*2.11. Apoptosis and Cell Proliferation Assays*

To perform Annexin V and propidium iodide (PI) staining, irradiated MCF-7 cells and mammospheres were trypsinized, washed with 1× PBS, centrifuged and stained with the Annexin V-FITC antibody (20 min, room temperature) and PI (0.02 mg/mL; Sigma, P4170). The percentage of apoptotic cells was evaluated using the *FACSCanto*™ flow cytometer (BD). A total of 1 <sup>×</sup> <sup>10</sup><sup>4</sup> cells were recorded per condition in three independent experiments. In the cell proliferation assay, irradiated MCF-7 cells and mammospheres were trypsinized, washed with 1× PBS, centrifuged and stained with Ki67. The stained cells were analyzed using the *FACSCanto*™ flow cytometer (BD).

#### *2.12. shRNA-Mediated Knockdown*

To generate knockdown cell lines, MCF-7 cells were stably transduced in the presence of polybrene (5 µg/mL) with Nrf2 (sc-37030-V), shRNA lentiviruses and control scrambled shRNA particles-A (sc-108080) obtained from Santa Cruz Biotechnology, USA. Transduced cells were then selected with puromycin (2 µg/mL) for up to 4 weeks.
