Patterns of differentiation in extraosseous Ewing's sarcoma cells. An in vitro study

The Transcription Factor FEZF1, a Direct Target of EWSR1-FLI1 in Ewing Sarcoma Cells, Regulates the Expression of Neural-Specific Genes

Ewing sarcoma is a rare pediatric tumor characterized by chromosomal translocations that give rise to aberrant chimeric transcription factors (e.g., EWSR1-FLI1). EWSR1-FLI1 promotes a specific cellular transcriptional program. Therefore, the study of EWSR1-FLI1 target genes is important to identify critical pathways involved in Ewing sarcoma tumorigenesis. In this work, we focused on the transcription factors regulated by EWSR1-FLI1 in Ewing sarcoma. Transcriptomic analysis of the Ewing sarcoma cell line A673 indicated that one of the genes more strongly upregulated by EWSR1-FLI1 was FEZF1 (FEZ family zinc finger protein 1), a transcriptional repressor involved in neural cell identity. The functional characterization of FEZF1 was performed in three Ewing sarcoma cell lines (A673, SK-N-MC, SK-ES-1) through an shRNA-directed silencing approach. FEZF1 knockdown inhibited clonogenicity and cell proliferation. Finally, the analysis of the FEZF1-dependent expression profile in A673 cells showed several neural genes regulated by FEZF1 and concomitantly regulated by EWSR1-FLI1. In summary, FEZF1 is transcriptionally regulated by EWSR1-FLI1 in Ewing sarcoma cells and is involved in the regulation of neural-specific genes, which could explain the neural-like phenotype observed in several Ewing sarcoma tumors and cell lines.

Peripheral Neuroectodermal Tumor-Ewing's Sarcoma of the Thumb With Local Recurrences and Pleural Metastases After 17 Years

We report a case of an 8-year-old boy who initially presented with a painful subungual mass that was diagnosed as a "glomus tumor" largely based on the clinical presenta tion. Local excision was performed, and the patient remained tumor free for 17 years, after which he experienced three local recurrences and massive pleural metastases within the next 2 years. The tumor was poorly differentiated with small round cells and increased mitotic activity on light microscopy. The precise nature of the tumor was difficult to characterize and was unraveled primarily by immunoperoxidase studies, particularly the diffuse strong positivity of HBA-71 (MIC 2) antibody, also called pe ripheral neuroectodermal tumor-Ewing's sarcoma antigen, which is reported to be fairly specific for these tumors, and the expression of neural markers Leu-7 (HNK-1 ) and neuron-specific enolase. In addition, ultrastructural examination revealed imma ture cell junctions, cell processes, and abundant pools of intracytoplasmic glycogen. Metastatic pleural tumor recurred very rapidly after excision, but showed a dramatic, although short-lasting, response to chemotherapy with cisplatin and etoposide. The thumb is an uncommon location for peripheral neuroectodermal tumor-Ewing's sar coma, and a 17-year, disease-free interval is most unusual for a malignant tumor of this nature. We discuss this case with respect to its unique clinical behavior and in the context of the differential diagnosis of small, round cell neoplasms. Int J Surg Pathol 2(2):147-156, 1994

Reprogramming of mesenchymal stem cells by oncogenes

Mesenchymal stem cells (MSCs) originate from embryonic mesoderm and give rise to the multiple lineages of connective tissues. Transformed MSCs develop into aggressive sarcomas, some of which are initiated by specific chromosomal translocations that generate fusion proteins with potent oncogenic properties. The sarcoma oncogenes typically prime MSCs through aberrant reprogramming. They dictate commitment to a specific lineage but prevent mature differentiation, thus locking the cells in a state of proliferative precursors. Deregulated expression of lineage-specific transcription factors and controllers of chromatin structure play a central role in MSC reprogramming and sarcoma pathogenesis. This suggests that reversing the epigenetic aberrancies created by the sarcoma oncogenes with differentiation-related reagents holds great promise as a beneficial addition to sarcoma therapies.

Ewing's sarcoma cells with CD57-associated increase of tumorigenicity and with neural crest-like differentiation capacity

The Ewing family of tumors (EFT) is an important group of pediatric malignancies with a guarded prognosis. Little is known about the heterogeneity of EFT cells, and the cellular origin of EFT is disputed. We now add evidence that EFT are heterogeneous by showing that EFT cells from spheres growing in serum-free medium are markedly more tumorigenic than adherently growing EFT cells. Furthermore, EFT cells strongly expressing CD57 (HNK-1), a surface marker for migrating and proliferating neural crest cells, are more tumorigenic than cells with low expression of CD57, possibly mediated in part by enhanced adhesion and invasion. We contribute to the controversy about the cellular origin of EFT by clonal analysis, showing that EFT cells can differentiate similar to neural crest cells. These data increase our knowledge about the pathogenesis and heterogeneity of EFT.

Mesenchymal stem cell features of Ewing tumors

The cellular origin of Ewing tumor (ET), a tumor of bone or soft tissues characterized by specific fusions between EWS and ETS genes, is highly debated. Through gene expression analysis comparing ETs with a variety of normal tissues, we show that the profiles of different EWS-FLI1-silenced Ewing cell lines converge toward that of mesenchymal stem cells (MSC). Moreover, upon EWS-FLI1 silencing, two different Ewing cell lines can differentiate along the adipogenic lineage when incubated in appropriate differentiation cocktails. In addition, Ewing cells can also differentiate along the osteogenic lineage upon long-term inhibition of EWS-FLI1. These in silico and experimental data strongly suggest that the inhibition of EWS-FLI1 may allow Ewing cells to recover the phenotype of their MSC progenitor.

A poorly differentiated synovial sarcoma (SYT/SSX1) expresses neuroectodermal markers: a xenografts and in vitro culture study

Synovial sarcoma (SS) is a neoplasm that poses diagnostic problems, due to its histologic heterogeneity. The poorly differentiated variant, in particular, may be histologically indistinguishable from other small round cell tumors. Detection of the synovial sarcoma-associated t(X;18) or SYT-SSX fusion transcripts may be necessary to confirm the diagnosis of SS in difficult cases. Most of SS carry a t(X;18) in about one third of cases as the sole cytogenetic abnormality. We evaluated a case of poorly differentiated synovial sarcoma and their derived tumors in nude mice xenografts and cell cultures. We used a panel of antibodies (including those to intermediate filament, nerve-sheath associated markers, and neuronal and neuroectodermal related antigens) to better establish the immunophenotype, supported by the ultrastructural evaluation. The tumor exhibited the distinctive cytogenetic abnormality t(X;18), together with a der(1)t(1;22)(p36;q12). Present results show that this poorly differentiated synovial sarcoma not only expresses conventional biologic and genetical markers for SS but also neuroectodermal features when transplanted into nude mice and cultured in vitro.

Translocation (10;11;22)(p14;q24;q12) characterized by fluorescence in situ hybridization in a case of Ewing's tumor

It is well recognized that the identification by classic cytogenetics of t(11;22)(q24;q12) is a useful aid in the accurate diagnosis of Ewing's sarcoma and related tumors. This translocation induces the EWS/FLI-1 fusion transcript, which can be detected by reverse transcription-polymerase chain reaction. Recent studies have also used fluorescence in situ hybridization (FISH) to demonstrate the translocation. The authors coupled classic cytogenetics and FISH on tumor cells from the original specimen, the local recurrence, and the pulmonary metastasis as well as from the xenografted tumors in a case of extraosseous Ewing's sarcoma. FISH analysis not only confirmed the cytogenetic results but also allowed the identification of a tumor-specific chromosome change, consistent with a complex translocation, t(10;11;22), as well as revealed other chromosomal rearrangements on both metaphases and interphase nuclei of each material. In addition this technique served to identify, in the interphase nuclei of the original tumor, the clone that became dominant, from the cytogenetic point of view, in the lung metastasis and in the nude mice xenografted tumors. Current results indicate that the use of FISH on metaphases and interphase nuclei is an easy and reliable approach to complement or even to substitute classic cytogenetic studies for the detection of specific chromosomal rearrangements, especially for determining complex translocations and for describing tumoral clones with different cytogenetic markers.

Primary malignant neuroepithelial tumors of the kidney: a clinicopathologic analysis of 146 adult and pediatric cases from the National Wilms' Tumor Study Group Pathology Center

Primary malignant neuroepithelial tumors of the kidney (NETKs) comprise a group of primitive, highly malignant neoplasms that histologically and clinically are not well characterized. A large cohort of 146 of these tumors, occurring in adults and children, has been collected at a single depository site, the National Wilms' Tumor Study Group (NWTSG) Pathology Center. The authors undertook a systematic retrospective review of the histologic, ultrastructural, and clinical features of these tumors, based on materials collected by the NWTSG and the consultation files of one of the authors (J.B.B.). Histologic features were generally those of primitive neural tumors with varying amounts of rosettes and neuropil; however, a large proportion of cases displayed unusual features such as spindle cells, ganglion cells, clear cell sarcoma-like foci, rhabdoid cells, epithelioid cells, and organoid foci. CD99 staining had been performed on 69 cases and showed membranous staining in 65. The NETKs were present in patients with a wide age spectrum, ranging from 1 month to 72 years (median, 18 years). EWS/FLI1 fusion analysis using reverse transcriptase-polymerase chain reaction and immunohistochemical stains for cytokeratin, chromogranin, and epithelial membrane antigen were performed successfully on a subset of 45 cases with available paraffin blocks. Only 13 of the 45 were fusion-positive, and there was no correlation between fusion status and histology, presence of rosettes, ultrastructural features, or cytokeratin positivity. CD99-negative cases were usually fusion-negative (six of seven cases), and all three chromogranin-positive cases were fusion-negative. Tumor staging, performed on 72 clearly defined and quantifiable cases by using NWTSG criteria, indicated that these are aggressive tumors, because only six were Stage 1, compared with 16 Stage 2, 31 Stage 3, and 19 Stage 4 lesions. The authors conclude that NETKs are a somewhat diverse group of generally aggressive, high-grade lesions that may present in a wide age range and are difficult to characterize without immunohistochemistry and cytogenetics/molecular biology.

Endometrial endometrioid carcinomas associated with Ewing sarcoma/peripheral primitive neuroectodermal tumor

Three uterine tumors, each consisting of endometrioid carcinoma and Ewing's sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) are described. The diagnosis of ES/pPNET in each case was first established in the hysterectomy specimen because each ES/pPNET was misinterpreted on the endometrial biopsy specimens as a high-grade homologous sarcoma. The ES/pPNET element in each case consisted of solid masses of small- to medium-sized round cells without Homer-Wright pseudorosettes, glial or ganglion cells, true rosettes with central lumens, or medulloepithelial tubules. Each ES/pPNET exhibited focal positive immunostaining for neuron-specific enolase, diffuse staining for vimentin, and strong cell membrane immunoreactivity for O13 (CD99), the last finding providing the first clue to the diagnosis of ES/pPNET in each case. The diagnosis in each case was confirmed by detection of EWS/FLI-1 fusion transcript through reverse transcription polymerase chain reaction. We also examined O13 immunoreactivity retrospectively in 40 cases of malignant mixed mullerian tumors (MMMT) with homologous or heterologous elements. O13 immunoreactivity was not observed in the malignant epithelium or in the homologous or heterologous sarcomas. The immunoreactivity of O13 in round cell endometrial sarcomas provides a clue to the diagnosis of ES/pPNET.

Translocation (X;18) in a biphasic synovial sarcoma with morphologic features of neural differentiation

The authors report a recurred neoplasm showing distinctive histologic, immunophenotypic, and ultrastructural features characteristic of biphasic synovial sarcoma with neural differentiation. The features include areas with a growth pattern of densely packed spindle cells in irregularly intersecting, broad fascicles, diffuse vimentin and HBA 71 immunoreactivity, expression of S-100 protein, and other neural markers. Moreover, areas with glandular structures and cellular expression of cytokeratin and epithelial membrane antigen were noted. Additionally, areas of neural-like growth pattern were positive for neuron-specific enolase, HNK-1, and protein gene product 9.5. Furthermore, cytogenetic analysis, two-color interphase fluorescence in situ hybridization, and reverse transcription polymerase chain reaction demonstrated the reciprocal translocation between chromosomes X and 18 associated with the different subtypes of tumor cells. The establishment and characterization of the tumor cell line are detailed. This cell line retains the distinct morphologic and genetic characteristics of the original biphasic synovial sarcoma with neural differentiation.

Diagnostic difficulties in extraosseous Ewing's sarcoma: a proposal for diagnostic criteria

Five cases diagnosed as extraosseous Ewing's sarcoma (EES) during a 15-year period, and the relevant literature, were reviewed. The diagnosis in these cases was difficult to confirm, mainly because the distinction between the osseous form of Ewing's sarcoma (OES) and either periosteal reactions or direct tumour invasion into adjacent bone by EES was often unclear. The literature suggests that other authors have also encountered difficulties. The authors believe that many cases reported as EES are likely to have been OES. This distinction has some importance, as the two conditions are usually treated in differing ways. The following criteria are proposed for the diagnosis of primary EES: (i) no evidence of bony involvement on magnetic resonance imaging; (ii) no evidence of increased uptake in bone or periosteum adjacent to the tumour on static isotope bone scan images; (iii) a small round cell tumour with no differentiating features on light microscopy, immunochemistry or electron microscopy; and (iv) demonstration of cytoplasmic glycogen.

Neurogenic potential of Ewing's sarcoma cells

We investigated the capacity of eight well-characterized Ewing's sarcoma cell lines to differentiate towards a neural phenotype. Ewing's sarcoma cells expressed the neuroectoderm-associated antigens such as nerve growth factor (NGF) receptor, N-CAM (6H7 and Leu-19) and Leu-7. Ewing's sarcoma cells also exhibited the potential for neural differentiation at the mRNA level; neuron-specific medium- and low-sized filament (NF-M and NF-L) expression was induced by dibutyryladenosine cyclic monophosphate. The pattern of expression of NF-L obtained by using alternative polyadenylation sites in Ewing's sarcoma cells differed from that in peripheral primitive neuroectodermal tumour (PNET) cells, and was similar to that in undifferentiated neural tissues. Furthermore, the NGF receptors detected by immunohistochemistry were found to be non-functional as assayed by c-fos induction with NGF treatment. The results indicate that Ewing's sarcoma cells maintain a primitive phenotype and have the potential to differentiate into a neural phenotype, indicating that Ewing's sarcoma is distinct from PNET.