Ewing Sarcoma

Adult cancer

SUMMARY

Ewing sarcoma is a type of children’s cancer that forms in bones or soft tissues close to the bone. Many factors can affect the prognosis (probability of recovery): age of the patient, state of the tumour, size, response to treatment, etc. Genetic causes are also relevant and changes in the progress of the tumour have been observed. The goal is to study the changes that influence the prognosis of the tumour, to use them as biomarkers for the disease.

OBJECTIVES AND METHODOLOGY OF THE PROJECT

Ewing’s Sarcoma (ES) was the first malignant disease clearly defined by the presence of gene translocations and fusions (mainly EWSR1-FLI1).

In a recent retrospective study, it has been shown, in the majority of patients studied to date, that the EWS-FLI1 fusion molecular variant has no impact on prognosis. This contradicts previous retrospective studies, which suggested a possible advantage in survival without relapse for patients with type-1 EWSR1-FLI1 fusions, highlighting the importance of the prospective validation of biological markers and proving the need for the proposed collaborative studies.

Our hypothesis is that secondary genetic alterations could potentially explain the most aggressive forms of ES, and could be used as prognostic biomarkers. It is expected that not just one biomarker but rather a combination of markers will provide the most informative prognostic algorithm for patients with ES.

Our group has recently published the findings of a retrospective multi-centre study in which patients whose tumours show a 1q gain have a worse prognosis, regardless of the stage, tumour volume, and other classic clinical-pathological parameters.

The objective of this proposal is to carry out a prospective validation of the gains of 1q chromosomes, and of the loss of the 16q chromosome in samples of patients with ES included in the EuroEwing European protocol. Specifically, we will assess FISH technology to potentially validate the alterations in copy number variations (1q gain and 16 alterations) and, as an exploratory objective, we will conduct high-performance prospective studies of the copy number variations in Ewing Sarcoma.

This study will be conducted jointly by the Sarcoma Molecular Pathology group of the Cancer Research Centre-IBMCC/University Hospital of Salamanca, and the Pathology Department of the University Clinical Hospital of Valencia/University of Valencia.

Our proposal falls within the framework of the PROVABES European consortium, which gathers five of the most competitive European groups in ES research and is dedicated to the prospective validation of both biomarkers of this disease.

Currently, we are determining the variations in copy number alterations (CNA) in SE tumours using the OncoScan v3 platform from Affymetrix. Up to now, we have analysed 48 parafinnised samples, sent by the PROVABES consortium, from patients included in the 2008 EWING protocol. We have also used this technology to analyse material from 16 SE tumours from the Bio-bank of the University Hospital Virgen del Rocio (Seville). In the initial analysis of these tumours, we detected chromosomic aberrations consistent with those described in recent works (Diagram). For example, trisomy of the 8th chromosome is observed in 50% of cases both sets of samples, and also a complete gain on chromosome 12 in 18%. In terms of the 1q gain, we have observed this in 15% of cases in the PROVABES samples; in the local samples we have not yet observed cases with this alteration, but we are widening the number of cases. Loss on 16q is observed in the expected proportion in both sample sets (14 – 15%)

In terms of more discrete or specific events, the most significant findings are consistent in many cases between the two sets, and even with the cell line panel. These alterations include very specific gains and losses of the genetic material in specific loci, which we have not found precedents for in Ewing’s Sarcoma. There are proteins which are involved in the detoxification of carcinogens and therapeutic drugs, and have been associated with an increase in susceptibility or resistance to treatment in various types of cancer. There are also previously unobserved events such as gains in a particular locus and alterations in pseudogenes. We have also observed a new micro-deletion which involves CDKN2A (p16) on chromosome 9 (PROVABES samples), an alteration which is characteristically observed in Ewing’s Sarcoma.

The OncoScan samples also include somatic mutations for 9 cancer genes. In the tumour samples, we have detected different mutations at occurrences slightly higher than those described in other studies. We have also detected a lower occurrence of other mutations, which must be confirmed by sequencing.

We are currently continuing to widen the number of cases analysed, in order to be able to confirm all the observed findings. The biological significance or prognostic/predictive value of these new events will be determined very soon, using the local sample set, for which we have detailed clinical information.