Approaching Ewing sarcoma

Single-cell RNA profiling identifies diverse cellular responses to EWSR1/FLI1 downregulation in Ewing sarcoma cells

BACKGROUND

The EWSR1/FLI1 gene fusion is the most common rearrangement leading to cell transformation in Ewing sarcoma (ES). Previous studies have indicated that expression at the cellular level is heterogeneous, and that levels of expression may oscillate, conferring different cellular characteristics. In ES the role of EWSR1/FLI1 in regulating subpopulation dynamics is currently unknown.

METHODS

We used siRNA to transiently suppress EWSR1/FLI1 expression and followed population dynamics using both single cell expression profiling, CyTOF and functional assays to define characteristics of exponentially growing ES cells and of ES cells in which EWSR1/FLI1 had been downregulated. Novel transcriptional states with distinct features were assigned using random forest feature selection in combination with machine learning. Cells isolated from ES xenografts in immune-deficient mice were interrogated to determine whether characteristics of specific subpopulations of cells in vitro could be identified. Stem-like characteristics were assessed by primary and secondary spheroid formation in vitro, and invasion/motility was determined for each identified subpopulation. Autophagy was determined by expression profiling, cell sorting and immunohistochemical staining.

RESULTS

We defined a workflow to study EWSR1/FLI1 driven transcriptional states and phenotypes. We tracked EWSR1/FLI1 dependent proliferative activity over time to discover sources of intra-tumoral diversity. Single-cell RNA profiling was used to compare expression profiles in exponentially growing populations (si-Control) or in two dormant populations (D1, D2) in which EWSR1/FLI1 had been suppressed. Three distinct transcriptional states were uncovered contributing to ES intra-heterogeneity. Our predictive model identified ~1% cells in a dormant-like state and ~ 2-4% cells with stem-like and neural stem-like features in an exponentially proliferating ES cell line and in ES xenografts. Following EWSR1/FLI1 knockdown, cells re-entering the proliferative cycle exhibited greater stem-like properties, whereas for those cells remaining quiescent, FAM134B-dependent dormancy may provide a survival mechanism.

CONCLUSIONS

We show that time-dependent changes induced by suppression of oncogenic EWSR1/FLI1 expression induces dormancy, with different subpopulation dynamics. Cells re-entering the proliferative cycle show enhanced stem-like characteristics, whereas those remaining dormant for prolonged periods appear to survive through autophagy. Cells with these characteristics identified in exponentially growing cell populations and in tumor xenografts may confer drug resistance and could potentially contribute to metastasis.

Successful Spontaneous Pregnancy after Treatment for Ewing Sarcoma including Sacrectomy

Ewing sarcomas are highly malignant bone tumors and usually occur in childhood. Radiation therapy, chemotherapy, and surgical methods increase the survival rate of the affected patient, but infertility and reduced reproductive capacity are common late effects of pediatric cancer treatment.

IL6 secreted by Ewing sarcoma tumor microenvironment confers anti-apoptotic and cell-disseminating paracrine responses in Ewing sarcoma cells

Background

The prognosis of patients with Ewing sarcoma (ES) has improved over the course of the last decades. However, those patients suffering from metastatic and recurrent ES still have only poor chances of survival and require new therapeutic approaches. Interleukin-6 (IL6) is a pleiotropic cytokine expressed by immune cells and a great variety of cancer cells. It induces inflammatory responses, enhances proliferation and inhibits apoptosis in cancer cells, thereby promoting chemoresistance.

Methods

We investigated expression of IL6, its receptors and the IL6 signal transduction pathway in ES tumor samples and cell lines applying reverse transcriptase PCR, immunoblot and immunohistochemistry. The impact of IL6 on cell viability and apoptosis in ES cell lines was analyzed by MTT and propidium iodide staining, migration assessed by chorioallantoic membrane (CAM) assay.

Results

Immunohistochemistry proved IL6 expression in the stroma of ES tumor samples. IL6 receptor subunits IL6R and IL6ST were expressed on the surface of ES cells. Treatment of ES cells with rhIL6 resulted in phosphorylation of STAT3. rhIL6 protected ES cells from serum starvation-induced apoptosis and promoted migration. IL6 blood serum levels were elevated in a subgroup of ES patients with poor prognosis.

Conclusions

These data suggest that IL6 contributes to ES tumor progression by increasing resistance to apoptosis in conditions of cellular stress, such as serum starvation, and by promotion of metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1564-7) contains supplementary material, which is available to authorized users.

Successful Pregnancy After Sacrectomy Combined With Chemotherapy and Radiation for Ewing Sarcoma: Case Report and Literature Review

BACKGROUND

Ewing sarcoma is considered to have a poor prognosis. Recent advances in multidisciplinary management have resulted in a marked improvement in long-term survival.

CASE

We describe a case of successful pregnancy in a patient who underwent sacrectomy combined with multi-agent chemotherapy and radiotherapy for Ewing sarcoma. The patient was diagnosed with Ewing sarcoma of the sacrum at the age of 16. The ovaries were transposed, the uterus was shielded, and a gonadotropin-releasing hormone agonist was used during treatment to protect ovarian function. The patient spontaneously conceived at the age of 27. After an uneventful pregnancy, the patient delivered a healthy neonate at term by cesarean section.

SUMMARY AND CONCLUSIONS

Successful pregnancy and delivery can be achieved after multi-modality treatment with pretreatment intervention for fertility preservation.

Do patients with ewing's sarcoma continue with sports activities after limb salvage surgery of the lower extremity?

BACKGROUND

Limb salvage surgery has evolved to become the standard method of treating sarcomas of the extremities with acceptable oncologic results. However, little information exists relative to the activity level or ability to participate in sports after tumor reconstructions.

QUESTIONS/PURPOSES

The aims of the study were to answer the following questions: (1) Which sports activity levels and what types of sports can be expected in the long term after tumor reconstruction? (2) Which frequency durations are patients with Ewing's sarcoma able to perform in long-term followup after local control? (3) Do surgical complications affect sports activity level?

METHODS

Thirty patients (13 females, 17 males; mean age, 18 ± 8 years; range, 2-36 years at diagnosis; mean followup 16 ± 6 years [minimum, 5 years]) were included. Tumors were located in the pelvis, femur, tibia, and fibula. Surgical procedures included surgical resections alone (n = 8), surgical resection with biological reconstruction (n = 9), or endoprosthetic reconstruction (n = 13). We assessed UCLA sports activity levels, kinds of sports as well as the frequency per week and the duration of each training unit at long term (minimum followup, 5 years).

RESULTS

In long-term followup 83% patients (25 of 30) were performing athletic activity regularly. The hours/week of sports depended on type of surgery and were highest after resections in the pelvis and femur (5.8) and were lowest after megaprosthetic reconstruction of the pelvis (1.0). Patients undergoing biologic reconstructions were able to perform high-impact sports. UCLA sports activity levels were high after joint-preserving vascularized fibula for tibia reconstruction (7.4) and after megaprosthetic reconstruction of the lower extremity (6.3-6.4) and were low after tumors located in the fibula (4.2). Complications during followup did not significantly influence sports activity in long-term survivors.

CONCLUSIONS

Long-term survivors can achieve high levels of sports activity in many instances. Tumor sites are associated with the postoperative sports activity levels. This information can help surgeons counsel patients in terms of athletic expectations after limb salvage reconstruction for patients with Ewing's sarcoma.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Do long term survivors of ewing family of tumors experience low bone mineral density and increased fracture risk?

BACKGROUND

Multimodal treatment regimens for Ewing's sarcoma have led to survival rates approaching 70% of patients with no metastases at diagnosis. However, these treatments have long-term side effects. Low bone mineral density (BMD) and risk of fractures can occur owing in part to chemotherapy and limited mobility from local control of the primary tumor.

QUESTIONS/PURPOSES

We performed this study to answer the following questions: (1) Do long-term survivors of the Ewing family of tumors sustain low BMD? (2) Which factors are associated with BMD in these patients? (3) Do they experience fractures? (4) Are BMD and fractures associated with each other?

METHODS

We queried our institutional registry to identify all known survivors of Ewing tumors who were treated before 2005. Of 100 such patients, 67 (67%) responded to a postal survey to participate in this study, and an additional 11 (11%) patients were excluded according to prespecified criteria. In the remaining 56 long-term survivors (27 females, 29 males; mean±SD age at followup, 32±10 years; mean followup, 15±7 years), BMD was measured by dual-energy x-ray absorptiometry and history of fractures was assessed using a questionnaire. Associations were tested using univariate and multivariate models by stepwise variable selection procedure, including Bonferroni correction.

RESULTS

Thirty-one of 56 (56%) patients had a pathologic BMD. Seven (13%) had osteoporosis and 24 (43%) had osteopenia. Factors related to low BMD after Bonferroni correction were the length of time between surgery and followup and the BMI at followup. Twenty-one patients reported 29 fractures. With the numbers available, BMD levels were not associated with fractures.

CONCLUSIONS

We could not confirm some potentially important predictors for fractures to be associated with clinical events of interest. However, the data are valuable as hypothesis-generating pilot data for future, multicenter prospective studies. If BMD changes cannot explain the propensity of fractures, there may be other bone characteristics like microarchitectural changes of bone to more accurately explain the effect.

LEVEL OF EVIDENCE

Level IV, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.

The value of high-dose chemotherapy in patients with first relapsed Ewing sarcoma

BACKGROUND

Prognosis of patients with relapsed Ewing sarcoma (ES) is poor. The 5-year overall survival (OS) is 13%. We analyzed high-dose chemotherapy (HDtx) versus conventional chemotherapy (CHtx) in patients with relapsed ES.

PROCEDURE

Data from 239 patients with first relapse, registered during 2000-2011 in the ES relapse registry of the Cooperative Ewing Sarcoma Study Group (CESS) were analyzed.

RESULTS

Of 239 patients, 200 received various non-HDtx second-line CHtx regimens. Seventy-three patients had additional HDtx followed by autologous stem cell rescue. The 2-year event-free survival (EFS) was 10% (SE = 0.02) in patients treated without HDtx and 45% (SE = 0.09) in patients treated with HDtx. In a second step, we focused on those patients who achieved complete remission (CR) or partial remission (PR) after four to six cycles of conventional second-line CHtx. Here, the 2-year EFS was 31% (SE = 0.08) without additional HDtx and 44% (SE = 0.09) with additional HDtx. In addition, multivariate regression analysis indicates absence of HDtx treatment, with a Hazard ratio (HR) of 2.90 (95% CI 1.41-6.0), and early relapse, with a HR of 4.76 (95% CI 2.31-9.78), as independent prognostic factors for EFS.

CONCLUSION

Additional HDtx may contribute to further reduce the risk of further events in patients who respond to conventional second-line CHtx.

A Novel Role of IGF1 in Apo2L/TRAIL-Mediated Apoptosis of Ewing Tumor Cells

Insulin-like growth factor 1 (IGF1) reputedly opposes chemotoxicity in Ewing sarcoma family of tumor (ESFT) cells. However, the effect of IGF1 on apoptosis induced by apoptosis ligand 2 (Apo2L)/tumor necrosis factor (TNF-) related apoptosis-inducing ligand (TRAIL) remains to be established. We find that opposite to the partial survival effect of short-term IGF1 treatment, long-term IGF1 treatment amplified Apo2L/TRAIL-induced apoptosis in Apo2L/TRAIL-sensitive but not resistant ESFT cell lines. Remarkably, the specific IGF1 receptor (IGF1R) antibody α-IR3 was functionally equivalent to IGF1. Short-term IGF1 incubation of cells stimulated survival kinase AKT and increased X-linked inhibitor of apoptosis (XIAP) protein which was associated with Apo2L/TRAIL resistance. In contrast, long-term IGF1 incubation resulted in repression of XIAP protein through ceramide (Cer) formation derived from de novo synthesis which was associated with Apo2L/TRAIL sensitization. Addition of ceramide synthase (CerS) inhibitor fumonisin B1 during long-term IGF1 treatment reduced XIAP repression and Apo2L/TRAIL-induced apoptosis. Noteworthy, the resistance to conventional chemotherapeutic agents was maintained in cells following chronic IGF1 treatment. Overall, the results suggest that chronic IGF1 treatment renders ESFT cells susceptible to Apo2L/TRAIL-induced apoptosis and may have important implications for the biology as well as the clinical management of refractory ESFT.

CD99/MIC2 Constitutes a Differentiation Antigen of a Human Osteoblast Cell Line

BACKGROUND

The histological origin of the Ewing's family of tumors (EFT) is still not clear. Since these small cell bone tumors may originate from osteogenic stem cells, the presence of the CD99/MIC2 antigen, known to be overexpressed in EFT, was studied in a human osteoblast cell line in response to differentiation inducers.

METHODS

The HBA-71 monoclonal antibody directed to the CD99/MIC2 antigen was used to stain a human osteoblast cell line as well as the two EFT cell lines KAL and EW-2 after pretreatment of the cells with the differentiation inducers calcitriol and the histone deacetylase (HDAC) inhibitors sodium butyrate (NaB), sodium phenylacetate (NaPA) as well as N, N'-hexamethylen-bis-acetamide (HMBA). Alkaline phosphatase (ALP) levels were determined as cellular differentiation marker.

RESULTS

Significant expression of the CD99/MIC2 antigen, yielding a molecular weight of 32 kD in Western blotting, was found in the human osteoblast cell line. Pretreatment of the osteoblasts with calcitriol and HMBA increased ALP content and suppressed the CD99/MIC2 antigen. Calcitriol had no major effect on CD99/MIC2 expression of both EFT cell lines, but HMBA enhanced ALP activity in KAL cells and downregulated CD99/MIC2. EW-2 cells exhibited reduced levels of both CD99/MIC2 and ALP.

CONCLUSIONS

This study supports the role of CD99/MIC2 as differentiation antigen of osteoblasts and a Ewing's sarcoma cell line with neuroectodermal phenotype. Response to calcitriol is absent or low in the two EFT cell lines tested.

Risk of recurrence and survival after relapse in patients with Ewing sarcoma

BACKGROUND

The prognosis in patients with relapsed Ewing sarcoma is unfavorable. Our investigation identifies factors predicting for the outcome following relapse.

PROCEDURE

We analyzed type of relapse, time to relapse and overall survival after relapse (OSr) in 714 patients with first recurrence. All patients had been treated within the Cooperative Ewing Sarcoma Studies (CESS) 81 or 86, or the European Intergroup CESS (EICESS 92). OSr time was calculated from diagnosis of first relapse to last follow-up or death.

RESULTS

Median follow-up time from diagnosis of primary disease was 2.2 years (mean = 4.0; range: 0.2-24.9). Relapse sites were local in 15%, combined local and systemic in 12%, and systemic in 73%. Among patients with a localized primary tumor, 20% relapsed locally, while 12% showed combined and 68% systemic relapse. When the primary disease was disseminated, 82% developed systemic, 13% combined, and 5% local relapse. Five-year OSr was 0.13 (SE = 0.01). Outcome following local relapse, with a 5-year survival rate of 0.24 (P < 0.001), was superior to outcome after systemic or combined recurrence. Five-year OSr was 0.07 (SE = 0.01) in patients who relapsed 0-2 years after the diagnosis of primary disease, as compared to a 5-year OSr of 0.29 (SE = 0.03) when relapse occurred later.

CONCLUSIONS

5-year OSr in Ewing sarcoma is poor (<0.2). Prognostically favorable factors are: late onset (>2 years) and strictly localized relapse.

Pathobiologic markers of the ewing sarcoma family of tumors: state of the art and prediction of behaviour

Over the past three decades, the outcome of Ewing sarcoma family tumor (ESFT) patients who are nonmetastatic at presentation has improved considerably. The prognosis of patients with metastatic disease at the time of diagnosis and recurrence after therapy remains dismal. Drug-resistant disease at diagnosis or at relapse remains a major cause of mortality among patients diagnosed with ESFT. In order to improve the outcome for patients with potential relapse, there is an urgent need to find reliable markers that either predict tumor behaviour at diagnosis or identify therapeutic molecular targets at the time of recurrence. An improved understanding of the cell of origin and the molecular pathways that regulate tumorigenicity in ESFT should aid us in the search for novel therapies for ESFT. The purpose of this paper is thus to outline current concepts of sarcomagenesis in ESFT and to discuss ESFT patterns of differentiation and molecular markers that might affect prognosis or direct future therapeutic development.