The investigation began as a large-scale computational sweep. The team integrated bulk transcriptomic datasets, single-cell RNA sequencing and spatial transcriptomics from lung adenocarcinoma patients, cross-referencing these molecular maps with clinical cohorts that had received immune checkpoint blockade. Using weighted gene co-expression network analysis, survival meta-analysis and tissue enrichment scoring, they hunted for stromal cell subpopulations whose presence tracked with aggressive disease and poor immunotherapy outcomes. That search converged on a single culprit: a myofibroblastic cancer-associated fibroblast subset defined by high expression of MMP11, alongside the canonical contractile genes ACTA2 and TAGLN. These MMP11-positive myCAFs were enriched not only in primary lung tumors but also in metastatic lesions, and their abundance correlated with advanced tumor stage, metastatic spread, shorter overall survival and markedly reduced benefit from checkpoint inhibitors.

What makes this finding technically significant is the way the team moved beyond correlation. Spatial transcriptomic deconvolution, a computational method that infers which cell types occupy which physical niches within a tissue section, showed that MMP11-positive myCAFs consistently co-localized with SPP1-positive macrophages, a pro-tumor myeloid population that was itself enriched in malignant and metastatic lung adenocarcinoma tissue. The researchers then confirmed this spatial partnership in human clinical specimens using multiplex immunohistochemistry, a staining technique that visualizes several protein markers simultaneously on a single tissue slide. The two cell types were not merely neighbors in the same tumor; they occupied the same microanatomical neighborhoods, suggesting a functional relationship rather than coincidental distribution.

To identify the molecular language spoken between these cells, the team performed ligand-receptor interaction analysis on their single-cell and spatial data, complemented by virtual gene knockout experiments that computationally predicted the downstream consequences of removing specific signaling molecules. WNT5A emerged as the dominant macrophage-derived mediator linking SPP1-positive macrophages to myCAF activation. WNT5A is a member of the Wingless-related integration site family, a group of secreted glycoproteins that orchestrate embryonic development, tissue patterning and, in cancer, a bewildering array of pro-tumor behaviors. In this context, the analysis indicated that WNT5A released by macrophages acts on fibroblasts, driving them toward a matrix-remodeling, contractile state.

The mechanistic story has two halves. On the macrophage side, the researchers found that SPP1-positive macrophages exhibited activation of transcriptional programs governed by the non-canonical NF-kappaB factors NFKB2 and RELB. When they generated macrophages that overexpressed SPP1 in vitro, levels of Nfkb2, Relb and WNT5A protein all rose, placing SPP1 upstream of a signaling cascade that culminates in WNT5A production. This is a notable detail because it ties a well-known pro-tumor macrophage marker to a specific transcriptional pathway and a specific secreted output, giving the field a concrete molecular handle on a cell type that has often been described only by its marker genes.

On the fibroblast side, the team built a macrophage-CAF co-culture system in which SPP1-overexpressing macrophages and MMP11-overexpressing fibroblasts could interact directly. When fibroblasts were stimulated with WNT5A, they showed activation of YAP-associated signaling and increased expression of INHBA, the gene encoding the activin A subunit. YAP, the transcriptional co-activator downstream of the Hippo pathway, is a well-established sensor of mechanical forces and tissue stiffness, and its activation in fibroblasts is a hallmark of the myofibroblastic state. Functionally, WNT5A-stimulated fibroblasts migrated more readily, contracted more forcefully and deposited more extracellular matrix than their untreated counterparts. Each of these behaviors contributes to the desmoplastic reaction, the dense fibrous scar tissue that many solid tumors build around themselves.

The in vivo experiments brought the story into living systems. The researchers established murine tumor models and evaluated them with in vivo imaging, flow cytometry, atomic force microscopy, hematoxylin and eosin staining, Masson staining and multiplexed immunohistochemistry. Atomic force microscopy deserves particular mention: it measures tissue stiffness at the nanoscale by probing the physical resistance of the extracellular matrix, providing a direct readout of the mechanical remodeling that the fibroblasts were predicted to drive. The results were consistent with the in vitro findings. When WNT5A signaling was activated in the tumor microenvironment, collagen deposition increased, tissue stiffness rose, and MMP11-positive CAFs accumulated.

Most consequentially for patients, WNT5A activation impaired the therapeutic efficacy of PD-1 blockade in these animal models. Flow cytometry revealed reduced infiltration of CD8-positive T cells into the tumors, the very effector cells that anti-PD-1 antibodies are designed to unleash. The picture that emerges is a coherent immunosuppressive circuit: SPP1-positive macrophages, driven by NFKB2/RELB programs, secrete WNT5A; WNT5A activates YAP/INHBA signaling in fibroblasts; the fibroblasts remodel and stiffen the matrix; and the resulting dense, rigid stroma excludes cytotoxic T lymphocytes, leaving checkpoint inhibitors with little to work with even when the drug successfully engages its target on T cells.

The clinical implications are substantial. Immune checkpoint blockade has reshaped outcomes in lung adenocarcinoma, yet primary and acquired resistance remain stubborn problems, and stromal exclusion of T cells is one of the best-documented mechanisms of failure. By identifying SPP1-positive macrophages and MMP11-positive myCAFs as a spatially coupled, functionally linked pair, and by pinpointing WNT5A as the bridge between them, the study offers a set of potential biomarkers and drug targets. Patients whose tumors are rich in MMP11-positive myCAFs might be identified in advance as unlikely to benefit from PD-1 monotherapy and steered toward combination strategies. Meanwhile, the WNT5A-YAP axis suggests that disrupting macrophage-fibroblast communication could soften the tumor matrix, restore T-cell infiltration and resensitize tumors to immunotherapy. The authors note that their findings highlight a potential therapeutic strategy to overcome immune checkpoint blockade resistance, though translating that insight into clinics will require inhibitors capable of safely modulating WNT signaling in humans.

Methodologically, the study is also a demonstration of how modern cancer biology is increasingly conducted. No single technique carried the argument; instead, bulk transcriptomics established population-level associations, single-cell RNA sequencing resolved the relevant cell states, spatial transcriptomics and multiplex immunohistochemistry anchored those states in physical tissue architecture, virtual knockout and co-culture experiments tested causal mechanisms in vitro, and mouse models with mechanical measurements confirmed the circuit in vivo. The human specimens were obtained under ethics approval from Zhejiang Cancer Hospital, and the work was supported by the National Natural Science Foundation of China and the Traditional Chinese Medicine Scientific Research Foundation of Zhejiang Province. As with any study that combines computational inference with experimental validation, the next step will be independent confirmation in larger immunotherapy cohorts and the development of clinically tractable ways to interrupt the WNT5A signal. If those hurdles can be cleared, the stromal conversation between macrophages and fibroblasts may become one more vulnerable link in the armor that lung adenocarcinomas use to shield themselves from the immune system.

Subject of Research: The role of SPP1-positive macrophage-derived WNT5A in MMP11-positive myofibroblastic cancer-associated fibroblast activation, matrix remodeling, and immunotherapy resistance in lung adenocarcinoma.

Article Title: SPP1⁺ macrophage-derived WNT5A contributes to MMP11⁺ myCAF-mediated matrix remodeling and immunotherapy resistance in lung adenocarcinoma

Article References: Wang, M., Zhang, P., Li, X., Shao, L., Dai, S., & Chen, Z. (2026). SPP1⁺ macrophage-derived WNT5A contributes to MMP11⁺ myCAF-mediated matrix remodeling and immunotherapy resistance in lung adenocarcinoma. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-09069-y

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09069-y

Keywords: lung adenocarcinoma, WNT5A, SPP1 macrophages, cancer-associated fibroblasts, MMP11, matrix remodeling, immunotherapy resistance, PD-1 blockade, tumor microenvironment, YAP signaling, single-cell RNA sequencing, spatial transcriptomics

The work, published in Molecular Cancer, addresses a long-standing frustration in tumor biology. Cancer-associated fibroblasts, or CAFs, have been recognized for decades as central players in stromal remodeling, immune exclusion, and drug resistance, but most classifications of these cells have been static snapshots. Pathologists and single-cell biologists could label fibroblasts as myofibroblastic, inflammatory, or antigen-presenting subtypes, yet the field lacked a causal account of how tumor cells instruct fibroblasts to adopt these pathogenic identities in the first place. The new study set out to answer precisely that question: does the tumor merely coexist with certain fibroblast states, or does it actively manufacture them?

To map the landscape, the team performed integrative single-cell RNA sequencing on lung adenocarcinoma specimens, constructing a detailed stromal atlas of the disease and tracing fibroblast lineage trajectories. Rather than falling into discrete categories, fibroblasts in these tumors followed a continuous differentiation path that converged on a myofibroblast-like endpoint marked by MMP11 expression. This MMP11-positive subset carried a transcriptional program dominated by extracellular matrix remodeling and collagen organization, and its gene-expression signature overlapped strongly with markers of immune exclusion. Across multiple independent patient cohorts, the abundance of this fibroblast state tracked with worse clinical outcomes, suggesting it is not a bystander but an active participant in disease progression.

The next question was mechanistic: what turns ordinary fibroblasts into MMP11-producing matrix builders? The researchers co-cultured tumor cells with fibroblasts and found that different lung adenocarcinoma cell lines varied dramatically in their ability to trigger the program. When they separated the tumor cells’ influence into soluble factors and extracellular vesicles, the vesicle fraction carried most of the programming activity. Extracellular vesicles are nanoscale lipid-enclosed particles that cells release to shuttle proteins, lipids, and nucleic acids to recipient cells, functioning as a kind of biological postal system. Using isolation and functional fractionation techniques, the team demonstrated that removing vesicles from tumor-conditioned media largely abolished the induction of the MMP11-positive state, while purified vesicles restored it.

To identify the cargo responsible, the researchers turned to quantitative proteomics of the vesicles themselves, comparing vesicles with high CAF-programming activity against those with low activity using both data-dependent and data-independent acquisition mass spectrometry. One protein stood out: secreted phosphoprotein 1, better known as SPP1 or osteopontin, a secreted glycoprotein previously implicated in metastasis and immune regulation. SPP1 was selectively enriched in the vesicles that most potently drove fibroblast reprogramming, indicating that the tumor does not simply dump a generic mix of molecules into its vesicles but actively sorts specific signaling proteins into them.

The mechanistic chain was then traced to its receptor. Vesicle-associated SPP1, the study found, engages primarily the CD44 receptor on the surface of fibroblasts. This binding activates the PI3K-AKT signaling pathway, a canonical pro-survival and pro-growth cascade, and sustains the transcriptional changes that push fibroblasts into the MMP11-positive phenotype. Genetic and pharmacologic perturbations confirmed the pathway’s causality: blocking SPP1, CD44, or PI3K-AKT signaling prevented the fibroblast reprogramming in co-culture systems. In other words, the tumor-to-stroma communication is not diffuse background noise but a specific, druggable ligand-receptor axis.

The clinical implications emerged clearly from multiplex immunofluorescence staining of lung adenocarcinoma specimens. Tumors rich in MMP11-positive fibroblasts showed dense collagenous matrix deposition, physical exclusion of T cells from the tumor nests, and reduced intratumoral immune infiltration. In cohorts of patients treated with chemo-immunotherapy, the presence of this fibroblast state predicted poorer responses, consistent with the idea that a matrix-rich, immune-excluded microenvironment undermines the ability of checkpoint inhibitors to mobilize anti-tumor T cells. The findings thus provide a mechanistic bridge between a specific stromal cell state and the well-known clinical problem of immunotherapy resistance in lung cancer.

Crucially, the study went beyond correlation and tested whether interrupting the EV-SPP1 axis could reverse the process in living organisms. In immunocompetent mouse models of lung tumor growth and metastasis, disrupting the pathway reduced the development of MMP11-positive CAFs, loosened the dense stromal architecture, and revived anti-tumor T-cell immunity. Most strikingly, combining EV-SPP1 pathway disruption with PD-1 immune checkpoint blockade made tumors substantially more sensitive to the immunotherapy, transforming a resistant microenvironment into one that immune cells could penetrate and attack. This positions the vesicle cargo protein not just as a biomarker but as a candidate therapeutic target in its own right.

The broader significance of the work lies in reframing how scientists think about the tumor microenvironment. Rather than treating fibroblast diversity as an intrinsic property of stromal cells, the study shows that tumor cells can actively author the identity of their neighbors through targeted vesicle-mediated delivery of signaling proteins. This tumor-instructed model of stromal reprogramming suggests that effective immunotherapy strategies in lung adenocarcinoma may need to target the communication lines between cancer cells and fibroblasts, not only the immune checkpoints themselves. If the EV-SPP1-CD44-PI3K-AKT circuit can be safely intercepted in patients, it could convert a large fraction of immune-excluded, therapy-resistant lung tumors into ones that respond to existing treatments, offering a rational path to combination regimens built on the biology of intercellular vesicle trafficking.

Subject of Research: Tumor-derived extracellular vesicle SPP1 programming of MMP11-positive cancer-associated fibroblasts driving immune exclusion in lung adenocarcinoma

Article Title: Extracellular vesicle–enriched SPP1 programs MMP11⁺ fibroblast states to drive immune exclusion in lung adenocarcinoma

Article References: He, X., Qian, L., Zhao, D., Wang, G., Zhang, X., Ye, Y., Li, L., Wen, Y., & Zhang, L. (2026). Extracellular vesicle–enriched SPP1 programs MMP11⁺ fibroblast states to drive immune exclusion in lung adenocarcinoma. Molecular Cancer. https://doi.org/10.1186/s12943-026-02785-5

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02785-5

Keywords: lung adenocarcinoma, cancer-associated fibroblasts, extracellular vesicles, SPP1, MMP11, immune exclusion, tumor microenvironment, immunotherapy resistance, PD-1 blockade, PI3K-AKT signaling, CD44, single-cell RNA sequencing