Pediatric peripheral neuroectodermal tumors, oncogenes, and differentiation

Chromogranin A regulates neuroblastoma proliferation and phenotype

Neuroblastoma is a commonly encountered solid tumor in early childhood with high neuroplasticity, and differentiation therapy is hypothesized to lead to tumor mass shrinkage and/or symptom relief. CgA is a tissue specific protein restricted to the diffuse neuroendocrine system, and widely expressed in neuroblastomas. Using knockdown and knockout approaches to deplete CgA levels, we demonstrated that CgA loss inhibits SH-SY5Y cell proliferation and leads to a morphological shift with increased expression of Schwann and extracellular matrix specific molecules, and suppression of chromaffin features. We further confirmed the effects of CgA in a series of neuroblastoma cells with [BE(2)-M17 and IMR-32] and without (SK-N-SH) N-Myc amplification. We demonstrated that CgA depletion reduced IGF-II and IGFBP-2 expression, increased IGFBP-3 levels, and suppresses IGF downstream signaling as evidenced by reduced AKT/ERK pathway activation. This was further supported by an increased anti-proliferative effect of the ERK inhibitor in the CgA depleted cells. In an in vivo xenograft neuroblastoma model, CgA knockdown led to increased S-phenotypic marker expression at both protein and mRNA levels. Together these results suggest that CgA maintains IGF secretion and intracellular signaling to regulate proliferation and differentiation in neuroblastomas.

Detection of EWS/FLI-1 by Immunostaining. An Adjunctive Tool in Diagnosis of Ewing's Sarcoma and Primitive Neuroectodermal Tumour on Cytological Samples and Paraffin-Embedded Archival Material

Purpose. Recently we showed that the 68-kDa fusion protein derived from the EWS/FLI1 hybrid gene can be specifically detected by Western blotting using a polyclonal antibody to the C-terminal of FLI1 on biopsy material from Ewing's sarcoma. The aim of this study was to investigate whether this antibody also could be used for immunocytochemistry and immunohistochemistry in diagnosis of Ewing's sarcoma.

Methods. Immunostaining on paraffin-embedded archival material, fine-needle aspirates and tumour touch imprints from Ewing's sarcomas and primitive neuroectodermal tumours (PNET) for detection of the fusion protein was performed. Most cases were also analysed by Western blotting.Tumours of differential diagnostic importance were also included.

Results. Eighty per cent (12/15 cases) of the Ewing tumours exhibited a positive immunoreactivity for the FLI1 antibody. The signal was mainly localised in the nuclei of the tumour cells, which seems reasonable since EWS/FLI1 is a transcription factor. The signal was found to be specific since it did not appear when the blocking peptide was added to the antibody solution.Moreover, two other types of small-round cell tumours (i.e. neuroblastoma and alveolar rhabdomyosarcoma) were negative as well as most normal tissues.

Discussion. Immunostaining of histological and cytological specimens with the FLI1 antibody can be of diagnostic relevance in Ewing tumours carrying t(11;22).The absence of immunoreactivity in non-Ewing cells is most likely due to a low expression of the wild-type FLI1 protein.

EWS/ETS proteins promote expression and regulate function of the homeodomain transcription factor BRN3A

Ewing's sarcoma family tumors (ESFTs or EFTs) express neuronal markers, which indicates they may originate from cells at least partly committed to neuronal lineage. However, recent publications suggest EFT originates in mesenchymal stem cells, and EWS/ETS fusion proteins characteristic of EFT activate neuronal marker expression to confer a neural phenotype on EFT. Here we show that the neuronal marker BRN3A/POU4F1 is expressed abundantly at the protein level in primary EFT but not in rhabdomyosarcoma and neuroblastoma, and EFT cells exhibit high activity of the BRN3A proximal autoregulatory region. EWS/FLI-1 siRNA reduces BRN3A expression and promoter activity and EWS/ETS proteins are bound to the BRN3A locus, suggesting a direct function for EWS/ETS proteins in control of BRN3A expression. Differentiation-associated and autoregulatory activities of BRN3A are respectively impaired and altered in EFT cells, and EWS/FLI-1 siRNA can restore some BRN3A function. A potentially novel function for BRN3A in EFT cells is identified. These results extend the hypothesis that EWS/ETS proteins induce expression of neuronal markers such as BRN3A in EFT by showing that the function of those same markers may be restricted or controlled in an EWS/ETS-dependent manner.

The promise of telomere length, telomerase activity and its regulation in the translocation-dependent cancer ESFT; clinical challenges and utility

The Ewing's sarcoma family of tumours (ESFT) are diagnosed by EWS-ETS gene translocations. The resulting fusion proteins play a role in both the initiation and maintenance of these solid aggressive malignant tumours, suppressing cellular senescence and increasing cell proliferation and survival. EWS-ETS fusion proteins have altered transcriptional activity, inducing expression of a number of different target genes including telomerase. Up-regulation of hTERT is most likely responsible for the high levels of telomerase activity in primary ESFT, although telomerase activity and expression of hTERT are not predictive of outcome. However levels of telomerase activity in peripheral blood may be useful to monitor response to some therapeutics. Despite high levels of telomerase activity, telomeres in ESFT are frequently shorter than those of matched normal cells. Uncertainty about the role that telomerase and regulators of its activity play in the maintenance of telomere length in normal and cancer cells, and lack of studies examining the relationship between telomerase activity, regulators of its activity and their clinical significance in patient samples have limited their introduction into clinical practice. Studies in clinical samples using standardised assays are critical to establish how telomerase and regulators of its activity might best be exploited for patient benefit.

Extraskeletal Ewing's sarcoma in a great toe of a young boy

Extraskeletal Ewing's sarcoma (EES) is a rare, soft tissue, malignant neoplasm histologically similar to skeletal Ewing's sarcoma. It occurs mainly in adolescents and young adults, and affects extremities in 36% of cases and central locations (commonly paravertebral regions) in the remainder. The differential diagnosis includes other small, blue, round cell tumours. A clinical case of EES involving a great toe in a young boy is reported. EES diagnosis was confirmed by features of histological analysis and immunohistochemistry, and by the presence of the t(11;22) chromosomal translocation.

DNA microarrays reveal relationship of Ewing family tumors to both endothelial and fetal neural crest-derived cells and define novel targets

Ewing family tumors (EFTs) are small round blue cell tumors that show features of neuroectodermal differentiation. However, the histogenetic origin of EFTs is still a matter of debate. We used high-density DNA microarrays for the identification of EFT-specific gene expression profiles in comparison with normal tissues of diverse origin. We identified 37 genes that are up-regulated in EFTs compared with normal tissues and validated expression of these genes in EFTs by both conventional and quantitative reverse transcription-polymerase chain reaction. The expression pattern of EFT-associated genes in normal tissues indicated a high similarity between EFTs and fetal and neuronal as well as endothelial tissues and supports the concept that a primitive neural crest-derived progenitor at the transition to mesenchymal and endothelial differentiation is transformed in EFTs. EFT-associated genes could be used for molecular discrimination between EFTs and other small round blue cell tumors and clearly identified a cell line (SK-N-MC) that was initially established as neuroblastoma as being an EFT. Ectopic expression of the EFT-specific EWS-FLI1 fusion protein in human embryonic kidney (HEK293) cells was not sufficient to induce the complete EFT-specific gene expression signature, suggesting that the EFT-specific gene expression profile is not just a consequence of EWS-FLI1 expression but depends on the histogenetic background of the EFT stem cell.

Molecular cytogenetic parameters in Ewing sarcoma

To evaluate possible genomic instability and possible random aneuploidy, we applied comparative genomic hybridization and fluorescence in situ techniques, and evaluated telomerase activity in 16 cases of Ewing sarcoma (EWS) and compared the results to 7 controls. Common secondary aberrations (gains of chromosomes 8 and 12) were found in the study group. There was a direct correlation between the detection of random aneuploidy and development of tumor relapse (P = 0.0047). Other detectable abnormal parameters (secondary) and high telomerase activity were also more common among the cases with relapse but did not reach a statistical significance (probably because of the small sample size). In EWS, the detection of random aneuploidy seems to be a sensitive parameter in the prediction of tumor relapse.

High-dose chemoradiotherapy (HDC) in the Ewing family of tumors (EFT)

EFT is defined by the expression of ews/ets fusion genes. The type of the fusion transcript impacts on the clinical biology. EFT requires risk adapted treatment. A risk-adapted treatment is determined by tumor localisation, tumor stage and volume. For metastatic and relapsed disease the pattern of spread and the time of relapse are the determinants of risk stratification. Staging of Ewing tumors has been considerably improved by magnetic resonance imaging and modern isotope scanning techniques. However, the determination of the extent of the metastatic spread in particular number of involved bones remains an unresolved issue. The prognosis for high-risk Ewing tumors has been improved by multimodal and high-dose radio/chemotherapy (HDC). The concepts for high-dose therapy in Ewing tumors are based on dose response and dose intensity relationships. In single agent HDC most experience exists with Melphalan. Several chemotherapeutic agents have been used in combination HDC with or without TBI such as Adriamycin, BCNU, Busulphan, Carboplatin, Cyclophosphamide, Etoposide, Melphalan, Thiotepa Procarbazin and Vincristine. To date, superiority of any high-dose chemotherapy regimen has not been established. However, the clinical biology, the pattern of spread and the time of relapse determine the prognosis of patient who are eligible for HDC. In particular, patients with multifocal bone or bone marrow metastases have a poorer prognosis than patients with lung metastases. In addition, patients with a relapse within 24 months have a poorer prognosis than patients with a relapse later than 24 months after diagnosis. This review will analyze the results of single- and multi-agent chemotherapy with respect to agent combination, dose and risk stratum of patient population. Future therapeutic modalities for the treatment of EFT might encompass immunotherapeutic and genetic strategies including allogeneic stem cell transplantation.

Expression of the HMGI(Y) gene products in human neuroblastic tumours correlates with differentiation status

HMGI and HMGY are splicing variants of the HMGI(Y) gene and together with HMGI-C, belong to a family of DNA binding proteins involved in maintaining active chromatin conformation and in the regulation of gene transcription. The expression of the HMGI(Y) gene is maximal during embryonic development, declines in adult differentiated tissues and is reactivated in most transformed cells in vitro and in many human cancers in vivo. The HMGI(Y) genomic locus is frequently rearranged in mesenchymal tumours, suggesting a biological role for HMGI(Y) gene products in tumour biology. HMGIs are both target and modulators of retinoic acid activity. In fact, HMGI(Y) gene expression is differentially regulated by retinoic acid in retinoid-sensitive and -resistant neuroblastoma cells, while HMGI-C participates in conferring retinoic acid resistance in some neuroblastoma cells. In this paper we show that HMGI and HMGY isoforms are equally regulated by retinoic acid in neuroblastoma cell lines at both RNA and protein levels. More importantly our immunohistochemical analysis shows that, although HMGI(Y) is expressed in all neuroblastic tumours, consistently higher levels are observed in less differentiated neuroblastomas compared to more differentiated ganglioneuromas, indicating that HMGI(Y) expression should be evaluated as a potential diagnostic and prognostic marker in neuroblastic tumours.

Ewing sarcoma family of tumors

The Ewing sarcoma family of tumors (ESFT) shares a common neural histogenesis, tumor genetics, and a fascinating biology, all of which hold the promise of identifying new therapeutic targets. The genetic hallmark of ESFT is the presence of the t(11;22)(q24;q12), which creates the EWS/FLI1 fusion gene and results in the expression of a chimeric protein. This article reviews much of the important work that has been reported over the past year regarding the biology and therapy of ESFT. Major studies include the observation that the early region (E1A) of human adenovirus type 5 is directly linked to and may initiate production of the EWS/FLI1 fusion transcript in normal human fibroblasts and keratinocytes. In addition, there is new information regarding the function of EWS/FLI1 and downstream signals by which it acts. New clinical information continues to support the addition of ifosfamide to standard chemotherapy regimens and help further refine prognostic features, including biologic features that may someday allow better risk stratification and therapy design.

Recognition of neuroectodermal tumors by melanoma-specific cytotoxic T lymphocytes: evidence for antigen sharing by tumors derived from the neural crest

Melanomas from different patients have been shown to express shared tumor antigens, which can be recognized in the context of the appropriate MHC class I molecules by cytolytic T cells. To determine if T-cell-defined melanoma antigens are expressed on other tumors of neuroectodermal origin, four melanoma-specific cytotoxic T lymphocyte (CTL) cultures derived from tumor-infiltrating lymphocytes (TIL) were tested for lysis of a panel of 23 HLA-A2+ neuroectodermal tumor cell lines of various histologies, including retinoblastoma (1), neuroblastoma (8), neuroepithelioma (6), astrocytoma (2), neuroglioma (1), and Ewing's sarcoma (5). Low expression of MHC class I and/or ICAM-1 molecules was found on 22 of 23 neuroectodermal tumor lines, and could be enhanced by treatment with interferon gamma (IFN gamma). Following IFN gamma treatment, three Ewing's sarcoma lines were lysed by at least one melanoma TIL culture, and levels of lysis were comparable to melanoma lysis by these TIL. Lysis could be inhibited by monoclonal antibodies directed against MHC class I molecules and against CD3, indicating specific immune recognition of tumor-associated antigens. None of the other neuroectodermal tumors tested were lysed by TIL, but they could be lysed by non-MHC-restricted lymphokine-activated killer cells. This demonstration of immunological cross-reactivity between melanomas and Ewing's sarcomas, two tumors of distinct histological types with a common embryonic origin, has implications for the developmental nature of these CTL-defined tumor antigens. It also raises the possibility that specific antitumor immunotherapies, such as vaccines, may be reactive against more than one form of cancer.

Differentiation therapy is potentiated by chemotherapy and hyperthermia in human and canine brain tumor cells in vitro

Human glioblastoma (U-87MG) and canine glioma (canine brain tumor [CBT]) cell lines were tested in vitro for their therapeutic sensitivity to sequential treatment with differentiating agents and chemotherapy or hyperthermia. Both cell lines responded to the inducer combination dibutyryl adenosine-3',5'-cyclic monophosphate/sodium butyrate by the formation of cytoplasmic processes detectable within 7 hours and attained approximately 90% morphological differentiation within 2 days of exposure. The clonogenicity of CBT and U-87MG cells gradually decreased after 1 to 7 days of exposure to the inducer combination, but this treatment alone failed to kill the cells. After the removal of the inducers, both lines dedifferentiated and the rate of clonogenesis increased. 1,3-bis-(2-Chloroethyl)-1-nitrosourea administered to CBT and U-87MG cells before or after 3 days of treatment with inducers potentiated the antiproliferative effects of the differentiating agents. Cisplatin administered to U-87MG cells enhanced the antiproliferative effect of the differentiating agents to a greater extent when added before the inducers rather than after differentiation was stimulated. The sequential treatment of CBT cells with a 44 degrees C heat pulse for 30 minutes followed by differentiating agents produced an additive potentiation of cell killing, whereas the reverse sequence did not. Hyperthermia pretreatment at 44 degrees C for 15 minutes or at 42 degrees C for 30 minutes failed to enhance the antiproliferative effects of inducing agents.(ABSTRACT TRUNCATED AT 250 WORDS)