Cell cycle analysis was carried out as previously described. Briefly, cells were seeded into 6well plates and grown for 24 hours. Drugs were then added, and cells were incubated for additional 48 hours. DMSO at appropriate concentrations was added to control wells. After incubation, floating and adherent cells were collected and concentrated by centrifugation. The cell pellet was fixed with 70% ice-cold ethanol, rinsed twice in PBS, and stained with 30 µg/mL of propidium iodide (PI). DNA content was measured using the Attune NxT flow cytometer (Thermo Fisher Scientific) at Ex. 488 nm/Em. 550-630 nm. Results were analyzed using FlowJo software (BD, Ashland, OR). The dose-response curves were constructed by plotting the ratios of cells in G2/M phases to the total number of cells and fitting the data to a cooperative Hill's binding equation to determine the IC50 value: