free nucleic acids, circulating tumour cells and extracellular vesicles as a so-called liquid biopsy of cancer. Here, we review the potential of emerging circulating biomarkers in the management of neuroblastoma and highlight challenges to their implementation in the clinic.

Co-expression of IL-15 enhances anti-neuroblastoma effectivity of a tyrosine hydroxylase-directed DNA vaccination in mice

Long-term survival of high-risk neuroblastoma (NB) patients still remains under 50%. Here, we report the generation, in vitro characterization and anti-tumor effectivity of a new bicistronic xenogenic DNA vaccine encoding tyrosine hydroxylase (TH) that is highly expressed in NB tumors, and the immune stimulating cytokine interleukin 15 (IL-15) that induces cytotoxic but not regulatory T cells. The DNA sequences of TH linked to ubiquitin and of IL-15 were integrated into the bicistronic expression vector pIRES. Successful production and bioactivity of the vaccine-derived IL-15- and TH protein were shown by ELISA, bioactivity assay and western blot analysis. Further, DNA vaccine-driven gene transfer to the antigen presenting cells of Peyer’s patches using attenuated Salmonella typhimurium that served as oral delivery system was shown by immunofluorescence analysis. The anti-tumor effect of the generated vaccine was evaluated in a syngeneic mouse model (A/J mice, n = 12) after immunization with S. typhimurium (3× prior and 3× after tumor implantation). Importantly, TH-/IL-15-based DNA vaccination resulted in an enhanced tumor remission in 45.5% of mice compared to controls (TH (16.7%), IL-15 (0%)) and reduced spontaneous metastasis (30.0%) compared to controls (TH (63.6%), IL-15 (70.0%)). Interestingly, similar levels of tumor infiltrating CD8⁺ T cells were observed among all experimental groups. Finally, co-expression of IL-15 did not result in elevated regulatory T cell levels in tumor environment measured by flow cytometry. In conclusion, co-expression of the stimulatory cytokine IL-15 enhanced the NB-specific anti-tumor effectivity of a TH-directed vaccination in mice and may provide a novel immunological approach for NB patients.

PCR-based amplification of circulating RNAs as prognostic and predictive biomarkers - Focus on neuroblastoma

Metastatic disease is a major challenge for cancer cure, haematogenous spread and subsequent growth of tumour cells at distant sites being the cause of most cancer deaths. Molecular characterization and detection of the tumour cells responsible for haematogenous spread may increase understanding of the biology of metastasis, help improve patient management and allow evaluation of novel treatments to prevent and eradicate this disease. The bone marrow is a common site to which tumour cells metastasize, from which they may re-circulate to other organs with a favourable microenvironment for growth. The detection of tumour cells in blood suggests one route for metastasis, and provides an accessible, minimally invasive liquid sample through which it may be possible to monitor and detect minimal disease and early signs of metastasis. Significant improvements in the sensitivity and specificity of tumour cell detection have been made, such that it is now possible to unambiguously detect a single tumour cell in over 10 million normal cells. However, the clinical impact of such low level disease and how to interpret the natural variation that can arise from sequential sampling of bone marrow aspirates and blood is currently largely unknown. This commentary will focus on the technical advancements and application of reverse transcriptase polymerase chain reaction to detect cancer mRNAs in bone marrow and blood, and discuss the potential clinical impact of this test in neuroblastoma.

Clinical Significance of Tyrosine Hydroxylase mRNA Transcripts in Peripheral Blood at Diagnosis in Patients with Neuroblastoma

Purpose

The purpose of this study is to investigate the clinical significance of tyrosine hydroxylase (TH) expression in peripheral blood (PB) at diagnosis in patients with neuroblastoma.

Materials and Methods

TH mRNA expression in PB was measured by reverse transcription quantitative real-time polymerase chain reaction in 210 patients who were newly diagnosed with neuroblastoma from July 2005 to June 2015 and the clinical significance of TH expression in PB at diagnosis was evaluated.

Results

TH expression was positive in 60 patients (28.6%). Fifty of 60 TH-positive patients had metastatic tumors and the remaining 10 had localized tumors. TH expression was associated with high-risk features (i.e., advanced stage, older age, unfavorable pathology, and MYCN amplification) at diagnosis. Among TH-positive patients, higher TH expression level was observed in high-risk patients than in low- or intermediate-risk patients (p=0.035). The probability of 5-year progression-free survival (PFS) was lower in TH-positive patients than in TH-negative patients (63.8±6.9% vs. 94.7±2.1%, p < 0.001). In analysis confined to high-risk patients, the 5-year probability of PFS remained lower in TH-positive patients (55.7±8.2% vs. 89.6±5.8%, p < 0.001). Among TH-positive patients, a higher expression level of TH was associated with a worse outcome. In multivariate analyses, positive TH expression in PB at diagnosis was an independent poor prognostic factor for PFS.

Conclusion

The treatment intensity should be tailored according to TH expression in PB at diagnosis.

Expression of Wilms tumor gene in high risk neuroblastoma: complementary marker to tyrosine hydroxylase for detection of minimal residual disease

BACKGROUND

Neuroblastoma (NB) is an enigmatic tumor that often presents with metastatic disease at diagnosis and it is this aggressive propensity which places it among the deadliest pediatric tumors despite intensive multimodal therapy including hematopoietic stem cell transplantation (HSCT). We have previously demonstrated that Wilms tumor 1 gene (WT1) is a surrogate marker of proliferation in leukemia. To determine the potential association between WT1 and a known marker of NB, tyrosine hydroxylase (TH) in this high risk group of patients.

METHODS

A total of 141 random samples from 34 patients were obtained, at diagnosis (n=27), during therapy (n=95), in clinical remission (n=13), and at the time of relapse (n=6). Quantitative RT-PCR was used for the evaluation of the level of gene expression using specific primers.

RESULTS

Although similar gene expressions were demonstrated in both controls when evaluating both genes, significant difference was found at each clinical time point. Furthermore, when comparing patient samples from diagnosis to clinical remission and diagnosis to clinical relapse, individual gene expression varied. WT1 demonstrated significance (P=0.0002) and insignificance (P=0.06) whereas TH remained non-significant (P=0.2, P=0.09) respectively.

CONCLUSIONS

WT1 gene is indicative of cellular proliferation in NB and for this reason it can be adjuvant to TH for the detection minimal residual disease (MRD).

Stability of PCR targets for monitoring minimal residual disease in neuroblastoma

In neuroblastoma (NB) patients, minimal residual disease (MRD) can be detected by real-time quantitative PCR (qPCR) using NB-specific target genes, such as PHOX2B and TH. However, it is unknown whether the mRNA levels of these targets vary either during treatment or at relapse. If marker genes are not stably expressed, estimation of MRD levels in bone marrow (BM) or peripheral blood will be hampered. We studied the stability of a panel of qPCR markers in primary tumors at diagnosis compared with i) paired metastasis (n = 7), ii) treated (n = 10), and iii) relapse (n = 6) tumors. We also compared relative expression of the targets in iv) primary tumors and BM at diagnosis (n = 17), v) BM and peripheral blood at diagnosis (n = 20), vi) BM at diagnosis and during treatment (n = 26), and vii) BM from different puncture sides (n = 110). Especially at diagnosis, PCR target expression is quite stable. Accurate quantification is possible when expression level can be related to the primary tumor; however, PCR target expression can alter on treatment and at relapse. If the median value of relative expression of a panel of PCR targets is used, most variations due to treatment and outgrowth of subclones level out, allowing for reliable application and quantification of MRD-PCR targets in NB patients.

Cellular kinetics of neuroblastoma and the role of surgery

Neuroblastoma is known for its peculiar cellular kinetics, which has provoked some controversy regarding surgical treatment. Highly sensitive exploration systems using reverse transcription polymerase chain reaction (RT-PCR) methods have been developed to detect neuroblastoma cells. In our series of 49 patients with advanced neuroblastoma, circulating tumor cells (CTC) were detected by this system in 55.6% of the stage 4 patients who were examined, suggesting that the primary lesion may release tumor cells into the peripheral blood. The Kaplan-Meier survival rate was significantly lower among the patients with CTC or chemotherapy-insensitive bone marrow micrometastasis, compared with those without detectable micrometastasis (33.8 vs. 87.5%, P < 0.05). In contrast, a stage 3 patient with MYCN amplification exhibited drastic local relapse without systemic dissemination of the disease. Two patients were positive for CTC without an identifiable primary site. These observations indicate that the local growth of the primary tumor and tumor cell dissemination may be regulated by different molecular mechanisms in neuroblastomas. MYCN amplification seemed to be more closely associated with localized tumor growth but was minimally correlated with CTC positivity. High-risk neuroblastoma may include two separate subgroups characterized by different cellular kinetics: a local risk cohort and a systemic risk cohort. Surgical strategies for neuroblastoma should be determined with taking this cellular kinetics into consideration.

Measurement of tyrosine hydroxylase transcripts in bone marrow using biopsied tissue instead of aspirates for neuroblastoma

BACKGROUND

Molecular detection of tyrosine hydroxylase (TH) transcripts by quantitative RT-PCR (qRT-PCR) is a sensitive method to detect neuroblastoma (NB) cells in the bone marrow (BM). However, its clinical utility following chemotherapy has not been thoroughly investigated.

PROCEDURES

TH transcripts in the BM were measured by qRT-PCR both at diagnosis and during the course of chemotherapy. The results were analyzed with respect to assay timing, tumor volume and histological findings.

RESULTS

TH transcripts were detected in 100% of BM aspirates at diagnosis in cases with concurrent tumor involvement in the BM section; however, the proportion of TH transcript positive BM aspirates in cases with concurrent tumor involvement in the BM section gradually decreased following chemotherapy (55.5% after three cycles, 28.6% after six cycles and 0% after nine or more cycles of chemotherapy). Decreased proportion of TH transcript positive BM aspirates was associated with reduced tumor volume in the BM and differentiation of tumors into mature forms during chemotherapy. When qRT-PCR was performed with both aspirated and biopsied tissue during chemotherapy, TH transcripts were detected in BM tissue not only in all of the histology-positive cases but also in some of the histology-negative cases, while the proportion of TH transcript positive BM aspirates was low, even in histology-positive cases.

CONCLUSIONS

Measurement of TH transcripts in BM aspirates does not appear to be clinically useful during or after chemotherapy. Therefore, molecular monitoring of NB cells during or after chemotherapy using BM tissue is more optimal than testing on BM aspirates.

Consensus criteria for sensitive detection of minimal neuroblastoma cells in bone marrow, blood and stem cell preparations by immunocytology and QRT-PCR: recommendations by the International Neuroblastoma Risk Group Task Force

Disseminating disease is a predictive and prognostic indicator of poor outcome in children with neuroblastoma. Its accurate and sensitive assessment can facilitate optimal treatment decisions. The International Neuroblastoma Risk Group (INRG) Task Force has defined standardised methods for the determination of minimal disease (MD) by immunocytology (IC) and quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) using disialoganglioside G(D2) and tyrosine hydroxylase mRNA respectively. The INRG standard operating procedures (SOPs) define methods for collecting, processing and evaluating bone marrow (BM), peripheral blood (PB) and peripheral blood stem cell harvest by IC and QRT-PCR. Sampling PB and BM is recommended at diagnosis, before and after myeloablative therapy and at the end of treatment. Peripheral blood stem cell products should be analysed at the time of harvest. Performing MD detection according to INRG SOPs will enable laboratories throughout the world to compare their results and thus facilitate quality-controlled multi-centre prospective trials to assess the clinical significance of MD and minimal residual disease in heterogeneous patient groups.

Circulating clonotypic B cells in classic Hodgkin lymphoma

Although Hodgkin and Reed-Sternberg (HRS) cells are B lymphoid cells, they are unlike any normal cells of that lineage. Moreover, the limited proliferative potential of HRS cells belies the clinical aggressiveness of Hodgkin lymphoma (HL). More than 20 years ago, the L428 HL cell line was reported to contain a small population of phenotypic B cells that appeared responsible for the continued generation of HRS cells. This observation, however, has never been corroborated, and such clonotypic B cells have never been documented in HL patients. We found that both the L428 and KM-H2 HL cell lines contained rare B-cell subpopulations responsible for the generation and maintenance of the predominant HRS cell population. The B cells within the HL cell lines expressed immunoglobulin light chain, the memory B-cell antigen CD27, and the stem cell marker aldehyde dehydrogenase (ALDH). Clonal CD27(+)ALDH(high) B cells, sharing immunoglobulin gene rearrangements with lymph node HRS cells, were also detected in the blood of most newly diagnosed HL patients regardless of stage. Although the clinical significance of circulating clonotypic B cells in HL remains unclear, these data suggest they may be the initiating cells for HL.

Cyclin D1, a novel molecular marker of minimal residual disease, in metastatic neuroblastoma

Accurate monitoring of minimal residual disease (MRD) is critical for the management of metastatic neuroblastoma (NB). We evaluated cyclin D1 (CCND1), a cell-cycle control gene, as a novel MRD marker of NB. Using quantitative reverse transcriptase-polymerase chain reaction, we studied CCND1 expression in 133 solid tumors of different histological types, including 39 NB tumors, and examined its potential clinical utility as an early response marker in the bone marrows before and after treatment of 118 stage 4 patients enrolled after induction chemotherapy in an immunotherapy protocol. Based on 40 normal marrow and peripheral blood samples, a CCND1 transcript value greater than the mean + 2 SD was defined as positive. Sensitivity of this assay was one NB cell in 10(6) normal mononuclear cells. CCND1 transcript levels were high in NB, breast cancer, and Ewing family tumors. Among the NB patients evaluated, early (2.5 months from protocol entry) marrow response was strongly associated with both progression-free (P=0.0001) and overall survival (P=0.0006). CCND1 response remained predictive of survival among a subset of 66 patients who had no histological evidence of marrow disease before immunotherapy. We conclude that CCND1 has potential clinical utility as a novel molecular marker of MRD in the bone marrow of patients with metastatic NB.

Standardisation of operating procedures for the detection of minimal disease by QRT-PCR in children with neuroblastoma: Quality assurance on behalf of SIOPEN-R-NET

The clinical utility of detecting minimal residual disease (MRD) in children with neuroblastoma (NB) by quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) is not clear. This in part reflects the lack of uniform methodology for analysis and reporting. Reference laboratories across Europe have therefore established standard operating procedures (SOPs) for the detection of NB cells by QRT-PCR. Haemopoietic samples are collected into PAXgene blood RNA tubes, which stabilise mRNA for 48 h at room temperature and more than 6 months at -80 degrees C. Tyrosine hydroxylase (TH) was selected as the target for NB cell detection, expression is normalised to beta2-microglobulin and reported using the DeltaDeltaCt method. The sensitivity of QRT-PCR increased from 58% to 90% following the development of SOPs. A robust, transferable, objective method for the detection of NB cells by QRT-PCR has been defined to improve the power and consistency of studies on MRD in children with NB.

Pilot study to evaluate MYCN expression as a neuroblastoma cell marker to detect minimal residual disease by RT-PCR

This pilot study was performed to determine whether MYCN expression warrants further investigation as a tumor marker to detect low levels of residual neuroblastoma (NB). Seven NB cell lines and 30 bone marrow (BM) samples from patients with high-risk NB were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) for MYCN expression, and for the established NB marker tyrosine hydroxylase. MYCN was expressed in all 7 NB cell lines, but not in normal peripheral blood, CD34 cells, or BM. In dilution studies using cell lines with or without DNA amplification of MYCN, 1 NB cell in 10 to 10 nucleated blood cells was detectable by RT-PCR. MYCN was identified in all 21 BM samples in which tumor cells were identified by histologic examination, including 4 samples in which tyrosine hydroxylase was not detected. Additionally, expression of both markers was detected in 5 samples that were negative by histology but presumably contained low levels of tumor cells, consistent with the greater sensitivity of RT-PCR compared with morphologic methods. Detection of MYCN RNA was independent of MYCN DNA amplification status. The selective expression of MYCN in tumor cells, and the sensitivity of detection of MYCN by RT-PCR noted in this and other studies, supports further evaluation of MYCN as a NB marker for molecular detection of minimal residual disease.

Prognostic significance of circulating tumour cells enumerated after filtration enrichment in early and metastatic breast cancer patients

BACKGROUND

We previously found a higher incidence of circulating tumour cells (CTCs) in women with metastatic breast cancer compared to early disease. In this study, we present follow-up data to explore the prognostic significance of these findings.

METHODS

CTCs were quantified by immunostaining and direct visualization after centrifugation and filtration enrichment of peripheral blood from 131 patients. Time to progression (TTP) and overall survival (OS) were defined as interval from first blood sampling to first documented disease progression, or death respectively. Lifetime data was analysed using Kaplan-Meier method, log-rank test and Cox proportional hazards model.

RESULTS

Follow-up data is available for 123 patients. In early disease, median CTC>or=4 best distinguished patients with shorter TTP (p=0.05, log-rank test). In univariate analysis, tumour size, grade, lymphovascular invasion (LVI) and receptor status significantly related to TTP but none of the covariates related to OS. In multivariate analysis, T stage was the only independent predictor of TTP. In metastatic disease, median CTC>or=13 optimally identified patients with shorter TTP (p=0.01). In univariate analysis, median CTC level >or=13 and prior lines of chemotherapy predicted for TTP while in multivariate analysis, median CTC level >or=13 was the only significant independent prognostic factor (p=0.02). No relationship between CTC level and OS was found in this subgroup.

CONCLUSION

Median CTC level determined in the course of treatment predicts for TTP in metastatic breast cancer. In early breast cancer, an association was found between CTC level and TTP although this did not reach statistical significance (p=0.05).

Potential Application of ELAVL4 Real-Time Quantitative Reverse Transcription-PCR for Detection of Disseminated Neuroblastoma Cells

Background: Reliable detection of neuroblastoma cells in bone marrow (BM) is critical because BM involvement influences staging, risk assessment, and evaluation of therapeutic response in neuroblastoma patients. Standard cytomorphologic examination of BM aspirates is sensitive enough to detect single tumor cells. Consequently, more sensitive and specific detection methods are indispensable.

Methods: We used real-time quantitative reverse transcription-PCR (QPCR) of the tyrosine hydroxylase (TH), GD2 synthetase (GALGT), and embryonic lethal, abnormal vision, Drosophila-like 4 (ELAVL4) genes to detect disseminated neuroblastoma cells. We assessed assay sensitivity by addition experiments and then analyzed 97 neuroblastic tumor, BM, peripheral blood (PB), or peripheral blood stem cell (PBSC) samples from 30 patients. The QPCR results were compared with those of a standardized immunocytochemical assay.

Results: The molecular markers were highly expressed in all evaluated tumor samples. In addition, 32%, 11%, and 38% of all BM, PB, and PBSC samples scored positive for TH, GALGT, or ELAVL4, respectively. The TH and ELAVL4 assays could detect 1 neuroblastoma cell in 106 mononuclear cells. By contrast, the GALGT QPCR assay could detect 1 neuroblastoma cell in 104 mononuclear cells. We assessed the potential prognostic value of TH, GALGT, and ELAVL4 QPCR by analyzing subsequent samples from 3 patients with stage 4 disease. Preliminary results indicated that persistence of high ELAVL4 expression has prognostic value.

Conclusions: ELAVL4 QPCR can be used to detect residual neuroblastoma cells in clinical samples. However, combination of several molecular markers and screening techniques should be considered to ensure reliable detection of rare neuroblastoma cells.

Tumor cell dynamics and metastasis in advanced neuroblastoma

This study deals with the advancement process of neuroblastoma through clinical observations and circulating tumor cell exploration. Clinical feature, tumor biology, and circulating tumor cell detected by the previously described polymerase chain reaction (PCR) method were analyzed in 31 patients with advanced neuroblastoma treated in our department since 1991 through 2004. Treatment was completed in 28 patients, of whom 17 are alive without the disease and 11 died. The primary lesion was not confirmed in 2 patients with disseminated metastasis, both of whom showed positive circulating tumor cell. Circulating tumor cell was positive in 6 of 9 examined at their first appearance at the hospital, all had stage 4 disease, and 4 of the 6 (66.7%) died of systemic spread of the disease. N-myc was amplified in 15 patients, of whom only 2 (13.3%) died of systemic metastasis. N-myc amplification did not correlate with positive circulating tumor cell. A certain population of neuroblastoma may provide circulating tumor cells from the early period of the disease to form metastatic lesions independently of the primary lesion, which must be regulated by factors other than N-myc. Circulating tumor cells may suggest higher risk for systemic dissemination and poor prognosis.

Standardization of the immunocytochemical detection of neuroblastoma cells in bone marrow

Standard cytomorphological examination of bone marrow (BM) aspirates does not appear to be sensitive enough to detect single neuroblastoma cells. The SIOPEN Neuroblastoma Bone Marrow Committee developed a sensitive and reproducible anti-GD2 immunocytochemical assay and introduced morphological and immunocytological criteria for the interpretation of results. Fixed cytospins were incubated with a commercially available anti-GD2 monoclonal antibody and an APAAP kit. Cells fulfilling all morphological and immunocytological criteria were called criteria-positive cells (CPCs). Not convincingly interpretable cells fulfilled some, but not all, criteria, and negative cells displayed only exclusion criteria. The genetic profile of doubtful cells was checked by fluorescence in situ hybridization. Ideally, 3 x 10(6) cells were analyzed to reach a 95% probability of detecting one tumor cell in 1 x 10(6) mononuclear cells. Four quality control rounds were organized to validate the method. A total of 111 quality control samples were analyzed. Two main improvements were achieved: in discordant cases, the range between the lowest and highest reported result was reduced by half, and discordant results were only found in samples with less than 10 CPCs per 1 x 10(6). This article describes the first internationally standardized protocol to detect and quantify rare neuroblastoma cells by immunocytochemistry. This method is an indispensable tool for multicenter studies evaluating the clinical significance of minimal residual disease in neuroblastoma.

Measuring circulating neuroblastoma cells by quantitative reverse transcriptase-polymerase chain reaction analysis

BACKGROUND

Histologic examination of bone marrow (BM) is an accepted clinical standard for the detection of metastatic neuroblastoma (NB). Circulating tumor cells in peripheral blood (PB) derive from depots other than BM, and its measurement may provide additional information in the management of patients with NB.

METHODS

One hundred twenty patients with Stage 4 NB were evaluated for tumor cell content in PB by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) analysis of GD2 synthase mRNA with a sensitivity of 1 NB cell in 10(6) normal cells. These findings were correlated with qRT-PCR analysis of their simultaneously sampled BM aspirates and 5 standard modalities of disease detection (histology, computed tomography/magnetic resonance imaging, bone scan, metaiodobenzylguanidine scan, and urinary homovanillic acid/vanillylmandelic acid levels).

RESULTS

Detection of GD2 synthase transcript was found in 62 patients: Eleven patients had positive (+) samples in their BM and PB (BM+PB+), 38 patients had BM+PB-negative (BM+PB-) specimens, and 13 patients had BM-PB+ samples. BM+PB+ paired samples had the highest transcript levels. When the extent of disease was scored (from 0 to 5) according to the number of positive disease detection modalities, the magnitude of the transcript level correlated with disease score. Ninety-one percent of patients with BM+PB+ samples had evidence of disease in >/= 3 modalities, whereas 97% of patients with BM-PB- samples and 100% of patients with BM-PB+ samples had low disease scores </= 2. Marker positivity in BM correlated with disease score. Patients who had positive marker in BM or PB had higher rates of relapse and death compared with patients who had negative marker. Kaplan-Meier analysis demonstrated a significantly greater risk of death for patients who had BM+PB+ specimens compared with patients who had BM-PB- samples (P = 0.03).

CONCLUSIONS

BM monitoring should continue to be an integral part of disease follow-up for patients with Stage 4 NB. PB monitoring to complement tumor surveillance in the BM can be informative.

Detection of Neuroblastoma Cells in Bone Marrow and Peripheral Blood by Different Techniques

PURPOSE

Detection of metastatic tumor cells in bone marrow (BM) and peripheral blood (PB) of children with neuroblastoma is crucial for prognosis and planning of therapy. Aims of this large descriptive repeated survey were to evaluate the diagnostic accuracy of different techniques in diagnostic samples obtained at several disease course time points and to correlate positive results with patient clinical features and outcome.

EXPERIMENTAL DESIGN

BM aspirates, trephine biopsies, PB, and peripheral blood stem cell (PBSC) samples from Italian children with neuroblastoma were analyzed by morphological and histologic techniques, as well as by immunocytochemistry (IC) for disialoganglioside GD(2) and reverse transcription-PCRs (RT-PCRs) for tyrosine hydroxylase (TH) and pgp9.5 genes. The diagnostic odd ratio (DOR) was used to measure the accuracy of the different techniques.

RESULTS

A total of 2,247 evaluations were done on 561 BM, 265 PB, and 69 PBSC samples from 247 patients. IC showed the best accuracy. Whereas TH RT-PCR accuracy was satisfactory, that of pgp9.5 was very low. Positive results obtained by IC in BM and PB samples at diagnosis from stage 1, 2, and 3 patients correlated with unfavourable outcome. No correlation was found between positive results obtained by IC or TH RT-PCR in BM, PB, and PBSC samples from stage 4 patients and their outcome.

CONCLUSIONS

Because of its elevated diagnostic accuracy, IC may represent a useful adjunct to conventional morphological techniques, especially in view of its potential prognostic role in patients with localized disease. Longitudinal multicenter studies are warranted to definitely establish the clinical usefulness of TH RT-PCR.

Comparison of two methods for evaluating bone marrow metastasis of neuroblastoma: Reverse transcription-polymerase chain reaction for tyrosine hydroxylase and magnetic resonance imaging

BACKGROUND

The presence of bone marrow (BM) metastasis and circulating tumor cells in patients with neuroblastoma is a significant prognostic factor at diagnosis and might antedate detection of a relapse by other diagnostic studies. In this study, the clinical value of reverse transcription-polymerase chain reaction (RT-PCR) to amplify mRNA for tyrosine hydroxylase (TH) and magnetic resonance imaging (MRI) during the clinical course of patients with advanced neuroblastoma, was evaluated.

METHODS

Four patients with Stage 1, 4 or 4S neuroblastoma, were studied. BM and peripheral blood (PB), including peripheral blood stem cell (PBSC), samples were examined for TH mRNA using RT-PCR. Concurrently, MRI detection of BM metastasis was used.

RESULTS

In all cases, except one that had no evidence of BM invasion, TH mRNA in BM and PB at diagnosis were positive, and TH mRNA at diagnosis disappeared after chemotherapy. In two cases, although involvement in the neurocentrum BM was detected by MRI, TH mRNA in the iliac crest BM was negative. The pathological area still remained on MRI after intensive therapy.

CONCLUSION

RT-PCR for TH mRNA might be the most sensitive method for the detection of occult neuroblastoma cells in BM and PB. However, because invasion of the BM by neuroblastoma may have a focal distribution, sampling errors can occur. Therefore, not only RT-PCR but also MRI, need to be used to rule out marrow involvement, especially at diagnosis and BM relapse.

Detection and treatment of minimal residual disease in high-risk neuroblastoma

Intensive, myeloablative therapy supported by autologous hematopoietic stem-cell transplantation (AHSCT) has improved the outcome for children with high-risk neuroblastoma. However, >50% of patients develop recurrent neuroblastoma, often from minimal residual disease (MRD). Immunocytological and reverse transcriptase polymerase chain reaction (RT-PCR) for genes highly expressed in neuroblastoma both can detect small amounts of MRD in blood and bone marrow, and detection of MRD at certain levels during therapy has prognostic value. Radionucleotide scans using meta-iodobenzaguanidine (MIBG) imaging allows sensitive detection of neuroblastoma in patients, but whether or not all MIBG-positive disease detected after AHSCT will progress remains to be defined and is complicated by use of post-AHSCT therapy. Selective removal of tumor cells from marrow or blood stem cells harvested for AHSCT could decrease recurrence by preventing infusion of tumorigenic cells with AHSCT. Treating MRD after AHSCT with the differentiation-inducing retinoid 13-cis-retinoic acid significantly /improved EFS of high-risk neuroblastoma patients. Randomized clinical trials in the Children's Oncology Group are testing the value of purging blood stem cells and also whether post-AHSCT therapy with an anti-GD2 monoclonal antibody (combined with cytokines) improves outcome over use of 13-cis-retinoic acid alone. New approaches to treating neuroblastoma MRD that are in early clinical trials include the cytotoxic retinoid fenretinide and the hu14.18-IL2 immunocytokine. It is anticipated that testing novel approaches to treating neuroblastoma MRD will be the subject of future phase-III randomized trials.

Micrometastases in neuroblastoma: are they clinically important?

Despite advances in the treatment of neuroblastoma (NBL), recurrence and metastases continue to pose major problems in clinical management. The relation between micrometastases and the development of secondary disease is not fully understood. However, accurate methods to detect low numbers of tumour cells may allow the evaluation of their role in the disease process, and by implication the possible benefits of eliminating them. Although there is substantial evidence for the increased sensitivity of current molecular methods for the detection of NBL cells compared with more conventional cytology, the clinical relevance and usefulness of detecting this disease remain controversial. The primary goal of current translational research must be to evaluate the clinical relevance of micrometastatic disease detected by these methods in multicentre prospective clinical outcome studies. Only then can the clinical usefulness of these methods be defined so that they may be introduced into relevant clinical practice.

[Conditions for the development of a program of reverse transcriptase-polymerase chain reaction for molecular staging of prostatic cancer]

OBJECTIVE

To determine accurately the conditions for the development of tests using RT-PCR for PSA in patients with prostate cancer.

METHOD

Gen amplification of PSA in cultures of the human prostate tumoral cell line LNCaP with RT-PCR under hot-start conditions, and verification through enzyme restriction digestion of the PCR product. Also, calculation of the PCR test limit of detection through serial dilutions of LNCaP cells in peripheral blood mononucleate cells.

RESULTS

A highly specific, easy to perform, reproducible RT-PCR protocol has been developed. The lowest limit of detection reached was 1 PSA synthesising cell per 10(6) peripheral blood mononucleate cells.

CONCLUSIONS

RT-PCR is a highly sensitive technique that allows detection of small numbers of PSA producing cells in peripheral blood. This experience allows to establish with precision the conditions for the development of RT-PCR tests for PSA.

Detection of micrometastasis of neuroblastoma to bone marrow and tumor dissemination to hematopoietic autografts using flow cytometry and reverse transcriptase-polymerase chain reaction

BACKGROUND

The identification of neuroblastoma metastases to bone marrow (BM) is requisite in staging disease for risk-adopted therapy. However, micrometastases were not elucidated fully.

METHODS

Flow cytometry (FCM) with CD45/CD56/CD81 and reverse transcriptase-polymerase chain reactions (RT-PCR) for tyrosine hydroxylase (TH) transcripts were used to evaluate neuroblastoma in bilateral BM aspirates at diagnosis, BM autografts, peripheral blood stem cell (PBSC) collections, and CD34(+) cell products of 27 children.

RESULTS

TH transcripts were amplified in histology-negative (H(-)) BM specimens from seven patients (four patients with Stage 3 disease, two with Stage 4 disease, and one with Stage 4S disease), revealing a prevalence of submicroscopic metastasis. The median number of CD45(-)CD81(+)CD56(+) cells in four H(-) TH(-) BM samples from two patients with Stage 1 and Stage 2 disease, respectively, was comparable to that encountered in 10 normal BM controls (0.003% [range, 0.002-0.004%] vs. 0.004% [0-0.008%], P = 0.724). In six H(-) TH(+) BM specimens from three patients whom were otherwise diagnosed with neuroblastoma Stage 3, 0.031% (0.009-0.06%) CD45(-)CD81(+)CD56(+) cells were detected. Besides, 1.474% (0.088-3.009%) CD45(-)CD81(+)CD56(+) cells were identified in four H(-) TH(+) BM specimens from two patients at Stage 4. TH transcripts were evident in four of five BM autografts and in 22 of 45 (48.9%) PBSC specimens. FCM demonstrated 0.018% and 0.049% CD45(-)CD81(+)CD56(+) cells in two TH(+) BM autografts, respectively. The number of CD45(-)CD81(+)CD56(+) cells was higher in 19 TH(+) PBSC specimens than in 20 TH(-) PBSC specimens (0.026% [0.006-1.128%] vs. 0% [0-0.009%], P < 0.0001). CD34(+) cell selection achieved 2.9 (2.1-3.5) log depletion of CD45(-)CD81(+)CD56(+) cells in four manipulated products, rendering six of seven PBSC autografts TH-free.

CONCLUSIONS

FCM in combination with RT-PCR evaluated neuroblastoma micrometastasis and assessed the purity of hematopoietic autografts for transplant. However, the clinical relevance remains to be elucidated.

New splicing variants for human Tyrosine Hydroxylase gene with possible implications for the detection of minimal residual disease in patients with neuroblastoma

Expression of Tyrosine Hydroxylase (TH) is frequently seen in neuroblastomas, the most common extracranial tumor in children, and TH mRNA detection is used for the analysis of microcirculating or micrometastatic disease in this neoplasia. TH is known to have at least seven isoforms produced by alternative splicing of the N-terminal region (exons 1-4), although no other splicing variants have been described downstream. TH expression was analyzed in six samples of neuroblastoma by RT-PCR using highly restrictive conditions and primers between exons 5 and 12, a region of the gene previously considered to be constant. In the analyzed samples we found two novel TH mRNAs, one lacking exon 8, and another lacking exons 8+9. These new splicing variants are described in a region of TH previously reported to be conserved, and that has been used for the design of reverse transcriptase-polymerase chain-reaction assays for the detection of minimal residual disease [Eur. J. Cancer, 27 (1991) 762]. The splicing pattern characteristic of every tumor could allow the monitoring of the minimal residual disease in a tumor-specific manner.

Quantitative analysis of tyrosine hydroxylase mRNA for sensitive detection of neuroblastoma cells in blood and bone marrow

BACKGROUND

Sensitive monitoring of minimal residual disease may improve the treatment of neuroblastoma in children. To detect and monitor neuroblastoma cells in blood and bone marrow, we developed a quantitative method for the analysis of tyrosine hydroxylase mRNA.

METHODS

We used real-time reverse transcription-PCR. The calibrator was constructed from a segment of tyrosine hydroxylase mRNA that included the target. Blood and bone marrow samples from 24 children with neuroblastoma and 1 child with ganglioneuroma were analyzed. Controls were blood samples from the cords of 40 babies, from 58 children 6 months to 15 years of age, and from 34 healthy adults, as well as from 12 children with other diseases.

RESULTS

The detection limit was approximately 70 transcripts/mL. All 144 blood controls were below this limit. At diagnosis, blood tyrosine hydroxylase mRNA was higher in children with widespread disease (stage 4/4S; n = 6; range, 203-46,000 transcripts/mL) than in patients with localized disease (stages 1-3; n = 6; </=83 transcripts/mL; P = 0.002). Bone marrow from all five children with localized disease had concentrations <72 transcripts/mL, whereas five of six stage 4 patients had increased concentrations (6,000-8,000,000 transcripts/mL; P <0.05). In nine children in whom tyrosine hydroxylase mRNA was measured repeatedly, the results corresponded to the clinical course.

CONCLUSION

Quantitative analysis of tyrosine hydroxylase mRNA in blood and bone marrow is reliable and easy to perform and may be used for upfront staging, prognostic assessment, and treatment monitoring of neuroblastoma.

Flow cytometric immunophenotyping test for staging/monitoring neuroblastoma patients

Ten years ago, we made an incidental flow cytometric observation while immunophenotyping biopsy and marrow samples from children suspected to have leukemia/non-Hodgkin's lymphoma, but were subsequently diagnosed with neuroblastoma. The samples contained neoplastic CD45(-) cells that had an extremely bright CD56(+) (beyond the fourth decade on a four-decade scale) population distinguishable from CD45(+)CD56(usual density+) natural killer lymphocytes as well as other CD45(-)CD56(usual density+) nonhematopoietic tumors such as small cell carcinoma or melanoma. Following the "rare event" philosophy of selecting one negative and two positive antigens, we initially tried a "cocktail" of CD45(-)CD56(very bright+) neuron-specific enolase (NSE)(cytoplasmic+). We later modified the procedure to a more clinically applicable "lysed whole blood" CD45(-)CD56(very bright+) ganglioside GD2(+) cocktail to improve turnaround time (eliminating the cell permeabilization step for cytoplasmic NSE analysis), specificity, and sensitivity of the assay. A total of 123 marrow/tissue/fluid samples were analyzed by the various forms of the assay. Clearly interpretable samples had an 83% specificity and a 100% sensitivity. The three-color GD2 assay has successfully detected cells in marrow samples to a level of 0.002% (1 per 10(5) cells) using patient samples (not artificially "spiked" material). We added CD81 expression of the neuroblastoma cells as a fourth color and now use this rare event clinical test to help stage and monitor all patients with neuroblastoma.

Detection procedures for neuroblastoma cells metastatic to blood and bone marrow: blinded comparison of chromogranin A heminested reverse transcription polymerase chain reaction to tyrosine hydroxylase nested reverse transcription polymerase chain reaction and to anti-GD2 immunocytology

Specific and sensitive tumor cell detection is becoming increasingly important for diagnosing and staging as well as for the therapeutic management of neuroblastoma patients. We propose a chromogranin A heminested reverse transcription polymerase chain reaction (CgA hn RT-PCR) procedure for the detection of neuroblastoma minimal residual disease in peripheral blood and bone marrow samples. The results were checked in comparison with the presently available procedures (i.e., with the tyrosine hydroxylase nested RT-PCR [TH n RT-PCR] and with the immunocytochemical approach using anti-GD2 antibodies). Controls from healthy patients or from people with unrelated disease (12 samples of bone marrow and 23 samples of peripheral blood) and serial dilution experiments using neuroblastoma cell lines (SKNLP, SKNFI, STA6, STA8) showed CgA hn RT-PCR full specificity and sensitivity ranging from 10(3) to 10(6) (depending on the cell line). The results compared favorably with those obtained using TH n RT-PCR. Preliminary data obtained analyzing bone marrow and peripheral blood specimens from stage IV neuroblastomas showed substantially overlapping results between CgA and TH n RT-PCR procedures. Our data support the potential usefulness of CgA heminested RT-PCR as a specific and sensitive procedure for minimal disease detection in neuroblastoma. A prospective evaluation of this tool in clinical studies might be warranted.

Outcome of high-risk neuroblastoma using a dose intensity approach: improvement in initial but not in long-term results

BACKGROUND

Stage 4 and MYCN amplified (MNA) neuroblastoma in children have a poor prognosis. Our aim was to increase initial and long-term response in this population.

PROCEDURE

High-risk children were studied according to the International Neuroblastoma Staging System, then treated with high-dose cyclophosphamide and high-dose carboplatin, followed by surgery and autologous stem cell transplant or maintenance chemotherapy.

RESULTS

From June 1992 to December 1998, 83 children were admitted in the study (72 stage 4> 1 year, 5 stage 4 MNA infants, and 6 MNA stage 3 children); tumor tissue was obtained from 73, MYCN was performed in 65, being amplified in 21 (32%). Induction chemotherapy was administered in the expected time in 35% of patients. Its toxicity was mainly hematologic followed by infections, and there were 3 chemotherapy-related deaths. Delayed surgery was performed on 60 patients with complete or >90% resection in 80% of cases. Chemotherapy plus surgery produced some response in 90% of patients, 53% were in CR/VGPR; 49 children received autologous SCT, and 16 received maintenance chemotherapy for 9 months. Follow-up ranges are 1-87 months, mean 30 months. S and EFS at 4 years are 0.33 (SD 0.02).

CONCLUSIONS

High-dose cyclophosphamide and high-dose carboplatin are effective in the initial treatment of neuroblastoma; combined with surgery they produce some response in most patients. Nevertheless, the CR/VGPR rate reaches only 53%. Survival time has also been prolonged but most patients relapse with metastases.

GD2 synthase: a new molecular marker for detecting neuroblastoma

BACKGROUND

Neuroblastomas (NBs) almost ubiquitously express the ganglioside GD2. GD2 synthesis is dependent on the key enzyme GD2 synthase. Thus, GD2 synthase transcript may prove to be a potential molecular marker of NB.

METHODS

Seventy-seven NB tumor tissues of all stages, 5 NB cell lines, and 26 normal bone marrows (BMs) and peripheral blood (PBL) samples, as well as 26 non-NB remission-BMs were analyzed for the expression of GD2 synthase by a highly sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) and chemiluminescence detection. One hundred fifty-two NB BMs were tested and comparisons were made among three independent detection techniques, namely GD2 synthase RT-PCR, immunofluorescence (IF), and histology (HIST).

RESULTS

GD2 synthase transcript was present in 5 of 5 cell lines and in 77 of 77 tumors tested. Among 116 marrows that were positive by at least 1 of the 3 methods, 78% were detectable by GD2 synthase, 68% by IF, and 46% by HIST. Seventy-six percent of positive BMs that were obtained during treatment and follow-up had GD2 synthase expression, whereas only 29% were HIST positive. Correlation between RT-PCR and IF was high (P = 0.001), and positivity by 3 out of 3 methods was strongly correlated with poor survival (P < 0.01). Of note, marrows tested at the time of chemotherapy were positive by at least 2 out of 3 methods and were associated with adverse outcome (P = 0.01). Serial samples (n = 28) in 5 patients demonstrated close agreement between RT-PCR and patient disease status.

CONCLUSIONS

The current study found that molecular detection of GD2 synthase transcript in NB BMs may have potential value in detecting rare tumor cells.

Ganglioside GM2/GD2 synthetase mRNA is a marker for detection of infrequent neuroblastoma cells in bone marrow

GalNAcbeta1-4(NeuAcalpha2-3)Galbeta1-4Glcbeta1-Cer (GM2)/GalNAcbeta1-4(NeuAcalpha2-8NeuAcalpha2-3)Galbeta1-4Glcbeta1-1Cer (GD2) synthetase [beta-1,4-N-acetyl-galactosaminyl transferase (GalNAc-T)] mRNA, which encodes a key glycosyltransferase for ganglioside GD2 synthesis, was assessed as a molecular marker for detecting metastatic neuroblastoma cells in bone marrow (BM). GalNAc-T mRNA expression by neuroblastoma cell lines (n = 15), primary untreated neuroblastoma tumors (n = 29), morphologically normal BM (n = 22), peripheral blood stem cells (n = 10) from patients with cancers other than neuroblastoma, and blood mononuclear cells from normal donors (n = 17) was assessed by using reverse transcriptase-polymerase chain reaction (RT-PCR) and electrochemiluminescence detection assay (RT-PCR/ECL). BM harvested from 15 neuroblastoma patients was tested before and after ex vivo immunomagnetic bead purging, and results were compared to immunocytological analysis of the same specimens. All neuroblastoma cell lines (mean, 653 x 10(3) ECL units) and primary tumors (mean, 683 x 10(3) ECL units) were positive for significant expression of GalNAc-T mRNA compared to normal blood and BM cells. The RT-PCR/ECL assay could detect GalNAc-T mRNA in 100 pg of total RNA, and in a mixture of one neuroblastoma cell among 10(7) normal BM or blood cells. Eight of 15 autologous BM cells harvested from patients with neuroblastoma had tumor cells detectable by immunocytology, and all 15 were positive for GalNAc-T mRNA. After ex vivo purging, none of the BM cells was immunocytology-positive, but six remained positive by the RT-PCR/ECL assay. GalNAc-T mRNA provides a specific and sensitive molecular marker for RT-PCR/ECL detection of infrequent neuroblastoma cells in BM.

Circulating neuroblastoma cells detected by reverse transcriptase polymerase chain reaction for tyrosine hydroxylase mRNA are an independent poor prognostic indicator in stage 4 neuroblastoma in children over 1 year

PURPOSE

In this prospective, multicenter study, the independent prognostic power of neuroblastoma cells detected by reverse transcriptase polymerase chain reaction (RT-PCR) for tyrosine hydroxylase (TH) mRNA was evaluated.

PATIENTS AND METHODS

The clinical significance of disease detected by RT-PCR in peripheral blood from children at diagnosis was compared with established prognostic markers [ie, age, lactate dehydrogenase (LDH), neuron-specific enolase, ferritin, and MYCN gene amplification] by multivariate analysis. The value of disease detection by RT-PCR during treatment and follow-up was also examined.

RESULTS

TH mRNA was detected in peripheral blood from 33 of 49 (67%) children with stage 4 neuroblastoma > 1 year old at diagnosis and was a significant predictive factor for overall survival [hazard ratio (HR) = 2.40, 95% confidence interval (CI) 1.19 to 4.84, P =.014) and event-free survival (HR = 2.09, 95% CI 1.06 to 4.17, P =.034) in a multivariate analysis. Detection of disease in blood from clinically disease-free children was related to increased risk of death (HR 2.54, 95% CI 1.42 to 4.55, P =.0014).

CONCLUSION

TH mRNA in peripheral blood of children with neuroblastoma is a poor prognostic indicator, reflecting the propensity for dissemination via the bloodstream. When combined with a serum LDH > 1500 IU/L, this is the most powerful poor prognostic model at diagnosis for children > 1 year old with stage 4 disease. The detection of TH mRNA in peripheral blood from clinically disease-free children is related to increased risk of relapse and death.

Reverse transcriptase polymerase chain reaction (RT-PCR) detection of melanoma-related transcripts in the peripheral blood and bone marrow of patients with malignant melanoma. What have we learned?

The detection of circulating tumor cells (CTC) and bone marrow micrometastases (BMM) by reverse transcriptase polymerase chain reaction (RT-PCR) may help predict recurrence and survival in malignant melanoma (MM). Since the appearance of the original article by Smith et al. in 1991 (Lancet 338:1227), several groups have attempted the detection of CTC and BMM in MM using RT-PCR for melanocytic specific markers, mainly tyrosinase mRNA. Most studies show that tyrosinase is not present in the PB and BM of control individuals without MM. The PCR positivity rates in MM are extremely variable, ranging from 0% to 100%. There was a correlation between RT-PCR and stage in some but not all of the studies. These disparate findings could in part be explained by differences in RNA extraction and blood separation techniques, to unrecognized contamination leading to false positive results, or differences in patient selection. Despite these discrepancies, we and others have shown that RT-PCR for tyrosinase mRNA in PB is able to predict overall survival (OS) and disease-free survival (DFS) in a statistically significant manner. In AJCC stage II-IV patients rendered surgically free of disease, we found that blood tyrosinase positivity was an independent predictor of OS and DFS. We also found that BM tyrosinase positivity is an independent predictor of DFS in the same group of patients. RT-PCR may help identify subgroups of patients at high risk for early relapse for more aggressive adjuvant therapy. Large prospective studies and interlaboratory quality assurance initiatives are necessary to confirm the accuracy and prognostic value of these RT-PCR assays.

Minimal residual disease at the time of peripheral blood stem cell harvest in patients with advanced neuroblastoma

BACKGROUND

Despite treatment with high-dose myeloblative chemotherapy and peripheral blood stem cell (PBSC) rescue, a high proportion of children with neuroblastoma relapse and die. Re-infusion of PBSC contaminated with tumour at the time of autologous transplantation may play a significant role in this relapse. In this study the frequency of tumour contamination in PB from children with neuroblastoma has been investigated.

PROCEDURE

Minimal residual disease was measured using RT-PCR for tyrosine hydroxylase (TH) mRNA in PBSCs from patients with advanced neuroblastoma. PBSCs from 18 patients in complete clinical remission were studied.

RESULTS

Studies in other cancers have suggested minimal contamination of PBSCs with tumour cells; TH mRNA was detected by RT-PCR in 50% (9/18) of PBSC harvests. Seventy-seven percent (7/9) of patients with TH mRNA in PBSC died of disease compared to 44% (4/9) who were TH mRNA-negative.

CONCLUSIONS

Therefore, the presence of TH mRNA in PBSCs appeared to be associated with an unfavourable outcome, although this was not statistically significant. In summary, RT-PCR for TH mRNA is a sensitive method for the identification of tumour cells in PBSC harvest. The presence of TH mRNA in PBSC harvest may reflect disease status and be associated with an unfavourable outcome, although long-term clinical outcome studies in a larger patient cohort are required.

Disease outcome may be predicted by molecular detection of minimal residual disease in bone marrow in advanced neuroblastoma: a pilot study

PURPOSE

This pilot study focussed on whether sequential molecular detection of minimal residual disease (MRD) in bone marrow (BM) could predict the outcome of patients with advanced neuroblastoma.

PATIENTS AND METHODS

Bone marrow samples from 21 patients older than age 12 months with stage IV neuroblastoma were sequentially examined for tumor cell contamination by detecting tyrosine hydroxylase (TH) messenger ribonucleic acid (mRNA) using reverse transcription-polymerase chain reaction (RT-PCR). Twenty patients received myeloablative therapy with hematopoietic stem cell transplantation after achieving complete remission.

RESULTS

All BM samples of patients except that of one patient was cytologically positive for neuroblastoma cells at diagnosis, and they became negative for neuroblastoma cells within 3 months by cytologic examination. By RT-PCR analysis, BM samples of all patients were positive for TH mRNA at diagnosis, and samples of 19 patients became negative for TH mRNA 1 to 13 months after the start of chemotherapy. Six patients whose BM samples became negative for TH mRNA within 4 months after the start of chemotherapy remained alive without evidence of disease (median 76 mos, range 36-91). In contrast, out of 15 patients whose BM samples remained positive, 10 patients had relapse develop and 9 patients died from disease (median 15 mos, range 10-25). There was a statistically significant difference in disease-free survival between the two groups (P < 0.05).

CONCLUSION

Persistence of MRD in BM may predict poor prognosis in advanced neuroblastoma.

Outcome prediction by molecular detection of minimal residual disease in bone marrow for advanced neuroblastoma

BACKGROUND

We have determined whether sequential molecular detection of minimal residual disease (MRD) in bone marrow (BM) could predict the outcome of patients with advanced neuroblastoma (NB).

PROCEDURE

Bone marrow samples from 19 patients over 12 months of age with stage 4 neuroblastoma were sequentially examined for tumor cell contamination by detecting tyrosine hydroxylase (TH) mRNA using reverse transcription-polymerase chain reaction (RT-PCR). All patients received repetitive multi-drug chemotherapy including cisplatin, cyclophosphamide or ifosphamide, adriamycin, and etoposide or vincristine. Seventeen patients received myeloablative therapy with hematopoietic stem cell transplantation after achieving complete remission.

RESULTS

All but one patient were histologically positive for tumor cells in BM samples at diagnosis, and they became negative for tumor cells within 3 months histologically. By the RT-PCR analysis, all patients were positive for TH mRNA in BM samples at diagnosis, and they became negative for TH mRNA 1 to 13 months after the start of chemotherapy. Six patients whose BM samples became negative for TH mRNA within 4 months after the start of chemotherapy remained alive without evidence of disease (median 61 months, range 20-76). In contrast, 12 of 13 patients whose BM samples remained positive at that time developed relapse and 10 of them died of disease (median 24 months, range 13-43). There was a statistically significant difference in survival between the two groups (P < 0.05). No significant difference of clinical characteristics by the MRD positivity at 4 months after the start of chemotherapy.

CONCLUSIONS

Persistence of MRD in BM at 4 months after the start of chemotherapy could predict poor prognosis in advanced neuroblastoma.

In vivo cytoreduction studies and cell sorting--enhanced tumor-cell detection in high-risk neuroblastoma patients: implications for leukapheresis strategies

PURPOSE

To improve autologous leukapheresis strategies in high-risk neuroblastoma (NB) patients with extensive bone marrow involvement at diagnosis.

PATIENTS AND METHODS

Anti-G(D2) immunocytochemistry (sensitivity, 1 in 10(5) to 10(6) leukocytes) was used to evaluate blood and bone marrow disease at diagnosis and during the recovery phase of the first six chemotherapy cycles in 57 patients with stage 4 NB and bone marrow disease at diagnosis. A total of 42 leukapheresis samples from the same patients were evaluated with immunocytology, and in 24 of these patients, an anti-G(D2) immunomagnetic enrichment step was used to enhance tumor-cell detection.

RESULTS

Tumor cytoreduction was much faster in blood compared with bone marrow (3.2 logs after the first cycle and 2.1 logs after the first two cycles, respectively). Bone marrow disease was often detectable throughout induction, with a trend to plateau after the fourth cycle. By direct anti-G(D2) immunocytology, a positive leukapheresis sample was obtained in 7% of patients after either the fifth or sixth cycle; when NB cell immunomagnetic enrichment was applied, 25% of patients had a positive leukapheresis sample (sensitivity, 1 in 10(7) to 10(8) leukocytes).

CONCLUSION

Standard chemotherapy seems to deliver most of its in vivo purging effect within the first four cycles. In patients with overt marrow disease at diagnosis, postponing hematopoietic stem-cell collection beyond this point may not be justified. Tumor-cell clearance in blood seems to be quite rapid, and earlier collections via peripheral-blood leukapheresis might be feasible. Immunomagnetically enhanced NB cell detection can be highly sensitive and can indicate whether ex vivo purging should be considered.

Surgical treatment of neuroblastoma with micrometastasis

BACKGROUND/PURPOSE

The aim of this study was to define the role of surgery in neuroblastoma with micrometastasis, which is detectable only by the polymerase chain reaction (PCR) method.

METHODS

Fifty samples (peripheral blood 9, bone marrow 41) were harvested sequentially from 27 neuroblastoma patients, and the micrometastases were examined using the previously described single-step PCR method. The results were reviewed with the clinical courses.

RESULTS

Radical surgery was performed in 9 patients with bone marrow micrometastasis. Event-free survival was obtained in 2 patients with stage IV disease (25.0%) for a follow-up period of 2 to 6 years in this group. Both patients received intraoperative radiation and subsequent autologous bone marrow transplantation (ABMT) using purged marrow. Radical surgery was performed in 18 patients without micrometastasis, and 6 of 9 advanced patients (66.7%) survived without the disease including 4 patients who received unpurged stem cell transplantation.

CONCLUSIONS

Persistent micrometastasis in bone marrow should be considered predictive as a poor prognostic factor in neuroblastoma. Intensive local control with surgery and radiation is important for the patients with micrometastasis and should be followed by ABMT using purged marrow. Unpurged marrow may be safely used if the single-step PCR detects no micrometastasis.