RSL3 Mitigates Doxorubicin Resistance in Breast Cancer via Targeted Disruption of Glycolytic Flux

Breast cancer (BC) continues to be a representative malignancy globally, with its inherent heterogeneity and chemotherapy resistance posing significant therapeutic obstacles. Doxorubicin (Dox), a commonly utilized chemotherapeutic agent, is often constrained by dose-dependent toxicities and acquired resistance, which ultimately lead to suboptimal clinical outcomes in numerous BC patients. Co-treatment of Dox with RSL3, a small-molecule compound that inactivates glutathione peroxidase 4 (GPX4), was shown in this study to synergistically inhibit BC cell viability and proliferation at low doses in vitro and in vivo. In vitro tests showed that RSL3 exacerbated Dox-induced cell cycle arrest and apoptosis, markedly potentiating the cytotoxicity of Dox against BC cells. Mechanistically, RSL3 triggered ferroptosis-dependent ROS accumulation, leading to glycolytic impairment characterized by reduced intracellular ATP and pyruvate concentrations levels and downregulation of HKII, PFKP, and PKM2. Supplementation with exogenous sodium pyruvate ameliorated RSL3-induced glycolytic dysfunction, restored the changes in apoptosis-related protein expression caused by RSL3/Dox co-treatment, and reduced RSL3/Dox-induced cell apoptosis. Besides, according to in vivo studies, the combination of RSL3 and Dox further suppressed BC tumor growth without inducing significant adverse effects. On these accounts, RSL3 makes BC cells more sensitive to Dox by inducing glycolytic dysfunction, implying that RSL3/Dox co-treatment could be a viable therapeutic approach for BC patients.