With modern polychemotherapy Ewing’s sarcoma exhibit remarkable chemosensitivity leading to 5-year survival rates approaching 60–70%. However, in the last decade, no significant progress has been achieved in terms of improved cure rates and quality of life. In addition, prognosis is poor either in relapsed patients and in patients with metastasis at diagnosis. Thus, it is imperative to develop novel therapeutic strategies and to identify markers for risk-adapted therapies. The PROTHETS European Consortium through collaborative studies defined prognostic markers and new therapeutic targets in the Ewing’s sarcoma family of tumours (ESFT), to provide rigorous scientific justifications for the development of clinical trials for this rare disease. Genetic studies have been performed for the screening of high-risk patients and patients responding differently to chemotherapy. Between others, these studies identified in gluthation metabolism a major pathway regulating Ewing’s sarcoma chemoresistance. The prognostic relevance of glutathione metabolism pathway was validated by RT-PCR and the expression of MGST1, the microsomal glutathione transferase (GST), was found to clearly predict EWS prognosis. MGST1 expression was associated with doxorubicin chemo sensitivity. This prompted to assess the in vitro effectiveness a new anticancer agent (NBDHEX) that efficiently inhibits GST enzymes.. The consortium have collected more than 600 cases in specific tissue arrays for validation studies. Their use allowed the identification of some markers of prognosis, either conventional or new (ki-67, adhesion proteins, GAL3BP). Overall, theses studies started to define possible forthcoming risk-adapted strategies. Another goal of the project was the creation of new tools and drugs as well as the optimization of molecular approaches against three therapeutic targets, EWS-FLI1, CD99 and IGF-IR that have great potential in terms of clinical application. The studies on IGF-IR have provide the rationale for the currently on-going clinical studies in Ewing’s sarcoma.
Bone tumours may recur locally even after wide surgical excision and systemic chemotherapy. Local control of growth may be accomplished by the addition of cytostatic drugs such as methotrexate (MTX) to bone cement used to fill the defect after surgery and to stabilise the reconstructive prosthesis. We have studied the elution kinetics of MTX and its solvent N-methyl-pyrrolidone (NMP) from bone cement and their biological activities in five cell lines of osteosarcoma and in osteoblasts, and compared them with the effects of the parent compounds alone and in combination. Our findings show that MTX is released continuously over months at concentrations highly cytotoxic to osteosarcoma cells and suggest that the impregnated bone cement would be effective in the long term. Proliferating osteoblasts, however, were much less sensitive towards MTX. The dose-response relationship for NMP and experiments with MTX/NMP-mixtures show that the eluted concentrations of solvent are not toxic and do not influence the effects of MTX. We suggest that bone cement containing MTX dissolved in NMP releases the drug in a suitable and effective way and may be of value in the treatment of bone tumours.
