Ferroptosis Resistance: Redundant Antioxidant Networks Are a Barrier to Cancer Therapy.

Ferroptosis is an iron-dependent, lipid peroxidation-driven form of regulated cell death that has emerged as a promising strategy for targeting therapy-resistant cancers. However, both intrinsic and acquired resistance to ferroptosis-inducing agents (FINs) limit their clinical efficacy. Here, we propose an integrated framework in which ferroptosis resistance arises from coordinated redox, metabolic, lipid, iron, and transport adaptations that collectively suppress lipid peroxidation and promote tumor survival. Central to this network is the cysteine-glutathione-GPX4 axis, supported by parallel GPX4-independent systems including FSP1-CoQ10, DHODH-CoQ10, GCH1-BH4, and NQO1-NADPH pathways. These antioxidant systems are reinforced by NRF2-driven transcriptional programs, iron sequestration mechanisms, lipid remodeling that reduces polyunsaturated fatty acid availability, and ATP-binding cassette (ABC) transporters that regulate drug and glutathione flux. Tumor heterogeneity further enhances ferroptosis resistance by generating metabolically distinct cellular subpopulations that differ in their susceptibility to lipid peroxidation. We discuss emerging therapeutic strategies designed to overcome these coordinated defense mechanisms, including simultaneous targeting of GPX4 and FSP1, metabolic reprogramming, iron-directed therapies, and nanoparticle-based delivery systems. Collectively, these observations support a systems-level model in which durable ferroptosis-based cancer therapy will require disruption of multiple interconnected resistance mechanisms rather than inhibition of a single molecular target.