Colony formation experiments were carried out by plating ~100 cells per well into 6-well dishes. Following a 10-day incubation at 37°C, the number of colonies (> 50 cells) was scored using standard methods [23 (link)]. Cell proliferation was gauged by the 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 5-Ethynyl-2ʹ-Deoxyuridine (EdU) assays using the MTT Cell Proliferation Assay Kit (Biovision, Wehrheim, Germany) and Cell-Light EdU Apollo488 In Vitro Kit (Ribobio), respectively, as per the accompanying protocols and standard methods [24 (link),25 (link)]. Cell apoptosis was determined using the Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) Apoptosis Kit (BD Biosciences, Cowley, UK) as described elsewhere [12 (link)].