Fig. 2
Spheroid growth delay after irradiation. a Each 1000 cancer cells were seeded alone or together with 1000 fibroblasts in ULA plates to form spheroids. One day after seeding, spheroids were irradiated with 5 Gy or mock-treated. Spheroid growth was recorded over 14 days, starting on day 1 after irradiation. Size bars are 500 µm. b Spheroid area was determined by image analysis and recorded as function of day after irradiation. Indicated are mean and SD from 3 to 4 independent experiments with 8 replicates each. Growth can be described by a simple exponential fit (Y(t) = Y0*exp(k*t)) between days 1 and 10 for MCF-7, and between days 1 and 14 for BT474. c Results of exponential fitting of individual growth curves for each spheroid, with k indicating the growth rate and Y0 indicating spheroids area on day 0, are shown in a swarm plot together with means and SD. Tukey’s multiple comparison test following two-way ANOVA was used to detect significant differences between the means of the independent groups. A p value ≤ 0.05 was considered statistically significant. Single, double and triple asterisks indicate significant differences with p-values of < 0.05, < 0.01 and < 0.001, respectively