Comparison of parental MDA-MB-231 cells and escapers. Parental cells and escapers were treated with 100 nM doxorubicin for 24 h, then cultured in a fresh medium and analyzed on the 4th day (D1+4). (a) Analysis of population doublings per day. (b) Quantitative analysis of autophagic index based on densitometry of LC3B protein level in untreated and bafilomycin A (BAF)- or chloroquine (CQ)-treated cells. (c) The protein level of Rubicon; densitometry analysis of western blot bands from four independent experiments. (d,e) Percentage of SA-β-gal- and BrdU-positive cells. Data are calculated as the percentage of the total cell population. (f) Amount of IL-8, IL-6 and VEGF secreted by cells on consecutive days after doxorubicin treatment. (g) The average number of γH2AX foci per cell. (h) Representative immunofluorescence images of parental cells and escapers stained for γH2AX (green) and Hoechst (blue). Scale bars: 50 μm. Statistics: bars: mean value, error bars: SEM, each point: mean value ± 0.95 confidence interval, n = 4. Statistical significance (in relation to non-treated (NT) or parental cells): ** p < 0.01, *** p < 0.001, between samples: # p < 0.05, ## p < 0.01, ### p < 0.001.