Euro Ewing Consortium

International Clinical Trials to Improve Survival from Ewing Sarcoma

Abstracts from young researchers at January 2017 EEC meeting, supported by Peter Pan Charity

Six young researchers from Europe, working on Ewing sarcoma, were awarded travel bursaries to attend the EEC meeting in London in January 2017. Funding was donated by the Peter Pan charity and was granted for two spoken presentations and four posters.

Emmy Fleuren, The Institute of Cancer Research

Presentation: Diversity and similarities of activated pathways in Ewing sarcoma: insights from sarcoma phosphoprotemics

What are you trying to find out?

We aim to identify novel and clinically relevant targets for Ewing sarcoma (ES). Because multiple targets can act together for maintaining tumour progression, it is critical to obtain the complete picture of activated signalling networks in ES to deduce a rational and effective treatment regimen.

What have you found?

Using a phosphoproteomics approach, we revealed multiple activated targets and pathways in ES cell lines, including FAK1, Src-family kinases and DDR2. Although targeting of these kinases has potential for treating a subset of ES, we also show that on the molecular level, ES cells did not cluster together. This emphasizes a need for personalized treatments for targeted therapies.

Why is this important?

Our results stress the importance of incorporating personalized treatment regimens with respect to targeted therapies in ES, and we provide rational targets to focus on. This is very important information because at the moment all ES patients treated with similar, standard treatment protocols.

Gloria Pedot, University Children’s Hospital Zurich

Presentation: USP19 modulates EWS-FLI1 protein turnover and is a new therapeutic target for Ewing sarcoma

In the majority of patients, Ewing sarcoma expresses the fusion oncoprotein EWS-FLI1, an aberrant transcription factor. Continuous expression of EWS-FLI1 is mandatory for tumor cells to survive and proliferate.
We want to investigate the factors which regulate the degradation of the fusion protein and lead to tumor cell death. We showed that EWS-FLI1 stabilizes upon proteasome inhibition indicating that EWS-FLI1 is a substrate of the ubiquitin system. We identified ubiquitin specific protease 19 (USP19) to modulate the ubiquitin modification of EWS-FLI1 and its stability. Depletion of USP19 reduced EWS-FLI1 levels and correlated with decreased cell growth in vitro and tumor delay in vivo. By mass spectrometry we identified the critical lysine 380 as responsible residue of EWS-FLI1 degradation.
Our findings provide relevant insights into the importance of targeting EWS-FLI1 turnover and will allow us to investigate compounds affecting the fusion protein stability and develop novel therapeutic strategies.

Christiane Schaefer, University Children’s Hospital Münster

Poster: Potential EWS-FLI1-FOXM1-BUB1B axis contributes to mitotic cell cycle control in Ewing sarcoma

What are you trying to find out?

EWS-FLI1 represents the main oncogenic driver in Ewing sarcoma, direct targeting remains unsolved. Therefore, we would like to identify EWS-FLI1 cooperating genes, which contribute to tumor formation. These genes will be further validated to expand existing therapeutic strategies and to reduce treatment toxicities.

What have you found?

For the first time, we could show a connection between EWS-FLI1 oncogene and the cell
cycle regulator BUB1B in ES. Loss of BUB1B leads to reduced proliferation and nearly
abolished colony formation potential in distinct ES cell lines.

Why is this important?

This data is representing basic molecular findings to further understand Ewing sarcoma tumorigenesis and contributing genes.

Mariona Chicón Bosch, University of Leeds

Poster: Cancer stem-like cells: The story behind the poor outcome of Ewing’s sarcoma patients

The outcome for patients with metastatic Ewing’s sarcoma (ES) is usually poor, with only 1 in 5 young people surviving to 5 years. Increasing evidence suggests that there is a small population of cancer cells within tumours called ES cancer stem-like cells (ES-CSCs), that are responsible for disease progression and relapse, which are not eradicated by current cytotoxic treatments.
Our group has been able to identify these ES-CSC clones and successfully maintain them in the laboratory, providing a unique renewable resource to study the heterogeneity of these cells and understand what makes them resistant to current treatments. We are currently investigating how to overcome this resistance with the goal of identifying novel targets to design more effective therapy.
In our opinion ES-CSCs are responsible for refuelling tumour growth, progression and relapse. We expect improved outcomes for some patients may be realised once we understand how to kill these ES-CSCs.

Elizabeth Roundhill, University of Leeds

Poster: ABC transporter and heat shock proteins; targets to overcome multi-drug resistance in Ewing’s sarcoma

Resistance to chemotherapy is a major obstacle for the successful treatment of many Ewing’s sarcoma (ES) patients. Resistance is often caused by increased levels of ABC transporter proteins on the ES cell surface, where these proteins pump chemotherapy drugs out of the cells to reduce chemotherapy-induced cell kill.
Some ABC transporter proteins, such as MRP1, are expressed inside the cell and are transported by HSP90β to the mitochondria where they reduce the activation of the cell death cascade. Blocking HSP90β activity sensitises ES cells to chemotherapy drugs by decreasing mitochondrial MRP1 activity. Therefore, HSP90 inhibition is a novel method to decrease resistance to chemotherapy drugs in ES.

Karen Manias, The University of Birmingham

Poster: A systematic review of chemotherapy in metastatic, refractory or relapsed Ewing sarcoma in children and young adults

What are you trying to find out?

We are trying to find out which is the best chemotherapy treatment to use in young patients with Ewing Sarcoma who have relapsed, unresponsive or metastatic disease.

What have you found?

We have undertaken a systematic literature review to find all research studies conducted between 1998-2015 evaluating chemotherapy in relapsed and metastatic Ewing Sarcoma. We found 21 studies involving 376 patients. The studies were very different from each other in terms of study design, patients and treatments, which made it difficult to assess which was the best treatment and which study gave the most trustworthy answer.  There were no randomised-controlled trials that could have helped us compare treatments in a reliable way.

Why is this important?

This study is important because we have discovered there is very little evidence to help doctors choose the best treatment for these patients. We have shown that well-designed, high quality randomised controlled trials are needed to answer this question properly.