Effect of radiation on Ewing tumour subpopulations characterized on a single-cell level: Intracellular cytokine, immunophenotypic, DNA and apoptotic profile

Purpose: Adhesion molecules, cytokines and their corresponding cell-surface receptors are involved in intercellular signalling pathways, radioresistance and metastasis-mediating mechanisms of malignant cells. The aim was the characterization of changes in the marker profile of Ewing tumour cell subpopulations under the influence of radiation. Materials and methods: Three Ewing tumours were characterized in vitro and in vivo in a xenograft model before and after radiation by five-parameter flow cytometry. Antibodies directed against cell surface and intracellular antigens, apoptosis-associated markers and the DNA dye 7-aminoactinomycin D were used. Results: Tumour cell subpopulations were identified by expression of adhesion molecules and cytokine receptors, intracellular cytokines, apoptotic markers and DNA content. Heterogeneous changes of flow cytometric profile were identified on tumour cell subpopulations after radiation. Conclusions: The changed profile of tumour cells under radiation might be associated with biological changes of tumour subpopulations in view of radioresistance and metastatic potential and might be useful to identify intercellular regulation mechanisms and to define parameters being predictive for a response to therapy.