A continuous ferroptosis-to-apoptosis landscape identifies ferroptosis biomarkers and repressors for cancer therapy

Ferroptosis, a cell death pathway driven by lipid peroxidation, is implicated in several human diseases including cancer. Although ferroptosis is entwined with apoptosis, it currently has no characteristic biomarkers or gene signature. In this project we established a continuous phenotypic gradient between ferroptosis and apoptosis and coupled it to transcriptomic and metabolomic landscapes. Omics and mechanistic studies revealed that ferroptosis was associated with enhanced MITF activity, lysosomal function, glutaminolysis, TCA cycle, and activation of ATF4, while its transition into apoptosis was attributed to enhanced ER-stress, ATF4/CHOP switch and PE/PC metabolic shift. The gradual ferroptosis-to-apoptosis transcriptomic landscape was used to generate a unique, unbiased transcriptomic predictor, the Gradient Gene Set (GGS), which classified ferroptosis and apoptosis with high accuracy. Further GGS optimization and datasets analysis of various ferroptotic and apoptotic responses revealed highly specific ferroptosis biomarkers, which were robustly validated in vitro and in vivo. A subset of the GGS was correlated with poor prognosis in breast cancer patients and in PDX models and was found to consist of different ferroptosis repressors, including PDAP1, whose knockdown suppressed breast tumor growth in a mouse model. Collectively, this study highlights molecular switches between ferroptosis and apoptosis, uncovering a highly prognostic predictive ferroptosis gene signature, pointing to a few ferroptosis repressors for targeted breast cancer therapy.