Polysaccharides from Huaier induce autophagy-dependent ferroptosis to inhibit breast cancer stem cells in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive subtype with poor prognosis and limited treatment options, largely due to the presence of breast cancer stem cells (BCSCs) that contribute to chemotherapy resistance, metastasis, and relapse. In this study, we investigated the therapeutic potential of polysaccharides from Huaier (PS-T) in targeting BCSCs via a novel mechanism involving autophagy-dependent ferroptosis. We first identified a 17-gene stemness signature from TCGA data of 167 TNBC patients, which correlated with poor prognosis. Using this signature, we developed a prognostic model that demonstrated strong predictive power for TNBC survival. In vitro, PS-T treatment significantly reduced the stemness markers POU5F1, SOX2, and NANOG, and decreased the ALDH(+) and CD44highCD24low BCSC populations in a dose-dependent manner. PS-T also suppressed colony formation and mammosphere growth in ALDH(+) TNBC cells. Ferroptosis induction was confirmed by increased intracellular reactive oxygen species (ROS) and lipid peroxidation, with these effects reversed by ferroptosis inhibitors. Mechanistically, PS-T downregulated GPX4, a key regulator of ferroptosis, through an autophagy-dependent pathway. This process was further enhanced by PS-T-induced upregulation of acid sphingomyelinase (ASM), which facilitated autophagic degradation of GPX4. In vivo, PS-T treatment significantly reduced tumor formation from ALDH(+) TNBC cells. Overall, our findings suggest that PS-T inhibits BCSC stemness and promotes ferroptosis, providing a promising therapeutic strategy for improving the prognosis of TNBC patients.