Fig. 4: Overexpression of ABCC1 promotes resistance to BCL-2 inhibitors by reducing intracellular drug concentrations.

A RT-qPCR analysis of ABCC1 mRNA expression in HL-60 wild-type (WT) and ABCC1-overexpressing (OE) cells. Fold change of ABCC1 expression in ABCC1-OE cells compared to WT. Data are presented as mean values. Significance was determined with an unpaired Student’s t test with two-tailed P value as indicated. n = 3 technical replicates, n = 1 experimental replicate. B Representative flow cytometric measurement of intracellular ABCC1 levels in HL-60 WT and ABCC1-OE cells. The corresponding gating strategy is depicted in Supplementary Fig. 6C. C Heatmap of GI₅₀ values [nM] of 5-day viability assays with indicated drugs in HL-60 WT and ABCC1-OE cells. n = 3 experimental replicates. D RT-qPCR analysis of ABCC1 mRNA expression of MOLM-13-Cas9 AAVS1.1 and ABCC1-KO-2 clones, transduced with either empty vector (e.V.) or an ABCC1-overexpressing (OE) construct. Levels were normalized to ACTB levels and to the expression of MOLM-13-Cas9 AAVS1.1 e.V. Data are presented as mean values. Significance was determined with an unpaired Student’s t test with two-tailed P value as indicated. n = 2 technical replicates, n = 1 experimental replicate. E Dose–response curves of AZD-4320 in MOLM-13-Cas9 AAVS1.1 or ABCC1-KO-2 clones transduced with either empty vector (e.V.) or an ABCC1-OE construct after 5 days of treatment. Data are presented as mean values ± SD. n = 3 experimental replicates. F Intracellular concentrations of AZD-4320 in HL-60 WT and ABCC1-OE cells determined using LC-MS/MS. The normalized peak area represents the relative compound concentration in the samples. Combined results of hydrophilic interaction liquid chromatography (HILIC) and reversed phase chromatography (RP) are depicted. Boxes represent interquartile ranges, horizontal lines represent the mean, whiskers indicate lower and upper limits. Significance was determined with an unpaired Student’s t test with two-tailed P value as indicated. n = 2 experimental replicates. G Median fluorescence intensity (MFI) of Calcein in HL-60 WT and ABCC1-OE cells treated either with DMSO or Reversan [10 µM] for 45 h. The corresponding flow cytometric gating strategy is depicted in Supplementary Fig. 6D. Data are presented as mean values ± SD. Significance was determined with an unpaired Student’s t test with two-tailed P value as indicated. n = 3 experimental replicates. H Median fluorescence intensity (MFI) of Calcein normalized to DMSO in HL-60 WT and ABCC1-OE cells treated with DMSO, Venetoclax or AZD-4320 at indicated concentrations for 45 h. Data are presented as mean values ± SD. Significance compared to DMSO was determined with an unpaired Student’s t test with two-tailed P value as indicated. n = 3 experimental replicates. The corresponding flow cytometric gating strategy is depicted in Supplementary Fig. 6D. A, C–H Source data are provided as a Source Data file.