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 research team, led by senior author Michelle Vaz, Ph.D., instructor in oncology, and co-senior author Stephen Baylin, M.D., Virginia and D.K. Ludwig Professor of Cancer Research and co-director of the Cancer Genetics and Epigenetics Program, set out to model lung cancer from its very earliest stages. Rather than starting with fully malignant cells, they used laboratory-grown lung organoids, tiny three-dimensional structures containing multiple lung cell types, created from normal mouse lung tissue. These organoids were exposed to cigarette smoke condensate, a concentrated collection of the chemicals and particles found in cigarette smoke, for up to six months. Key early findings were then confirmed in organoids generated from normal human lung tissue, lending the work translational weight.

What the researchers observed over those six months was a gradual, coordinated shift in the biology of the stem cells. The exposed cells increasingly acquired characteristics associated with a precancerous, tumor-permissive state. At the same time, the team documented progressive changes in two epigenetic mechanisms that govern gene activity without altering the underlying DNA sequence. The first was DNA methylation, the addition of chemical tags to regions of DNA that help control whether genes are switched on or off. The second was chromatin accessibility, a measure of how tightly or loosely DNA is packaged within the cell nucleus, which determines how readily the cellular machinery can reach and read specific genes. Together, these mechanisms reshaped gene expression across the different stem cell populations.

Among the most notable changes was the suppression of inflammatory and immune signaling pathways, along with genes involved in programmed cell death, the built-in suicide program that normally eliminates damaged or dangerous cells. One gene affected in particular was ZBP1, a key regulator of inflammatory cell death. Silencing this defensive machinery, the researchers found, was especially pronounced in cells that would later prove susceptible to KRAS-driven transformation, suggesting that dampening these normal cell-death defenses may help incipient cancer cells survive long enough to become fully malignant.

The critical question was whether this smoke-induced reprogramming actually made the cells more vulnerable to cancer-causing mutations. To test this, the investigators introduced either mutant KRAS, one of the most common oncogenes in smoking-related lung cancer, or knocked out TP53, a crucial tumor suppressor gene, in organoids that had and had not undergone six months of smoke exposure. The engineered cells were then implanted into mice. The result was striking: only the smoke-exposed organoids carrying one of the genetic alterations formed tumors. Cigarette smoke exposure alone did not produce tumors, and neither did introducing the mutations into unexposed control organoids. Neither factor was sufficient on its own; the two had to act in sequence.

“What this tells us is that the genetic event alone is not sufficient,” Vaz explained. She and Baylin emphasize that cells must first undergo changes wrought by chronic cigarette smoke exposure before mutations like KRAS or TP53 loss can drive them into full transformation. This helps resolve a long-standing puzzle in cancer biology: mutations in genes such as KRAS and TP53 are known drivers of non-small cell lung cancer, the most common form of the disease, yet the same mutations can also be found in normal or precancerous tissue, implying that mutations by themselves are not enough to ignite cancer.

Even more surprising was what happened when the smoke-primed cells transformed. The genetic alterations produced two entirely different forms of non-small cell lung cancer, and each appeared to select for a different stem cell population. Smoke-exposed organoids with mutant KRAS developed poorly differentiated cancers with features of lung adenocarcinoma, and single-cell RNA sequencing traced these tumors back to an altered cell state derived from bronchioalveolar stem cells, which reside where the lung airways meet the alveoli, the tiny air sacs where gas exchange occurs. Smoke-exposed organoids lacking TP53, by contrast, developed squamous cell carcinomas, which traced to an altered state derived from basal stem cells, the cells that maintain and repair the lining of the airways.

“It was very interesting that when we introduced KRAS or loss of TP53, each seemed to select for a particular type of stem cell state,” Vaz said. “We did not engineer the genetic event into a particular cell type. This is what the mutations selected for.” In other words, the chronic smoke exposure had created distinct precancerous cellular environments, and each cancer-driving mutation thrived in a different one. The type of lung cancer that develops, the findings suggest, depends on both the mutation that occurs and the molecular identity of the cell in which it takes hold, a convergence of environmental exposure, epigenetic change and genetics at the earliest stages of tumor evolution.

The human data lent further support to the mechanism. Analysis of lung adenocarcinoma samples from patients showed significantly lower expression of ZBP1 and related interferon pathway genes, part of the immune response, in tumors carrying KRAS mutations compared with those carrying TP53 mutations. This mirrors what the organoids revealed in the laboratory and points to a possible shared signature between the mouse and human disease. The researchers note that the altered stem cell states identified in the study could eventually serve as molecular markers for recognizing the earliest evolution of different NSCLC subtypes, potentially pointing toward strategies for identifying people at elevated risk and intervening before cancer develops, though additional experimental validation is still needed.

The work also opens therapeutic questions. “What’s exciting as a next step is whether we can learn more about these cell death pathways and whether some can be targeted, specifically in the KRAS versus TP53 setting,” Vaz said. “Can we combine that with epigenetic therapy or immunotherapy and help tumors that currently do not respond to treatment, respond better?” Further study of the epigenetic changes occurring within individual stem cell states, she added, could uncover new therapeutic vulnerabilities. The research was supported by the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation, The Hodson Trust, an American Lung Association Lung Cancer Discovery Award, the Evelyn Grollman Glick Scholar Award, a Johns Hopkins University Discovery Award, TEDCO, the National Institute of Environmental Health Sciences, National Institutes of Health grant R01ES011858, National Cancer Institute grants R01CA229240 and R01CA230995, the Sidney Kimmel Comprehensive Cancer Center Support Grant P30CA006973, and the Van Andel Research Institute through the Van Andel Research Institute–Stand Up To Cancer Epigenetics Dream Team. In addition to Vaz and Baylin, the research team included Na Wang, Raksha Padaki, Sara-Jayne Thursby, Ray-Whay Chiu Yen, Leslie Cope, Malcolm Brock, Edward Gabrielson and Hariharan Easwaran.

Subject of Research: How cigarette smoke-induced epigenetic reprogramming of lung stem cells determines susceptibility to specific lung cancer-driving mutations

Article Title: Cigarette smoke may prime lung stem cells for different types of lung cancer

Article References: Cigarette smoke may prime lung stem cells for different types of lung cancer. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: lung cancer, cigarette smoke, stem cells, epigenetics, KRAS, TP53, organoids, non-small cell lung cancer, DNA methylation, adenocarcinoma, squamous cell carcinoma, ZBP1

The research, led by Wanqiu Huang and Jinjing Ni together with colleagues at Shanghai Jiao Tong University School of Medicine and collaborating institutions, focuses on a histone modification known as H2BK16ac. This tag refers to the acetylation of lysine 16 on histone H2B, one of the proteins around which DNA is wound. Acetylation of histone tails generally loosens the chromatin structure, making genes more accessible to the transcription machinery. When the researchers examined macrophages infected with Salmonella, they found that this acetylation mark on H2BK16 was actively removed. The deacetylation was carried out by two enzymes, HDAC1 and HDAC3, which strip acetyl groups from histones and thereby tighten chromatin at specific genomic locations.

The consequence of this chromatin tightening was the transcriptional silencing of a gene called Id3, which encodes Inhibitor of Differentiation 3. ID3 is a member of the helix-loop-helix protein family and is known to influence the behavior of various immune cells, but its role in macrophage-mediated antibacterial defense had not been clearly defined. The new study shows that when Salmonella drives H2BK16 deacetylation through HDAC1 and HDAC3, the Id3 gene is switched off, and macrophages lose an important layer of antimicrobial capacity. This finding places ID3 at the center of an infection-induced epigenetic pathway that directly shapes how macrophages respond to bacterial challenge.

To establish that ID3 genuinely strengthens macrophage defenses, the team performed both loss-of-function and gain-of-function experiments. When ID3 was removed or reduced, macrophages showed a weakened inflammatory response and diminished antimicrobial activity. Conversely, when ID3 was increased, macrophages displayed enhanced antibacterial function. These results demonstrate that ID3 is not a passive bystander in the infection response but an active contributor to the macrophage arsenal against invading bacteria.

The mechanistic heart of the study lies in how ID3 controls the expression of another protein, Z-DNA binding protein 1, commonly abbreviated as ZBP1. ZBP1 is a sensor that recognizes certain nucleic acid structures and participates in immune signaling. The researchers discovered that a transcription factor called E2A binds to the ZBP1 gene and represses its transcription. ID3 counteracts this repression by sequestering E2A, effectively pulling it away from the ZBP1 promoter. With E2A occupied by ID3, the ZBP1 gene is free to be transcribed, and macrophages maintain robust ZBP1 expression. This sequestration mechanism reveals a precise molecular handoff in which ID3 acts as a decoy to relieve transcriptional braking on an antimicrobial effector gene.

The in vivo relevance of this circuit was tested in mice engineered to lack Id3 specifically in myeloid cells, the lineage that includes macrophages. When these myeloid-specific Id3-deficient mice were infected with Salmonella, they carried higher bacterial burdens and suffered greater pathological damage than control animals. This outcome confirms that the ID3-ZBP1 axis is not merely a cell-culture curiosity but a functional component of antibacterial immunity in living organisms. The data suggest that the integrity of this epigenetic pathway determines how effectively the host can contain systemic bacterial spread.

Perhaps the most translational aspect of the study involves a pharmacological intervention. The researchers treated infected mice with MS-275, an inhibitor of histone deacetylases that targets HDAC1 among other class I enzymes. Administration of MS-275 restored the H2BK16ac mark, reactivated the Id3 gene, and thereby rebuilt the ID3-ZBP1 signaling axis. In practical terms, the drug reversed the epigenetic silencing that Salmonella had imposed on macrophages. Mice receiving this treatment showed amelioration of systemic Salmonella infection, demonstrating that pharmacologically reopening the chromatin at Id3 can translate into meaningful protection against bacterial disease.

These findings carry several implications for the broader field of infection biology. First, they establish that pathogens do not merely evade immune detection; they actively reshape the epigenetic landscape of host immune cells to disable specific defense genes. The Salmonella-driven deacetylation of H2BK16 represents a concrete example of how bacterial infection can hijack the host’s own chromatin-modifying enzymes to silence protective transcriptional programs. Second, the study identifies ID3 as a previously underappreciated regulator of macrophage immunity, bridging histone acetylation status to the expression of a nucleic acid sensor involved in antimicrobial signaling. Third, the demonstration that an HDAC inhibitor can restore this axis in vivo suggests a therapeutic window in which epigenetic drugs, originally developed for oncology, might be repurposed as adjunct treatments for severe bacterial infections.

The work also raises questions that will likely drive future research. It remains to be seen whether other pathogens employ similar strategies to silence Id3 or related immune regulators through histone deacetylation. The precise kinetics of HDAC1 and HDAC3 recruitment to the Id3 locus during infection, and whether additional chromatin marks cooperate with H2BK16ac in this process, are areas that warrant deeper investigation. Furthermore, because ZBP1 has been implicated in antiviral as well as antibacterial pathways, the ID3-E2A-ZBP1 circuit could have relevance beyond Salmonella, potentially influencing how macrophages respond to a wider spectrum of infectious threats. The study by Huang, Ni, and colleagues thus opens a new line of inquiry into how epigenetic therapies might bolster innate immunity at a time when antibiotic resistance continues to limit conventional treatment options.

Subject of Research: Infection-driven epigenetic regulation of macrophage innate immunity through the H2BK16ac-ID3-ZBP1 axis

Article Title: Infection-driven epigenetics modulate macrophage innate immunity through the H2BK16ac-ID3-ZBP1 axis

Article References: Huang, W., Ni, J., Tang, H., Chen, Y., Zhou, T., Yu, J., Wang, Z., Wen, B., Yan, H., Wang, C., Tao, J., Lu, J., Zhao, G.-P., Wang, D., & Yao, Y.-F. (2026). Infection-driven epigenetics modulate macrophage innate immunity through the H2BK16ac-ID3-ZBP1 axis. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06432-6

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06432-6

Keywords: macrophage, innate immunity, epigenetics, histone acetylation, H2BK16ac, ID3, ZBP1, Salmonella, HDAC1, HDAC3, E2A, MS-275

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

Inflammasomes are cytosolic signaling complexes assembled by pattern recognition receptors in response to a wide array of danger-associated and pathogen-associated molecular patterns. Among the best characterized is the NLRP3 inflammasome, which can be activated by an extraordinary diversity of stimuli, ranging from extracellular ATP and crystalline substances such as monosodium urate to perturbations in cellular homeostasis including mitochondrial dysfunction and ionic flux. Structural studies, notably cryo-electron microscopy analyses, have revealed that NLRP3 oligomerizes into a large ring-like platform that recruits the adaptor protein ASC through pyrin domain interactions. ASC in turn nucleates the polymerization of procaspase-1 filaments through its caspase recruitment domain, creating a branched, star-shaped assembly that has become iconic in the field of innate immunity.

The review emphasizes how this hierarchical assembly process, in which a receptor seeds adaptor polymerization which then seeds effector activation, is a recurring architectural principle across inflammasome families. DNA-sensing receptors such as AIM2 and the Pyrin family of receptors, as well as the more recently described sensors like NLRP1 and CARD8, all converge on the same downstream machinery despite recognizing fundamentally different ligands. This convergence explains how a limited set of adaptor and effector molecules can translate an enormous diversity of upstream danger signals into a uniform cellular response: the activation of inflammatory caspases, cleavage of the cytokine precursors pro-interleukin-1 beta and pro-interleukin-18, and induction of a lytic form of cell death known as pyroptosis.

Pyroptosis itself has been structurally dissected at the level of its executioner, gasdermin D. Activated inflammatory caspases cleave gasdermin D to release an N-terminal fragment that oligomerizes into membrane pores, causing osmotic lysis and the release of intracellular contents, including mature interleukin-1 beta. Recent structures of gasdermin pores have clarified how the positively charged face of the oligomer interacts with membrane lipids and how pore formation is regulated. This level of mechanistic detail has direct pharmacological implications, because small molecules that block gasdermin pore formation or inflammasome assembly could dampen pathological inflammation in conditions as varied as gout, atherosclerosis, type 2 diabetes, inflammatory bowel disease, and neurodegenerative disease, all of which have been linked to excessive inflammasome activity.

Beyond canonical inflammasomes, the review devotes substantial attention to PANoptosis, a recently articulated form of inflammatory programmed cell death that integrates features of pyroptosis, apoptosis, and necroptosis within a single, coordinated complex termed the PANoptosome. Unlike a classical inflammasome, a PANoptosome contains components from multiple cell death pathways simultaneously, including Z-DNA-binding protein 1, or ZBP1, which senses Z-form nucleic acids generated during viral infection, together with receptor-interacting protein kinases and other death-domain proteins. Structural and biochemical studies suggest that these complexes assemble through a web of homotypic and heterotypic domain interactions, creating a platform capable of activating multiple death effector machineries in parallel and amplifying inflammatory signaling to a degree that neither pathway could achieve alone.

ZBP1 has emerged as a particularly instructive example of how structural insights inform PANoptosome biology. Its two Z-nucleic acid binding domains recognize the unusual left-handed conformation of Z-DNA and Z-RNA, which accumulates in cells infected with viruses such as influenza A. Upon ligand binding, ZBP1 engages RIPK3 through RHIM domain interactions, and in certain contexts also recruits NLRP3 and ASC, thereby coupling viral sensing directly to necroptosis, pyroptosis, and cytokine release. Mutations that disrupt these interactions protect mice from lethal influenza-associated inflammation, underscoring the in vivo importance of this pathway and highlighting RHIM-mediated interactions as a potential drug target in severe viral pneumonia and other contexts of pathogenic inflammation.

One of the central themes of the review is that autoinhibition is a universal feature of innate immune sensors, reflecting the danger of accidental self-destruction if these potent inflammatory pathways are triggered spuriously. NLRP3, for example, is held in an inactive conformation by its LRR domain folding back onto the nucleotide-binding domain, a constraint released through a multi-step activation process involving NEK7 binding, deubiquitination, and translocation to the Golgi or endosomal membranes. Similar autoinhibitory mechanisms govern NLRP1, which releases its inhibitory function upon proteasomal degradation of an N-terminal regulatory segment, and pyrin, which is restrained by phosphorylation-dependent sequestration through binding to 14-3-3 proteins. Structural biology has provided atomic-level explanations for how disease-associated mutations, including those causing cryopyrin-associated periodic syndromes and familial Mediterranean fever, destabilize these autoinhibited states and drive constitutive inflammasome activation.

The therapeutic implications of this structural knowledge are considerable and span several classes of intervention. Direct inhibitors of NLRP3, such as MCC950 and its derivatives, have demonstrated efficacy in preclinical models of numerous inflammatory diseases and are progressing through clinical evaluation. Second-generation approaches include compounds that block ASC speck formation, inhibitors of inflammatory caspases, gasdermin D antagonists designed to prevent pore formation, and agents targeting upstream cytokine signaling through blockade of interleukin-1 family receptors. For PANoptosome-driven diseases, particularly severe viral infections and certain hereditary autoinflammatory syndromes, strategies that interrupt specific protein-protein interfaces, such as the RHIM-dependent interaction between ZBP1 and RIPK3, represent an emerging frontier. The review argues that structural data, by revealing precisely where and how these complexes assemble, will be indispensable for the rational design of such inhibitors.

Challenges nonetheless remain substantial. Inflammasome components are large, flexible, and often membrane-associated, complicating structural determination of full assemblies in physiologically relevant states. Much of the available structural information derives from isolated domains, truncated constructs, or oligomers assembled in vitro, and bridging the gap between these reductionist structures and the behavior of intact complexes in living cells remains a priority. Moreover, the redundancy and interconnection of inflammatory cell death pathways mean that blocking one arm may simply redirect signaling through another, arguing for combination approaches informed by a systems-level understanding of PANoptosome architecture and regulation.

Taken together, the review frames inflammasomes and PANoptosomes not as isolated curiosities of innate immunity but as a structurally unified family of molecular decision-making machines whose misregulation underlies a broad spectrum of human disease. As cryo-electron microscopy, cryogenic electron tomography, and single-molecule imaging continue to reveal these assemblies at ever higher resolution in increasingly native contexts, the prospect of precisely targeted anti-inflammatory therapeutics, capable of silencing pathological inflammation while preserving beneficial host defense, moves steadily closer to reality.

Subject of Research: Structural and mechanistic analysis of innate immune sensors that assemble inflammasomes and PANoptosomes

Article Title: Innate immune sensors of inflammasomes and PANoptosomes: structural–mechanistic insights and therapeutic implications

Article References: Upadhyay, S., Nagampalli, R., Resende, S., & Kanneganti, T.-D. (2026). Innate immune sensors of inflammasomes and PANoptosomes: structural–mechanistic insights and therapeutic implications. Cell Research. https://doi.org/10.1038/s41422-026-01287-9

Image Credits: AI Generated

DOI: 10.1038/s41422-026-01287-9

Keywords: innate immunity, inflammasome, PANoptosis, PANoptosome, NLRP3, ZBP1, ASC, caspase-1, gasdermin D, pyroptosis, structural biology, anti-inflammatory therapeutics