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. 2019 Apr 18;13(5):1249–1267. doi: 10.1002/1878-0261.12483

Figure 1.

Figure 1

Establishment of an isogenic model of acquired radioresistant breast cancer cells. Proliferation of parental (A) MCF‐7 and (B) MDA‐MB‐231 cells was assessed by the MTT assay for 24, 48 and 72 h after irradiation with increasing doses (0, 2, 4 and 8 Gy) of irradiation. (C) Clonogenic survival of parental MCF‐7 and MDA‐MB‐231 cells was assessed by colony formation in response to treatment with increasing doses (0, 2, 4 and 8 Gy) of irradiation. (D) Schematic overview of fractionated treatment schedule for establishment of radioresistant breast cancer cells. Parental cells were exposed to 2 Gy of irradiation to reach a total dose of 30 Gy. Radioresistance of MCF‐7RR and MDA‐MB‐231RR cells was confirmed by clonogenic assays after 4 Gy of irradiation. The SF of irradiated (IR+) MCF‐7RR (E) and MDA‐MB‐231RR (F) cells was normalized by the SF of non‐irradiated (IR−) cells. Representative images of the results of the clonogenic assays for MCF‐7RR and MDA‐MB‐231RR cells are shown in (E) and (F). Error bar indicates the SD from three independent experiments. **P < 0.01; *P < 0.05 by Student's t‐test.