Cryptotanshinone promotes ferroptosis in glioblastoma via KEAP1/NRF2/HMOX1 signaling pathway

Glioblastoma multiforme (GBM) is a common and highly malignant brain tumor characterized by heterogeneity, invasiveness, and resistance to therapy. Inducing ferroptosis in GBM represents a promising therapeutic strategy that inhibits angiogenesis. Natural ingredients in anti-tumor adjuvants are increasingly reported to promote cell death with fewer side effects. Salvia miltiorrhiza Bunge has been widely proven to have significant anti-tumor activity, but its mechanism remains unclear and not deeply understood. This study aimed to investigate the mechanisms by which the compound cryptotanshinone (CTS) induces cell death in glioblastoma (GBM). Our findings revealed that cryptotanshinone, a lipophilic compound, exhibited the most significant anti-tumor activity against GBM. We observed that cryptotanshinone triggered ferroptosis in GBM cells both in vitro and in vivo. RNA sequencing analysis (RNA-seq) revealed that cryptotanshinone led to the upregulation of heme oxygenase 1 (HMOX1), a key protein that facilitates the release of iron ions, which is essential for the induction of ferroptosis. Knocking down HMOX1 could restore ferrous ion levels and Glutathione peroxidase 4 (GPX4) expression to antagonize GBM ferroptosis induced by cryptotanshinone. An in vivo study also showed that cryptotanshinone inhibited GBM growth and upregulated HMOX1 expression without significant side effects. Mechanistically, we found that cryptotanshinone, acting as a protein-protein interaction (PPI) inhibitor of nuclear factor erythroid 2-related factor 2 (NRF2) and Kelch-like ECH-associated protein 1 (KEAP1), promoted the dissociation of NRF2 from KEAP1, enhancing NRF2 nuclear translocation and the transcription of HMOX1. Together, our results revealed that cryptotanshinone is a novel ferroptosis inducer for GBM treatment.