Effects of radiation on FAS trafficking. MCF7 and SUM159 cells were treated with a 0 and 5 Gy dose of radiation and stained with anti-FAS Ab 24 h after irradiation. FAS expression was analyzed by ImageStream flow cytometry. Panel A: Radiation exposure increased the total FAS intensity in the radiation-responsive cell line MCF7, but had little effect on the radiation-nonresponsive cell line, SUM159. Panel B: Images of FAS staining in SUM159 cells demonstrated that FAS was expressed both on the cell surface and in the cytoplasm. Panel C: To evaluate the localization of FAS, we generated masks for cytoplasmic and membrane FAS to quantify their intensity. Panels D and E: In response to radiation, both cytoplasmic and membrane FAS increased in the MCF7 cell line. In contrast, SUM159 had high levels of membrane and cytoplasmic FAS before and after irradiation.