Eriocalyxin B induces ferroptosis through SIRT3 inhibition in triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC), a highly aggressive and heterogeneous breast cancer subtype, remains clinically challenging due to the paucity of actionable therapeutic targets. The unique metabolic landscape of TNBC, characterized by elevated iron and lipid levels, renders it particularly susceptible to ferroptosis, positioning this cell death modality as a promising therapeutic avenue. Eriocalyxin B (Eri B), a natural diterpenoid, exhibits multifaceted anticancer properties that warrant further investigation.

Object

To elucidate the therapeutic mechanism of Eri B-induced ferroptosis in TNBC.

Method

In this study, the anti-proliferative effects of Eri B on TNBC cells were evaluated using cell colony formation assays, three-dimensional tumor sphere formation assays, EdU incorporation assays, and analysis of the proliferation marker Ki-67. The anti-metastatic potential of Eri B was assessed through wound healing assays, transwell migration assays, immunofluorescence staining, and western blot analysis. Furthermore, RNA sequencing (RNA-seq), flow cytometry, transmission electron microscopy, and western blotting demonstrated that Eri B induces ferroptosis in TNBC cells. Molecular docking, surface plasmon resonance (SPR), and cellular thermal shift assays (CETSA) provided evidence of a direct interaction between Eri B and signal transducer and activator of transcription 3 (STAT3). Moreover, the efficacy and underlying mechanism of Eri B were further validated through SIRT3 overexpression experiments and by employing a STAT3 activator, colivelin. In vivo anti-TNBC activity was confirmed using a xenografted tumor model combined with bioluminescence imaging.

Result

For the first time, we demonstrate that Eri B exhibits significant antitumor activity both in vitro and in vivo through the induction of ferroptosis. RNA-seq analysis enabled us to identify and confirm that Eri B induces ferroptosis and oxidative stress by inhibiting sirtuin 3 (SIRT3), which subsequently modulates the nuclear factor erythroid 2-related factor 2 (NRF2)-glutathione peroxidase 4 (GPX4) signaling pathway. Moreover, our findings reveal that Eri B suppresses SIRT3 transcription by directly targeting STAT3, thereby regulating the SIRT3-sterol regulatory element-binding transcription factor 1 (SREBP1)-peroxisome proliferator-activated receptor α (PPARα) -mediated fatty acid metabolism and cellular redox homeostasis.

Conclusion

In summary, our findings suggest that Eri B functions as a novel inducer of ferroptosis in TNBC, demonstrating potential therapeutic value through the inhibition of SIRT3 in TNBC.