T and NK cell mediated immunotherapy in Ewing's sarcoma (P03.040 amended version of December 2006)

ES is the second most common primary malignant bone tumor in childhood and
adolescence. In the last decades, the introduction of (neo-)adjuvant
chemotherapy combined with radical resection of the tumor and optional
radiotherapy has resulted in an improved overall survival from less than 30% to
60-70%. However, further intensification of chemotherapeutic interventions has
not resulted in an additional improvement in survival, indicating that a
significant subgroup of ES patients is resistant to currently used cytostatic
agents. Therefore, novel therapeutic modalities are required to improve outcome
in high risk and relapsed patients. The therapeutic potential of T and/or NK
cell-mediated immunotherapy in the treatment of various types of malignancies
has been demonstrated in preclinical and clinical studies. However, at present
experimental evidence on the susceptibility of ES to autologous and/or
allogeneic T/NK cell-mediated effector mechanisms is limited. In addition, the
occurrence and functional relevance of immune evasion mechanisms in the various
clinical stages of ES is undefined.

We hypothesize that NK and/or T cell-mediated immunotherapy may represent a
novel therapeutic option for patients with refractory and/or metastatic ES.
Therefore, we will study molecular mechanisms that determine the susceptibility
of ES to T and NK cell mediated immunotherapy in both an autologous and
allogeneic setting. The final aim is to provide evidence for the implementation
of NK and/or T cell-mediated immunotherapy strategies in future clinical
studies.

On a large cohort of both historical and prospectively obtained primary ES and
ES cell lines representing various stages of disease the following studies will
be performed we will:
1. Characterize in primary ES and ES cell lines the expression of gene
products/proteins that are known to be involved in T/NK cell-mediated
recognition, directional migration and immune-mediated cytolysis, study the
expression of candidate T cell target antigens, and identify potential immune
evasion strategies in ES.
2. Evaluate the correlation between immunological phenotype and clinical
behavior/outcome.
3. Characterize the NK and T cell effector potential towards ES cell lines and
the correlation with (immunological) phenotype, and provide evidence whether
allogeneic effector cells act favorably in comparison with autologous
effectors.

The burden for the participants is very limited. The extra tumor biopsy is
performed during the regular session The marrow aspirate is performed under
routine anesthesia when the central venous access is being implanted. The extra
blood samples will be obtained via the central venous access together with a
routine blood examination. Based on our experience with these procedures, the
additional risk associated with participation in this study is negligible.