Effects of hERG1 blockers on MSC-induced chemoresistance of leukemic cells. (A) The 697 cell line was cultured with or without MSCs and exposed to doxorubicin (0.1 μg/mL) with or without the hERG1 inhibitors WAY (20μM), sertindole (1μM), erythromycin (100μM), and R-roscovitine (20μM). The percentage of annexin V⁺/propidium iodide⁻ cells was evaluated after 48 hours of culture. Values are means ± SD of 3 experiments, each performed in quadruplicate. (B) 697 cells were treated with siRNA hERG1 and siRNA scramble and then cultured with or without MSCs and exposed to doxorubicin (0.1 μg/mL) with or without E4031 (20μM). The percentage of annexin V⁺/propidium iodide⁻ cells was evaluated after 48 hours of culture. Values in all panels are means ± SD of 3 experiments, each carried out in triplicate. Inset, flow cytometric analysis of hERG1 surface expression in 697 cells transfected with siRNA hERG1 (bottom) and transfected with siRNA scramble control (top). (C) Primary leukemic cells (n = 6) were exposed to doxorubicin (0.1 μg/mL) with or without the hERG1 inhibitors E4031 (20μM), WAY (20μM), and erythromycin (100μM). The percentage of annexin V⁺/propidium iodide⁻ cells was evaluated after 48 hours of culture. MFI values of hERG1 are reported in the top right corner of each panel. Values in all panels are means ± SD of triplicate experiments.