Necroptosis is not the quiet, orderly cell death most people know. Apoptosis, the classical pathway, is caspase-dependent and immunologically silent: cells shrink, package their debris, and are tidily consumed without alarming their neighbors. Necroptosis is the opposite. It is caspase-independent, regulated by the RIPK3–MLKL signaling axis, and ends in plasma membrane rupture. When the phosphorylated executioner protein MLKL oligomerizes and translocates to the cell surface, the membrane disintegrates and releases damage-associated molecular patterns, or DAMPs, into the surrounding tissue. Those DAMPs stoke inflammation, turning individual cell death into a broader alarm signal. Previous work has shown that hyperglycemic oxidative stress can shift cells away from apoptosis and toward this RIPK-dependent necrotic fate, making necroptosis a plausible nexus between high blood sugar and tissue injury.

To test whether that link reaches the dental pulp, the researchers induced type 1 diabetes in male Sprague-Dawley rats using a single high dose of streptozotocin, a compound that alkylates DNA in pancreatic beta cells and rapidly abolishes insulin production. Twenty animals received the toxin while ten controls received phosphate-buffered saline. After 49 days, fifteen of the injected rats had sustained fasting blood glucose levels exceeding 250 milligrams per deciliter—by the study’s endpoint, glucose climbed above 600 milligrams per deciliter—while two animals died and three spontaneously reverted to normoglycemia and were analyzed separately. The hyperglycemic rats gained essentially no weight over seven weeks, in stark contrast to the steady growth of the control group, and blood work revealed the expected systemic fallout: elevated liver enzymes, higher total cholesterol, reduced white blood cell counts, and sharply increased neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios, both markers of activated systemic inflammation.

The centerpiece of the study was a simple but elegant measurement technique. Early in the experiment, under isoflurane anesthesia, the team cut a small reference notch into each rat’s lower incisor, four millimeters from the interdental papilla, taking care not to injure the pulp. Because rodent incisors grow continuously, the distance between that notch and the cutting edge advances at a rate that reflects the tooth’s elongation. By creating new notches every two to three days and measuring the linear distance between them, the researchers built a longitudinal growth curve for each animal across the entire 49-day experiment.

Those curves told a clear, phase-specific story. During the first twelve days—while the rats were still undergoing skeletal growth—incisor growth rates were statistically indistinguishable between healthy and hyperglycemic animals, with slopes of roughly 0.46 versus 0.44 millimeters per day. A subtle divergence then appeared during a two-day transition window around days 12 to 14, when growth rates first separated, though absolute tooth lengths had not yet noticeably changed. The impairment became dramatic in the final phase, from day 14 onward: healthy rats accelerated to a slope of about 0.59 as their skeletons matured and incisor elongation dominated, whereas diabetic rats remained stuck at roughly 0.41, a difference significant under both the primary Welch’s t-test and a non-parametric sensitivity analysis.

The diagnostic implications were remarkable. In the early phase, incisor growth carried essentially no information about glycemic status, with a receiver operating characteristic area under the curve of just 0.527—no better than a coin flip. During the transition, discrimination improved to an AUC of 0.693. But in the sustained phase, growth kinetics achieved complete empirical separation between the groups: an AUC of 1.000, an average precision of 1.000, and a threshold window between roughly 0.45 and 0.55 millimeters per day in which sensitivity, specificity, and predictive values all reached 1.000 within this dataset. Leave-one-out cross-validation using the individual growth slope correctly classified every animal. The authors are careful to note that a perfect AUC in a small sample reflects separation within this cohort rather than externally validated accuracy, but the signal is undeniably strong.

What makes the slowing teeth biologically interesting is what was happening inside them. Using a split-mouth design, the team examined one mandible histologically and cultured dental pulp cells from the other. Hematoxylin and eosin staining showed no overt disruption of the dentin–pulp architecture in either group—the tissue looked structurally intact. Yet immunohistochemistry told a different molecular story. Hyperglycemic rats displayed far more widespread immunoreactivity for 4-hydroxynonenal, a lipid peroxidation product and canonical marker of oxidative stress, throughout the periodontal ligament and dental pulp. They also showed altered distribution of PGAM5, a mitochondrial stress-associated phosphatase that has been implicated in mitochondrial dynamics and regulated cell-death signaling, notably appearing within the dentin matrix itself.

The cellular analyses reinforced the pattern. Dental pulp cells derived from hyperglycemic rats, when exposed to a standardized lipopolysaccharide challenge, produced significantly higher intracellular reactive oxygen species than cells from healthy controls, as measured with an H2DCFDA fluorescence assay. Enzyme-linked immunosorbent assays and Western blotting showed elevated levels of the core necroptosis machinery—MLKL, phosphorylated MLKL, RIPK3, and phosphorylated RIPK3—along with increased PGAM5, including its cleaved form. Intriguingly, the three rats that spontaneously recovered normoglycemia showed molecular marker levels and incisor growth rates indistinguishable from healthy controls, suggesting that both the biochemical alterations and the growth phenotype track sustained glycemic status rather than a transient early hyperglycemic insult. When growth kinetics from these recovered animals were grouped with healthy rats, complete separation from the persistently hyperglycemic group was retained.

The authors propose a coherent biological framework, while stressing that causality was not directly established. Sustained hyperglycemia drives oxidative stress; oxidative stress favors RIPK-dependent necrosome formation and MLKL recruitment and phosphorylation; PGAM5-related mitochondrial responses may participate in a context-dependent manner; and the resulting pro-inflammatory, membrane-rupturing cell death environment could impair the odontogenic stem and progenitor cell niches that continuously replenish the growing incisor. Because elodont tooth elongation depends on the coordinated activity of apical epithelial and mesenchymal niches, microvascular support, odontoblast differentiation, and dentin mineralization, the incisor is an unusually sensitive integrator of systemic physiological disturbance—an active biological response rather than a passive symptom of a sick animal.

The translational horizon is necessarily modest: continuously growing incisors are rodent-specific, so the growth parameter itself will live in the preclinical world, where it could refine animal monitoring under the 3Rs framework by replacing repeated blood draws with repeated notches. But the mechanistic question it opens is broadly relevant. Diabetes is already associated with pulpal vasculopathy, advanced glycation end-product accumulation, impaired reparative capacity, and more aggressive periapical inflammation. If chronic metabolic dysregulation can push the dental pulp of a growing animal into necroptotic signaling, the same question deserves asking in humans—particularly children with type 1 diabetes, whose dental maturation, eruption timing, and root development might carry fingerprints of their metabolic history. Confirmation in larger cohorts, pathway-specific interventions, and time-resolved molecular sampling will be needed to turn this association into mechanism, but the notion that a notch on a rat’s tooth can reveal the hidden cost of high blood sugar is a compelling start.

Subject of Research: Necroptosis-related signaling and elodont incisor growth retardation in hyperglycemic rats

Article Title: Association between dental pulp necroptosis-related signaling and elodont incisor growth retardation in hyperglycemic rats

Article References: Kim, M. G., Amara, H. B., Thomsen, P., Asa’ad, F., & Park, C. H. (2026). Association between dental pulp necroptosis-related signaling and elodont incisor growth retardation in hyperglycemic rats. Journal of Advanced Research. https://doi.org/10.1016/j.jare.2026.10.027

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.10.027

Keywords: necroptosis, type 1 diabetes, dental pulp, elodont incisor, hyperglycemia, RIPK3, MLKL, PGAM5, oxidative stress, streptozotocin, odontogenesis, biomarker

Cold tumors earn their name through a combination of cell-intrinsic and cell-extrinsic defenses. During oncogenesis, cancers are sculpted by immune surveillance and emerge only after disabling antigen processing and presentation, often through loss of β2-microglobulin or downregulation of major histocompatibility antigens, impairing interferon-γ signaling, and blunting cytotoxic T-cell activity. Beyond these internal evasions, immune-desert and immune-excluded tumors also lack the external cues an adaptive response requires: a microenvironment free of suppressive cancer-associated fibroblasts, tumor-associated macrophages, and myeloid-derived suppressor cells, and sufficient adjuvanticity — the danger signals, or damage-associated molecular patterns, needed to activate dendritic cells and drive cross-priming of CD8-positive T cells. Overcoming both layers of resistance, the authors contend, is precisely what ZBP1-driven signaling is built to do.

ZBP1, short for Z-form nucleic acid binding protein 1 and formerly known as DAI, is an interferon-stimulated gene product equipped with two N-terminal Zα domains that selectively bind nucleic acids in the left-handed Z conformation — unusual helical forms of both RNA and DNA. When ZBP1 encounters Z-form nucleic acids, likely oligomerizing through a process of Z-NA bridging followed by RHIM-domain self-association, liquid-liquid phase separation, and condensate formation, it recruits the kinase RIPK3 through homotypic RHIM interactions. Activated RIPK3 then phosphorylates MLKL, which oligomerizes, migrates to cellular membranes, and punches pores, triggering necroptosis — a lytic, highly inflammatory form of programmed cell death. ZBP1 can also engage RIPK1 through the same RHIM-dependent mechanism, coupling Z-NA sensing directly to NF-κB-driven inflammatory transcription, so the pathway inflames tissue even when cells survive.

The pathway’s virological credentials are central to its therapeutic appeal. During influenza A virus and certain herpesvirus infections, replicating viruses generate nuclear Z-RNAs that ZBP1 detects, initiating an inside-out necroptotic program in which RIPK3 and MLKL are activated within the nucleus, rupturing the nuclear envelope, spilling genomic DNA into the cytosol, and culminating in cell death. Post-necroptotic zombie cells can continue releasing cytokines and danger signals long after membrane rupture, prolonging the inflammatory consequences. Even sub-lethal necroptosis can be durably inflammatory: MLKL pores can leak inflammatory mediators without killing the cell, and ESCRT-III-driven membrane repair can close those pores for at least 16 hours in cultured fibroblasts, with cells eventually dephosphorylating MLKL, reversing phosphatidylserine exposure, and resuming robust growth. Influenza-surviving cells can maintain a type I interferon-driven inflammatory state for days or weeks, and RIPK3 can independently activate NF-κB- and IRF-3-dependent gene expression programs even in cell types refractory to necroptotic rupture, such as cortical neurons.

Translated to oncology, these mechanisms attack every major barrier to checkpoint inhibitor responsiveness at once. Frank necroptosis releases a rich repertoire of damage-associated molecular patterns and cytokines that activate innate sensing pathways, and in tandem with RIPK1- and RIPK3-mediated transcriptional programming it boosts the mobilization, activation, and antigen loading of antigen-presenting cells, driving cross-priming of cytotoxic T lymphocytes. The immunogenicity of the pathway is rooted in evolution: the adaptive immune system evolved to respond to pathogens, not tumors, and ZBP1-triggered programs are de facto antiviral defenses that both eliminate the infected or transformed cell and supply the adjuvant cues for full adaptive immune activation. The catch is that tumors know this too. Many cancers epigenetically silence RIPK3, removing the signaling conduit that ZBP1 needs, and thereby escaping necroptotic elimination during their evolution.

The Fox Chase team highlights an exploitable loophole: while tumor cells frequently lose the ZBP1-RIPK3 machinery, stromal cells within the tumor microenvironment often retain it intact. Inflammatory cancer-associated fibroblasts, or iCAFs, are a particularly attractive target. Although iCAF-rich tumors are characterized by elevated regulatory T cells, impaired cytotoxic CD8 T-cell activity, and extensive fibrotic remodeling, the iCAFs themselves remain competent for ZBP1 and RIPK3 signaling. Preclinical studies show that activating ZBP1 within iCAFs can potently reverse checkpoint inhibitor unresponsiveness, meaning the pathway can be reignited inside the tumor mass even when the malignant cells themselves are genetically deaf to the signal. This reframing turns a suppressive stromal compartment into a therapeutic vulnerability.

How, then, to switch ZBP1 on in the clinic? One strategy targets ADAR1, the p150 isoform of which quench Z-RNAs by binding, editing, and sequestering them before ZBP1 can see them. No clinically viable ADAR1 inhibitors exist yet, but several routes are advancing: all-trans retinoic acid induces proteasomal degradation of ADAR1 and synergizes with PD-1 blockade in pancreatic cancer models; a structurally specific PROTAC called Z-PROTAC selectively degrades ADAR1; and the nuclear export inhibitor selinexor traps ADAR1 p150 in the nucleus, relieving cytoplasmic suppression of ZBP1 and promoting beneficial ZBP1-dependent signaling during antitumor immune responses.

A second family of approaches forces Z-form nucleic acids to accumulate directly. The curaxin compound CBL0137 induces the B-to-Z transition in genomic DNA; ZBP1, which shuttles between cytoplasm and nucleus, detects the resulting nuclear Z-DNA, activates RIPK3, and triggers necroptosis that boosts checkpoint responses in preclinical cold tumor models. CBL0137 is now being tested as an adjuvant to nivolumab and ipilimumab in a Phase I trial for refractory or recurrent melanoma — a rational setting given that 30 to 40 percent of melanoma patients show primary resistance and another 20 to 25 percent eventually acquire it. On the RNA side, spliceosome inhibition with agents such as pladienolide B causes intron retention and the accrual of endogenous retroelement-derived Z-RNAs that ZBP1 directly senses; in small cell lung cancer models this induced ZBP1-dependent death in necroptosis-competent tumor cells and fibroblasts and enhanced immunotherapy responsiveness. Disrupting mRNA 3-end processing works similarly: inhibiting the CPSF3 nuclease with JTE-607, or deleting the exoribonuclease XRN1, causes aberrantly elongated readthrough transcripts laden with Z-forming retroelements to pile up in the nucleus, mirroring what happens during influenza and herpesvirus infections when viral proteins block CPSF activity.

Oncolytic viruses constitute a third and especially actionable class. Talimogene laherparepvec, the FDA-approved oncolytic herpes simplex virus for advanced melanoma, generates copious Z-RNA — mostly from disrupted termination of host pre-mRNAs caused by the viral ICP27 protein blocking CPSF. But HSV-1 also encodes a RHIM-containing protein, ICP6, that blocks ZBP1-RIPK3 signaling in human cells, so the authors argue that engineered HSV-1 variants with a non-functional ICP6 RHIM could be even more powerful checkpoint adjuvants than the approved virus. Pelareorep, an oncolytic reovirus, has shown promise with checkpoint inhibitors in early trials of pancreatic adenocarcinoma and hormone receptor-positive metastatic breast cancer and induces necroptotic death, though whether it activates ZBP1 through Z-RNA remains unproven. Oncolytic influenza A viruses, whose NS1 protein potently disrupts CPSF, represent a still untapped way of triggering the pathway.

Toxicity is the sobering counterweight, because ZBP1-driven necroptosis is anything but benign — during severe influenza it drives the pulmonary immunopathology that makes the disease lethal, and systemically induced ZBP1 activity risks necroinflammatory injury in vulnerable tissues such as lung and gastrointestinal epithelium. The authors therefore propose a prime-trigger-release paradigm: first prime the tumor microenvironment to express ZBP1, for instance by intra-tumoral delivery of a replication-deficient adenovirus encoding interferon-γ; then trigger activation with a pharmacologic Z-NA inducer such as CBL0137 or a CPSF3 inhibitor; finally, let the released antigens and danger signals propagate systemically under checkpoint blockade. Localized activation could achieve an abscopal-like systemic tumor control while sparing healthy tissue. Immune-excluded cancers with dense fibrotic stroma — pancreatic adenocarcinoma, cholangiocarcinoma, desmoplastic melanoma — are flagged as the most compelling initial targets, where ZBP1 ignition in fibroblasts may dismantle stromal walls and grant T cells access to tumor nests. If the strategy survives those tests, a sensor forged by millennia of antiviral warfare may become one of immunotherapy’s most versatile ignition keys.

Subject of Research: ZBP1-driven necroptotic and inflammatory signaling as a strategy to overcome resistance to immune checkpoint inhibitors in immunologically cold tumors

Article Title: Leveraging ZBP1 signaling for cancer immunotherapy

Article References: Desai, P., Wen, C., & Balachandran, S. (2026). Leveraging ZBP1 signaling for cancer immunotherapy. Frontiers in Cell Death, 5, Article 1841599. https://doi.org/10.3389/fceld.2026.1841599

Image Credits: AI Generated

DOI: 10.3389/fceld.2026.1841599

Keywords: ZBP1, necroptosis, RIPK3, MLKL, immune checkpoint inhibitors, cold tumors, Z-RNA, Z-DNA, ADAR1, cancer-associated fibroblasts, oncolytic viruses, cancer immunotherapy

The study was led by researchers at the Chinese Academy of Sciences in Shanghai, including co-corresponding author Liming Sun. The team set out to answer a question that has received surprisingly little attention in cancer biology. Most work on metastasis has focused on how cancer cells acquire the ability to migrate in the first place, Sun explains. Far fewer studies have asked what ultimately happens to those migrating cells if they stay stuck under the kind of chronic physical stress they would encounter inside a densely packed tumor. That gap in knowledge motivated the new research.

To address it, the researchers stepped away from one of the field’s most entrenched habits: the two-dimensional cell culture. In a flat plastic dish, cancer cells grow under essentially no confinement, spreading freely across a surface that bears little resemblance to living tissue. In the body, by contrast, solid tumors are crowded, pressurized environments. As cancer cells proliferate and migrate within confined spaces, they are subjected to progressively increasing compressive forces. The team built three-dimensional experimental systems designed to capture these conditions, allowing them to observe how pressure and mechanical confinement shape cell growth and survival over time.

A central focus of the work was a specific stage of cancer cell behavior called the mesenchymal-to-amoeboid transition, or MAT. This is a biological switch in which a cell abandons an elongated, adhesive mode of migration in favor of a polarized, highly deformable one. Rather than crawling along surfaces, amoeboid cells round up and squeeze through tight spaces, a strategy that lets cancer cells rapidly adapt to physical barriers without waiting for slow changes in gene transcription. It is an efficient escape mechanism, and it is one of the ways tumors become invasive. But the new study shows that this same highly deformable state carries a hidden vulnerability.

When the researchers subjected these cells to prolonged mechanical confinement, they found that the physical pressure alone was enough to trigger cell death. The mechanism the team identified was necroptosis, a regulated form of necrotic cell death that cells can deploy as an alarm signal. Sun described the discovery as an entirely unexpected mechanism: in these cells, prolonged mechanical confinement is not merely a physical obstacle, but an active signal that switches on the necroptosis program. In other words, the tumor’s own crowded architecture can be read by individual cancer cells as a danger signal, and the response is self-destruction.

The implications reach in two directions. First, the finding reframes mechanical stress inside tumors as a potential protective factor rather than a purely adverse condition. Second, because physical pressure alone can activate the death pathway, it suggests a therapeutic opening. Combining existing cancer therapies with approaches that push cells toward necroptosis could, in principle, reinforce the body’s own defenses against tumor growth and spread. The researchers suggest that treatments designed to potentiate this pressure-sensing death pathway might make tumors less able to seed metastases, the process responsible for most cancer deaths.

The study also points to a possible clinical marker. The protein MLKL is the executor molecule that triggers necroptosis when cells are under physical pressure. According to the researchers, MLKL could potentially be developed as a biomarker to predict how likely a tumor is to metastasize. The logic is straightforward: tumors containing lower levels of MLKL would be expected to have a weaker pressure-triggered death program, and therefore a greater likelihood of spreading. If validated, measuring MLKL in tumor samples could help oncologists identify which patients carry the most dangerous, migration-prone cancers.

Interestingly, the team reports that the necroptosis pathway activated under confinement operates independently of RIPK3, a kinase that is conventionally considered a core initiator of necroptotic death. The study, titled Long-term confinement triggers RIPK3-independent necroptosis in amoeboid cancer cells to shape tumor evolution, suggests that mechanical stress recruits the cell death machinery through a route that bypasses this canonical regulator. That detail matters both mechanistically and clinically, because it indicates that cells in crowded tumors have evolved—or at least access—an alternative wiring diagram for necroptosis, one that future drugs would need to engage if the goal is to deliberately activate the pathway in patients.

The researchers plan to continue studying the molecular mechanism in greater detail, both to deepen the general understanding of necroptosis and to look for new opportunities to activate MLKL therapeutically in cancer. They are also investigating how activated MLKL stops metastasis before confining and killing the cancer cells, a sequencing question that could clarify exactly when and where the death program intervenes in the metastatic cascade. Answering that will require understanding how the mechanical signal is converted into a biochemical one inside the cell, and how long a cell must remain confined before the program becomes irreversible.

Beyond cancer, the work carries a broader methodological message. The hope, Sun says, is that by using experimental systems that better reflect the physical conditions cells experience in living tissues, researchers can learn more about what fundamentally determines whether a cell lives or dies. The study was supported by the National Key Research and Development Program of China, the CAS Youth Interdisciplinary Team, the National Natural Science Foundation of China, and the innovative research team of high-level local universities in Shanghai. For a field that has spent decades interrogating the genetic and chemical cues of cancer, this study is a reminder that physics—pressure, crowding, confinement—is not background noise. It is a signal, and sometimes it is a weapon the body already possesses.

Subject of Research: Mechanical confinement triggering necroptotic cell death in migrating cancer cells within dense tumors

Article Title: When cancer cells are squeezed into tightly packed tumors, cancer stops spreading

Article References: When cancer cells are squeezed into tightly packed tumors, cancer stops spreading. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: cancer, metastasis, necroptosis, mechanical confinement, MLKL, RIPK3, mesenchymal-to-amoeboid transition, tumor biology, cell death, biomarker, Developmental Cell, 3D cell culture

Necroptosis first came into sharp focus in the late 2000s, when researchers showed that a kinase called RIPK3 could switch tumor necrosis factor signaling away from apoptosis and toward necrosis. The pathway was soon mapped in detail. When caspase-8, the enzyme that normally executes apoptosis, is inhibited, RIPK1 and RIPK3 phosphorylate one another and assemble into an amyloid-like signaling complex sometimes called the necrosome. RIPK3 then phosphorylates MLKL, a pseudokinase that translocates to the plasma membrane and disrupts it, killing the cell. The pathway can be triggered not only by TNF but also by Toll-like receptors, interferons, and the Z-nucleic acid sensor ZBP1, and it plays documented roles in viral defense, inflammatory disease, and neurodegeneration. Because every one of these steps depends on the precise assembly and disassembly of protein complexes, the pathway is exquisitely sensitive to post-translational modifications, and none is more pervasive than ubiquitination.

Ubiquitination is the cell’s universal labeling system. Ubiquitin, a small 76-amino-acid protein, is attached to lysine residues on target proteins through an enzymatic cascade: an E1 activating enzyme hands ubiquitin to an E2 conjugating enzyme, and an E3 ubiquitin ligase performs the final, decisive step of recognizing the substrate and catalyzing transfer. Because E3 ligases choose their substrates, they are the true arbiters of what gets tagged and what does not. The tags themselves come in varieties with very different meanings. A single ubiquitin or a K48-linked chain usually condemns a protein to destruction by the proteasome, whereas K63-linked and linear (M1-linked) chains act as scaffolds that assemble signaling complexes, particularly in the NF-kappaB pathway. E3 ligases fall into structurally distinct families, including the really-interesting-new-gene (RING) ligases that include the large cullin-RING assemblies, the HECT-domain ligases that pass ubiquitin through an intermediate, and the RBR ligases that combine features of both. Many of these enzymes are themselves dysregulated in cancer, which is precisely why their grip on necroptosis matters.

The clearest examples of E3-mediated control center on RIPK1, the gateway kinase of the pathway. The deubiquitinating enzyme CYLD must strip K63-linked chains from RIPK1 within the TNF-induced necrosome before the complex can become a competent necroptosis machine, a finding that established ubiquitin editing as a gatekeeper of programmed necrosis. On the writing side, the E3 ligase PELI1 (Pellino1) ubiquitinates RIPK1 and acts as a dual modulator, influencing both necroptosis and apoptosis while also controlling levels of the anti-apoptotic protein c-FLIP. TRAF6, another RING-type ligase best known for its immune signaling roles, regulates the abundance of RIPK1 and suppresses the RIPK1-RIPK3-MLKL cascade, and studies cited in the review show that this affects colorectal cancer progression. A20, a ligase-deubiquitinase hybrid that restrains NF-kappaB signaling, has been shown to suppress spontaneous necroptosis in acute myeloid leukemia, and that suppression mediates chemotherapy resistance, a striking example of ubiquitin control determining treatment outcome.

RIPK3 and MLKL, the downstream executors, are equally entangled in ubiquitin biology. TRIM25, a member of the tripartite-motif ligase family, ubiquitinates RIPK3 and thereby inhibits TNF-induced necrosis, positioning it as a potential tumor-sensitizing target. The U-box ligase CHIP controls necroptosis through ubiquitylation-dependent, lysosome-mediated degradation of RIPK3, and clinical data from non-small cell lung cancer suggest that CHIP and RIPK3 levels carry prognostic weight. More recently, opposing regulation of K63-linked polyubiquitination of RIPK3 by the ligase SMURF1 and the deubiquitinase USP5 has been shown to tune the pathway, while the cullin-RING substrate adaptor SPOP mediates ubiquitination of both RIPK1 and RIPK3, promoting apoptosis and protecting against necroptosis. Even MLKL itself is tagged: site-specific ubiquitination redirects it to endosomes, a modification that in infected cells helps route intracellular bacteria such as Listeria and Yersinia to lysosomes. The AMPK-Parkin axis adds another layer, with the Parkin ligase helping to inhibit the necrosome and thereby restraining both necroptosis and tumorigenesis.

The inhibitor-of-apoptosis (IAP) proteins occupy a special place in this story because they are both E3 ubiquitin ligases and established drug targets. cIAP1, cIAP2, and XIAP ubiquitinate components of TNF receptor signaling and keep necroptotic complexes in check. Pellino-1 has been shown to confer chemoresistance in lung cancer cells by upregulating cIAP2 through K63-linked polyubiquitination, and the TRIP-Br1 oncoprotein stabilizes XIAP to inhibit apoptosis, autophagy, and necroptosis under nutrient-deprived conditions, helping tumor cells survive starvation. The therapeutic payoff is already visible: SMAC mimetics, drugs that degrade IAPs, are in clinical development for cancer, with agents such as xevinapant being tested with radiation in head and neck cancer and tolinapant (ASTX660) evaluated in colorectal cancer. By removing the ubiquitin-ligase brake on death receptor signaling, these compounds can sensitize tumors to TNF-alpha, TRAIL, and radiotherapy, in part by liberating the necroptosis machinery.

What makes the review by Wei and Sun timely is its insistence that E3 ligase control of necroptosis is not a laboratory curiosity but a determinant of cancer behavior in both directions. Necroptosis can suppress tumors by killing malignant cells and, through the release of antigens and the involvement of RIPK1-dependent signaling in dying cells, by priming CD8-positive T cell responses, raising interest in engineering necroptotic tumor cell vaccines for immunotherapy. Yet it can also promote cancer. Tumor cells can induce necroptosis in endothelial cells through death receptor 6, opening gaps in the vasculature that facilitate metastasis, and in pancreatic cancer, necroptosis has been shown to enhance so-called don’t-eat-me signals and induce macrophage extracellular traps that promote liver metastasis. Chronic necroptotic inflammation can also feed tumor-promoting microenvironments. Which way the balance tips depends heavily on the ubiquitin-editing enzymes that decide when and where the pathway fires.

This duality explains why the E3 ligases themselves are attractive drug targets, and why targeting them is technically demanding. Cullin-RING ligases, HECT ligases, and RBR ligases have all yielded small-molecule modulators in drug discovery programs, and the success of molecular glue degraders and PROTAC degraders, which hijack E3 ligases to destroy disease proteins, has energized the field. In principle, one could inhibit a ligase such as TRAF6 or TRIM25 to unleash necroptosis in a tumor that has locked the pathway down, or boost a protective ligase to suppress the inflammatory necroptosis that fuels metastasis. The complication is context: the same enzyme can protect in one tissue and promote disease in another, and E3 ligases typically have dozens of substrates beyond the necroptosis machinery, raising the specter of on-target toxicity in normal tissues that rely on these enzymes for immune homeostasis.

Wei and Sun argue that the next phase of the field will require mapping which E3 ligases act on which necroptosis substrates in which tumor types, and identifying biomarkers, such as CHIP, RIPK3, or BIRC3 expression, that predict whether a patient’s tumor is primed for necroptotic death or defended against it. The convergence of ubiquitin biology and cell death research is producing a picture in which cancer is not simply a matter of genes gone bad, but of molecular tags gone wrong. If the ubiquitin code of necroptosis can be read and rewritten with the same precision now being applied to protein degradation, the explosive form of cell death may finally become a controllable weapon against cancer, rather than the unpredictable force it has so often appeared to be.

Subject of Research: Regulation of necroptotic cell death by E3 ubiquitin ligases and its implications for cancer therapy

Article Title: E3 ubiquitin ligase-mediated necroptosis: regulatory mechanisms and therapeutic implication in cancer

Article References: Wei, M., & Sun, A. (2026). E3 ubiquitin ligase-mediated necroptosis: regulatory mechanisms and therapeutic implication in cancer. Molecular Biology Reports, 53(1), Article 1698. https://doi.org/10.1007/s11033-026-12900-w

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12900-w

Keywords: necroptosis, E3 ubiquitin ligases, ubiquitination, RIPK1, RIPK3, MLKL, cancer therapy, IAP antagonists, TRIM25, TRAF6, inflammation, tumor microenvironment

To understand why this matters, it helps to picture the two signaling complexes that form after TNF binds its receptor, TNFR1. At the plasma membrane, TNFR1 recruits RIPK1 through its death domain to build complex I, a platform that activates the IKK/NF-κB and MAPK pathways and thereby promotes cell survival and inflammatory gene transcription. When complex I is destabilized, RIPK1 can instead nucleate cytosolic complexes: complex IIa, containing RIPK1, FADD and caspase 8, which drives apoptosis; or, when caspase 8 is inhibited, complex IIb, the RIPK1–RIPK3 necrosome that initiates necroptosis, a lytic form of cell death in which activated RIPK3 phosphorylates MLKL, sending it to the plasma membrane to rupture the cell. RIPK1 is a component of all these assemblies, but the biochemical event that converts it from a prosurvival scaffold in complex I into a prodeath kinase in complex II has remained elusive.

The search began with an unbiased genetic approach. The team, led by Haohao Lu and Tongde Du in the laboratory of Sudan He at the Suzhou Institute of Systems Medicine, together with She Chen and Henning Walczak, conducted a CRISPR–Cas9 screen in human HT-29 colon cancer cells using a guide RNA library targeting genes encoding ubiquitin E3 ligases, deubiquitinating enzymes and other ubiquitination-associated proteins. The cells were challenged with a necroptosis-inducing cocktail of TNF, a Smac mimetic and the pan-caspase inhibitor z-VAD, a combination known as TSZ. After four rounds of selection, the single guide RNA targeting HERC4 emerged as the most enriched hit among all the E3 ligases and deubiquitinases tested, marking the enzyme as a prime suspect in the cell death machinery.

Validation followed swiftly across cell types. HERC4-knockout lines generated in HT-29, LS 174T, THP-1 and Jurkat cells all showed marked resistance to necroptosis, surviving doses of TSZ that killed their wild-type counterparts. Reintroducing HERC4, even at subphysiological levels, restored sensitivity to the death stimulus. Crucially, the loss of HERC4 did not merely blunt a downstream effector: phosphorylation of RIPK1, RIPK3 and MLKL, the sequential activations that define the necroptosis pathway, were all significantly reduced in HERC4-deficient cells. MLKL oligomerization and its translocation to the plasma membrane, the final steps before necroptotic rupture, were likewise suppressed. The same protection appeared in mouse embryonic fibroblasts and in a second necroptosis model using a TAK1 inhibitor, establishing HERC4 as a driver acting upstream of the canonical RIPK1–RIPK3–MLKL axis in both human and mouse cells.

Because HERC4 is a ubiquitin ligase, the next question was which protein it decorates. Coexpression experiments showed that HERC4 increased polyubiquitination of RIPK1 but not of RIPK3. Using mutant ubiquitin restricted to single linkage types, the researchers found that HERC4 specifically catalyzes K63-linked chains, a modification classically associated with signal transduction rather than protein degradation, and indeed HERC4-mediated ubiquitination did not lead to RIPK1’s destruction. In vitro assays with recombinant proteins confirmed that HERC4 directly ubiquitinates RIPK1, and mapping experiments showed that the intermediate domain of RIPK1 binds the HECT domain of HERC4, the region that carries the ligase’s catalytic activity.

Mass spectrometry then pinpointed the exact modification site. Among the ubiquitinated peptides recovered from RIPK1, one, EubKVYQMLQK, appeared exclusively when HERC4 was present and was absent with a catalytically inactive HERC4 mutant. The fragmentation spectrum unmasked lysine 627 on human RIPK1 as the ubiquitination site, a residue within the death domain that is highly conserved across species and corresponds to K612 in the mouse protein. This was a striking finding, because earlier work had shown that substituting this very lysine prevents TNF-induced cell death, hinting that ubiquitination there might be a necessary licensing step. A catalytically inactive HERC4 mutant, engineered on the basis of AlphaFold3 predictions by mutating H1023, C1025 and D1030, still bound RIPK1 but could no longer ubiquitinate it, and cells expressing this mutant were markedly resistant to necroptosis, proving that the ligase activity itself is what matters.

The mechanism that emerges is elegant and precise. HERC4 does not act indiscriminately: its interaction with RIPK1 occurs only under apoptotic or necroptotic stimulation, not with TNF alone, and is abolished by the RIPK1 kinase inhibitor necrostatin 1s. The team showed that HERC4 selectively recognizes RIPK1 that has been autophosphorylated at serine 166, the hallmark of RIPK1 kinase activation, since an S166A mutant lost the interaction while phosphomimetic S166D and S166E variants enhanced it. Sequential immunoprecipitation of the TNFR1 signaling complexes revealed that HERC4 is absent from membrane-bound complex I and instead binds complex I-derived, S166-phosphorylated RIPK1 once it has been released into the cytosol. There, HERC4’s K63-linked ubiquitination of the death domain enables RIPK1 to oligomerize, both with itself and with FADD, nucleating the assembly of complex IIa and, when caspases are blocked, the RIPK1–RIPK3 necrosome. Gel-filtration analysis confirmed that intact HERC4, but not the catalytic mutant, permits the formation of high-molecular-weight complexes containing phosphorylated RIPK1, RIPK3, MLKL and caspase 8.

Importantly, HERC4’s role is confined to the death arm of TNF signaling. The enzyme is dispensable for NF-κB activation: HERC4 knockout left phosphorylation of P65, IκBα, TAK1 and IKKα/β untouched, and it did not alter RIPK1 ubiquitination at K377, the cIAP1/2-mediated modification in complex I that supports survival signaling. This separation is what makes HERC4 so attractive as a drug target. Blocking it would, in principle, disarm TNF’s lethal potential while leaving its beneficial inflammatory and prosurvival functions intact, an effect similar to direct RIPK1 kinase inhibition but achieved one step upstream, at the licensing event itself.

The in vivo evidence is compelling. Mice lacking HERC4 were born and bred normally, indicating the protein is not essential for development. But when challenged with an overdose of TNF, a model of systemic inflammatory response syndrome, all wild-type littermates succumbed within 28 hours, whereas 80 percent of HERC4-deficient mice survived. The protected animals showed lower serum IL-6, reduced caspase 3 and PARP cleavage in the intestine, less cecal tissue damage on histology, and markedly reduced RIPK1 autophosphorylation. In a second model of acute liver injury induced by TNF and D-galactosamine, nearly all wild-type mice reached humane endpoints within four to six hours, while more than 70 percent of HERC4-deficient mice survived, with lower ALT and AST liver enzymes, reduced IL-6, suppressed hepatic caspase 3 activation and diminished histological damage.

The discovery resolves a long-standing conundrum in cell death biology: why RIPK1’s kinase activity, whose only known substrate is RIPK1 itself, is essential for TNF-induced death. The answer is that autophosphorylation at S166 creates the molecular tag that HERC4 recognizes, and HERC4’s ubiquitination of the death domain is what converts the phosphorylated kinase into a competent nucleator of the death complexes. Beyond inflammatory diseases such as SIRS, colitis and liver injury, the finding may reach into oncology, where necroptosis’s immunogenic nature has been proposed as a way to stimulate antitumor immunity, and where HERC4 has previously been implicated as a tumor suppressor. By supplying RIPK1 with what the authors call its license to kill, HERC4 now stands as both a mechanistic keystone of TNF signaling and a promising target for diseases driven by aberrant cell death.

Subject of Research: HERC4-mediated ubiquitination of RIPK1 as the molecular switch initiating TNF-induced cell death and inflammation

Article Title: HERC4-mediated ubiquitination licenses RIPK1 to initiate TNF-induced cell death

Article References: Lu, H., Du, T., Li, L., Cao, D., Li, K., Liu, L., Li, R., Yu, X., Hou, S., Wang, X., Shi, M., Liu, Y., Ma, F., Chen, S., Walczak, H., & He, S. (2026). HERC4-mediated ubiquitination licenses RIPK1 to initiate TNF-induced cell death. Nature Structural & Molecular Biology. https://doi.org/10.1038/s41594-026-01871-y

Image Credits: AI Generated

DOI: 10.1038/s41594-026-01871-y

Keywords: HERC4, RIPK1, TNF, ubiquitination, necroptosis, apoptosis, RIPK3, MLKL, inflammation, E3 ligase, liver injury, cell death signaling

To appreciate why this matters, it helps to understand that cell death is not a single process but a family of genetically programmed routines with very different consequences for the immune system. Pyroptosis, mediated by pore-forming gasdermin proteins, necroptosis, driven by the RIPK kinases and the pseudokinase MLKL, and ferroptosis, an iron-dependent form of lipid peroxidation, are the most inflammatory forms, spilling cellular contents that alarm neighboring tissue. Apoptosis, executed by caspase-3, caspase-6 and caspase-7, is by contrast mostly immunosilent, allowing cells to be quietly dismantled and cleared. Although cell death programs in intestinal epithelial cells are known to be major drivers of inflammatory bowel disease, it has remained unclear exactly which epithelial cells undergo which form of death, whether these processes can be therapeutically targeted, and whether they could serve as clinical markers of impending relapse.

The research team tackled these questions with unusual scale and rigor. They analyzed more than 900 biopsies as well as three-dimensional organoids grown from the gut tissue of controls and of inflammatory bowel disease patients with quiescent or mildly active disease, including individuals treated with biologics or small molecules, the so-called advanced therapies. From patients with Crohn’s disease and ulcerative colitis alike, the investigators collected noninflamed, marginally inflamed and inflamed biopsies. Transcriptomic analyses revealed something unexpected: even though many of these patients were clinically quiescent or already on advanced therapies, transcriptional signatures of tumor necrosis factor and interferons, together with apoptotic gene programs, were still dysregulated in their intestinal tissue.

Protein-level analyses reinforced the message. Western blotting of patient samples showed increased apoptotic and necroptotic signaling in both ulcerative colitis and Crohn’s disease, and this signaling correlated with the degree of inflammation. The spatial pattern was particularly telling. While necroptosis was elevated in noninflamed biopsies, apoptosis, whether occurring alone or alongside necroptotic markers, was found mostly in histologically inflamed samples. This ordering suggested a sequence: necroptosis precedes apoptosis during the development of lesions, with the two death programs marking different stages of the same pathological trajectory rather than representing independent phenomena.

Digging deeper with bioinformatic analyses, the authors identified a distinctive cluster of intestinal epithelial cells expressing NOS2, the gene encoding inducible nitric oxide synthase, together with ZBP1, a protein involved in multiple cell death complexes, and MLKL, the executioner of necroptosis. This cluster, which was also detectable in independent datasets, expressed genes typically associated with inflammatory macrophages, an unusual identity for epithelial cells. Spatial analyses then placed these cells precisely at the top of colonic crypts, and beneath them, in the lamina propria, the investigators found cells expressing tumor necrosis factor, coinciding with an increase in CD4-positive T cells expressing interferon gamma. In other words, the epithelial cells poised for death were sitting in an inflammatory niche saturated with the two cytokines most strongly implicated in inflammatory bowel disease.

To test whether this niche was functionally meaningful, the team established three-dimensional colonocyte organoids and exposed them to tumor necrosis factor and interferon gamma. The cytokine combination induced the inflammatory macrophage-like transcriptional program in the epithelial cells, along with necroptotic and apoptotic gene signatures. At the protein level, the researchers confirmed processing of caspase-3, caspase-8, caspase-9 and caspase-10, together with activation and cleavage of RIPK3 and MLKL. The organoids were undergoing mitochondrial apoptosis, although nonlethal necroptotic signaling was also detected, hinting that the two pathways can run in parallel within the same cells. Further mechanistic work showed that inducible nitric oxide synthase was necessary to license apoptosis, which was driven by the pro-apoptotic protein PUMA, tying the inflammatory chemistry of the gut directly to the cell’s decision to self-destruct.

The most clinically striking result came from longitudinal follow-up. The authors tracked their cohort of inflammatory bowel disease patients for 24 to 36 months and found a significant increase in the necroptotic marker phosphorylated RIPK3, and a trend toward increased apoptotic cleaved caspase-3, in patients who subsequently relapsed. These were patients who, at the time of the original analyses, showed no major signs of inflammation. A protein signature detectable in a biopsy could therefore flag, months in advance, which patients in remission are quietly heading toward a flare, potentially transforming how clinicians time treatment intensification, monitoring intervals and therapeutic withdrawals.

The study also carries important lessons for drug development. With regard to necroptosis, the authors found that the classical pattern of RIPK1, RIPK3 and MLKL activation was not consistently observed across all patients; instead, unique patterns were associated with different subgroups of individuals. This heterogeneity suggests that clinical trials of RIPK1 inhibitors would benefit from careful patient stratification, since a one-size-fits-all approach may obscure benefit in the subgroups whose biology actually depends on this pathway. Similarly, the precise identification of inducers of epithelial cell death, such as inducible nitric oxide synthase and PUMA, opens concrete targets for new therapeutic interventions aimed at promoting epithelial healing during disease.

Important questions remain open. Histological assessment of inflamed and noninflamed biopsies cannot yet predict whether a noninflamed piece of tissue is healing or harboring a future inflammatory lesion, so further studies are needed to prove the necroptotic-to-apoptotic axis in real time. The authors also suggested that necroptosis and apoptosis may occur simultaneously in the same cell, a process reminiscent of PANoptosis, a form of cell death characterized by the simultaneous activation of multiple death pathways, but visualization at the single-cell level will be needed to confirm this. There is also the question of pyroptosis. The authors identified activated gasdermin E, a pore-forming member of the gasdermin family, in their samples, and a recent separate study showed that type III interferons, which are particularly elevated in inflammatory bowel disease biopsies, correlate with ZBP1, activated caspase-8 and cleaved gasdermin C, and drive pyroptotic death of reparative stem cells that delays lesion repair. Whether the necroptotic-to-apoptotic pathway is integrated with pyroptotic programs, or whether cell type, location and timing separate these events, is now a central question for the field.

Culture systems add another layer of complexity. The identification of tumor necrosis factor plus interferon gamma as a potent driver of the necroptotic-to-apoptotic axis in three-dimensional organoids is notable, but under those experimental conditions the authors did not recapitulate the type III interferon-induced cell death or gasdermin C activation previously shown in two-dimensional organoid cultures, which are more differentiated and well defined. Tumor necrosis factor and interferon gamma have previously been found to induce pyroptosis together with apoptosis and necroptosis in the context of lung viral infections, while during acute respiratory distress syndrome type III interferons showed the capacity to induce apoptosis in mice and humans. Future studies will therefore need to address how different culture conditions, tissue origin across distinct regions of the intestinal tract, and specific cell subtypes shape the response to different inflammatory milieus and the selection of different death pathways. Even with those caveats, the study stands as an important foundation, both for a better mechanistic understanding of inflammatory bowel disease and for the development of improved intervention strategies, offering clinicians a potential early-warning system written in the language of dying cells.

Subject of Research: A necroptotic-to-apoptotic cell death axis in intestinal epithelial cells that predicts relapse in inflammatory bowel disease

Article Title: No time to die: cell death predicts IBD relapse

Article References: Zanoni, I. (2026). No time to die: cell death predicts IBD relapse. Cell Research. https://doi.org/10.1038/s41422-026-01304-x

Image Credits: AI Generated

DOI: 10.1038/s41422-026-01304-x

Keywords: inflammatory bowel disease, Crohn's disease, ulcerative colitis, necroptosis, apoptosis, pyroptosis, intestinal epithelial cells, TNF, interferon gamma, RIPK3, organoids, disease relapse

Osteocytes are the most abundant cells in bone, making up roughly ninety percent of all bone cells, and they orchestrate the constant remodeling dialogue between bone formation and bone resorption. When glucocorticoid excess strikes, trabecular bone—the spongy lattice inside vertebrae and the ends of long bones—suffers the most visible early damage. But clinicians have long observed that cortical bone, the compact shell that provides most of the skeleton’s strength, also deteriorates under prolonged steroid exposure, and that this cortical thinning correlates strongly with nonvertebral fractures. The new research provides a mechanistic account of how the cells inside cortical bone are driven to self-destruction and how their demise translates directly into mineral loss from the surrounding matrix.

The investigative team used a well-established mouse model of glucocorticoid-induced osteoporosis, in which animals receive chronic prednisolone or methylprednisolone treatment sufficient to reproduce the human pattern of rapid bone loss. Using histomorphometry, micro-computed tomography, and dynamic bone labeling, they documented substantial cortical porosity, cortical thinning, and loss of mechanical integrity. Strikingly, the loss was accompanied by a marked depletion of osteocytes within the cortical compartment and by empty lacunae—minute cavities that once housed living cells—scattered throughout the cortex. This pattern suggested that osteocyte death itself, rather than merely elevated resorption by the classic bone-dissolving osteoclasts, might be a primary event in the pathology.

To define the mode of osteocyte death, the researchers examined the molecular machinery of necroptosis, a form of regulated necrosis distinguished from apoptosis by its explosive, membrane-rupturing character and its capacity to release intracellular contents that inflame surrounding tissue. Necroptosis is executed by a signaling complex in which receptor-interacting protein kinase 1 and receptor-interacting protein kinase 3 activate the executioner protein mixed lineage kinase domain-like pseudokinase, or MLKL, which oligomerizes and punches holes in the cell membrane. In the steroid-treated mice, the team found robust activation of this pathway specifically in cortical osteocytes: phosphorylated RIPK3 and phosphorylated MLKL accumulated within lacunar cells, while markers of apoptosis were comparatively modest. Genetic or pharmacological interference with the pathway therefore became the decisive test of causality.

When the researchers crossed their glucocorticoid-treated mice with animals lacking functional MLKL, or when they treated mice with a selective RIPK1 kinase inhibitor, the picture changed dramatically. Cortical bone loss was substantially attenuated: cortical thickness was preserved, porosity declined, and biomechanical testing showed that bones retained significantly more of their strength compared with steroid-treated controls carrying intact necroptosis machinery. Osteocyte lacunae remained populated, and the hallmarks of inflammatory cell death faded. Inhibiting apoptosis, by contrast, produced only modest skeletal protection, reinforcing the conclusion that necroptosis is the dominant death program through which glucocorticoids destroy the osteocyte network in cortical bone.

The most provocative element of the study is the mechanism the authors propose for how dying osteocytes cause resorption of the mineral that surrounds them. Under normal physiological conditions, osteocytes can participate in a process called osteocytic osteolysis, in which stressed or starved osteocytes demineralize and degrade their own perilacunar matrix, releasing calcium and remolding their immediate microenvironment. The study demonstrates that necroptotic death converts this finely regulated process into a destructive free-for-all. As necroptotic osteocytes rupture, they release damage-associated molecular patterns and lysosomal enzymes that acidify the perilacunar space and dissolve the adjacent mineralized collagen matrix. In essence, each dying cell excavates the bone around it, generating the microscopic porosity that, when multiplied across millions of lacunae, hollows out the cortex from within.

Supporting this mechanism, the researchers tracked perilacunar remodeling with dynamic imaging and found that steroid exposure dramatically expanded the demineralized halos around individual lacunae, a signature of aggressive osteocytic osteolysis. They also showed that products released from necroptotic osteocytes could recruit and activate osteoclast precursors, coupling the internal excavation to conventional resorption on bone surfaces. This dual mechanism—autolytic matrix degradation by the dying cells themselves followed by secondary osteoclast activation—offers a coherent explanation for the peculiar severity and speed of glucocorticoid-induced cortical loss, which has never been fully accounted for by osteoclast activity alone.

The clinical implications are considerable. Current management of glucocorticoid-induced osteoporosis relies on calcium and vitamin D supplementation and antiresorptive agents such as bisphosphonates, which dampen osteoclast function but do nothing to protect osteocytes from dying. If necroptosis inhibition shields osteocytes from steroid toxicity in humans as it does in mice, a fundamentally new class of preventive therapy becomes conceivable: drugs that preserve the cellular network inside bone, maintaining the mechanosensory and regulatory functions that keep remodeling balanced, while simultaneously stemming the perilacunar erosion that undermines cortical strength. Inhibitors targeting the RIPK1–RIPK3–MLKL axis are already in clinical development for inflammatory and neurodegenerative diseases, which could accelerate translation into skeletal medicine.

The authors are careful to frame their conclusions within the limits of the model system. Necroptosis is a context-dependent process, and its contribution to bone loss may vary with dose, duration of steroid exposure, age, and species. Human bone biopsies from patients on long-term glucocorticoid therapy will be needed to confirm that the same molecular signature of phosphorylated MLKL and perilacunar demineralization appears in cortical osteocytes in vivo. Nonetheless, the convergence of genetic, pharmacological, and structural evidence in this study provides an unusually complete causal chain, linking a specific cell death program to a specific mode of matrix destruction and to a measurable functional outcome in the skeleton.

Beyond the immediate therapeutic horizon, the work reframes how scientists think about the skeleton’s response to stress. Osteocytes, once viewed as inert placeholders, are now firmly established as the command centers of bone, and their death by necroptosis represents a catastrophic failure of that command infrastructure. The finding that the same cells whose death is triggered by steroid excess then participate in dismantling their own mineralized surroundings blurs the boundary between cell death and bone resorption, suggesting that in disease states the two processes are woven together. For the millions of patients worldwide who depend on glucocorticoids, the study offers a concrete molecular target for keeping their skeletons intact—and a reminder that some of the most important cells in bone are the ones buried deepest inside it.

Subject of Research: Necroptosis of osteocytes as a mechanism of cortical bone resorption in glucocorticoid-induced osteoporosis

Article Title: Osteocyte necroptosis drives cortical bone resorption via osteocytic osteolysis in glucocorticoid-induced osteoporosis

Article References: Rong, X., Ren, Q., Kou, Y., Ji, Y., Cao, T., Zhang, W., Zhang, Z., Liu, H., Hasegawa, T., & Li, M. (2026). Osteocyte necroptosis drives cortical bone resorption via osteocytic osteolysis in glucocorticoid-induced osteoporosis. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03329-y

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03329-y

Keywords: osteocytes, necroptosis, glucocorticoid-induced osteoporosis, cortical bone, osteocytic osteolysis, MLKL, RIPK3, bone resorption, osteoclasts, perilacunar remodeling, Cell Death Discovery, bone fractures

Inflammatory bowel disease affects millions of people worldwide, and its hallmark is a self-perpetuating loop of tissue damage. Barrier breakdown in the intestinal epithelium allows microbial products to flood the underlying tissue, where resident macrophages respond by releasing cytokines that recruit and activate further immune cells. When this response fails to resolve, the mucosa becomes a chronic battlefield. Current therapies, including corticosteroids, anti-TNF antibodies, and integrin blockers, help many patients but lose effectiveness in a substantial fraction, which is why researchers continue to search for checkpoints within innate immune cells that could be exploited pharmacologically.

The new work focuses on PANoptosis, an inflammatory form of programmed cell death that has attracted intense attention since it was first defined. Unlike apoptosis, which quietly removes cells without alarming the immune system, PANoptosis combines features of pyroptosis, apoptosis, and necroptosis in a single, highly inflammatory package. At its core sits a multiprotein assembly called the PANoptosome, which in many contexts is organized around the sensor protein ZBP1, a nucleic acid receptor better known for detecting viral RNA. When ZBP1 is engaged, it recruits RIPK3, caspase-8, and other partners, driving cells to die in a way that releases danger signals and amplifies inflammation. Uncontrolled ZBP1-driven PANoptosis has been implicated in several sterile inflammatory diseases, making it a tempting but delicate target.

Using mouse models of colitis, the research team found that NINJ2 expression in intestinal macrophages changed markedly as inflammation developed. When the researchers deleted the Ninj2 gene specifically in myeloid cells, the animals fared substantially worse: colitis induced by dextran sulfate sodium produced greater weight loss, more pronounced colon shortening, higher histological damage scores, and elevated levels of pro-inflammatory cytokines such as TNF, IL-1β, and IL-6. The worsened disease was not simply a matter of more macrophages arriving in the tissue. Instead, the macrophages that remained appeared locked into a hyperinflammatory state, suggesting that NINJ2 normally functions as an intrinsic regulator of how these cells respond to danger.

The mechanistic thread connecting NINJ2 to disease severity ran directly through the ZBP1 pathway. In macrophages lacking NINJ2, the investigators documented increased activation of the molecular machinery of PANoptosis, including enhanced phosphorylation of RIPK3 and mixed lineage kinase domain-like protein, the executioner of necroptosis, together with evidence of caspase activation and gasdermin cleavage. Levels of ZBP1 itself rose in the absence of NINJ2, and the assembly of the PANoptosome appeared more robust. Conversely, when the team reduced ZBP1 genetically in the NINJ2-deficient setting, the exaggerated inflammatory response was tamed and colitis pathology eased, placing ZBP1 downstream of NINJ2 in the causal chain and confirming that the benefit of NINJ2 depends on keeping this sensor in check.

To probe how NINJ2 accomplishes this restraint, the researchers examined transcriptional regulation. Their data indicate that NINJ2 influences the expression of ZBP1 at the level of messenger RNA, effectively lowering the dose of the danger sensor available to assemble into a PANoptosome. This dose-control mechanism matters because ZBP1 is unusual among innate immune receptors: it can be activated not only by foreign RNA but also by endogenous nucleic acid motifs, meaning that even modest increases in its abundance can lower the threshold for spontaneous inflammatory cell death. By holding ZBP1 transcription down, NINJ2 appears to act as a dimmer switch on an otherwise hair-trigger pathway.

Cell culture experiments reinforced the picture. When macrophages were stimulated with inflammatory ligands, those lacking NINJ2 died more readily and secreted more cytokines, while restoring NINJ2 expression rescued both outcomes. The rescue was abolished when ZBP1 was experimentally elevated, underlining the epistatic relationship between the two proteins. The team also observed that the PANoptosome components physically associated more extensively in NINJ2-deficient cells, consistent with a model in which NINJ2 limits both the quantity of ZBP1 and the downstream assembly of the death complex. Together, the in vivo and in vitro results form a coherent loop: NINJ2 restrains ZBP1, restrained ZBP1 limits PANoptosis, and limited PANoptosis means fewer danger signals to perpetuate intestinal inflammation.

What makes the discovery particularly striking is NINJ2’s résumé. The protein was originally characterized in the nervous system, where it is strongly upregulated in Schwann cells after peripheral nerve injury and contributes to axonal regeneration and remyelination. Its presence in macrophages had been noted, but its immunological function was largely unexplored. The new data suggest a broader physiological role in which the same molecule that helps damaged nerves recover also helps immune tissue recover from inflammatory assault. That kind of cross-system redeployment is increasingly common in immunology, where molecules first discovered in one organ are later found to be central choreographers of innate immune behavior elsewhere.

The therapeutic implications are tentative but concrete. If NINJ2’s protective effect can be mimicked, either by small molecules that increase its expression in intestinal macrophages or by delivery systems that supply the protein or its downstream effectors, patients with inflammatory bowel disease might gain a treatment that works at the source of cytokine storm rather than neutralizing individual cytokines after release. Targeting upstream regulators also carries risks, however. PANoptosis serves host defense, particularly against viruses, so wholesale suppression could impair pathogen clearance. The NINJ2-ZBP1 axis is attractive precisely because it appears to modulate the pathway’s set point rather than abolish it, but any clinical translation would need to define carefully how much damping is safe. Biomarkers of NINJ2 expression in patient biopsies could help identify which individuals are most likely to benefit.

Open questions remain. The precise molecular contacts, if any, between NINJ2 and the transcriptional machinery governing ZBP1 have not been fully mapped, and it is not yet clear whether NINJ2 acts directly on the ZBP1 promoter or through intermediate regulators. It is also unknown whether the pathway operates identically in human intestinal macrophages, which differ from their murine counterparts in several respects. Nonetheless, by connecting a nerve-associated protein to the ZBP1-PANoptosis cascade in the gut, the study adds a new node to the network that decides when macrophages choose inflammatory death, and it offers researchers a fresh candidate for intervention in a disease that still lacks a durable cure for many patients. Follow-up work will determine whether raising NINJ2 in the inflamed intestine can turn that candidate into a therapy.

Subject of Research: The role of NINJ2 in regulating macrophage ZBP1-PANoptosis during inflammatory bowel disease

Article Title: NINJ2 alleviates inflammatory bowel disease by regulating the macrophage ZBP1-PANoptosis pathway

Article References: Peng, H., Yu, Y., Du, Y., Guo, X., Yu, Q., Xu, C., & Song, W. (2026). NINJ2 alleviates inflammatory bowel disease by regulating the macrophage ZBP1-PANoptosis pathway. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03353-y

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03353-y

Keywords: NINJ2, inflammatory bowel disease, PANoptosis, ZBP1, macrophages, colitis, innate immunity, cell death, cytokines, intestinal inflammation, RIPK3, Schwann cells

Necroptosis and ferroptosis are distinct biological programs, but both can culminate in catastrophic loss of plasma-membrane integrity and the release of inflammatory intracellular contents. Necroptosis is a kinase-driven form of regulated necrosis that is typically associated with the receptor-interacting protein kinase 1, receptor-interacting protein kinase 3, and mixed lineage kinase domain-like pseudokinase axis. In response to signals such as tumor necrosis factor, pathogen-associated stress, damage-associated molecular patterns, or certain chemical insults, RIPK1 and RIPK3 can assemble into a signaling platform known as the necrosome. This promotes phosphorylation and oligomerization of MLKL, which then moves to the plasma membrane and disrupts its architecture. The resulting cellular rupture can release damage-associated molecular patterns and amplify local inflammation.

Ferroptosis follows a different molecular route. It is driven by iron-dependent oxidative damage to membrane lipids, particularly phospholipids containing polyunsaturated fatty acids. When intracellular iron availability and reactive oxygen species increase, susceptible lipids can undergo a chain reaction of peroxidation. Under normal conditions, antioxidant systems limit this process. Glutathione peroxidase 4 is one of the principal defenses because it reduces toxic lipid hydroperoxides to less-reactive lipid alcohols. Ferroptosis suppressor protein 1 provides another protective mechanism by supporting the regeneration of reduced coenzyme Q10, a radical-trapping antioxidant. When these systems are overwhelmed or disabled, lipid peroxide accumulation destabilizes membranes and can ultimately produce irreversible cell damage.

Although the initiating signals differ, the two pathways can be influenced by overlapping cellular conditions. Redox imbalance, mitochondrial dysfunction, altered lipid metabolism, iron handling, and inflammatory signaling may affect both necroptotic and ferroptotic sensitivity. In some disease settings, suppression of one form of regulated death may also shift cellular stress toward another. This possibility is particularly important in acute and chronic organ injuries, where damaged tissues may contain multiple cell populations exposed to cytokines, hypoxia, metabolic disruption, and oxidative stress at the same time. According to the review, these interconnections create a rationale for investigating compounds that can modulate more than one regulated-death mechanism.

The NecroFerrin concept is based on combining two pharmacological activities within a single molecular framework. One activity would interfere with necroptotic signaling, potentially by inhibiting RIPK1-dependent events. The second would limit the propagation of lipid radicals and thereby reduce ferroptotic membrane damage. The review highlights RIPROStatins as an example of this strategy. These compounds are described as combining RIPK1 inhibition with radical-trapping antioxidant properties, bringing together suppression of a protein-kinase-controlled pathway and chemical interception of the lipid oxidation reactions that drive ferroptosis. Such a design is intended to address both upstream signaling and downstream membrane injury.

The proposed mechanism also involves molecular systems that connect protein quality control with oxidative cell death. The review discusses heat shock protein 90 as one example of a cellular chaperone that can influence these pathways. HSP90 helps stabilize and regulate numerous proteins, and it may participate in chaperone-mediated autophagic degradation of GPX4 under certain conditions. Because GPX4 is central to the removal of lipid peroxides, changes in its abundance or activity can strongly affect ferroptotic vulnerability. This relationship illustrates why a compound’s effects may extend beyond a single signaling protein: cellular chaperones, autophagy, antioxidant capacity, iron metabolism, and membrane composition can collectively determine whether a stressed cell survives or crosses the threshold into regulated necrosis.

The review places NecroFerrins within the broader field of polypharmacology, which seeks to use one compound to influence several biologically connected targets. In complex diseases, single-target drugs may be limited by pathway redundancy, compensatory signaling, or the simultaneous activation of multiple injury programs. A molecule that blocks RIPK1-dependent necroptosis while also neutralizing lipid radicals could, in principle, provide broader protection than either a selective necroptosis inhibitor or a ferroptosis inhibitor alone. However, the authors emphasize that dual activity does not automatically translate into therapeutic success. The balance between potency, selectivity, tissue distribution, metabolic stability, and toxicity will determine whether such molecules can be developed into useful treatments.

This caution is especially relevant because necroptosis and ferroptosis are not exclusively harmful processes in every biological context. Regulated cell death contributes to host defense, tissue remodeling, elimination of damaged cells, and responses to infection. Broadly suppressing these mechanisms could therefore interfere with beneficial immune or homeostatic functions. In addition, the same compound may behave differently across organs because cells vary in their expression of RIPK1, RIPK3, MLKL, GPX4, FSP1, antioxidant enzymes, iron-storage proteins, and lipid-processing pathways. Rigorous studies will be required to establish whether a candidate NecroFerrin acts through the intended mechanisms in living tissues and whether it can protect organs without producing undesirable immunological or metabolic effects.

The authors present the dual-inhibition concept as a framework for future chemical biology rather than as a completed therapeutic solution. Experimental validation will need to distinguish direct pathway inhibition from nonspecific antioxidant or cytoprotective effects. Researchers will also need to determine how these molecules perform in disease models involving ischemia-reperfusion injury, inflammation, infection, neurodegeneration, or organ fibrosis, where regulated cell-death pathways may operate simultaneously. Biomarkers of necroptosis, ferroptosis, lipid peroxidation, iron status, and inflammatory damage could help identify patients or disease stages most likely to benefit. By viewing regulated cell death as an interconnected network, the review argues that future drug discovery may move beyond the question of how to inhibit one pathway and instead ask whether several converging mechanisms can be controlled with a carefully designed single molecule.

Subject of Research: Cells

Article Title: NecroFerrins as dual therapeutic inhibitors targeting necroptosis and ferroptosis

Web References: https://doi.org/10.70401/fos.2026.0041 ; https://smart.servier.com/ ; https://creativecommons.org/licenses/by/4.0/

References: Delehouzé, Claire, and Stéphane Bach. “NecroFerrins as dual therapeutic inhibitors targeting necroptosis and ferroptosis.” Ferroptosis and Oxidative Stress. DOI: 10.70401/fos.2026.0041.

Image Credits: Claire Delehouzé and Stéphane Bach, 2027; adapted from Servier Medical Art, licensed under CC BY 4.0.

Keywords: Necroptosis, ferroptosis, NecroFerrins, RIPK1, RIPK3, MLKL, lipid peroxidation, GPX4, FSP1, oxidative stress, regulated cell death, polypharmacology, RIPROStatins