The research team, led by Professor Wang Chuanxin of Shandong University, tackled the problem with a dual-technology strategy that has become the gold standard for dissecting complex tissues: single-cell RNA sequencing to resolve the identities and states of individual cells, combined with spatial transcriptomics to preserve the crucial information that conventional dissociation destroys — where each cell sits relative to its neighbors. Applying this integrative approach to human tissue samples spanning the disease trajectory from non-atrophic gastritis through atrophic gastritis to early gastric cancer, the investigators constructed a spatially resolved transcriptional atlas of gastric carcinogenesis at its most biologically ambiguous stage.

The central finding is conceptually striking. Early gastric cancer, the team demonstrates, arises from an inflammation-driven, highly coordinated microenvironmental state that they term the inflammation-associated spatial niche. This is not merely inflamed tissue; it is a structured ecological unit in which three features converge in the same physical location. First, epithelial cells within the niche selectively maintain stem-like transcriptional programs, retaining a developmental plasticity that most differentiated gastric epithelium has surrendered. Second, the niche emits enhanced inflammatory chemotactic signaling, continuously recruiting immune cells from the surrounding microvasculature. Third, the recruited immune landscape is skewed, with immunosuppressive cell populations becoming regionally enriched precisely where the pre-malignant epithelium resides.

This spatial colocalization is the key insight. Stemness, chemoattraction, and immune evasion are often studied as separate hallmarks of cancer, each with its own literature and its own molecular candidates. The new data show that in early gastric tumorigenesis these programs are not parallel events happening in the same place by coincidence; they are mutually reinforcing components of a single niche. The epithelial cells secrete inflammatory chemokines that draw in myeloid cells, and the resulting immune milieu in turn supports the epithelium’s undifferentiated state. The niche behaves as a self-sustaining engine, and its physical integrity — the precise adjacency of its cellular components — appears to be a prerequisite for malignant progression.

Mechanistically, the study identifies the SOX9-CXCL axis as the regulatory module that knits the niche together. SOX9, a transcription factor best known for its roles in development and stem cell maintenance, emerges here as a downstream effector of the inflammatory niche within the epithelial compartment. Its activity is linked to the expression of CXCL-family chemokines, which are the ligands for CXCR2-bearing receptors on myeloid cells. In practical terms, the axis converts epithelial stemness into a recruitment signal: the more the pre-malignant epithelium holds onto its stem-like identity, the more strongly it summons macrophages and other myeloid cells, and the more the local immune environment is remodeled toward a tumor-permissive configuration. This provides a concrete molecular bridge between two phenomena — epithelial plasticity and immune microenvironment reshaping — that have historically been investigated in isolation.

The therapeutic implications follow directly from the mechanism. Because the niche depends on chemokine-mediated recruitment and on macrophage survival and polarization signals, the team tested whether dismantling those dependencies could collapse the niche. Their experiments indicate that concurrent targeting of the CXCR2-mediated chemokine signaling pathway and the CSF1R-mediated macrophage pathway effectively disrupts the structural integrity of the inflammatory niche, and that this dual intervention significantly suppresses early gastric cancer progression. The logic is elegant: CXCR2 blockade cuts the recruitment lines that keep the niche stocked with pro-tumor myeloid cells, while CSF1R inhibition undermines the differentiation and maintenance of the macrophages already embedded in the tissue. Neither pathway alone achieves what the combination does, mirroring a principle well established in oncology — that microenvironmental dependencies are most effectively broken in parallel.

For clinicians, the work offers a reframing of risk. Current surveillance of patients with atrophic gastritis and intestinal metaplasia relies largely on histological grading and endoscopic detection of visible lesions, an approach that can miss the spatial cues that precede overt neoplasia. If the inflammation-associated spatial niche can be identified — through spatially resolved biomarkers, molecular imaging, or targeted biopsy strategies — it could serve as an earlier and more precise indicator of which regions of the stomach are genuinely committed to malignant transformation. Risk stratification would shift from asking whether a patient has metaplasia to asking where, within the mucosa, the coordinated niche state has taken hold. The study’s authors position this as a novel framework for early gastric cancer risk stratification and intervention, one that targets the niche rather than isolated tumor cell populations.

Conceptually, the paper contributes to a broader movement in cancer research away from reductionism. The dominant paradigm of the past two decades has been cell-autonomous: identify the driver mutation, the clonal expansion, the checkpoint escape. That framework has produced extraordinary therapies, but it struggles with cancers like gastric carcinoma, which arise on a foundation of chronic inflammation and evolve within a densely social tissue environment. By elevating the spatial niche to the status of a fundamental regulatory unit — a unit with its own composition, signaling logic, and vulnerability — the study aligns gastric carcinogenesis with ecological and evolutionary models of cancer in which the microenvironment is not a passive backdrop but an active participant in initiation. The methodological corollary is equally important: without spatial transcriptomics, the colocalization of stemness, chemotaxis, and immunosuppression would have been invisible, averaged away in bulk sequencing or decontextualized in single-cell suspensions.

The translational horizon extends beyond treatment into prevention. Chronic Helicobacter-associated inflammation affects enormous populations worldwide, yet only a minority progress to cancer, and predicting which patients will do so remains imprecise. A niche-based model suggests that the decisive variable may be the emergence of this coordinated spatial state, potentially detectable years before dysplasia becomes endoscopically visible. Interventions that prevent niche assembly — or that dissolve it once formed — could in principle arrest the process at a stage where the epithelium is still plastic rather than irreversibly transformed. The SOX9-CXCL axis, sitting at the junction of epithelial intrinsic programming and extrinsic immune recruitment, is an obvious candidate for biomarker development and, eventually, pharmacological targeting.

As with any study built on human tissue sampling and multi-omic correlation, the causal chain from niche assembly to malignant transformation will require further experimental validation, and the therapeutic disruption of CXCR2 and CSF1R pathways demonstrated here will need to be tested in appropriate models and, ultimately, clinical settings. But the conceptual contribution is already clear. Early gastric cancer, the most critical and least understood stage of gastric carcinogenesis, now has a spatial address: an inflammation-associated niche in which stemness is maintained, macrophages are recruited, and immune surveillance is locally disarmed. Mapping that address — and learning to demolish it — may prove to be one of the more consequential shifts in how the field approaches inflammation-driven cancers.

Subject of Research: Spatial niche mechanisms driving early gastric cancer initiation

Article Title: How does early gastric cancer arise? The key role of the spatial niche

Article References: How does early gastric cancer arise? The key role of the spatial niche. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: early gastric cancer, spatial transcriptomics, single-cell RNA sequencing, inflammation, SOX9-CXCL axis, tumor microenvironment, macrophages, CXCR2, CSF1R, epithelial stemness, gastric carcinogenesis, immunosuppression

The research team, working at the University of Florida, engineered mice in which FAPs could be selectively eliminated at will. They crossed animals carrying a tamoxifen-activated Cre recombinase driven by the Pdgfra promoter, which is active in FAPs, with mice carrying a diphtheria toxin A gene inserted into the Rosa26 locus. When adult mice, aged twelve to thirteen weeks, received five consecutive daily injections of tamoxifen, the toxin switched on inside FAPs and killed them. Three weeks later, the researchers found that FAP abundance in the muscle had plummeted by roughly 90 percent. The consequences were dramatic and systemic: total body mass and lean mass fell in both males and females, hindlimb muscles including the tibialis anterior, extensor digitorum longus and soleus shrank significantly, and even the spleen, liver and inguinal fat pads lost substantial weight, shrinking by up to 30 percent.

Crucially, the atrophy was not selective. Because the three muscles examined span a range of metabolic and contractile properties, the wasting appeared to be entirely independent of fiber type. Yet when the team tested muscle function directly, a surprising picture emerged. Absolute maximum isometric force was significantly reduced in both fast-twitch and slow-twitch muscles of the FAP-depleted mice, exactly as expected from smaller muscles. But when force was normalized to the muscle’s reduced cross-sectional area, the so-called specific force was completely unchanged. The contractile machinery inside each fiber was working perfectly fine. Even eccentric contractions, which subject muscles to damaging lengthening forces, revealed no increase in fragility. In other words, the muscle was losing quantity, not quality.

One long-standing hypothesis held that FAPs keep muscle healthy by supporting the neuromuscular junction, the synapse where nerves command fibers to contract. FAPs do cluster physically around these junctions, and previous work had suggested their deletion triggers synaptic degeneration and denervation-like atrophy. To test this rigorously, the researchers performed whole-mount immunofluorescence on the junctions of the EDL and soleus muscles, labeling presynaptic nerve terminals with antibodies against neurofilament and synaptic vesicle proteins, and postsynaptic acetylcholine receptors with fluorescently tagged alpha-bungarotoxin. The result was unambiguous: complete overlap between pre- and postsynaptic structures, intact endplate gutters, no fragmentation, and normal terminal Schwann cell morphology. Functional testing told the same story. When the team compared force produced by direct muscle stimulation against force evoked through the nerve, the ratios were equivalent in control and FAP-depleted mice, indicating flawless synaptic transmission. Molecular markers of denervation, such as shifts in acetylcholine receptor subunit genes, were also absent.

With the neuromuscular hypothesis ruled out for this acute setting, the team turned to the timeline of the wasting itself. Longitudinal body composition measurements revealed that most of the lean mass loss occurred during the active tamoxifen dosing window, not during the weeks of washout that followed. Apoptotic FAPs, identified by cleaved caspase 3 staining, were detectable as early as one day after the first injection. By day three, FAP numbers had collapsed. And by day five, the muscle was flooded with innate immune cells: myeloperoxidase-positive neutrophils and CD68-positive macrophages arrived in a massive, synchronized wave. The temporal sequence was telling. Cell death came first, immune infiltration followed, and only then did the muscle begin to visibly shrink.

Transcriptional profiling filled in the molecular plot. The researchers tracked two families of genes over time: atrogenes, which include the E3 ubiquitin ligases Trim63 and Fbxo32 and the autophagy markers Ulk1 and Sqstm1, and inflammatory chemokines and cytokines. An early spike in atrogene expression at day one occurred in both control and experimental mice and was attributed to the stress of tamoxifen treatment itself. But at day five, only the FAP-depleted muscles mounted a second, powerful surge of proteolytic gene expression. Preceding that surge, chemokine expression exploded. Ccl2, Ccl12, Cxcl1 and Cxcl2 rose fifty- to one-hundred-fold above control levels, peaking at day three, precisely before the atrogene wave. Interleukin-6, a cytokine with well-established links to muscle catabolism, climbed roughly fifteen-fold and stayed elevated. Notably, circulating IL-6 rose only modestly, showing that this was a fiercely local inflammatory response rather than a systemic one, and the entire transcriptional storm resolved by day twenty-eight, marking the atrophy as acute rather than chronic.

The most counterintuitive finding came when the researchers removed the immune cells themselves. Using clodronate liposomes to deplete macrophages and an anti-Ly6G antibody to eliminate neutrophils, they tested whether the infiltrating cells were culprits or protectors. The answer was neither simple nor expected: depleting either population, or both simultaneously, made the muscle wasting significantly worse. Even control mice with fully intact FAPs lost muscle when their myeloid cells were cleared. Macrophage depletion blunted the expression of Ccl2 and Ccl12, identifying macrophages as a likely source of those chemokines, yet this reduction failed to rescue muscle mass or fiber size. Neutrophil depletion, meanwhile, pushed Cxcl1 and Cxcl2 even higher, correlating with heightened atrogene expression and more severe atrophy. The infiltrating immune cells, it seems, perform essential housekeeping, clearing debris from the dying progenitors and resolving tissue stress, and their absence leaves the muscle more vulnerable, not less.

If the cells were not the problem, perhaps their signaling was. The team turned to pharmacology, treating mice with either SB225002, a selective antagonist of the CXCR2 receptor through which CXCL1 and CXCL2 act, or VBP15, also known as vamorolone, a dissociative anti-inflammatory steroid that inhibits the NF-kappa-B pathway, a central transcriptional regulator of wasting programs. Both interventions produced striking protection. Treated FAP-depleted mice retained their lean mass and fat mass, their muscles kept significantly more wet weight and fiber cross-sectional area, and their atrogene expression was substantially suppressed. Critically, immunofluorescence confirmed that neither drug changed the number of immune cells entering the tissue. The protection came from quieting inflammatory signaling, not from blocking infiltration. The two drugs also worked through distinguishable mechanisms: vamorolone broadly suppressed chemokine expression, while CXCR2 blockade triggered a compensatory rise in CXCL1 and CXCL2, a classic feedback loop when ligands can no longer engage their receptor.

The study’s authors are careful about what these results do and do not prove. Because eliminating FAPs necessarily involves killing them, the design cannot fully separate the loss of FAP-derived trophic support from the consequences of cell death itself. The transient drop in muscle Igf1 expression and the modest rise in myostatin hint that trophic factors may contribute, yet previous work showing that deleting Igf1 specifically from FAPs does not shrink muscle argues against trophic loss as the primary driver. The authors suggest that the early atrophy reflects the inflammatory fallout of progenitor death rather than evidence that FAPs actively protect muscle mass under normal conditions, though they acknowledge that other FAP-derived factors likely matter for long-term homeostasis, particularly given that transplanting FAPs back into muscle partially rescues the atrophy.

The implications reach well beyond this mouse model. Inflammation has long been recognized as a driver of muscle wasting in cancer cachexia, sarcopenia and chronic disease, and therapies that blunt inflammatory signaling are actively pursued. This study adds a crucial nuance: the same immune cells can be simultaneously protective and destructive, depending on whether one removes the cells or modulates their signals. Physical depletion of myeloid populations worsened wasting, while receptor-level and transcriptional modulation of their inflammatory output preserved muscle. For clinicians and drug developers, the lesson is that the target is not the inflammatory cells themselves but the molecular conversations they conduct, particularly the CXCL1/2-CXCR2 axis and the NF-kappa-B pathway it feeds. As the population ages and muscle wasting syndromes impose enormous clinical burdens, understanding how the death of a single supporting cell type can ignite a self-sustaining cycle of inflammation and proteolysis may prove to be one of the most consequential insights in muscle biology.

Subject of Research: Mechanisms of inflammation-mediated skeletal muscle atrophy following fibro-adipogenic progenitor ablation in mice

Article Title: Fibro‐Adipogenic Progenitor Ablation Triggers Muscle Atrophy Through Cell Death‐Induced Inflammation

Article References: Luo, Y. E., Lee, Y. I., Abe‐Teh, Z., Young, R. Y., Wei‐LaPierre, L., & Barton, E. R. (2026). Fibro‐Adipogenic Progenitor Ablation Triggers Muscle Atrophy Through Cell Death‐Induced Inflammation. Journal of Cachexia, Sarcopenia and Muscle, 17(5), Article e70393. https://doi.org/10.1002/jcsm.70393

Image Credits: AI Generated

DOI: 10.1002/jcsm.70393

Keywords: fibro-adipogenic progenitors, skeletal muscle atrophy, inflammation, CXCR2, NF-kappa-B, neuromuscular junction, macrophages, neutrophils, cachexia, sarcopenia, chemokines, vamorolone

The enzyme in question is lysine methyltransferase 9, or KMT9, a histone-modifying protein that previous work from the same group had already implicated in prostate tumor growth and androgen receptor signaling. In the new study, published in the journal Molecular Cancer, Jon Peñarando, Eric Metzger, Roland Schüle, and colleagues demonstrate that KMT9 does far more than drive cancer cell proliferation. It actively constructs the molecular barriers that prevent the immune system from recognizing and destroying the tumor, making it a uniquely attractive target for combination approaches designed to sensitize prostate cancer to immunotherapy.

At the center of the discovery is a chemokine signaling axis that functions as a cellular summons for immunosuppressive cells. The researchers found that KMT9 regulates the expression of C-X-C motif chemokine ligands, including CXCL5, which are secreted by prostate tumor cells and bind to the C-X-C motif chemokine receptor 2, CXCR2, on the surface of circulating myeloid cells. This ligand-receptor interaction acts as a homing beacon, drawing polymorphonuclear myeloid-derived suppressor cells, or PMN-MDSCs, into the tumor. Once recruited, these cells populate the tumor immune microenvironment in large numbers, creating a dense myeloid shield around the malignant glands.

PMN-MDSCs are among the most potent enemies of antitumor immunity. They suppress cytotoxic T cell responses through multiple mechanisms, including depletion of the amino acid arginine, production of reactive oxygen species, and interference with T cell trafficking. Using genetically engineered mouse models of prostate cancer in which Pten and Trp53, two frequently altered tumor suppressor genes, are deleted in prostate epithelium, the team showed that tumors with intact KMT9 were heavily infiltrated by these suppressive myeloid cells. When the researchers ablated the Kmt9a gene specifically in the prostate, the picture changed dramatically: PMN-MDSC recruitment collapsed, and cytotoxic T cells flooded into the tumor glands, showing clear signs of activation such as granzyme B expression.

The spatial dimension of this effect proved just as important as the cellular one. Advanced single-cell spatial phenotyping revealed that in tumors with functional KMT9, cytotoxic T cells were largely excluded from the tumor epithelium, lingering instead in the surrounding stroma where they could not make contact with their targets. This immune-excluded pattern is one of the recognized hallmarks of tumors that resist checkpoint blockade, since drugs like anti-PD-1 antibodies can only reinvigorate T cells that are physically close to the cancer cells they are meant to kill. Loss of KMT9 converted this excluded architecture into an inflamed, T cell-infiltrated landscape, precisely the configuration associated with immunotherapy responsiveness.

But KMT9’s contribution to immune evasion did not end with recruitment of suppressor cells. In a second, mechanistically distinct arm of the study, the researchers found that KMT9 also arms the tumor cells themselves against T cell attack. Chromatin immunoprecipitation sequencing showed that KMT9 binds directly to the promoter of the gene encoding arginase 1, ARG1, an enzyme that catabolizes L-arginine, an amino acid essential for T cell function and proliferation. By driving ARG1 expression in prostate tumor cells, KMT9 renders them resistant to T cell-mediated cytotoxicity, effectively allowing them to survive even when killer lymphocytes do manage to engage them.

The therapeutic implications of this dual mechanism were tested in preclinical experiments. When mice carrying Kmt9a-deficient prostate tumors were treated with SB225002, a CXCR2 inhibitor, tumor growth was inhibited to a greater degree than with either intervention alone, confirming that the chemokine axis is a clinically relevant vulnerability downstream of KMT9. Similarly, combining Kmt9a loss with numidargistat, a pharmacological inhibitor of ARG1, produced enhanced suppression of tumor growth. These combination experiments suggest that even partial disruption of the KMT9 pathway could be amplified by drugs that target the individual immune-evasion mechanisms it controls.

Importantly, the team connected their mouse findings to human disease by analyzing data from the TCGA prostate adenocarcinoma cohort, which comprises 500 prostate tumor samples and 52 healthy prostate controls. The analysis showed that KMT9 expression is elevated in prostate tumors relative to normal tissue and that high KMT9 levels correlate with shorter progression-free survival, underscoring the clinical relevance of the pathway. The consistency between the murine genetic models, the human genomic data, and the pharmacological studies lends considerable weight to the conclusion that KMT9 is not an artifact of a single experimental system but a genuine driver of immune evasion in prostate cancer.

For a field searching for ways to unlock immunotherapy in prostate cancer, the study offers a compelling conceptual framework. Rather than targeting the tumor’s defenses one at a time, inhibiting KMT9 would strike at the epigenetic master switch that controls both the recruitment of immunosuppressive myeloid cells through CXCR2 ligand expression and the intrinsic resistance of tumor cells through ARG1. Ablation of KMT9α in the mouse models produced inhibition of prostate tumor growth accompanied by a massive reduction in PMN-MDSC recruitment and a significant increase in cytotoxic T cell activation and infiltration of the tumor glands, a triple effect that few single agents have achieved in this disease.

Considerable work remains before these findings reach the clinic. KMT9 inhibitors are still in early stages of development, and the safety of systemically targeting a methyltransferase with functions in normal tissue is not yet established. The study’s authors note that their findings establish KMT9 as a therapeutic target to reprogram the immunosuppressive landscape and potentially improve the clinical efficacy of current immunotherapies, a formulation that anticipates future trials combining KMT9-directed agents with checkpoint blockade. If those efforts succeed, the stubborn resistance of prostate cancer to immunotherapy, one of the most frustrating puzzles in modern oncology, may finally begin to yield, not to a smarter antibody or a stronger checkpoint inhibitor, but to an epigenetic enzyme that had been quietly building the tumor’s defenses all along.

Subject of Research: The role of the lysine methyltransferase KMT9 in shaping the immunosuppressive tumor immune microenvironment of prostate cancer

Article Title: KMT9 drives T cell exclusion and dysfunction by promoting PMN-MDSCs infiltration and ARG1 expression in prostate cancer

Article References: Peñarando, J., Willmann, D., Sum, M., Jia, Y., Berlin, C., Braun, L. M., Chen, Z., Urban, S., Jung, M., Duteil, D., Metzger, D., Gratzke, C., Zeiser, R., Greschik, H., Schüle, R., & Metzger, E. (2026). KMT9 drives T cell exclusion and dysfunction by promoting PMN-MDSCs infiltration and ARG1 expression in prostate cancer. Molecular Cancer. https://doi.org/10.1186/s12943-026-02801-8

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02801-8

Keywords: KMT9, prostate cancer, tumor immune microenvironment, PMN-MDSCs, CXCL5, CXCR2, ARG1, cytotoxic T cells, cancer immunotherapy, epigenetics, histone methyltransferase, immune evasion