The Annexin V-APC/7-AAD Apoptosis Kit (Abnova, #KA3808) was used for the apoptosis analysis by flow cytometry. Cells were harvested, counted, and washed in the binding buffer. Cells were then stained with annexin V-APC and 7-ADD, and analyzed by a flow cytometer (BD Biosciences, San Jose, CA) as recommended by the manufacturer. Results were analyzed by the FlowJo software (version 10.1, Ashland, OR). ALDH assays were performed as described previously.21 (link) All experiments were performed in triplicate.