Recent studies have indicated that promoting ferroptosis is a promising approach to attenuate drug resistance of
cancer cells. Hence, this study aimed to induce ferroptosis in
osteosarcoma cells, thereby increasing the sensitivity to
cisplatin.
Osteosarcoma cells MG63 and Saos-2 were incubated with increasing doses of
cisplatin to generate
cisplatin-resistant strains, MG63/DDP and Saos-2/DDP.
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry assays were performed to evaluate cell proliferation and cell death, respectively.
Malondialdehyde (MDA),
reactive oxygen species (ROS), and
lipid oxidation in cells were measured to evaluate the degree of cell ferroptosis. MG63/DDP and Saos-2/DDP cells showed increased viability and decreased death rate compared with MG63 and Saos-2 cells, respectively, upon
cisplatin treatment. Western blotting analysis indicated that
protein levels of p-STAT3 (Ser727), nuclear factor erythroid 2-related factor 2 (Nrf2), and
glutathione peroxidase 4 (GPx4) in drug-resistant strains increased significantly in response to
cisplatin. Co-treatment with
cisplatin and agonists of ferroptosis,
Erastin, and RSL3, remarkably increased MDA, ROS,
lipid oxidation, and sensitivity to
cisplatin, in MG63/DDP and Saos-2/DDP cells. Similar results were observed by co-treatment of cells with
cisplatin and a STAT3 inhibitor. The reduction of
protein levels of p-STAT3 (Ser727), Nrf2, and GPx4 in MG63/DDP and Saos-2/DDP cells resulted in increased ferroptosis and sensitivity to
cisplatin. These results indicate that
cisplatin-resistant
osteosarcoma cells inhibited ferroptosis after exposure to low doses of
cisplatin. However, ferroptosis agonists and STAT3 inhibitor reactivated ferroptosis in the cells and consequently increased sensitivity to
cisplatin. This study demonstrates a new approach to attenuate resistance of
osteosarcoma to
cisplatin in vitro .