ABCA3 expression induces resistance to DXR and GO in myeloid cells. (A) MTT assays (Cell Growth Determination kit, Sigma-Aldrich) determining the survival proportions of HEK 293T cells nontransfected and those transfected (using JetPrime) with the plasmids pEGFP-N3 and pEGFP-N3-ABCA3 encoding ABCA3 fused to GFP. (B) MTT assays of HAP1 parental cells and HAP1 cells knocked out for ABCA3 (HAP-ABCA3-KO) using CRISPR-Cas9–induced indels (product ID HZGHC006065c005, Horizon Discovery) upon increasing concentrations of DXR (48-hour incubation). (C) Uptake of DXR in HAP1 parental cells and HAP1-ABCA3-KO cells. The mean fluorescence intensity (MFI) was measured by flow cytometry analysis HAP1 cells after 6-hour exposure to increasing concentrations of DXR. (D) gammaH2AX expression in HAP1 parental cells and HAP1-ABCA3-KO cells exposed to DXR. The primary antiphospho-gammaH2AX antibody (Ser139; Cell Signaling Technology) and secondary anti-rabbit APC-linked antibody (Cell Signaling Technology) was used. (A-D) The mean +/− SEM (n = 3) and P values from Sidak’s multiple analyses are shown (*P < .05; **P < .01; ***P < .001).