Missense ‘hotspot’ mutations localized in six p53 codons account for 20% of TP53 mutations in human cancers. Hotspot p53 mutants have lost the tumor suppressive functions of the wildtype protein, but whether and how they may gain additional functions promoting tumorigenesis remain controversial. Here, we generated Trp53 Y217C , a mouse model of the human hotspot mutant TP53 Y220C . DNA damage responses were lost in Trp53 Y217C/Y217C ( Trp53 YC/YC ) cells, and Trp53 YC/YC fibroblasts exhibited increased chromosome instability compared to Trp53 -/- cells. Furthermore, Trp53 YC/YC male mice died earlier than Trp53 -/- males, with more aggressive thymic lymphomas. This correlated with an increased expression of inflammation-related genes in Trp53 YC/YC thymic cells compared to Trp53 -/- cells. Surprisingly, we recovered only one Trp53 YC/YC female for 22 Trp53 YC/YC males at weaning, a skewed distribution explained by a high frequency of Trp53 YC/YC female embryos with exencephaly and the death of most Trp53 YC/YC female neonates. Strikingly, however, when we treated pregnant females with the anti-inflammatory drug supformin (LCC-12), we observed a fivefold increase in the proportion of viable Trp53 YC/YC weaned females in their progeny. Together, these data suggest that the p53 Y217C mutation not only abrogates wildtype p53 functions but also promotes inflammation, with oncogenic effects in males and teratogenic effects in females.

Ferroptosis has emerged as an actionable target to eliminate therapy-resistant and metastatic cancers1. However, which ferroptosis surveillance systems may offer a therapeutic window to leverage redox maladaptation in cancer remains unclear. In melanoma, glutathione peroxidase 4 (GPX4) impedes ferroptosis during haematogenous metastasis, but is dispensable during lymphatic metastasis2. Here, using a metastatic mouse melanoma model selected for lymph node metastasis, we show that lymph-node-derived metastatic cells exhibit markedly diminished expression of glutamate-cysteine ligase (GCLC) and reduced glutathione (GSH) levels relative to their parental counterparts. This metabolic shift occurs within the hypoxic lymphatic niche. Under comparable low-oxygen conditions, GPX4 undergoes ubiquitination and proteasomal degradation. In response, lymph node metastatic cells acquire increased reliance on ferroptosis suppressor protein 1 (FSP1), which is localized with perinuclear lysosomes. These findings reveal that the reduced reliance on the GPX4 axis enables melanoma cells to shift toward FSP1 dependency. Notably, intratumoural monotherapy with selective FSP1 inhibitors (viFSP1 and FSEN1) effectively suppresses melanoma growth in lymph nodes, but not in subcutaneous tumours, emphasizing a microenvironment-specific dependency on FSP1. Thus, targeting FSP1 in the lymph nodes holds strong potential for blocking melanoma progression.

Rationale: Mantle-cell lymphoma (MCL) remains an aggressive and incurable cancer. Accumulating evidence reveals that abnormal iron metabolism plays an important role in tumorigenesis and in cancer progression of many tumors. Based on these data, we searched to identify alterations of iron homeostasis in MCL that could be exploited to develop novel therapeutic strategies. Methods: Analysis of the iron metabolism gene expression profile of a cohort of patients with MCL enables the identification of patients with a poor outcome who might benefit from an iron homeostasis-targeted therapy. We analyzed the therapeutic interest of ironomycin, known to sequester iron in the lysosome and to induce ferroptosis. Results: In a panel of MCL cell lines, ironomycin inhibited MCL cell growth at nanomolar concentrations compared with conventional iron chelators. Ironomycin treatment resulted in ferroptosis induction and decreased cell proliferation rate, with a reduced percentage of cells in S-phase together with Ki67 and Cyclin D1 downregulation. Ironomycin treatment induced DNA damage response, accumulation of DNA double-strand breaks, and activated the Unfolded Protein Response (UPR). We validated the therapeutic interest of ironomycin in primary MCL cells of patients. Ironomycin demonstrated a significant higher toxicity in MCL cells compared to normal cells from the microenvironment. We tested the therapeutic interest of combining ironomycin with conventional treatments used in MCL. We identified a synergistic effect when ironomycin is combined with Ibrutinib, Bruton's tyrosine kinase (BTK) inhibitor, associated with a strong inhibition of B-Cell receptor (BCR) signaling. Conclusion: Altogether, these data underline that MCL patients my benefit from targeting iron homeostasis using ironomycin alone or in combination with conventional MCL treatments.

Iron sustains cancer cell plasticity, yet it also sensitizes the mesenchymal, drug-tolerant phenotype to ferroptosis. This posits that iron compartmentalization must be tightly regulated. However, the molecular machinery governing organelle Fe(II) compartmentalization remains elusive. Here, we show that BDH2 is a key effector of inter-organelle Fe(II) redistribution and ferroptosis vulnerability during melanoma transition from a melanocytic (MEL) to a mesenchymal-like (MES) phenotype. In MEL cells, BDH2 localizes at the mitochondria–lysosome contacts (MLCs) to generate the siderophore 2,5-dihydroxybenzoic acid (2,5-DHBA), which ferries iron into the mitochondria. Fe(II) transfer by BDH2 supports mitochondrial bioenergetics, which is required to maintain lysosomal acidification and MLC formation. Loss of BDH2 alters lysosomal pH and MLC tethering dynamics, causing lysosomal iron sequestration, which primes MES cells for ferroptosis. Rescuing BDH2 expression, or supplementing 2,5-DHBA, rectifies lysosomal pH and MLCs, protecting MES cells from ferroptosis and enhancing their ability to metastasize. Thus, we unveil a BDH2-dependent mechanism that orchestrates inter-organelle Fe(II) transfer, linking metabolic regulation of lysosomal pH to the ferroptosis vulnerability of the mesenchymal, drug-tolerant cancer cells. Rizzollo et al. show that BDH2 participates in iron distribution between cellular compartments, which sets the threshold for the ferroptosis vulnerability of the melanoma cell phenotypes, ultimately affecting their metastatic capacity

The discovery that the ageing of lung stem cells drives iron insufficiency and reduces the capacity of the cells to form tumours has potential implications for the treatment of cancer and for regenerative medicine. Ageing of lung stem cells drives iron insufficiency.

Whereas genetic mutations can alter cell properties, nongenetic mechanisms can drive rapid and reversible adaptations to changes in their physical environment, a phenomenon termed 'cell-state transition'. Metals, in particular copper and iron, have been shown to be rate-limiting catalysts of cell-state transitions controlling key chemical reactions in mitochondria and the cell nucleus, which govern metabolic and epigenetic changes underlying the acquisition of distinct cell phenotypes. Acquisition of a distinct cell identity, independently of genetic alterations, is an underlying phenomenon of various biological processes, including development, inflammation, erythropoiesis, aging, and cancer. Here, mechanisms that have been uncovered related to the role of these metals in the regulation of cell plasticity are described, illustrating how copper and iron can be exploited for therapeutic intervention.

This symposium is the 6th Paris Sciences & Lettres (PSL) Chemical Biology meeting (2015, 2016, 2019, 2023, 2024, 2025) being held at Institut Curie. This initiative originally started in 2013 at Institut de Chimie des Substances Naturelles (ICSN) in Gif-sur-Yvette and was mostly focused on organic synthesis. It was then exported at Institut Curie to cover a larger scope, before becoming the official French Chemical Biology meeting. This year, around 200 participants had the opportunity to meet world leaders in chemistry and biology who described their latest innovations and future trends covering topics as diverse as prebiotic chemistry, activity-based protein profiling, high-resolution cell imaging, nanotechnologies, bio-orthogonal chemistry, metal ion signaling, ferroptosis, and biocatalysis.

Complex multicellular organisms are composed of distinct tissues involving specialized cells that can perform specific functions, making such life forms possible. Species are defined by their genomes, and differences between individuals within a given species directly result from variations in their genetic codes. While genetic alterations can give rise to disease-causing acquisitions of distinct cell identities, it is now well-established that biochemical imbalances within a cell can also lead to cellular dysfunction and diseases. Specifically, nongenetic chemical events orchestrate cell metabolism and transcriptional programs that govern functional cell identity. Thus, imbalances in cell signaling, which broadly defines the conversion of extracellular signals into intracellular biochemical changes, can also contribute to the acquisition of diseased cell states. Metal ions exhibit unique chemical properties that can be exploited by the cell. For instance, metal ions maintain the ionic balance within the cell, coordinate amino acid residues or nucleobases altering folding and function of biomolecules, or directly catalyze specific chemical reactions. Thus, metals are essential cell signaling effectors in normal physiology and disease. Deciphering metal ion signaling is a challenging endeavor that can illuminate pathways to be targeted for therapeutic intervention. Here, we review key cellular processes where metal ions play essential roles and describe how targeting metal ion signaling pathways has been instrumental to dissecting the biochemistry of the cell and how this has led to the development of effective therapeutic strategies.

Iron catalyses the oxidation of lipids in biological membranes and promotes a form of cell death called ferroptosis1. Defining where this chemistry occurs in the cell can inform the design of drugs capable of inducing or inhibiting ferroptosis in various disease-relevant settings. Genetic approaches have revealed suppressors of ferroptosis2-4; by contrast, small molecules can provide spatiotemporal control of the chemistry at work5. Here we show that the ferroptosis inhibitor liproxstatin-1 exerts cytoprotective effects by inactivating iron in lysosomes. We also show that the ferroptosis inducer RSL3 initiates membrane lipid oxidation in lysosomes. We designed a small-molecule activator of lysosomal iron-fentomycin-1-to induce the oxidative degradation of phospholipids and ultimately ferroptosis. Fentomycin-1 is able to kill iron-rich CD44high primary sarcoma and pancreatic ductal adenocarcinoma cells, which can promote metastasis and fuel drug tolerance. In such cells, iron regulates cell adaptation6,7 while conferring vulnerability to ferroptosis8,9. Sarcoma cells exposed to sublethal doses of fentomycin-1 acquire a ferroptosis-resistant cell state characterized by the downregulation of mesenchymal markers and the activation of a membrane-damage response. This phospholipid degrader can eradicate drug-tolerant persister cancer cells in vitro and reduces intranodal tumour growth in a mouse model of breast cancer metastasis. Together, these results show that control of iron reactivity confers therapeutic benefits, establish lysosomal iron as a druggable target and highlight the value of targeting cell states10.

Iron sustains cancer cell phenotypic and metabolic plasticity, yet it also sensitizes the mesenchymal/drug-tolerant persister phenotype to ferroptosis. This posits that iron compartmentalization must be tightly regulated. However, the molecular machinery governing organelle Fe2+ compartmentalization remains elusive. Here, we identified Bdh2, the mammalian homolog of the bacterial EntA, as a key effector of inter-organelle Fe2+ redistribution and ferroptosis vulnerability during melanoma transition from a melanocytic (MEL) to a mesenchymal-like (MES) phenotype. In metabolically proficient MEL cells, Bdh2 localizes at the mitochondria-lysosome contacts to generate the siderophore 2,5-dihydroxybenzoic acid (2,5-DHBA) that ferries iron into the mitochondria. Fe2+ transfer by Bdh2 endorses OXPHOS and ATP production, utilized by V-ATPase for lysosomal acidification and MLC maintenance. Loss of Bdh2 expression alters lysosomal pH and MLC tethering dynamics causing lysosomal iron sequestration, which primes MES cells for ferroptosis. Rescuing Bdh2 expression, or supplementing 2,5-DHBA, rectifies lysosomal pH and MLCs, protecting MES cells from ferroptosis and enhancing their ability to metastasize through the bloodstream. Thus, we unveiled a Bdh2-dependent evolutionary-conserved mechanism that orchestrates inter-organelle Fe2+ transfer, linking metabolic regulation of lysosomal pH to the ferroptosis vulnerability of the MES/drug-tolerant persister cells.

This symposium is the 5th PSL (Paris Sciences & Lettres) Chemical Biology meeting (2015, 2016, 2019, 2023, 2024) held at Institut Curie. This initiative originally started at Institut de Chimie des Substances Naturelles (ICSN) in Gif-sur-Yvette, with a strong focus on chemistry. It was then continued at the Institut Curie (2015) covering a larger scope, before becoming the official PSL Chemical Biology meeting. This latest edition hosted around 150 participants and was focused on the burgeoning field of ferroptosis, its mechanism and implications in health and disease. While not initially planned, it was felt that the next large Ferroptosis venue (CSHA, China) would not happen before late 2024. A discussion involving Conrad, Birsoy, Ubellacker, Brabletz and Rodriguez next to lake Como in Italy sponsored by the DKFZ, prompted us to fill in this gap and to organize a Ferroptosis meeting in Paris beforehand.

Iron catalyses the oxidation of lipids in biological membranes and promotes a form of cell death referred to as ferroptosis1-3. Identifying where this chemistry takes place in the cell can inform the design of drugs capable of inducing or inhibiting ferroptosis in various disease-relevant settings. Whereas genetic approaches have revealed underlying mechanisms of lipid peroxide detoxification1,4,5, small molecules can provide unparalleled spatiotemporal control of the chemistry at work6. Here, we show that the ferroptosis inhibitor liproxstatin-1 (Lip-1) exerts a protective activity by inactivating iron in lysosomes. Based on this, we designed the bifunctional compound fentomycin that targets phospholipids at the plasma membrane and activates iron in lysosomes upon endocytosis, promoting oxidative degradation of phospholipids and ferroptosis. Fentomycin effectively kills primary sarcoma and pancreatic ductal adenocarcinoma cells. It acts as a lipolysis-targeting chimera (LIPTAC), preferentially targeting iron-rich CD44high cell-subpopulations7,8 associated with the metastatic disease and drug resistance9,10. Furthermore, we demonstrate that fentomycin also depletes CD44high cells in vivo and reduces intranodal tumour growth in an immunocompetent murine model of breast cancer metastasis. These data demonstrate that lysosomal iron triggers ferroptosis and that lysosomal iron redox chemistry can be exploited for therapeutic benefits.

Supplementary Figure from Pharmacologic Reduction of Mitochondrial Iron Triggers a Noncanonical BAX/BAK-Dependent Cell Death

Inflammation is a complex physiological process triggered in response to harmful stimuli. It involves specialized cells of the immune system able to clear sources of cell injury and damaged tissues to promote repair. Excessive inflammation can occur as a result of infections and is a hallmark of several diseases. The molecular basis underlying inflammatory responses are not fully understood. Here, we show that the cell surface marker CD44, which characterizes activated immune cells, acts as a metal transporter that promotes copper uptake. We identified a chemically reactive pool of copper(II) in mitochondria of inflammatory macrophages that catalyzes NAD(H) redox cycling by activating hydrogen peroxide. Maintenance of NAD+ enables metabolic and epigenetic programming towards the inflammatory state. Targeting mitochondrial copper(II) with a rationally-designed dimer of metformin triggers distinct metabolic and epigenetic states that oppose macrophage activation. This drug reduces inflammation in mouse models of bacterial and viral (SARS-CoV-2) infections, improves well-being and increases survival. Identifying mechanisms that regulate the plasticity of immune cells provides the means to develop next-generation medicine. Our work illuminates the central role of copper as a regulator of cell plasticity and unveils a new therapeutic strategy based on metabolic reprogramming and the control of epigenetic cell states.

This symposium is the third PSL (Paris Sciences & Lettres) Chemical Biology meeting (2016, 2019, 2023) held at Institut Curie. This initiative originally started at Institut de Chimie des Substances Naturelles (ICSN) in Gif-sur-Yvette (2013, 2014), under the directorship of Professor Max Malacria, with a strong focus on chemistry. It was then continued at the Institut Curie (2015) covering a larger scope, before becoming the official PSL Chemical Biology meeting. This latest edition was postponed twice for the reasons that we know. This has given us the opportunity to invite additional speakers of great standing. This year, Institut Curie hosted around 300 participants, including 220 on site and over 80 online. The pandemic has had, at least, the virtue of promoting online meetings, which we came to realize is not perfect but has its own merits. In particular, it enables those with restricted time and resources to take part in events and meetings, which can now accommodate unlimited participants. We apologize to all those who could not attend in person this time due to space limitation at Institut Curie.

Persister cancer cells represent rare populations of cells resistant to therapy. Cancer cells can exploit epithelial-mesenchymal plasticity to adopt a drug-tolerant state that does not depend on genetic alterations. Small molecules that can interfere with cell plasticity or kill cells in a cell state-dependent manner are highly sought after. Salinomycin has been shown to kill cancer cells in the mesenchymal state by sequestering iron in lysosomes, taking advantage of the iron addiction of this cell state. Here, we report the chemo- and stereoselective synthesis of a series of structurally complex small molecule chimeras of salinomycin derivatives and the iron-reactive dihydroartemisinin. We show that these chimeras accumulate in lysosomes and can react with iron to release bioactive species, thereby inducing ferroptosis in drug-tolerant pancreatic cancer cells and biopsy-derived organoids of pancreatic ductal adenocarcinoma. This work paves the way toward the development of new cancer medicines acting through active ferroptosis.

Patients with estrogen receptor-positive (ER+) breast cancer, the most common subtype, remain at risk for lethal metastatic disease years after diagnosis. Recurrence arises partly because tumor cells in bone marrow become resistant to estrogen-targeted therapy. Here, we utilized a co-culture model of bone marrow mesenchymal stem cells (MSCs) and ER+ breast cancer cells to recapitulate interactions of cancer cells in bone marrow niches. ER+ breast cancer cells in direct contact with MSCs acquire cancer stem-like (CSC) phenotypes with increased resistance to standard antiestrogenic drugs. We confirmed that co-culture with MSCs increased labile iron in breast cancer cells, a phenotype associated with CSCs and disease progression. Clinically approved iron chelators and in-house lysosomal iron-targeting compounds restored sensitivity to antiestrogenic therapy. These findings establish iron modulation as a mechanism to reverse MSC-induced drug resistance and suggest iron modulation in combination with estrogen-targeted therapy as a promising, translatable strategy to treat ER+ breast cancer.