Defects in TP-53 function impair the induction of apoptosis in cancer cells by venetoclax. (A) BAX/BAK double-deficient RS4;11 cells, that are unable to undergo apoptosis, were treated with increasing doses (0-10 μM) of the DNA-damaging drugs cisplatin or fludarabine, or venetoclax (VEN) and γH2AX staining (an indicator of DNA damage) was examined by flow cytometry after 24 hours. Note that cisplatin and fludarabine, but not venetoclax, induced DNA damage, even in the absence of apoptotic cell death. Data are representative of ≥3 independent experiments. (B) WT or TP53 KO clones of MOLM-13 cells were treated with IC₂₀ doses of venetoclax or DMSO (vehicle control) for 3 days. Mitochondrial metabolism was examined by using the Seahorse Mito Stress Test Kit. Error bars indicate SD of 8 replicate samples. (C) Activation of BAX (detected by antibody 1E5) or BAK (detected by antibody G317-2), both early events in apoptosis signaling (x-axes), and loss of cytochrome c (a later event; y-axes) in TP53 WT or TP53 KO RS4;11 cells were determined by flow cytometry 6 hours after treatment with IC₅₀ doses of venetoclax. Data are representative of ≥3 independent experiments.