101 Scientists have discovered a new way to target and kill cancer cells by activating iron stored in a part of the cell called the lysosome, offering hope for treating some of the most drug-resistant and aggressive tumours. In a major study published in Nature, researchers led by Raphaël Rodriguez at Institut Curie in Paris identified how a specialised process called ferroptosis can be precisely triggered within cancer cells. Unlike other forms of cell death, ferroptosis is driven by the oxidation of lipids, or fats, in cell membranes – especially when iron is involved. Until now, the exact role of iron in this process, and where it acts within cells, remained unclear. The team found that ferroptosis begins in lysosomes, cellular compartments responsible for breaking down waste. By using a modified version of an existing compound, Liproxstatin-1, they showed that the molecule could protect cells from ferroptosis by binding to iron in lysosomes. The same research revealed that when a different compound, RSL3, was used to block cellular defences, it triggered the oxidation of lysosomal membranes and began the ferroptosis process. Building on these findings, the researchers designed a new drug called fentomycin-1. This small molecule was engineered to enter cells, move into lysosomes, and activate the iron stored there. The result was a controlled destruction of cancer cell membranes. Fentomycin-1 proved particularly effective against cancers known for drug resistance and relapse, including pancreatic ductal adenocarcinoma and sarcomas. These cancers often have a high expression of a protein called CD44, which also correlates with high iron content and increased vulnerability to ferroptosis. In lab experiments, fentomycin-1 was able to kill cancer cells that had survived chemotherapy, known as drug-tolerant persisters. These persisters typically adopt a mesenchymal state – one that makes them more invasive and therapy-resistant—but this also makes them rich in iron and thus more susceptible to the effects of fentomycin-1. Animal tests provided further evidence. In a mouse model of breast cancer that had spread to lymph nodes, fentomycin-1 significantly slowed tumour growth and extended survival without harming normal tissues. The drug specifically reduced the population of CD44high cells, the very cells responsible for metastasis and relapse. What sets this research apart is its focus on subcellular precision. By pinpointing lysosomes as the launch site of ferroptosis and harnessing the unique chemistry of iron within them, the team has opened a new path for targeted cancer therapy. Their work also suggests that lysosomal iron, long considered a passive metal pool, is in fact a critical switch for initiating cell death. As drug resistance continues to hinder cancer treatment globally, these findings offer a blueprint for developing more effective, selective therapies that strike at the heart of tumour survival strategies.