Ewing Tumors (ET) are highly malignant, localized in bone or soft tissue and are molecularly defined by ews/ets translocations. DNA microarray analysis revealed a relationship of ET to both endothelium and fetal neural crest. We identified expression of histone methyl-transferase Enhancer of Zeste, Drosophila, Homolog 2 (EZH2) to be increased in ET. EZH2’s suppressive activity maintains stemness in normal and malignant cells.

Here, we found EWS/FLI1 bound to the EZH2 promoter in vivo and induced EZH2 expression in ET and mesenchymal stem cells. Down-regulation of EZH2 by RNA interference in ET suppressed oncogenic transformation by inhibiting clonogenicity in vitro. Similarly, tumor development and metastasis was suppressed in immunodeficient Rag2−/−γC−/− mice. EZH2-mediated gene silencing was shown to be dependent on histone deacetylase (HDAC) activity. Subsequent microarray analysis of EZH2 knock down, HDAC-inhibitor treatment and confirmation in independent assays revealed an undifferentiated phenotype maintained by EZH2 in ET. EZH2 regulated stemness genes such as nerve growth factor receptor (NGFR) as well as genes involved in neuroectodermal and endothelial differentiation (EMP1, EPHB2, GFAP, GAP43).

These data suggest that EZH2 might play a central role in Ewing Tumor pathology by shaping the oncogenicity and stem cell phenotype of this tumor.

Sclerosing epitheloid fibrosarcoma (SEF) is an extremely rare soft tissue sarcoma arising from connective tissue cells of mesenchymal origin. SEF mostly occurs in extraosseous sites in the soft tissue; however two cases of primary localization in the bone have been described. Despite benign cytological features the clinical course is complicated by a high local recurrence rate and late metastases. SEF represents a clinically challenging entity especially because no standardized treatment regimens are available.

We report a 16-year old female patient who showed persistent load-dependent pain focused on the right proximal tibia. Radiological evaluation revealed an osteolytic lesion and the diagnosis of a benign bone cyst was consented. The tumor was surgically removed. Only after recurrence of the tumor and repeated histopathological analysis diagnosis of SEF could be established.

Because of the bone localization of the tumor the patient underwent standardized neoadjuvant chemotherapy analogous to the European-American EURAMOS-1 protocol for the treatment of osteosarcoma followed by tumor resection and endoprothesis. Histopathological analysis of the resected tumor showed > 90% vital tumor cells suggesting no response to the neoadjuvant chemotherapy. Therefore, therapy was reassigned to the CWS protocol of the German Society for Pediatric Oncology and Hematology (GPOH) for treatment of soft tissue sarcoma. To date, the patient is alive and no metastases of the primary tumor can be detected.

SEF represents a taunting clinical entity due to deceptive histopathological features and rare occurrence. Localization in the bone represents an additional challenge with regards to the therapeutical approach. Standardized treatment regimens are currently not available for SEF. This case report, to our knowledge, is the first outlining a therapeutic approach in detail. Our data suggest that SEF may be resistant to a chemotherapy regimen containing Cisplatin, Doxorubicin and Metho-trexate despite close association to the bone, possibly indicative of the soft tissue histogenesis of this tumor. The response to the soft tissue sarcoma targeting CWS chemotherapy remains to be determined.

The rationale of adoptive T cell therapy is based on the attempt to circumvent pre-existing tolerance mechanisms by stimulating potentially tumor-reactive T cells ex vivo. Efforts to eradicate cancer by adoptive T cell transfer have been limited due to the difficulty of isolating tumor-reactive T cells present in low numbers in peripheral blood of tumor patients. Furthermore, the development of an effective immunotherapy in the autologous context is hampered by the deficit of an effective T cell repertoire against tumor antigens.

We have optimized the techniques for isolating and expanding antigen-specific allogeneic T cells. Following repetitive peptide-driven stimulations with HLA-A*0201 positive dendritic cells the responding HLA-A*0201 negative CD8+ T cells were stained with HLA-A*0201/peptide pentamers. Multimer-positive T cells were sorted and directly cloned by limiting dilution. Using this technique we have succeeded in establishing T cell clones directed against several HLA-A*0201-resticted peptides derived from Ewing Tumor (ET) specific antigens identified via previous DNA microarray analysis and supposed to play a central role in the pathogenesis of this tumor. These T cells not only specifically recognized peptide-pulsed target cells or antigen transfected cells in the context of HLA-A*0201 but also killed HLA-A*0201+ ET expressing the antigen while HLA-A*0201– ET were not affected.

Allogeneic, tumor specific T cells can be easily isolated via Peptide/HLA-multimer technology and may benefit therapeutic strategies in allogeneic stem cell transplantation.