Fig. 3

TP53 wild-type, ER+ breast cancer cells made senescent by chemotherapy are sensitive to tamoxifen. (a) TP53 wild-type, ER+ cells as indicated were plated in triplicate at 80,000 cells per well in a 24-well plate and then treated with 250 nM doxorubicin for 24 h. Seven days later, 1 μM, 5 μM, or 10 μM tamoxifen (Tam) or ethanol vehicle (ETOH) was added as indicated in the figure, with (gray bars) or without (black bars) the pan-caspase inhibitor QVD. MTT assay was performed 24 h later. Proliferating cells were plated similarly but treated with tamoxifen the next day. (b) MCF-7 cells infected using a lentiviral CRISPR Cas9 system with non-targeting (NT) or TP53 guide RNAs were sorted and then plated and treated with 250 nM doxorubicin as in (a). Upper panel: light microscopy images were captured for untreated, proliferating cultures or treated cultures as indicated 8 days following treatment. Scale bar is 100 μm. Lower panels: western blot for p53 (upper) and actin (lower). (c). TP53 mutant, ER+ cell lines as indicated were plated, treated, and MTT assay performed as in (a). Statistical analyses of these data are shown in Additional file 5: Table S3. Data are representative of at least two independent experiments