Polyamines — small, positively charged metabolites long studied for roles in cell growth and translation — directly chelate labile intracellular iron and thereby suppress ferroptosis, the iron-dependent form of regulated cell death, according to a study published August 14 in Cell. The finding repositions a class of abundant endogenous molecules as constitutive guardians of cellular redox homeostasis, with potential implications for cancer therapy and neurodegeneration research.
The work was led by Whitehead Institute and MIT researchers Pushkal Sharma, Whitney Henry, and Ankur Jain, with contributors from Koch Institute, Institut Curie, Broad Institute, and MIT's Department of Biology. The work identifies a non-enzymatic protective mechanism operating in parallel to the well-characterized glutathione peroxidase 4 (GPX4) pathway. Prior models of ferroptosis resistance have centered on enzymatic lipid repair; this study proposes that polyamines — principally spermine and spermidine — provide a chemical buffering layer by sequestering the labile iron pool (LIP), the redox-active Fe²⁺ fraction that drives Fenton chemistry and lipid peroxide generation.
Genome-wide screen connects polyamine depletion to ferroptosis sensitivity
The researchers conducted a genome-wide CRISPR knockout screen to identify synthetic lethal interactions with GPX4 loss. Polyamine depletion emerged as a top hit: cells lacking polyamine biosynthetic capacity were dramatically sensitized to ferroptosis when GPX4 was also inhibited. To investigate the mechanism, the team developed a genetically encoded fluorescent reporter for redox-active iron, enabling real-time, single-cell visualization of the LIP — a technical advance the paper presents as a significant methodological contribution alongside the biological findings.
Live-cell imaging with this reporter revealed a striking inverse correlation between intracellular polyamine levels and labile Fe²⁺ at single-cell resolution. Biochemical assays confirmed that spermine and spermidine directly coordinate Fe²⁺ through their multiple protonatable amine nitrogen atoms, forming stable chelate complexes analogous in principle to clinical iron chelators such as trientine. When polyamines were depleted, the LIP expanded; cells partially compensated by upregulating ferritin, the iron storage protein, but the paper reports this secondary response was insufficient to fully buffer the excess reactive iron.
Mechanistic and therapeutic implications
The study draws a direct line from polyamine abundance to ferroptosis susceptibility: high polyamine levels sequester Fe²⁺, reducing its availability to catalyze lipid peroxidation; depletion expands the LIP and, in the absence of GPX4 activity, produces synthetic lethality. The authors note this framework provides a mechanistic rationale for the ferroptosis-sensitizing effects of difluoromethylornithine (DFMO, eflornithine), an ornithine decarboxylase inhibitor already FDA-approved for neuroblastoma, suggesting that its clinical activity may partly reflect iron dyshomeostasis rather than effects on proliferation alone.