Survival of cancer cells following taxol-induced apoptosis is supported by ZEB1-mediated ferroptosis sensitivity

Chemotherapy remains the mainstay treatment of many solid cancers; however, resistance and recurrence compromise patient outcomes. We investigated chemotherapy resistance mechanisms in Triple Negative Breast Cancer (TNBC) by examining cells that survive chemotherapy-induced apoptotic caspase activation. Using a biosensor that permanently labels cells surviving executioner caspase activation with GFP, we identified a GFP+ population that survives transient paclitaxel treatment. These GFP+ cells display a stem-like invasive phenotype, altered mitochondrial metabolism, and increased drug resistance. Metabolomics profiling identified defects in TCA cycle metabolites and accumulation of polyunsaturated fatty acids (PUFAs). Mechanistically, surviving GFP+ cells exhibited Epithelial to Mesenchymal Transition (EMT) and ZEB1-regulated repression of GPX4 expression, resulting in increased sensitivity to ferroptotic cell death. Consistent with this, transforming growth factor- beta induced EMT also suppressed GPX4 and increased ferroptosis sensitivity in Normal Mouse Mammary epithelial cells. ZEB1 knockdown strongly reduced the GFP+ surviving fraction, identifying ZEB1 as a key regulator of apoptotic survival. Supplementation with arachidonic acid restored survival in ZEB1 knockdown cells, while the ferroptosis-protective drug, Ferrostatin-1, prevented the accumulation of GFP+ survivors, demonstrating that ferroptosis sensitivity is required for the survival of TNBC cells from chemotherapy-induced apoptosis. Together, these findings reveal a previously unrecognized link between ferroptosis and apoptosis and identify potential biomarkers and therapeutic vulnerabilities in a subset of chemotherapy-resistant TNBC.