Realgar Transforming Solution Triggers Ferroptosis-Associated Death in NB4 Leukemia Cells through Disruption of Iron Homeostasis and Suppression of the SLC7A11/GPX4 Axis.

Realgar (As4S4) has long been used in traditional medicine, yet its clinical application remains limited due to poor bioavailability and toxicity. Realgar transforming solution (RTS), a bioleached product generated through microbial transformation of realgar, exhibits enhanced anti-tumor activity; however, its underlying mechanism remains unclear. This study investigated whether ferroptosis contributes to the anti-leukemic effects of RTS in NB4 cells, focusing on iron homeostasis and the solute carrier family 7 member 11 (SLC7A11)/glutathione peroxidase 4 (GPX4) antioxidant axis. NB4 cells were treated with RTS, arsenic trioxide (ATO), or realgar, and cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Transcriptomic profiling, biochemical assays, fluorescence probes, flow cytometry, and Western blotting were employed to evaluate ferroptosis-related changes. RTS inhibited NB4 cell viability more effectively than ATO or realgar at comparable arsenic concentrations. Transcriptomic analysis indicated significant enrichment of ferroptosis-related pathways. RTS decreased glutathione and superoxide dismutase levels, increased malondialdehyde accumulation and lipid peroxidation, disrupted mitochondrial membrane potential, and elevated intracellular total iron and mitochondrial Fe2+ levels. Additionally, RTS downregulated SLC7A11 and GPX4 and altered the expression of iron metabolism-related proteins, including transferrin receptor protein 1, nuclear receptor coactivator 4, ferritin heavy chain 1, ferroportin 1, iron-responsive element-binding protein 2, and heme oxygenase 1. Moreover, ferrostatin-1 and deferoxamine mesylate partially rescued RTS-induced cytotoxicity and alleviated oxidative damage and iron overload. These results indicate that RTS induces ferroptosis-associated cell death in NB4 cells by disrupting iron homeostasis and inhibiting the SLC7A11/GPX4 axis, supporting further investigation of RTS as a modernized arsenic-based anti-leukemic formulation.