Fig. 1

Breast Cancer Stem/progenitors are TRAIL-Sensitive: (a) Cell Titre Blue assay performed on 6 cell lines treated for 18 h with 20 ng/ml TRAIL (T) or vehicle control (−). The viability of each line is shown as a percentage of its untreated control. (b) Colony-Forming Assay performed on 6 cell lines seeded at low density in the presence or absence of 20 ng/ml TRAIL for 10 days. The proportion of colonies formed is shown as a percentage of its untreated control. (c) Tumoursphere Assay performed on each cell line in the presence or absence of 20 ng/ml TRAIL. The proportion of tumourspheres for each cell line is shown as a percentage of its untreated control. (d) MCF-7 and MDA-MB-231 cell lines were treated for 18 h in the presence or absence of 20 ng/ml TRAIL, then subjected to tumoursphere Assay performed in the absence of TRAIL. The percentage of tumourspheres is shown relative to the number of cells seeded (e) Tumour Initiation in vivo. MCF-7 cells were pre-treated with 20 ng/ml TRAIL for 18 h then implanted into the mammary fat pad of nude mice at serial dilutions. The number of tumours formed relative to transplants was determined by palpation and confirmed by histological analysis at the end of the experiment. An estimation of the proportion of viable stem cells was performed using L-Calc software however a statistically significant comparison was not possible as control data was inconsistent with the model (f) Flow Cytometry of MCF-7 cells treated with TRAIL for 18 h and stained with fluorescence-conjugated antibodies to CD44 and ALDH. The percentage of marker-positive cells is shown relative to the number of cells analysed (*p < 0.05, paired t-test, error bars = SEM; all graphs represent means of 3 independent experiments)