Fig. 5
Measurement of ALDH1 activity and its role in tumorigenicity and resistance. a Percentage of parental and resistant cells with ALDH1 activity as determined by flow cytometry. The SKBR3 cell line represents a positive control in the Aldefluor assay. Data are presented as the mean ± SEM of three independent experiments. *resistant p < 0.05 vs. parental; **resistant p < 0.01 vs. parental (two-tailed Student’s t tests). b Percentage of viable ALDH1high and ALDH1low FACS-sorted BEZ235-resistant cells after 72 h of 0.3 μM of BEZ235 treatment. The results represent the mean ± SEM. **p < 0.01; ***p < 0.001, one-way ANOVA. c Resistant LMS cells were sorted by FACS based on ALDH1 activity and the positive and negative subpopulations of sorted cells were submitted to in vitro and in vivo tumorsphere assays. Representative images of cell sorting by FACS and phase contrast microscopy of tumorspheres formed by resIB136 cells after 15 days of culture in nonadherent conditions in vitro. Scale bars, 150 μM. d Number of tumorspheres formed after 15 days in ALDH1high and ALDH1low subpopulation. e Number of tumorspheres formed after 15 days by cells dissociated from tumorspheres. The results represent the mean ± SEM. **p < 0.01; ***p < 0.001, one-way ANOVA