Changed adhesion molecule profile of Ewing tumor cell lines and xenografts under the influence of ionizing radiation

Background: Adhesion molecules are involved in cell-cell and cell-matrix interactions and may be informative to characterize intercellular mechanisms of invasion and metastasis. This study was performed to characterize radiation-induced changes in the adhesion molecule profile of Ewing tumor subpopulations on a single cell level. Materials and Methods: In the present study, two Ewing tumors were characterized in vitro 4, 24 and 72 hours after radiation with 5 Gy and in vivo in a xenograft model 4, 6 and 15 days after radiation with 30 Gy, together with non-irradiated controls, by five parameter flow cytometry. Directly fluorescence-conjugated antibodies that were directed against adhesion molecules (LFA-1 (CD11a), HCAM (CD44), VLA-2 (CD49b), ICAM-1 (CD54), NCAM (CD56), LECAM-1 (CD62L) and CD86) were used. Annexin V and 7-AAD were used to characterize radiation-induced apoptosis. Results: Tumor cell subpopulations were identified by the expression of adhesion molecules, apoptotic markers and DNA content. Heterogeneous changes of the adhesion molecule profile were identified on tumor cell subpopulations after radiation. The expression of CD11a and CD62L correlated with the expression of apoptosis-associated markers. Conclusion: The changes of flow cytometric profile under radiation may potentially correlate with a changed metastatic potential of tumor cell subpopulations.