Altretamine induces ferroptosis in small cell lung cancer by promoting epigenetic silencing and lysosomal degradation of GPX4

Methods

Altretamine-triggered cytotoxicity and lipid peroxidation were determined by EdU, FerroOrange probes, etc. GPX4 promoter methylation was evaluated by Methylation-specific PCR, chromatin immunoprecipitation, etc. Altretamine-induced GPX4 degradation was examined by bio-layer interferometry, immunoprecipitation, etc.

Results: Altretamine mainly initiates ferroptosis in SCLC cells, accompanied by accumulation of intracellular ROS and lipid peroxidation. Mechanistically, altretamine facilitated the binding of DNMT3A to GPX4 promoter, leading to DNA methylation of GPX4 gene and subsequent transcriptional repression. Moreover, altretamine directly bound to GPX4 protein and accelerated the lysosomal degradation of GPX4 protein in a HSC70-dependent manner.

Inhibition of DNA demethylation by inactivating Ten-eleven translocation (TET) proteins synergistically strengthened the anti-SCLC activity of altretamine.Conclusions: Our findings revealed the first time that altretamine induced ferroptotic cell death by promoting DNMT3A-mediated epigenetic silencing of GPX4 gene and HSC70-mediated lysosomal degradation of GPX4 protein in SCLC cells. Altretamine alone or in combination with TET inhibitors is a valuable and credible strategy for the clinical treatment of SCLC.