Development and characterization of HAT-sensitive Ewing tumour cells for immunotherapy.

Background: Despite improvements in the treatment of patients with Ewing family tumours (EFT) during the past decades, the prognosis for patients with advanced disease is still unsatisfying. New treatment strategies have to be developed.
Materials and Methods: A hypoxanthine/aminopterin/thymidine (HAT)-sensitive EFT cell line was developed by repetitive treatment of the EFT cell line SK-N-MC with 8'-azaguanine (8AG). By using DNA microarrays, the gene expression profile of this cell line was characterized. Immunostimulatory activity was assessed by mixed lymphocyte/tumour cell culture (MLTC). Artificial fusion of tumour cells and dendritic cells was visualized by flow cytometry.
Results: After selection of 8AG-resistant cells, a cell line with high sensitivity for treatment with HAT was obtained. Expression of the X chromosome inactivation specific transcript XIST was higher in HAT-sensitive cells. Nevertheless, HAT-sensitive cells retained the EFT-associated gene expression profile. Moreover, in the presence of HAT, it was possible to use these cells without irradiation as stimulatory cells in MLTC or as fusion partner for dendritic cells.
Conclusion: HAT-sensitive EFT cells might be an interesting tool for the development of new immunotherapeutic approaches for the treatment of EFT.