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Cited by 25Ferroptosis and cancer prognosisCancer, Lipids, and MetabolismCancer Immunotherapy and Biomarkers

Secreted Apoe rewires melanoma cell state vulnerability to ferroptosis

Open access
More, Sanket, Bonnereau, Julie, Wouters, David, Spotbeen, Xander, Karras, Panagiotis, Rizzollo, Francesca, Killian, Theo, Venken, Tom +13 more·2024·Science Advances
DOI 10.1126/sciadv.adp6164PMC PMC11808924
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Abstract

A major therapeutic barrier in melanoma is the coexistence of diverse cellular states marked by distinct metabolic traits. Transitioning from a proliferative to an invasive melanoma phenotype is coupled with increased ferroptosis vulnerability. However, the regulatory circuits controlling ferroptosis susceptibility across melanoma cell states are unknown. In this work, we identified Apolipoprotein E ( APOE ) as the top lipid-metabolism gene segregating the melanoma MITF high /AXL low proliferative/ferroptosis-resistant from MITF low /AXL high invasive/ferroptosis-sensitive state. Mechanistically, ApoE secreted by the MITF high /AXL low cells protects the invasive phenotype from ferroptosis-inducing agents by reducing the content of peroxidation-prone polyunsaturated fatty acids and boosting GPX4 levels both in vitro and in vivo. Whole-exome sequencing indicates that APOE high expression in patients with melanoma is associated with resistance to ferroptosis, regardless of APOE germline status. In aggregate, we found a ferroptosis-resistance mechanism between melanoma cell states relying on secreted ApoE and APOE high expression as a potential biomarker for poor ferroptosis response in melanoma.

AI snapshot

Written from the paper’s full text.

TL;DR

Secreted ApoE from MITF^high/AXL^low proliferative melanoma cells protects MITF^low/AXL^high invasive melanoma cells from ferroptosis by remodeling PUFA/Lyso-PL metabolism and increasing GPX4. High APOE expression marks ferroptosis resistance in melanoma regardless of APOE germline variant.

Key findings

  • APOE was the top lipid-metabolism gene segregating proliferative MITF^high/AXL^low from invasive MITF^low/AXL^high melanoma states; ApoE was high intracellularly and secreted in proliferative cells and low/undetectable in invasive cells across cell lines, PDX trajectories, TCGA-SKCM, and patient RNAscope.
  • Secreted ApoE protected invasive cells from ferroptosis: in coculture, IKE-induced ferroptosis in M229R-EBFP cells dropped from 80% alone to 30–40% with M229-mCherry cells, and an ApoE-neutralizing antibody restored death to ~70%; protection was contact-independent.
  • Recombinant ApoE2/3/4 reduced Lyso-PUFA content and cPLA2 activity, lowered intracellular Ca²⁺, and after 6 days increased GPX4 and NRF2 target genes while reducing AXL; Lyso-AA resensitized ApoE-treated cells to ferroptosis, whereas Lyso-OA did not. Both receptor-binding and lipid-binding domains were required, and lipoprotein-deficient media abolished protection.
  • In vivo, rhApoE3 blunted IKE antitumor effects in Yumm 3.3 melanomas in Apoe−/− mice; IKE (40 mg/kg) reduced tumor burden, an effect countered by Lip-1 (20 mg/kg), and Gpx4 increased in rhApoE3-treated tumors. In TCGA-SKCM, APOE^high samples had lower ferroptosis scores irrespective of APOE variant.

Methods

  • In vitro human and murine melanoma cell lines, 2D and 3D spheroid cultures, conditioned-media and coculture assays, lipidomics, immunoblotting, qPCR, flow cytometry, RNAscope, and pharmacogenomic analysis of CTRP and TCGA-SKCM datasets.
  • In vivo subcutaneous Yumm 3.3 murine melanoma model in Rag2−/− Apoe−/− C57BL/6 female mice, with rhApoE3 pretreatment and daily intraperitoneal vehicle, IKE (40 mg/kg), or IKE plus Lip-1 (20 mg/kg) for 10 days.
  • Analyses included differential expression, overrepresentation analysis, Monocle trajectory analysis, GSVA-based ferroptosis score from FerrDB genes, Spearman correlations, t tests, and one-/two-way ANOVA.

Limitations

  • The paper states that the specific LDLR involved needs further study; other ApoE-mediated mechanisms such as direct iron binding or blocking ferritinophagy cannot be excluded; the exact molecular mechanism by which sApoE triggers GPX4 warrants further studies; and whether additional tumor microenvironmental factors endorse transition to a proliferative phenotype warrants future studies.
  • Evident from the text: in vivo work used murine Yumm 3.3 cells because human M229/M229R xenografts failed to grow proficiently; several experiments used n = 2–3; TCGA analysis found no significant difference between APOE variants and ferroptosis score; GPX4 differences between subtypes were a trend, not significant; and MITF changes after sApoE were not consistently observed.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1126/sciadv.adp6164

Cites

72 of 72 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

46 of 61 cited sources checked · 16 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    During multistage cell state transitions, cancer cells acquire a dependency on the ability to detoxify lipid peroxides.

    “In particular, during multistage cell state transitions, cancer cells acquire a dependency on the ability to detoxify lipid peroxides (6).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] V. S. Viswanathan, M. J. Ryan, H. D. Dhruv, S. Gill, O. M. Eichhoff, B. Seashore-Ludlow, S. D. Kaffenberger, J. K. Eaton, K. Shimada, A. J. Aguirre, S. R. Viswanathan, S. Chattopadhyay, P. Tamayo, W. S. Yang, M. G. Rees, S. Chen, Z. V. Boskovic, S. Javaid, C. Huang, X. Wu, Y.-Y. Tseng, E. M. Roider, D. Gao, J. M. Cleary, B. M. Wolpin, J. P. Mesirov, D. A. Haber, J. A. Engelman, J. S. Boehm, J. D. Kotz, C. S. Hon, Y. Chen, W. C. Hahn, M. P. Levesque, J. G. Doench, M. E. Berens, A. F. Shamji, P. A. Clemons, B. R. Stockwell, S. L. Schreiber, Dependency of a therapy-resistant state of cancer cells source

      The paper’s main text (indexed under Abstract; page unavailable) reports that cancer cells acquiring therapy-resistant, high-mesenchymal states can become dependent on GPX4, which detoxifies lipid peroxides. It examines several cell-state transitions, but does not establish that those transitions are multistage or that the dependency arises during a defined sequence of stages. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Premisecitation

    Oxidation of PUFAs containing phosphatidylethanolamine (PE) molecular species generates ferroptosis signals.

    “In particular, the oxidation of PUFAs containing phosphatidylethanolamine (PE) molecular species generates ferroptosis signals (18).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [18] V. E. Kagan, G. Mao, F. Qu, J. P. F. Angeli, S. Doll, C. S. Croix, H. H. Dar, B. Liu, V. A. Tyurin, V. B. Ritov, A. A. Kapralov, A. A. Amoscato, J. Jiang, T. Anthonymuthu, D. Mohammadyani, Q. Yang, B. Proneth, J. Klein-Seetharaman, S. Watkins, I. Bahar, J. Greenberger, R. K. Mallampalli, B. R. Stockwell, Y. Y. Tyurina, M. Conrad, H. Bayır, Oxidized arachidonic and adrenic PEs navigate cells to ferroptosis. Nat. Chem. Biol. 13, 81– 90 (2017). 27842066 PMC5506843 source

      The Discussion identifies oxidized arachidonic- and adrenic-acid-containing PE species as ferroptotic death signals, supporting the claim’s central point. The Results section on oxygenated PE in Gpx4 KO cells and kidney narrows this finding: only two of 36 oxidizable PUFA-containing PE species were identified as signal precursors. The claim does not convey that specificity. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Findingown data

    Inhibitors of secretory (varespladib) or lipoprotein-associated (darapladib) PLA2 failed to protect INV cells from IKE-induced ferroptosis within a non-cytotoxic concentration range.

    “By contrast, inhibitors of the secretory (varespladib) or lipoprotein-associated (darapladib) PLA2 used within a concentration range that was not cytotoxic per se (32, 33), failed to do so (fig. S5, B to D).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [32] W. Zheng, Q. Lin, M. A. Issah, Z. Liao, J. Shen, Identification of PLA2G7 as a novel biomarker of diffuse large B cell lymphoma. BMC Cancer 21, 927 (2021). 34404374 PMC8369790 source

      The Results section identifies darapladib as a PLA2G7 inhibitor and measures its cytotoxicity in DB and SU-DHL-2 lymphoma cells. It does not establish a non-cytotoxic concentration range in INV cells or test whether darapladib or varespladib protects those cells from IKE-induced ferroptosis. The cited paper therefore supports the inhibitor identification, but not the claimed experimental conditions or outcome. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [33] Y.-J. Wang, S.-B. Chang, C.-Y. Wang, H.-T. Huang, S.-F. Tzeng, The selective lipoprotein-associated phospholipase A2 inhibitor darapladib triggers irreversible actions on glioma cell apoptosis and mitochondrial dysfunction. Toxicol. Appl. Pharmacol. 402, 115133 (2020). 32668280 source
  • Premisecitation

    The drug-resistant U cancer cell state displays increased activity of enzymes promoting the synthesis and uptake of PUFAs such as arachidonic acid and linolenic acid.

    “The drug-resistant, U cancer cell state displays increased activity of enzymes promoting the synthesis and uptake of PUFAs (16, 17), such as arachidonic acid (AA, C20:4) and linolenic acid (C18:2), which are major substrates for ROS attack.”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [16] J. Du, Y. Su, C. Qian, D. Yuan, K. Miao, D. Lee, A. H. C. Ng, R. S. Wijker, A. Ribas, R. D. Levine, J. R. Heath, L. Wei, Raman-guided subcellular pharmaco-metabolomics for metastatic melanoma cells. Nat. Commun. 11, 4830 (2020). 32973134 PMC7518429 source

      The Discussion (page unavailable) reports upregulated lipid-unsaturation-associated activity in drug-resistant mesenchymal M381 cells, and the Results section on desaturases shows that a PUFA-synthesis enzyme contributes to their lipid-droplet unsaturation. But the Discussion says M381 had the lowest relative lipid-uptake activity, not increased uptake. The desaturases Results section also identifies C18:2 as linoleic acid, not linolenic acid. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [17] H. J. Lee, Z. Chen, M. Collard, F. Chen, J. G. Chen, M. Wu, R. M. Alani, J.-X. Cheng, Multimodal metabolic imaging reveals pigment reduction and lipid accumulation in metastatic melanoma. BME Front. 2021, 9860123 (2021). 37849907 PMC10521760 source

      Results §2.3 reports increased fatty-acid uptake in MITFlow/AXLhigh melanoma cells, and the Discussion says FADS2 can generate polyunsaturated fatty acids. The paper does not show increased uptake or synthesis of the named PUFAs in a drug-resistant U state; its measured uptake concerns palmitate and oleate, and its principal desaturation finding concerns monounsaturated sapienate. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • Premisecitation

    Mice carrying the human APOE4 variant exhibited reduced melanoma progression and metastasis relative to APOE2- and APOE3-bearing mice.

    “Mice carrying the human APOE4 variant exhibited reduced melanoma progression and metastasis relative to APOE2- and APOE3-bearing mice (46).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [46] B. N. Ostendorf, J. Bilanovic, N. Adaku, K. N. Tafreshian, B. Tavora, R. D. Vaughan, S. F. Tavazoie, Common germline variants of the human APOE gene modulate melanoma progression and survival. Nat. Med. 26, 1048– 1053 (2020). 32451497 PMC8058866 source

      The paper reports slower melanoma tumor progression and reduced metastatic progression in APOE4 mice compared with APOE2 mice (passage [1], section labeled Abstract; no page given). It lists APOE3 knock-in mice in Animal studies (passage [3]), but the passages found do not report either outcome relative to APOE3 mice, so that comparison is unsupported. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 35
  • May combine two claims. 36
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PLA2 consists of four major types: secretory PLA2 (sPLA2), cytosolic Ca2+-dependent PLA2 (cPLA2), Ca2+-independent PLA2 (iPLA2), and lipoprotein-associated PLA2 (lpPLA2).

    “PLA2 consists of four major types, secretory PLA2 (sPLA2), cytosolic Ca2+-dependent PLA2 (cPLA2) and Ca2+-independent PLA2 (iPLA2), and lipoprotein-associated PLA2 (lpPLA2) (27).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [27] A. M. Vasquez, V. D. Mouchlis, E. A. Dennis, Review of four major distinct types of human phospholipase A2. Adv. Biol. Regul. 67, 212– 218 (2018). 29248300 PMC5807221 source

      The Introduction (§1) identifies six major types of PLA2, including the four listed in the claim plus LPLA2 and AdPLA2. The paper reviews four types, but it does not say PLA2 consists of only those four. (LLM, conf=0.90)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Loss of GPX4 in invasive cancer cells with a mesenchymal and drug-resistant phenotype causes accumulation of lipid hydroperoxides that trigger ferroptosis.

    “At the same time, the loss of the lipid repair enzyme glutathione peroxidase 4 (GPX4) in invasive cancer cells with a mesenchymal and drug-resistant phenotype causes the accumulation of lipid hydroperoxides (lipid-ROS) triggering the iron-dependent cell death known as ferroptosis (7).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [7] S. J. Dixon, K. M. Lemberg, M. R. Lamprecht, R. Skouta, E. M. Zaitsev, C. E. Gleason, D. N. Patel, A. J. Bauer, A. M. Cantley, W. S. Yang, B. Morrison, B. R. Stockwell, Ferroptosis: An iron-dependent form of nonapoptotic cell death. Cell 149, 1060– 1072 (2012). 22632970 PMC3367386 source

      The Discussion (page unavailable in our copy) describes ferroptosis in cancer cells as iron-dependent death involving lethal lipid ROS. It does not establish that loss of GPX4 causes this process in invasive, mesenchymal, drug-resistant cancer cells; its account instead discusses inhibition of cystine uptake and RSL3, whose target it describes as uncertain. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Cancer cells become susceptible to lipoxygenase/Fenton reaction-induced lipid-ROS damage and are dependent on GPX4 activity to maintain viability.

    “While changes in the polyunsaturation of membrane lipids facilitate the invasive and motile cancer phenotype (9), cancer cells become susceptible to lipoxygenase/Fenton reaction–induced lipid-ROS damage and are dependent on the activity of GPX4 to maintain viability (6).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] V. S. Viswanathan, M. J. Ryan, H. D. Dhruv, S. Gill, O. M. Eichhoff, B. Seashore-Ludlow, S. D. Kaffenberger, J. K. Eaton, K. Shimada, A. J. Aguirre, S. R. Viswanathan, S. Chattopadhyay, P. Tamayo, W. S. Yang, M. G. Rees, S. Chen, Z. V. Boskovic, S. Javaid, C. Huang, X. Wu, Y.-Y. Tseng, E. M. Roider, D. Gao, J. M. Cleary, B. M. Wolpin, J. P. Mesirov, D. A. Haber, J. A. Engelman, J. S. Boehm, J. D. Kotz, C. S. Hon, Y. Chen, W. C. Hahn, M. P. Levesque, J. G. Doench, M. E. Berens, A. F. Shamji, P. A. Clemons, B. R. Stockwell, S. L. Schreiber, Dependency of a therapy-resistant state of cancer cells source

      The Abstract describes lipoxygenase-mediated lipid peroxidation and GPX4 protection against iron-mediated ferroptotic cell death; Extended Data Figure 10 shows that inhibiting lipoxygenases prevents death after GPX4 inhibition. The demonstrated GPX4 dependency is concentrated in therapy-resistant, high-mesenchymal cancer cells, not cancer cells generally. The copy describes iron-mediated reactions but does not specifically call them Fenton reactions. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Melanoma cells promote growth and invasion through the secretion of protumorigenic factors.

    “Given the ability of melanoma cells to promote growth and invasion through the secretion of protumorigenic factors (11–13), it is plausible that beyond cancer cell–intrinsic mechanisms, phenotype plasticity and ferroptosis vulnerability of drug-resistant clones may involve autocrine or paracrine circuits.”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [11] C. Kosnopfel, T. Sinnberg, B. Sauer, H. Niessner, A. Muenchow, B. Fehrenbacher, M. Schaller, P. R. Mertens, C. Garbe, B. K. Thakur, B. Schittek, Tumour progression stage-dependent secretion of YB-1 stimulates melanoma cell migration and invasion. Cancers 12, 2328 (2020). 32824741 PMC7464723 source
    • cites [12] G. Li, H. Schaider, K. Satyamoorthy, Y. Hanakawa, K. Hashimoto, M. Herlyn, Downregulation of E-cadherin and Desmoglein 1 by autocrine hepatocyte growth factor during melanoma development. Oncogene 20, 8125– 8135 (2001). 11781826 source
    • cites [13] E. J. Ekström, C. Bergenfelz, V. von Bülow, F. Serifler, E. Carlemalm, G. Jönsson, T. Andersson, K. Leandersson, WNT5A induces release of exosomes containing pro-angiogenic and immunosuppressive factors from malignant melanoma cells. Mol. Cancer 13, 88 (2014). 24766647 PMC4022450 source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    In melanoma, ferroptosis-inducing agents such as IKE or RSL3 combined with vemurafenib reduced colony formation of invasive melanoma cells in vitro, possibly because of their lower levels of glutathione.

    “In melanoma, ferroptosis-inducing agents, such as the system Xc− inhibitor imidazole ketone erastin (IKE) or (1S, 3R)-RSL3 (RSL3) combined with the BRAF kinase inhibitor vemurafenib, reduced colony formation of invasive melanoma cells in vitro, possibly because of their lower levels of glutathione (10).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [10] J. Tsoi, L. Robert, K. Paraiso, C. Galvan, K. M. Sheu, J. Lay, D. J. L. Wong, M. Atefi, R. Shirazi, X. Wang, D. Braas, C. S. Grasso, N. Palaskas, A. Ribas, T. G. Graeber, Multi-stage differentiation defines melanoma subtypes with differential vulnerability to drug-induced iron-dependent oxidative stress. Cancer Cell 33, 890– 904.e5 (2018). 29657129 PMC5953834 source

      The Results section on combination treatment (page unavailable) reports that erastin or RSL3 with vemurafenib substantially reduced long-term persisting melanoma cells in vitro. A separate Results section (page unavailable) links greater ferroptosis sensitivity in dedifferentiated cells to lower glutathione levels. The paper reports erastin, not IKE, and describes a reduction in persisting cells rather than specifically measuring colony formation of invasive cells. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Changes in the polyunsaturation of membrane lipids facilitate the invasive and motile cancer phenotype.

    “While changes in the polyunsaturation of membrane lipids facilitate the invasive and motile cancer phenotype (9), cancer cells become susceptible to lipoxygenase/Fenton reaction–induced lipid-ROS damage and are dependent on the activity of GPX4 to maintain viability (6).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [9] F. Baenke, B. Peck, H. Miess, A. Schulze, Hooked on fat: The role of lipid synthesis in cancer metabolism and tumour development. Dis. Model. Mech. 6, 1353– 1363 (2013). 24203995 PMC3820259 source

      The ‘Lipid metabolism and hypoxia’ section says changes in lipid desaturation could affect membrane fluidity and contribute to cancer cell migration. It does not specifically identify polyunsaturation of membrane lipids or establish that those changes facilitate both invasion and motility; the ‘Cancer cell migration’ section says the effect of global lipid-composition changes on migration is less clear. Page numbers were not available in our copy. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Ferroptosis is a cancer cell vulnerability caused by incorporating polyunsaturated fatty acids (PUFAs) into cellular membrane lipids.

    “Growing evidence indicates that this type of regulated cell death (RCD) represents a cancer cell vulnerability caused by incorporating polyunsaturated fatty acids (PUFAs) into cellular membrane lipids (8).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [8] J.-Y. Lee, W. K. Kim, K.-H. Bae, S. C. Lee, E.-W. Lee, Lipid metabolism and ferroptosis. Biology 10, 184 (2021). 33801564 PMC8000263 source

  • Classified as probably not a substantial claim.

    Premisecitation

    Binding of lipids is required for ApoE to acquire a biologically active conformation necessary for recognition and binding to members of the LDLR family and its internalization.

    “The binding of lipids is required for ApoE to acquire a biologically active conformation, which is necessary for recognition and binding to the members of the low-density lipoprotein receptor (LDLR) family and its internalization (24).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [24] P. S. Hauser, V. Narayanaswami, R. O. Ryan, Apolipoprotein E: From lipid transport to neurobiology. Prog. Lipid Res. 50, 62– 74 (2011). 20854843 PMC3022415 source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    ApoE has an N-terminal receptor binding domain (amino acids 1 to 191) and a C-terminal lipid-binding domain (amino acids approximately 225 to 299, with the major lipid-binding region at amino acids approximately 244 to 272), connected by a hinge region (amino acids approximately 165 to 215).

    “Structurally, ApoE has two main domains that are connected by a hinge region (amino acids ∼165 to 215); the N-terminal domain (amino acids 1 to 191) forms the receptor binding region, and the C-terminal domain (amino acids ∼225 to 299) harbors the major lipid-binding region (amino acids ∼244 to 272) (Fig. 4, A and C) (20).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [20] R. W. Mahley, K. H. Weisgraber, Y. Huang, Apolipoprotein E: Structure determines function, from atherosclerosis to Alzheimer’s disease to AIDS. J. Lipid Res. 50, S183– S188 (2009). 19106071 PMC2674716 source

      The “ApoE isoforms: structural differences predict function” section identifies the two domains, the N-terminal receptor-binding region (residues 1–191), and the C-terminal major lipid-binding region (approximately 225–299 and 244–272, respectively). It says a hinge separates the domains but does not give the claimed hinge range of approximately 165–215; a search for that range found no supporting passage. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    ApoE is known to import selenoprotein P (SELENOP), a major selenium-containing protein in plasma required for the synthesis of selenoenzymes such as GPX4.

    “ApoE is known to import selenoprotein P (SELENOP), a major selenium (Se)–containing protein in plasma that is required for the synthesis of selenoenzymes such as GPX4 (38, 39).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [38] Y. Jin, Y. W. Chung, M. K. Jung, J. H. Lee, K. Y. Ko, J. K. Jang, M. Ham, H. Kang, C. G. Pack, H. Mihara, I. Y. Kim, Apolipoprotein E-mediated regulation of selenoprotein P transportation via exosomes. Cell. Mol. Life Sci. 77, 2367– 2386 (2020). 31471680 PMC11104972 source

      The Introduction says SELENOP accounts for 50% of plasma selenium and supplies selenium for production of other selenoproteins. But the Results and Discussion describe ApoE as negatively regulating exosomal SELENOP uptake, not as an established importer; the Discussion presents a possible role in guiding uptake as a hypothesis requiring further study. The copy does not identify GPX4 as an example. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [39] N. Kitabayashi, S. Nakao, Y. Mita, K. Arisawa, T. Hoshi, T. Toyama, K.-A. Ishii, T. Takamura, N. Noguchi, Y. Saito, Role of selenoprotein P expression in the function of pancreatic β cells: Prevention of ferroptosis-like cell death and stress-induced nascent granule degradation. Free Radic. Biol. Med. 183, 89– 103 (2022). 35318102 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Each type of PLA2 has substrate-specific activity, and depending on the substrate, PLA2 can either promote or block ferroptosis.

    “Each type of PLA2 has a substrate-specific activity, and depending on the substrate, PLA2 can either promote or block ferroptosis (28–31).”
    Quote in the paperNot a substantial claim4 of 4 sources checked
    • cites [28] D. Chen, B. Chu, X. Yang, Z. Liu, Y. Jin, N. Kon, R. Rabadan, X. Jiang, B. R. Stockwell, W. Gu, iPLA2β-mediated lipid detoxification controls p53-driven ferroptosis independent of GPX4. Nat. Commun. 12, 3644 (2021). 34131139 PMC8206155 source

      The Results section reports that iPLA2β cleaves peroxidized lipids and suppresses p53-mediated ferroptosis; it also finds that iPLA2γ does not suppress ferroptosis in the tested cells. These findings support differences among PLA2 enzymes, but our copy does not establish that each type has a distinct substrate-specific activity or that a PLA2 promotes ferroptosis depending on its substrate. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [29] W.-Y. Sun, V. A. Tyurin, K. Mikulska-Ruminska, I. H. Shrivastava, T. S. Anthonymuthu, Y.-J. Zhai, M.-H. Pan, H.-B. Gong, D.-H. Lu, J. Sun, W.-J. Duan, S. Korolev, A. Y. Abramov, P. R. Angelova, I. Miller, O. Beharier, G.-W. Mao, H. H. Dar, A. A. Kapralov, A. A. Amoscato, T. G. Hastings, T. J. Greenamyre, C. T. Chu, Y. Sadovsky, I. Bahar, H. Bayır, Y. Y. Tyurina, R.-R. He, V. E. Kagan, Phospholipase iPLA2β averts ferroptosis by eliminating a redox lipid death signal. Nat. Chem. Biol. 17, 465– 476 (2021). 33542532 PMC8152680 source

      The Discussion (page not available in our copy) describes iPLA2β’s preference for arachidonoyl substrates and its anti-ferroptotic removal of peroxidized phospholipids. It speculates that activity toward triacylglycerols could indirectly enhance ferroptosis by diverting iPLA2β, but does not establish that each type of PLA2 has a distinct substrate specificity or that PLA2 types can directly promote or block ferroptosis depending on their substrate. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [30] O. Beharier, V. A. Tyurin, J. P. Goff, J. Guerrero-Santoro, K. Kajiwara, T. Chu, Y. Y. Tyurina, C. M. S. Croix, C. T. Wallace, S. Parry, W. T. Parks, V. E. Kagan, Y. Sadovsky, PLA2G6 guards placental trophoblasts against ferroptotic injury. Proc. Natl. Acad. Sci. U.S.A. 117, 27319– 27328 (2020). 33087576 PMC7959495 source

      The Discussion (page unavailable) says PLA2G6 metabolizes proferroptotic Hp-PE species and helps defend trophoblasts against ferroptosis. The Results (page unavailable) also show that PLA2G6 loss increases ferroptosis sensitivity. The paper does not establish that each type of PLA2 has substrate-specific activity or that PLA2 can promote ferroptosis depending on its substrate. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [31] Q.-Z. Tuo, Y. Liu, Z. Xiang, H.-F. Yan, T. Zou, Y. Shu, X.-L. Ding, J.-J. Zou, S. Xu, F. Tang, Y.-Q. Gong, X.-L. Li, Y.-J. Guo, Z.-Y. Zheng, A.-P. Deng, Z.-Z. Yang, W.-J. Li, S.-T. Zhang, S. Ayton, A. I. Bush, H. Xu, L. Dai, B. Dong, P. Lei, Thrombin induces ACSL4-dependent ferroptosis during cerebral ischemia/reperfusion. Signal Transduct. Target. Ther. 7, 59 (2022). 35197442 PMC8866433 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In neuronal cells, thrombin-mediated increases in cPLA2α activity sensitized these cells to ferroptosis in an ASCL4-dependent manner.

    “Consistent with our results, a recent study showed that in neuronal cells, thrombin mediated increases in cPLA2α activity sensitized these cells to ferroptosis in an ASCL4-dependent manner (31).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [31] Q.-Z. Tuo, Y. Liu, Z. Xiang, H.-F. Yan, T. Zou, Y. Shu, X.-L. Ding, J.-J. Zou, S. Xu, F. Tang, Y.-Q. Gong, X.-L. Li, Y.-J. Guo, Z.-Y. Zheng, A.-P. Deng, Z.-Z. Yang, W.-J. Li, S.-T. Zhang, S. Ayton, A. I. Bush, H. Xu, L. Dai, B. Dong, P. Lei, Thrombin induces ACSL4-dependent ferroptosis during cerebral ischemia/reperfusion. Signal Transduct. Target. Ther. 7, 59 (2022). 35197442 PMC8866433 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The ApoE-lipoprotein complex has been shown to alter the lipid profile of cancer and noncancerous cells.

    “The ApoE-lipoprotein complex has been shown to alter the lipid profile of cancer and noncancerous cells (47–49).”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [47] Y. He, J. Chen, Y. Ma, H. Chen, Apolipoproteins: New players in cancers. Front. Pharmacol. 13, 1051280 (2022). 36506554 PMC9732396 source

      The Lung cancer section says ApoE transports lipids and cholesterol between cells, and the Breast cancer section links ApoE expression to possible changes in fatty-acid production and cholesterol entry in breast cancer cells. Neither passage establishes that an ApoE-lipoprotein complex alters the lipid profiles of both cancerous and noncancerous cells. Page numbers are unavailable in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [48] Y. Huang, R. W. Mahley, Apolipoprotein E: Structure and function in lipid metabolism, neurobiology, and Alzheimer’s diseases. Neurobiol. Dis. 72, 3– 12 (2014). 25173806 PMC4253862 source

      The Introduction and “Structure and Function of ApoE Isoforms in Lipid Metabolism” sections (page numbers unavailable) say that apoE-containing lipoproteins transport lipids among cells and help regulate tissue lipid content. They do not report a demonstrated change in the lipid profiles of both cancer and noncancerous cells; the mention of neuroblastoma cells concerns neurite outgrowth, not their lipid profile. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites [49] P. Prasinou, I. Dafnis, G. Giacometti, C. Ferreri, A. Chroni, C. Chatgilialoglu, Fatty acid-based lipidomics and membrane remodeling induced by apoE3 and apoE4 in human neuroblastoma cells. Biochim. Biophys. Acta Biomembr. 1859, 1967– 1973 (2017). 28688796 source

      The Results and discussion report that apoE3 and apoE4 altered membrane fatty-acid composition in SK-N-SH neuroblastoma cells. The experiment used lipid-free apoE, not an ApoE–lipoprotein complex, and did not test noncancerous cells, so those parts of the claim are not supported by this paper. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several transcription factors including AP-1, CREB, ATF4, and NRF2 have been shown to regulate either directly or indirectly GPX4 levels in different cellular contexts.

    “Several transcription factors including AP-1 (60, 61), CREB (62, 63), ATF4 (64), and NRF2 (45, 65, 66) have been shown to regulate either directly or indirectly GPX4 levels in different cellular contexts.”
    Quote in the paperNot a substantial claim3 of 5 sources checked
    • cites [60] X. Ma, X. Dong, Y. Xu, N. Ma, M. Wei, X. Xie, Y. Lu, W. Cao, G. Lu, W. Li, Identification of AP-1 as a critical regulator of glutathione peroxidase 4 (GPX4) transcriptional suppression and acinar cell ferroptosis in acute pancreatitis. Antioxidants 12, 100 (2022). 36670963 PMC9854988 source
    • cites [61] S. Tang, J. Liu, F. Li, Y. Yan, X. Long, Y. Fu, AP-1 inhibitor induces ferroptosis via the PI3K/AKT pathway in multiple myeloma cells. Heliyon 10, e34397 (2024). 39104494 PMC11298940 source
    • cites [62] Z. Wang, X. Zhang, X. Tian, Y. Yang, L. Ma, J. Wang, Y. Yu, CREB stimulates GPX4 transcription to inhibit ferroptosis in lung adenocarcinoma. Oncol. Rep. 45, 88 (2021). 33846793 PMC8042667 source
    • cites [63] L. Cao, Y. Wang, J. Liu, X. Bai, X. Chi, Long non-coding RNA TPT1-AS1 inhibits ferroptosis in ovarian cancer by regulating GPX4 via CREB1 regulation. Am. J. Reprod. Immunol. 92, e13864 (2024). 39141012 source
    • cites [64] S. Zhu, Q. Zhang, X. Sun, H. J. Zeh, M. T. Lotze, R. Kang, D. Tang, HSPA5 regulates ferroptotic cell death in cancer cells. Cancer Res. 77, 2064– 2077 (2017). 28130223 PMC5392369 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Patients with melanoma harboring the APOE4 genetic variant have improved survival compared with carriers of the APOE2 and APOE3 variants.

    “Patients with melanoma harboring the APOE4 genetic variant have improved survival compared with carriers of the APOE2 and APOE3 variants (46).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [46] B. N. Ostendorf, J. Bilanovic, N. Adaku, K. N. Tafreshian, B. Tavora, R. D. Vaughan, S. F. Tavazoie, Common germline variants of the human APOE gene modulate melanoma progression and survival. Nat. Med. 26, 1048– 1053 (2020). 32451497 PMC8058866 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Recent studies indicated that melanoma progression is dependent on the APOE germline variant, and mice carrying the human APOE4 genetic variant showed an increased ability to repress Yumm3.3 melanoma growth and metastasis relative to hAPOE2- and hAPOE3-carrying mice.

    “Recent studies indicated that melanoma progression is dependent on the APOE germline variant, and mice carrying the human APOE4 genetic variant (hAPOE4) showed an increased ability to repress Yumm3.3 melanoma growth and metastasis relative to hAPOE2- and hAPOE3-carrying mice (46).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [46] B. N. Ostendorf, J. Bilanovic, N. Adaku, K. N. Tafreshian, B. Tavora, R. D. Vaughan, S. F. Tavazoie, Common germline variants of the human APOE gene modulate melanoma progression and survival. Nat. Med. 26, 1048– 1053 (2020). 32451497 PMC8058866 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Inhibition of calcium-independent iPLA2β fostered p53-driven ferroptosis and tumor suppression by depleting the pool of oxidized lipids in response to ROS-generating drugs.

    “In contrast, inhibition of the calcium-independent iPLA2β, which cleaves acyl tails from the glycerol backbone of lipids, fostered p53-driven ferroptosis and tumor suppression by depleting the pool of oxidized lipids in response to ROS-generating drugs (28).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [28] D. Chen, B. Chu, X. Yang, Z. Liu, Y. Jin, N. Kon, R. Rabadan, X. Jiang, B. R. Stockwell, W. Gu, iPLA2β-mediated lipid detoxification controls p53-driven ferroptosis independent of GPX4. Nat. Commun. 12, 3644 (2021). 34131139 PMC8206155 source

      The Results section on xenograft models reports that loss of iPLA2β enhances p53-mediated ferroptosis and p53-dependent tumor suppression. But the Results section on peroxidized membrane lipids says iPLA2β itself reduces their levels; the claim reverses that mechanism by saying inhibition depletes oxidized lipids. Page numbers are unavailable in our copy. (LLM, conf=0.92)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    In melanoma, ApoE is known to modulate the metastatic potential of melanoma cells by engaging with LRP1 and LRP8 receptor proteins.

    “In melanoma, ApoE is known to modulate the metastatic potential of melanoma cells by engaging with LRP1 and LRP8 receptor proteins (21).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] N. Pencheva, H. Tran, C. Buss, D. Huh, M. Drobnjak, K. Busam, S. F. Tavazoie, Convergent multi-miRNA targeting of ApoE drives LRP1/LRP8-dependent melanoma metastasis and angiogenesis. Cell 151, 1068– 1082 (2012). 23142051 PMC3753115 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    LRP1 is known to control cPLA2 activation and the consequent intracellular levels of AA via the MAPK signaling pathway.

    “While LRP1 is known to control cPLA2 activation and the consequent intracellular levels of AA via the MAPK signaling pathway (53)”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [53] L. Zhou, H. Y. Choi, W.-P. Li, F. Xu, J. Herz, LRP1 controls cPLA2 phosphorylation, ABCA1 expression and cellular cholesterol export. PLOS ONE 4, e6853 (2009). 19718435 PMC2729921 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    sApoE has been found to influence the transcriptome by modulating histone acetylation.

    “Of note, sApoE has been found to influence the transcriptome by modulating histone acetylation (68, 69).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [68] X. Li, J. Zhang, D. Li, C. He, K. He, T. Xue, L. Wan, C. Zhang, Q. Liu, Astrocytic ApoE reprograms neuronal cholesterol metabolism and histone-acetylation-mediated memory. Neuron 109, 957– 970.e8 (2021). 33503410 source
    • cites [69] A. Sen, T. J. Nelson, D. L. Alkon, Apoe4 and aβ oligomers reduce BDNF expression via HDAC nuclear translocation. J. Neurosci. 35, 7538– 7551 (2015). 25972179 PMC6705431 source

      The histone H3 acetylation and BDNF-expression sections (page not provided) show that ApoE3 and ApoE4, when administered with cholesterol, alter histone acetylation and BDNF gene expression. The paper does not demonstrate an effect on the transcriptome as a whole; its Discussion attributes a whole-transcriptome observation to previous work. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    While loss of MITF is sufficient to induce the invasive phenotype, the transition from an invasive to a proliferative phenotype requires the integration of additional signals and epigenetic modifications capable of stably rescuing MITF-driven transcription of proliferation and differentiation genes.

    “However, while loss of MITF is sufficient to induce the invasive phenotype, the transition from an invasive to a proliferative phenotype requires the integration of additional signals and epigenetic modifications capable of stably rescuing MITF-driven transcription of proliferation and differentiation genes (67).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [67] I. Arozarena, C. Wellbrock, Phenotype plasticity as enabler of melanoma progression and therapy resistance. Nat. Rev. Cancer 19, 377– 391 (2019). 31209265 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    Cell death in the sensitive NC/U melanoma subtypes was accompanied by an increase in BODIPY-C11 staining, which was blocked by liproxstatin (Lip-1).

    “Cell death in the sensitive NC/U subtypes was accompanied by an increase in BODIPY-C11 staining, which was blocked by the radical-trapping antioxidant (RTA) liproxstatin (Lip-1) (Fig. 1C and fig. S1B and C).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Melanoma cell lines cluster into four subtypes: melanocytic (M), transitory (T), neural crest (NC)-like, and undifferentiated (U).

    “We clustered these cell lines based on the enrichment for specific gene sets and transcription factors into four subtypes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The neural crest (NC)-like and undifferentiated (U) melanoma subtypes share low levels of MITF and up-regulation of AXL.

    “The more dedifferentiated neural crest (NC)–like and Undifferentiated (U) subtypes shared low levels of MITF and up-regulation of the receptor tyrosine kinase AXL (Fig. 1A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In single-cell RNA-seq from melanoma patient-derived xenografts, APOE was highly expressed in PRO melanoma lineages and down-regulated over time in drug-resistant NC-like and INV melanoma states with more metastatic potential.

    “APOE was highly expressed in the PRO melanoma lineages, while being down-regulated over time in the drug-resistant NC-like and INV melanoma states, with more metastatic potential (Fig. 2G and fig. S2D).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    ApoE protein levels were high both intracellularly and as a secreted protein in MITFhigh PRO melanoma cells, decreased progressively when transitioning from T to NC-like cells, and became undetectable in the MITFlow INV subtype.

    “Consistent with the RNA expression (fig. S2B), ApoE protein levels were high, both intracellularly and as a secreted protein, in MITFhigh PRO melanoma cells, while it decreased progressively when transitioning from the T to the NC-like cells, to become undetectable in the MITFlow INV subtype (Fig. 2, E and F, and fig. S2C).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    APOE was identified as the top differentially expressed gene, with high expression in PRO (M, T) and low expression in INV (NC, U) melanoma subtypes.

    “Apolipoprotein E (APOE) was identified as the top DE gene, exhibiting a high expression in PRO [cluster 1 (M, T)] and a low expression in INV [cluster 2 (NC, U)] (fig. S2A) subtypes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    3D cultures of ferroptosis-resistant M229 cells (MITFhigh, T subtype) were IKE resistant with no detectable signs of lipid peroxidation.

    “3D cultures of ferroptosis-resistant M229 cells (MITFhigh, T subtype) stably expressing mCherry were IKE resistant with no detectable signs of lipid peroxidation (Fig. 1, D and E).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Heterotypic spheroids formed by mixing M229R-EBFP and M229-mCherry cells in a 40:60 ratio organized into a central region mainly of PRO M229-mCherry cells surrounded by ferroptosis-sensitive M229R-EBFP cells, with each cell type making up about 50% of the spheroid after 3 days of coincubation.

    “These spheroids are organized in a central region formed mainly by the PRO M229-mCherry cells surrounded by the ferroptosis-sensitive M229R-EBFP cells, with each cell type making up ~50% of the spheroid after 3 days of coincubation (Fig. 3, E to G).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In drug-naive metastatic melanoma biopsies, the major population of MITFhigh PRO melanoma cells had high APOE expression, while the MITFlow INV cell population had significantly lower APOE levels.

    “Consistent with what we observed in melanoma cell lines and the PDX model, the major population of MITFhigh PRO melanoma cells had high APOE expression, while the MITFlow INV cell population harbored significantly lower APOE levels (Fig. 2, H and I).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Spheroids of ferroptosis-sensitive M229R cells (MITFlow, U subtype) underwent ferroptosis, accompanied by Lip-1-inhibitable Bodipy C11 staining of lipid peroxides.

    “Conversely, spheroids of ferroptosis-sensitive M229R cells (MITFlow, U subtype) underwent ferroptosis, accompanied by Lip-1–inhibitable Bodipy C11 staining of lipid peroxides (Fig. 1, D to F), thus phenocopying the responses observed in the 2D culture settings.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    APOE expression correlated with resistance to the class-2 ferroptosis inducers RSL3, ML210, and ML162, and showed a similar trend for the class-1 ferroptosis inducer Erastin.

    “Notably, APOE expression correlated with resistance to the class-2 FINs, RSL3, ML210, and ML162, and showed a similar trend for the class-1 FIN, Erastin (Fig. 3A and fig. S3B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    rhApoE3 blunted IKE-mediated cell death in all murine cell lines, although the protective effect was more pronounced in Yumm 3.3 cells.

    “When compared with their respective untreated cells, rhApoE3 blunted IKE-mediated cell death in all murine cell lines, although the protective effect was more pronounced in the Yumm 3.3 cells (Fig. 6B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The coexistence of MITFhighApoEhigh PRO cells with MITFlowApoElow INV melanoma cells is associated with resistance to ferroptosis, which can be reverted by the addition of ApoE-neutralizing antibody.

    “We found that the coexistence of MITFhighApoEhigh PRO cells with MITFlowApoElow INV melanoma cells is associated with resistance to ferroptosis, which can be reverted by the addition of ApoE-neutralizing antibody”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There was a trend toward high GPX4 expression among patients with the PRO melanoma subtype, although no significant difference in GPX4 expression was detected.

    “Although we did not detect a significant difference in the expression of GPX4, there was a trend toward high GPX4 expression among patients with the PRO melanoma subtype (Fig. 7D).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    All three variants of ApoE were able to reduce ferroptosis in invasive melanoma cells and elevate GPX4 expression while reducing the invasive marker AXL.

    “In line with this, all three variants of ApoE were able to reduce ferroptosis in invasive melanoma cells and elevate GPX4 expression while reducing the invasive marker AXL”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Expression of APOE irrespective of variant status showed a negative correlation with FPS, with significantly lower FPS in samples with higher APOE.

    “However, the expression of APOE irrespective of the variant status showed a negative correlation with FPS, with significantly lower FPS in samples with higher APOE, while, opposite to that, APOEhigh melanomas had low FPS (Fig. 7, F to H).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Murine melanoma cell lines Yumm 1.7, Yumm 2.1, and Yumm 3.3 were Sox10 positive and expressed very low levels of Apoe and Mitf.

    “All these murine melanoma cell lines were Sox10 positive and expressed very low levels of Apoe and Mitf (fig. S6A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In INV M238R cells exposed to ApoE-rich conditioned media from M229 PRO cells, a reduction in AXL accompanied by an increase in GPX4 was observed.

    “Also in INV M238R cells, we observed a similar trend, a reduction in the protein levels of AXL accompanied by an increase in the expression of GPX4 after the treatment with the ApoE-rich conditioned media from the M229 cells (fig. S5Q).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Patients harboring the PRO melanoma subtype exhibited high APOE levels (APOEhigh), while melanomas of the INV phenotype had a low level of APOE (APOElow).

    “Congruently with the in silico analysis described earlier (Fig. 2D), patients harboring the PRO melanoma subtype also exhibited high APOE levels (APOEhigh), while melanomas of the INV phenotype had a low level of APOE (APOElow) (Fig. 7C).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    APOE is one of the top genes differentiating melanoma cell states at the level of lipid metabolism and whose expression follows the dynamic evolution of melanoma states under therapeutic pressure.

    “We show that APOE, a member of the cholesterol metabolism pathway, is one of the top genes differentiating melanoma cell states at the level of lipid metabolism and whose expression follows the dynamic evolution of melanoma states under therapeutic pressure.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Gpx4 protein levels increased in rhApoE3-melanomas both in untreated conditions and following IKE, whereas this was not the case in parental ApoE3-untreated Yumm 3.3 melanomas.

    “we observed a clear trend indicating that Gpx4 protein levels increased in rhApoE3-melanomas both in untreated conditions and following IKE (Fig. 6E), whereas this was not the case in the parental, ApoE3-untreated, Yumm 3.3 melanomas (Fig. 6E).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Melanomas of patients annotated as PRO exhibited low FPS, while INV melanomas had a high FPS.

    “Consistent with the data in melanoma cells, melanomas of patients annotated as PRO exhibited low FPS, while INV melanomas had a high FPS (Fig. 7B).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    PLA2 can hydrolyze phospholipids including PC, PS, and PA into arachidonic acid.

    “We reasoned that, because of its ability to hydrolyze PLs, including PC, PS, and PA, into AA (26), PLA2 could be a potential target of the anti-ferroptosis activity of sApoE.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [26] J. B. Park, C. S. Lee, J.-H. Jang, J. Ghim, Y.-J. Kim, S. You, D. Hwang, P.-G. Suh, S. H. Ryu, Phospholipase signalling networks in cancer. Nat. Rev. Cancer 12, 782– 792 (2012). 23076158 source

  • Classified as probably not a substantial claim.

    Premisecitation

    Variation in nanomolar concentrations of intracellular Ca2+ impairs cPLA2 translocation to the cellular membrane and its subsequent activation.

    “Since variation in nanomolar concentrations of intracellular Ca2+ impairs cPLA2 translocation to the cellular membrane and its subsequent activation (37)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [37] J. D. Clark, L. L. Lin, R. W. Kriz, C. S. Ramesha, L. A. Sultzman, A. Y. Lin, N. Milona, J. L. Knopf, A novel arachidonic acid-selective cytosolic PLA2 contains a Ca2+-dependent translocation domain with homology to PKC and GAP. Cell 65, 1043– 1051 (1991). 1904318 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    PLA1 and PLA2 target the sn-1 and sn-2 positions of phospholipids, respectively, and hydrolyze the ester bond, releasing free fatty acids and Lyso-PLs.

    “PLA1 and PLA2 target the sn-1 and sn-2 positions of PLs, respectively, and hydrolyze the ester bond, releasing free fatty acids and Lyso-PLs (26).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] J. B. Park, C. S. Lee, J.-H. Jang, J. Ghim, Y.-J. Kim, S. You, D. Hwang, P.-G. Suh, S. H. Ryu, Phospholipase signalling networks in cancer. Nat. Rev. Cancer 12, 782– 792 (2012). 23076158 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Lyso-PLs are mainly synthesized by the enzymatic activity of phospholipases, of which three major classes differing in catalytic activity are known: PLA (consisting of A1 and A2), PLC, and PLD.

    “Lyso-PLs are mainly synthesized by the enzymatic activity of phospholipases (26), of which three major classes differing in the catalytic activity are known: PLA (consisting of A1 and A2), PLC, and PLD.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] J. B. Park, C. S. Lee, J.-H. Jang, J. Ghim, Y.-J. Kim, S. You, D. Hwang, P.-G. Suh, S. H. Ryu, Phospholipase signalling networks in cancer. Nat. Rev. Cancer 12, 782– 792 (2012). 23076158 source

  • May combine two claims.

    Interpretationown data

    Secretion of ApoE by PRO melanoma cells can attenuate ferroptosis in INV melanoma cells in a contact-independent manner, portraying sApoE as a lipid-ROS-protective autocrine signal in melanoma.

    “Hence, secretion of ApoE by PRO cells can attenuate ferroptosis in INV cells in a contact-independent manner, thus portraying sApoE as a lipid-ROS–protective autocrine signal in melanoma.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Together, these data highlight that sApoE blunts ferroptosis in INV melanoma by the activation of multiple effector mechanisms, involving an initial remodeling of AA metabolism followed by a progressive increase in GPX4 and a more general NRF2 antioxidant program.

    “Together, these data highlight that sApoE blunts ferroptosis in INV melanoma by the activation of multiple effector mechanisms, involving an initial remodeling of AA metabolism followed by a progressive increase in GPX4 and a more general NRF2 antioxidant program.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    This suggests the ability of sApoE to mitigate the invasive phenotype of melanoma cells while concomitantly reversing its ferroptosis-vulnerable status.

    “This suggests the ability of sApoE to mitigate the invasive phenotype of melanoma cells while concomitantly reversing its ferroptosis-vulnerable status.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The anti-ferroptosis role of melanoma sApoE is likely mediated by the activation of signaling pathways downstream of these receptors.

    “The anti-ferroptosis role of melanoma sApoE is likely mediated by the activation of signaling pathways downstream of these receptors, although the specific LDLR involved needs to be addressed in further studies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The anti-ferroptosis role of sApoE occurs first through remodeling of the lipidome of the mesenchymal-like cell state, and a secondary sApoE-mediated response leads to sustained expression of GPX4 and a concomitant, partial reversion of the invasive cell state.

    “Further mechanistic insights into the anti-ferroptosis role of sApoE revealed that it occurs first through the remodeling of the lipidome of the mesenchymal-like cell state. A secondary sApoE-mediated response leads to the sustained expression of GPX4 and a concomitant, partial reversion of the invasive cell state.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The anti-ferroptosis effect of APOE correlates with its expression, but it is independent of APOE-genetic variant.

    “Our study shows that the anti-ferroptosis effect of APOE correlates with its expression, but it is independent of APOE-genetic variant.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The FPS model quantifies ferroptosis sensitivity status of patients with melanoma based on ferroptosis-related genes and distinguishes ferroptosis sensitivity in melanoma samples based on their differentiation status.

    “We then constructed a ferroptosis score (FPS) model to quantify the ferroptosis sensitivity status of patients with melanoma based on ferroptosis-related genes mined from the FerrDB database, which could allow to distinguish ferroptosis sensitivity in melanoma samples based on their differentiation status.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Use of ApoE-neutralizing therapy in combination with ferroptosis-inducing agents may be of potential benefit.

    “our findings suggest that the use of ApoE-neutralizing therapy in combination with ferroptosis-inducing agents may be of potential benefit.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Target down-regulation was confirmed by immunoblotting.

    “Target down-regulation was confirmed by immunoblotting.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Animal procedures were approved by the Institutional Animal Care and Research Advisory Committee of the KU Leuven (ECD P073/2020) and were performed following institutional and national guidelines and regulations.

    “Animal procedures were approved by the Institutional Animal Care and Research Advisory Committee of the KU Leuven (ECD P073/2020) and were performed following the institutional and national guidelines and regulations.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The cPLA2 activity assay avoided measurement of iPLA2 and lpPLA2 activity by treating samples with bromoenol lactone and darapladib.

    “The supernatant was transferred to a prechilled microcentrifuge tube and treated with bromoenol lactone and darapladib for 10 min at 25°C to avoid measurement of iPLA2 and lpPLA2 activity, respectively, in the sample.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Cells were routinely checked for mycoplasma contamination using the Plasmotest kit.

    “The cells were routinely checked for mycoplasma contaminations using the Plasmotest kit (Invivogen) according to the manufacturer’s instructions.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Given the pleiotropic signaling effects elicited by sApoE downstream LDLR binding, it is likely that multiple transcription factors contribute to elevating GPX4 expression in invasive melanoma cells.

    “Given the pleiotropic signaling effects elicited by sApoE downstream LDLR binding, it is likely that multiple transcription factors contribute to elevating GPX4 expression in invasive melanoma cells.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Unless noted, samples were independent biological replicates.

    “Unless noted, samples were independent biological replicates.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The use of patient samples for the present study was approved by the Medical Ethics Committee of the UZ Leuven/KU Leuven (approval number S66737).

    “The use of from melanoma patients samples for the present study was approved by the Medical Ethics Committee of the UZ Leuven/KU Leuven (HBM) (approval number, S66737).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The sample size was not predetermined.

    “The sample size was not predetermined.”
    Quote in the paperNot a substantial claim
63 of 63

  • The paper relies on this without support.

    The regulatory circuits controlling ferroptosis susceptibility across melanoma cell states are unknown.

    “However, the regulatory circuits controlling ferroptosis susceptibility across melanoma cell states are unknown.”

  • The paper relies on this without support.

    Understanding of how the coexistence of reversible cellular states within the melanoma ecosystem affects the therapeutic efficacy of ferroptosis-inducing agents is largely incomplete.

    “Furthermore, our understanding of how the coexistence of (reversible) cellular states within the melanoma ecosystem affects the therapeutic efficacy of ferroptosis-inducing agents is largely incomplete.”

  • The paper relies on this without support.

    Phenotype plasticity and ferroptosis vulnerability of drug-resistant melanoma clones may involve autocrine or paracrine circuits.

    “Given the ability of melanoma cells to promote growth and invasion through the secretion of protumorigenic factors (11–13), it is plausible that beyond cancer cell–intrinsic mechanisms, phenotype plasticity and ferroptosis vulnerability of drug-resistant clones may involve autocrine or paracrine circuits.”

  • The paper relies on this without support.

    The panel of 12 melanoma cell lines represents cellular models of progressive differentiation.

    “To evaluate whether changes in the membrane lipid composition are causally linked to the differential sensitivity of melanoma cell states to ferroptosis, we analyzed a panel of 12 melanoma cell lines representing cellular models of progressive differentiation.”

  • The paper relies on this without support.

    Small-molecule GPX4 inhibitors have poor bioavailability.

    “Since small-molecule GPX4 inhibitors are known for their poor bioavailability, we use IKE as in vivo ferroptosis agent.”

  • The authors state this as an assumption.

    It is unknown whether the APOE germline genotype predicts susceptibility to ferroptosis in patients with melanoma.

    “However, it is unknown whether the APOE germline genotype predicts susceptibility to ferroptosis in patients with melanoma.”

  • The authors state this as an assumption.

    Previous studies did not address the role of secreted ApoE in lipid peroxidation–driven ferroptosis.

    “However, previous studies did not address the role of secreted ApoE in lipid peroxidation–driven ferroptosis.”

  • The paper relies on this without support.

    Calcium-dependent cPLA2α cleaves AA at the sn-2 position of glycerophospholipids to release AA from the membrane and may promote ferroptosis through iron- and LOX-dependent accumulation of lethal lipid peroxides following ASCL4- and LPCAT3-mediated PE re-esterification.

    “The calcium-dependent cPLA2α cleaves AA at the sn-2 position of glycerophospholipids to release AA from the membrane and may promote ferroptosis through the iron- and LOX-dependent accumulation of lethal lipid peroxides following ASCL4- and LPCAT3-mediated PE re-esterification.”
8 of 8

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Cocultured proliferative cell line has conflicting names

    Minor

    The Results name the proliferative coculture partner M299-mCherry, whereas the corresponding figure caption names it M229-mCherry.

  • Heterotypic spheroid seeding ratio is reversed

    Minor

    The Results state that M229R and M229 cells were mixed at a 40:60 ratio, respectively, but the Methods specify 60% M229R and 40% M229.

2 of 2

Cites

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Authors
More, S., Bonnereau, J., Wouters, D., Spotbeen, X., Karras, P., Rizzollo, F., Killian, T., Venken, T., Naulaerts, S., Vervoort, E., Ganne, M., Nittner, D., Verhoeven, J., Bechter, O., Bosisio, F., Lambrechts, D., Sifrim, A., Stockwell, B. R., Swinnen, J. V., Marine, J. C., & Agostinis, P.
Affiliations
  • VIB-KU Leuven Center for Cancer Biology (BE)
  • KU Leuven (BE)
  • VIB-KU Leuven Center for Brain & Disease Research (BE)
  • Universitair Ziekenhuis Leuven (BE)
  • Columbia University (US)
Corresponding author
Agostinis, Patrizia
ORCID
Venue
Science Advances
Publisher
American Association for the Advancement of Science (AAAS)
Published
2024-10-18
Volume
10
Issue
42
Pages
eadp6164-eadp6164
ISSN
2375-2548 (ISSN-L)
DOI
10.1126/sciadv.adp6164
PMC
PMC11808924
OpenAlex
W4403448074
Cited by
25
References
71
Citations by year
2026: 14 · 2025: 10 · 2024: 1
FWCI
6.33
Type
journal article
Language
en
Open access
Licence
cc-by-nc
Locations
  • Science Advances (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • Lirias (KU Leuven) (submittedVersion, cc-by-nc)
  • PubMed Central (submittedVersion, cc-by-nc)
  • Dépôt institutionnel de l'Université libre de Bruxelles (Université Libre de Bruxelles) (submittedVersion)
Funders
National Cancer Institute (R35CA209896)
Topics
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Ferroptosis and cancer prognosis
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Cancer, Lipids, and Metabolism
  • Health Sciences › Medicine › Oncology › Cancer Immunotherapy and Biomarkers
Keywords
melanoma, ferroptosis, apolipoprotein E, MITF, AXL, cell state heterogeneity, lipid metabolism, polyunsaturated fatty acids, GPX4, ferroptosis resistance, biomarkers, tumor invasion
MeSH terms
Ferroptosis, Phospholipid Hydroperoxide Glutathione Peroxidase, Animals, Apolipoproteins E, Humans, Melanoma, Gene Expression Regulation, Neoplastic, Cell Line, Tumor, Mice

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-19.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-19.

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Statistics and arithmetic are recomputed, not judged.

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