Sensitivity of ENKTL cell lines to the MCL-1 inhibitor S63845 increases upon IL-2 withdrawal or treatment with the BCL-XL inhibitor A-1331852. SNK6 (A), SNT15 (B), and MEC04 (C) cells were cultured in medium lacking IL-2 for 48 hours and were then treated with either 0.5 µM or 5 µM of the indicated BH3-mimetic drugs. Cell viability was determined by flow cytometry after staining with annexin V plus PI and data were normalized to DMSO-treated controls or DMSO-treated IL-2 deprived cells as appropriate. (D) Cell viability was determined after treatment with the BCL-XL inhibitor A-1331852 alone or in combination with either the BCL-2 inhibitor ABT-199 or the MCL-1 inhibitor S63845. Cell viability was determined by flow cytometry after staining with annexin V plus PI and data were normalized to DMSO-treated control cells. All compounds were used at a final concentration of 5 µM. Data in panels A and B are presented as means ± SD of 3 independent experiments, each performed in triplicates (n = 3). Significance was determined by the unpaired Student t test and corrected for multiple comparisons using the Holm-Sidak method. *P < .05; **P < .001.