Fig. 1.

H₂S-releasing doxorubicin is effective against resistant osteosarcoma cells. a Expression of ABCB1/Pgp in human doxorubicin-sensitive U-2OS cells and Saos-2 cells, and their doxorubicin-resistant variants (DX30, DX100, DX580) by immunoblotting. The β-tubulin expression was used as control of equal protein loading. The figure is representative of one out of four experiments. b, c Intracellular doxorubicin accumulation, measured after a 6 h incubation with 5 µM doxorubicin (dox) or H₂S-releasing doxorubicin (Sdox), by a fluorimetric assay in duplicates. Data are mean ± SD (n = 6 independent experiments). *p < 0.05 for DX cells vs. parental U-2OS or Saos-2 cells; °p < 0.001 for Sdox vs. dox. d, e Extracellular release of LDH measured spectrophotometrically in triplicates, in cells grown 24 h in drug-free medium (ctrl) or in medium containing 5 µM doxorubicin (dox) or H₂S-releasing doxorubicin (Sdox). Data are mean ± SD (n = 6 independent experiments). *p < 0.001 for treated vs. untreated cells; °p < 0.001 for Sdox vs. dox