Person:

Clemons, Paul

Ferroptosis, an iron-dependent, non-apoptotic cell death program, is involved in various degenerative diseases and represents a targetable vulnerability in certain cancers1. The ferroptosis-susceptible cell state can either preexist in cells arising from certain lineages or be acquired during cell-state transitions2–5. Precisely how ferroptosis susceptibility is dynamically regulated remains poorly understood. Using genome-wide CRISPR/Cas9 suppressor screens, we identify the peroxisome organelle as a critical contributor to ferroptosis sensitivity in human renal and ovarian carcinoma cells. By lipidomic profiling, we show that peroxisomes contribute to ferroptosis through the synthesis of polyunsaturated ether phospholipids (PUFA-ePLs), an understudied lipid class that provides substrates for lipid peroxidation, resulting in turn in induction of ferroptosis. Moreover, carcinoma cells that are initially sensitive to ferroptosis can switch to a ferroptosis-resistant state in vivo, a state associated with extensive PUFA-ePL downregulation. We further find that the pro-ferroptotic role of PUFA-ePLs can be extended beyond neoplastic cells to other cell types, including normal neurons and cardiomyocytes. Together, our work reveals important roles for the peroxisome–ether phospholipid axis in driving ferroptosis susceptibility and evasion, highlights PUFA-ePL as a distinct functional lipid group that is dynamically regulated during cell-state transitions, and suggests multiple regulatory nodes for therapeutic interventions in diseases involving ferroptosis.

We recently described glutathione peroxidase 4 (GPX4) as a promising target for killing therapy-resistant cancer cells via ferroptosis. The onset of therapy resistance by multiple types of treatment results in a stable cell state marked by high levels of polyunsaturated lipids and an acquired dependency on GPX4. Unfortunately, all existing inhibitors of GPX4 act covalently via a reactive alkyl chloride moiety that confers poor selectivity and pharmacokinetic properties. Here, we report our discovery that masked nitrile-oxide electrophiles, which have not been explored previously as covalent cellular probes, undergo remarkable chemical transformations in cells and provide an effective strategy for selective targeting of GPX4. The new GPX4-inhibiting compounds we describe exhibit unexpected proteome-wide selectivity and, in some instances, vastly improved physiochemical and pharmacokinetic properties compared to existing chloroacetamide-based GPX4 inhibitors. These features make them superior tool compounds for biological interrogation of ferroptosis and constitute starting points for development of improved inhibitors of GPX4.