Tumor Protein LRG1 Hijacks Neutrophil Mitochondria to Fuel Dangerous Vessel Growth in Bladder Cancer

Bladder cancer has long presented clinicians with a frustrating paradox: the tumors are often flush with blood vessels, yet those vessels are so structurally chaotic that they deliver little oxygen, little chemotherapy, and little room for immune cells to maneuver. A new study published in Advanced Science now offers a striking explanation for how this vascular dysfunction is manufactured, and it points to an unexpected culprit operating deep inside the tumor’s immune microenvironment. According to the research, a secreted protein called leucine-rich alpha-2-glycoprotein 1, or LRG1, orchestrates pathological blood vessel growth by sabotaging the mitochondria of neutrophils, the short-lived foot soldiers of the innate immune system, and thereby triggering the release of web-like structures known as neutrophil extracellular traps, or NETs.

The investigation began with a high-resolution survey of the bladder tumor landscape. The team integrated four public single-cell RNA sequencing datasets covering five normal bladder and nineteen bladder cancer samples, annotating cells into ten distinct lineages. Within the malignant compartment, LRG1 expression was markedly elevated, and non-negative matrix factorization revealed a specific tumor subcluster defined by high LRG1 output. When the researchers projected the marker genes of these subclusters onto bulk RNA sequencing cohorts from The Cancer Genome Atlas and independent datasets, the LRG1 meta-program was significantly associated with poorer overall survival. Clinically, the signal was even more compelling: serum LRG1 concentrations were substantially higher in patients with hematogenous metastasis than in those without, and histological staining showed dense LRG1 accumulation precisely in the vascular niche of metastatic tumors, where it colocalized with the endothelial marker CD31 while mural cell coverage, marked by alpha-SMA, was conspicuously reduced.

To test whether LRG1 was merely a bystander or an active driver, the researchers turned to genetically engineered mice lacking the Lrg1 gene. When MB49 bladder cancer cells were implanted into these animals, both subcutaneous and orthotopic tumors grew significantly more slowly than in wild-type controls, and lung metastases in a tail-vein model were drastically attenuated. Crucially, the tumor vasculature itself underwent a transformation. Microvessel density fell while average vessel diameter increased, a morphological hallmark of so-called vascular normalization. Pericyte coverage of the vessel wall improved, basement membranes became continuous and uniform rather than fragmented, and scanning electron microscopy revealed a pronounced reduction in the intraluminal endothelial inclusions that riddle leaky, pathological microvessels. Notably, the knockout mice showed no macroscopic abnormalities in major organs, suggesting that LRG1 is a pathological rather than a housekeeping factor and may be a relatively safe therapeutic target.

The pivotal clue to the mechanism came from single-cell transcriptomics performed on tumors overexpressing LRG1. After quality control retained 13,454 high-quality cells, unsupervised clustering identified six major lineages, and subclustering of the neutrophil compartment revealed four distinct subpopulations. One of these, designated C1, scored dramatically higher for a gene signature associated with neutrophil extracellular traps, and its proportion was markedly enriched in LRG1-overexpressing tumors compared with controls. Independent analysis of human data reinforced the picture: a NET-associated neutrophil subset defined by expression of NCF2 was expanded in tumor tissue relative to adjacent normal tissue, and gene set variation analysis across three bulk RNA sequencing cohorts showed a strong positive correlation between the LRG1 tumor meta-program and the abundance of this NET-forming subset.

Functional experiments then established LRG1 as both a recruiter and an activator of neutrophils. Conditioned medium from LRG1-overexpressing bladder cancer cells attracted freshly isolated human neutrophils far more effectively than control medium, while LRG1 knockdown reversed the effect, and flow cytometry confirmed that these differences were not explained by altered neutrophil survival. In vivo, depleting neutrophils with an anti-Ly6G antibody abolished the tumor-promoting effect of LRG1 overexpression entirely. Serological measurements in patients told a consistent story: circulating levels of cell-free DNA, myeloperoxidase, and neutrophil elastase, all canonical markers of NETosis, were elevated in bladder cancer patients and correlated positively with LRG1, with cell-free DNA showing a correlation coefficient of 0.59. Most strikingly, recombinant human LRG1 alone was sufficient to induce NET formation in purified neutrophils, upregulating MPO and citrullinated histone H3, the molecular fingerprints of NETs.

What do these NETs actually do to the vasculature? The answer, according to the study, is a two-faced assault. In vitro, intact NETs accelerated endothelial tube formation, increasing total tube length, capillary-like structures, and junctional nodes, while simultaneously inducing hyperpermeability in endothelial monolayers as measured by fluorescent dextran flux across cell layers. Bladder cancer cells were physically trapped within NET networks, an adhesion that DNase I digestion completely abolished, and exposure to intact NETs significantly enhanced cancer cell migration. In mice, an LPS-induced model of systemic NETosis accelerated tumor growth, but co-administration of DNase I, which degrades the extracellular DNA scaffolds of NETs, abrogated this effect. Immunofluorescence confirmed that NET accumulation stripped mural cells from tumor vessels, and DNase I treatment restored pericyte coverage and vascular integrity, mirroring in reverse the normalization seen in Lrg1-deficient animals.

The deepest mechanistic insight concerns how an extracellular protein persuades a neutrophil to self-destruct into a NET in the sterile, metabolically stressed environment of a tumor. Using pull-down assays followed by mass spectrometry, the team identified annexin A2, or ANXA2, as a direct binding partner of LRG1, an interaction confirmed by co-immunoprecipitation in primary human neutrophils and engineered cell lines. Truncation mutant experiments pinpointed the leucine-rich repeat domain of LRG1, amino acids 93 through 282, as essential for this binding. ANXA2, it turns out, functions as a chaperone that ferries activated Akt, phosphorylated at serine 473, into mitochondria, and this trafficking depends on ANXA2’s own phosphorylation at tyrosine 24. LRG1 binding obstructed ANXA2 phosphorylation and abolished the mitochondrial accumulation of active Akt. Engineered phosphomimetic ANXA2-Y24D mutants restored mitochondrial Akt localization, whereas phospho-dead Y24A mutants worsened the damage.

The downstream consequences for neutrophil metabolism were catastrophic. Recombinant LRG1 treatment triggered a massive surge in mitochondrial reactive oxygen species, a reduction in mitochondrial mass, severe depolarization of the mitochondrial membrane potential, and compromised ATP synthesis. Transmission electron microscopy provided direct visual confirmation: mitochondria in LRG1-treated neutrophils displayed swollen organelles, electron-dense matrices, and disorganized cristae, ultrastructural aberrations that the ANXA2-Y24D mutant partially ameliorated. This places the study squarely within an emerging paradigm in which mitochondrial, rather than purely cytosolic, reactive oxygen species drive NETosis, oxidizing mitochondrial DNA to yield highly immunogenic and pro-angiogenic extracellular traps. In effect, LRG1 acts as a metabolic reprogramming factor that short-circuits the energy machinery of innate immune cells, converting them into agents of vascular destruction.

The translational implications may prove the most consequential part of the story. In a retrospective cohort of twenty-nine bladder cancer patients treated with neoadjuvant cisplatin plus PD-1 blockade, non-responders showed synchronous upregulation of both LRG1 and the NET marker H3Cit, with nine of twelve non-responders classified as LRG1-high and ten of twelve as NETs-high, compared with far lower proportions among responders whose baseline characteristics were otherwise balanced. In mice, Lrg1 deficiency synergized with both cisplatin and anti-PD-1 therapy independently: cisplatin-treated knockout tumors showed increased DNA double-strand breaks and apoptosis, indicating deeper drug penetration, while anti-PD-1-treated knockout mice displayed augmented infiltration of CD8-positive cytotoxic T cells expressing elevated levels of Granzyme B. The authors propose that the LRG1-ANXA2-NETosis axis likely cooperates with the known endothelial TGF-beta/ALK1 pathway, jointly explaining the profoundly disorganized vasculature of bladder cancer, and they acknowledge that questions remain, including the functional role of tumor-specific glycosylation of LRG1 and the need for neutrophil-specific PAD4 knockout models to provide definitive genetic evidence. If those questions are answered, dismantling this axis could convert therapy-refractory, vessel-chaotic tumors into ones that drugs and immune cells can finally reach.

Subject of Research: LRG1-driven neutrophil mitochondrial dysfunction and NETosis in bladder cancer angiogenesis

Article Title: LRG1 Drives Pathological Angiogenesis by Disrupting Neutrophil Mitochondrial Homeostasis in Bladder Cancer

Article References: Chen, D., Zhang, C., Xue, S., Zeng, Y., Cui, H., Wang, C., Feng, J., Yan, L., & Zang, Y. (2026). LRG1 Drives Pathological Angiogenesis by Disrupting Neutrophil Mitochondrial Homeostasis in Bladder Cancer. Advanced Science, 13(56), Article e76604. https://doi.org/10.1002/advs.76604

Image Credits: AI Generated

DOI: 10.1002/advs.76604

Keywords: bladder cancer, LRG1, angiogenesis, neutrophil extracellular traps, NETosis, mitochondrial reactive oxygen species, ANXA2, vascular normalization, tumor microenvironment, single-cell RNA sequencing, immunotherapy resistance, pericyte coverage