MDR1 and TNF are biomarkers of birinapant response in human leukemic cell lines. (A) Whole-cell lysates from human leukemic cell lines were probed with the indicated antibodies, with actin used as the loading control. M# indicates the different membranes. MDR1 activity in KG1 (n = 4) (B), HEL (n = 3) (C), HL60 (n = 5) (D), NB4 (n = 4) (E), MOLM13 (n = 4) (F), MV4-11 (n = 3) (G), U937 (n = 2; error bars SD) (H), OCI-AML3 (n = 3) (I), THP1 (n = 3) (J), and OCI-AML2 (n = 2; error bars SD) (K) cells were investigated by Rho-123–retention assay, and cell viability was measured by flow cytometry analysis of PI and AxV exclusion after the cells were treated with Bir (0.016, 0.08, 0.4, 2, and 10 μM), with or without Tari (1 μM) and TNF (10 ng/mL), for 48 hours. Data are the mean ± SEM throughout, unless otherwise stated. P values were obtained by comparison of Bir alone and Bir/Tari treatment (red) or Bir/TNF and Bir/TNF/Tari treatment (purple) at the indicated concentrations and were determined by multiple t tests using the Holm-Sidak method. *P < .05; **P < .01; ***P < .001.