Neurogenic potential of Ewing's sarcoma cells

Trk inhibition reduces cell proliferation and potentiates the effects of chemotherapeutic agents in Ewing sarcoma

Ewing sarcoma (ES) is a highly aggressive pediatric cancer that may arise from neuronal precursors. Neurotrophins stimulate neuronal devlopment and plasticity. Here, we found that neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), as well as their receptors (TrkA and TrkB, respectively) are expressed in ES tumors. Treatment with TrkA (GW-441756) or TrkB (Ana-12) selective inhibitors decreased ES cell proliferation, and the effect was increased when the two inhibitors were combined. ES cells treated with a pan-Trk inhibitor, K252a, showed changes in morphology, reduced levels of β-III tubulin, and decreased mRNA expression of NGF, BDNF, TrkA and TrkB. Furthermore, combining K252a with subeffective doses of cytotoxic chemotherapeutic drugs resulted in a decrease in ES cell proliferation and colony formation, even in chemoresistant cells. These results indicate that Trk inhibition may be an emerging approach for the treatment of ES.

Mesenchymal to embryonic incomplete transition of human cells by chimeric OCT4/3 (POU5F1) with physiological co-activator EWS

POU5F1 (more commonly known as OCT4/3) is one of the stem cell markers, and affects direction of differentiation in embryonic stem cells. To investigate whether cells of mesenchymal origin acquire embryonic phenotypes, we generated human cells of mesodermal origin with overexpression of the chimeric OCT4/3 gene with physiological co-activator EWS (product of the EWSR1 gene), which is driven by the potent EWS promoter by translocation. The cells expressed embryonic stem cell genes such as NANOG, lost mesenchymal phenotypes, and exhibited embryonal stem cell-like alveolar structures when implanted into the subcutaneous tissue of immunodeficient mice. Hierarchical analysis by microchip analysis and cell surface analysis revealed that the cells are subcategorized into the group of human embryonic stem cells and embryonal carcinoma cells. These results imply that cells of mesenchymal origin can be traced back to cells of embryonic phenotype by the OCT4/3 gene in collaboration with the potent cis-regulatory element and the fused co-activator. The cells generated in this study with overexpression of chimeric OCT4/3 provide us with insight into cell plasticity involving OCT4/3 that is essential for embryonic cell maintenance, and the complexity required for changing cellular identity.

CD56 expression of neuroendocrine neoplasms on immunophenotyping by flow cytometry: a novel diagnostic approach to fine-needle aspiration biopsy

BACKGROUND

CD56 antigen or NCAM (neural cell adhesion molecule) has an established role in the diagnosis of non-Hodgkin lymphoma (NHL)-natural killer cell type and other hematologic malignancies. Therefore, it is included routinely in the panel of antibodies for flow cytometric (FC) analysis of suspected lymphomatous tissue specimens obtained from fine-needle aspiration biopsy (FNAB). The authors evaluated the role of CD56 expression on FC of neuroendocrine (NE) tumors. An initial diagnosis of NHL was suspected based on an on-site FNAB evaluation.

METHODS

Ten FNABs were identified from the cytopathology files at The Johns Hopkins Hospital, Baltimore, MD (2000-2001). Flow cytometric analysis was negative for NHL but revealed a CD56-positive nonlymphoid cell population. An FNAB evaluation was performed on air-dried Diff-Quik-stained smears and FC analysis used a fixed panel of 12 antibodies (B-cell markers, T-cell markers, CD33, CD56, and CD71). Immunoperoxidase staining (IPOX) was performed on the cell block sections from four of the tissue specimens using epithelial and NE markers, CD56, desmin, and O13 antibodies. Sites of FNAB included the lung (five cases), liver (one case), lymph node (three cases), and peritoneum (one case). Only one patient had a history of cancer at the time of FNAB.

RESULTS

All cytologic diagnoses were confirmed by histopathologic follow-up on resection or biopsy or both. Diagnoses included small cell carcinoma (eight cases), Merkel cell carcinoma (one case), and primitive neuroectodermal tumor/Ewing sarcoma (one case). All tissue specimens that underwent IPOX stained strongly with NE markers, with one tissue section staining only with O13.

CONCLUSIONS

CD56 expression by FC in the presence of negative immunostaining with lymphoid markers represented a unique yet highly specific method for the diagnosis of NE tumors by FNAB. This procedure eliminated the need for further IPOX studies on the already limited cytologic sample and provided a timely and accurate diagnosis.

Upregulation of Id2, an oncogenic helix-loop-helix protein, is mediated by the chimeric EWS/ets protein in Ewing sarcoma

The chromosomal translocation specifically linked to the Ewing sarcoma family results in the generation of fusion proteins comprising the amino terminal portion of EWS and the DNA-binding domain of ets transcription factors. The EWS/ets chimeric proteins act as aberrant transcription factors leading to tumorigenic processes. We searched for genes specifically activated in Ewing sarcoma cells but not in other tumor cell lines using the gene array technique, and found significantly enhanced expression of the Id2 gene. High levels of Id2 transcripts were detected in Ewing sarcoma cell lines and tumor tissues. The EWS/ets chimeric proteins activated the Id2 gene via the 5'-upstream promoter sequence. Chromatin-immunoprecipitation revealed a direct interaction of EWS/Fli-1 with the promoter regions of the Id2, TGF-beta type II receptor, cyclin D1, and c-myc genes. Since EWS/Fli-1 transactivates c-myc, a cooperative action of the chimeric protein and c-myc leads to overexpression of Id2. In the present study, we suggest that Id2 is a target of the chimeric proteins and that the c-myc/Id2 pathway plays a pivotal role in the tumorigenic processes provoked by EWS/ets proteins.

Neural cells derived from adult bone marrow and umbilical cord blood

Under experimental conditions, tissue-specific stem cells have been shown to give rise to cell lineages not normally found in the organ or tissue of residence. Neural stem cells from fetal brain have been shown to give rise to blood cell lines and conversely, bone marrow stromal cells have been reported to generate skeletal and cardiac muscle, oval hepatocytes, as well as glia and neuron-like cells. This article reviews studies in which cells from postnatal bone marrow or umbilical cord blood were induced to proliferate and differentiate into glia and neurons, cellular lineages that are not their normal destiny. The review encompasses in vitro and in vivo studies with focus on experimental variables, such as the source and characterization of cells, cell-tracking methods, and markers of neural differentiation. The existence of stem/progenitor cells with previously unappreciated proliferation and differentiation potential in postnatal bone marrow and in umbilical cord blood opens up the possibility of using stem cells found in these tissues to treat degenerative, post-traumatic and hereditary diseases of the central nervous system.

Lack of matrix metalloproteinase (MMP)-1 and -3 expression in Ewing sarcoma may be due to loss of accessibility of the MMP regulatory element to the specific fusion protein in vivo

Ewing sarcoma is a malignant bone and soft tissue tumor of children and young adults, which is known to be highly aggressive and invasive. It expresses specific chimeric genes (EWS-FLI-1, EWS-ERG, EWS-ETV1, and EWS-E1AF), the 3' portions of which are all members of the ETS family. ETS-related proteins, such as FLI-1, ERG, and E1AF, transactivate the promoters of matrix metalloproteinase (MMP) genes, which play important roles in the processes of invasion and metastasis. Therefore, we hypothesize that the Ewing sarcoma-specific chimeric genes also transactivate the MMP genes, contributing to the tumor's invasiveness and propensity for metastasis. To verify this hypothesis, we investigated the expression of MMPs in eight Ewing sarcoma cell lines. Surprisingly, MMP-1 and MMP-3 were not expressed at all in any of the cell lines. MMP-9 was expressed in four out of the eight cell lines, and MMP-2 and MT1-MMP in all of the cell lines. Ewing sarcoma-specific chimeric genes have been shown to transactivate the promoter of the MMP-1 gene by the reporter assay, and bind to the putative recognition sites in the MMP regulatory elements by the gel shift assay. However, an in vivo formaldehyde cross-linking study revealed that the chimeric protein did not bind to the predicted ETS recognition sites in the regulatory elements of the MMPs. These results indicate that the absence of the MMP expression in the tumor cells is at least in part due to the loss of accessibility of the ETS recognition sites in the regulatory elements of the MMP genes. Therefore, we should be careful before theorizing simply that a putative binding site is essential for the transcription of critical genes, since the binding of this fusion protein was found to be modulated in tumor cells in this study.

Brain from bone: efficient "meta-differentiation" of marrow stroma-derived mature osteoblasts to neurons with Noggin or a demethylating agent

Bone marrow stromal cells are able to differentiate into adipogenic, chondrogenic, myogenic, osteogenic, and cardiomyogenic lineages, all of which are limited to a mesoderm-derived origin. In this study, we showed that neurons, which are of an ectoderm-origin, could be generated from marrow-derived stromal cells by specific inducers, fibronectin/ornithine coating, and neurosphere formation. The neurons generated from marrow stroma formed neurites, expressed neuron-specific markers and genes, and started to respond to depolarizing stimuli as functional mature neurons. Among stromal cells, isolated mature osteoblasts which had strong in vivo osteogenic activity could be efficiently converted into functional neurons. This transdifferentiation or meta-differentiation was enhanced by Noggin, an inhibitor of bone morphogenetic proteins, in comparison with 5-azacytidine, a demethylating agent capable of altering the gene expression pattern. Marrow stroma is therefore a potential source of cells for neural cell transplantation.

Mesenchymal Chondrosarcoma: A Small Cell Neoplasm with Polyphenotypic Differentiation

We analyzed the clinicoradiographic, microscopic, and immunophenotypic features of 21 tumors from 13 patients with mesenchymal chondrosarcoma (11 primary and 10 metastatic) and addressed the issue of their potential polyphenotypic differentiation. The immunophenotypic profile of the tumors was analyzed by studying the expressions of the MIC2 gene protein (p30/32(MIC2)), S-100 protein, desmin, myoD1, myogenin, myoglobin, smooth-muscle actin, cytokeratin, neuron-specific enolase, and HMB-45. The expression of p30/32(MIC2) was typically restricted to the small cell component of the mesenchymal chondrosarcoma and could be documented in 17 tumors. The cartilaginous areas were positive for S-100 protein in 20 tumors. Scattered positivity of small cells for desmin was seen in 8 cases. In 2 primary tumors from different patients (1 intraosseous and 1 extraskeletal) a diffuse expression of desmin with focal coexpression of myoD1 was present within the small cell component of the tumor. The positivity for smooth-muscle actin was documented in 2 cases. Either the small cell or cartilaginous components were at least focally positive for neuron-specific enolase in 11 tumors. All tumors were negative for myogenin, myoglobin, cytokeratins (AE1/AE3, CAM5.2) and HMB-45. This study showed that, in addition to cartilaginous differentiation, mesenchymal chondrosarcomas may exhibit focal expression of desmin. In rare cases more diffuse rhabdomyoblastic differentiation can be seen within the small cell component of the tumor. Thus, mesenchymal chondrosarcoma is another primitive neoplasm with polyphenotypic differentiation and features that overlap those of other small cell malignances of bone and soft tissue. Int J Surg Pathol 8(4):291-301, 2000

Epithelial Phenotype in Ewing's Sarcoma/Primitive Neuroectodermal Tumor

Neural differentiation is an integral component of Ewing's sarcoma/primitive neuroectodermal tumor (PNET), which exhibits a continuous spectrum from minimal to prominent neural phenotype. Differentiation of Ewing's sarcomas/PNETs along other lineages or the expression of an epithelial phenotype is less common and-if present-may cause diagnostic difficulties. In this study we evaluated the frequency of epithelial differentiation in formalin-fixed and paraffin-embedded tissues of 33 (22 primary and 11 metastatic) Ewing's sarcomas/PNETs by using an immunohistochemical assay with several antikeratin antibodies. Focal positivity for low- or high-molecular-weight keratins was documented in 18% of the cases, and diffuse coexpression of low- and high-molecular-weight keratins was observed in two cases. Expression of the MIC-2 gene product was documented in 94% of the tumors. The primitive neural phenotype as revealed by expression of either neuron-specific enolase or synaptophysin was observed in 30% of the cases, but coexpression of both neural markers was present in only 15% of the tumors. This study documents that, in addition to primitive neural differentiation, Ewing's sarcomas/PNETs frequently exhibit focal positivity for keratins, with rare strong diffuse coexpression of both low- and high-molecular-weight keratins. The findings indicate that the expression of an epithelial phenotype, at least in a focal fashion, is a relatively frequent finding in otherwise typical Ewing's sarcomas/PNETs. Int J Surg Pathol 8(1):59-65, 2000

Expression of neural cell adhesion molecules and neurofilament protein isoforms in Ewing's sarcoma of bone and soft tissue sarcomas other than rhabdomyosarcoma

In a previous study, it was shown that rhabdomyosarcomas widely express "neural" markers, such as neural cell adhesion molecules (N-CAM) and neurofilament protein isoforms. In the current study, a series of Ewing's sarcomas of bone and soft tissue sarcomas other than rhabdomyosarcoma was probed for the same antigens. It was found that N-CAM was widely expressed in the various sarcoma types, except Ewing's sarcomas, though less than in rhabdomyosarcomas. Similar to rhabdomyosarcomas, neurofilament isoforms were found throughout all sarcoma types but were largely restricted to those expressed early in neurogenesis, that is, poorly phosphorylated medium-weight isoforms. Neurofilament expression was most extensive in Ewing's sarcomas. It was concluded that the expression of "neural" markers (N-CAM, neurofilaments) is widespread in sarcomas and does not signify a neural tumor. The absence of N-CAM expression in Ewing's sarcoma may be helpful in its distinction from other sarcomas.

Engagement of CD99 induces apoptosis through a calcineurin-independent pathway in Ewing's sarcoma cells

Programmed cell death (PCD) is a prominent feature of the development of the immune and nervous systems. In both systems, widespread PCD occurs in primitive progenitor cells during development. In this study, we demonstrated that Ewing's sarcoma (ES) cells, undifferentiated neural precursors, underwent apoptosis upon engagement of CD99 with anti-CD99 monoclonal antibody. Apoptosis via CD99 occurred only in the undifferentiated state of ES cells, but not in differentiated ES cells. CD99-induced apoptosis in ES cells appeared to require de novo synthesis of RNA and protein as well as caspase activation. Cyclosporin A, known to be a potent inhibitor of both calcineurin activation and mitochondrial permeability transition pore opening, inhibited CD99-mediated apoptosis, whereas FK-506, a specific calcineurin inhibitor, did not, indicating the induction of CD99-mediated apoptosis through a calcineurin-independent pathway. Furthermore, the dying cells displayed the reduction of mitochondrial transmembrane potential (delta psi m). These results suggest that CD99 engagement induce CsA-inhibitable mitochondrial permeability transition pore opening, followed by a reduction of delta psi m and caspase activation, thereby leading to apoptosis. Based on these results, we suggest the possible involvement of CD99 in the apoptotic processes that occur during nervous system development and also its application in immunotherapeutic trials for ES cases.

Molecular analysis of Ewing's sarcoma: another fusion gene, EWS-E1AF, available for diagnosis

Ewing's sarcoma, one of the most malignant tumors of children and young adults, expresses specific chimeric genes, e.g. EWS-FLI-1, EWS-ERG, EWS-ETV1 and EWS-FEV. In this paper, we extensively characterized a new fusion gene, EWS-EIAF by means of whole cDNA sequencing, RNA blot analysis, DNA blot analysis and chromosomal analysis, and showed it to be available for the diagnosis of Ewing's sarcoma and to participate in the oncogenesis of Ewing's sarcoma. Furthermore, we conducted a genetic analysis of Ewing family tumors in conjunction with immunohistochemical analysis and ultrastructural analysis. Our results demonstrate some limitations of both genetic analysis and histopathological analysis, and establish the relationship between neurogenic phenotypes and chimera genes.