Colony formation assays

The procedure for colony formation assay was carried out as previously described (28, 29). In short, 1×10³ cells were plated into each well in 6-well plates. The next day, the cells were treated with vehicle or Roscovitine (10 μM, Cat# HY-30237, MedChemExpress). After about 16 days of treatment, the cells were fixed with 4% paraformaldehyde for 15 min, stained with (0.5% w/v) crystal violet for 1 h, and then gently rinsed with running water. The cell colonies with more than 50 cells were counted, and the survival curve was generated using linear regression.