Fibroblasts, the abundant benign cells present within the tumor stroma, have traditionally been considered passive components of the tumor microenvironment. However, this new research illustrates their dynamic role in modulating angiogenesis, the process of new blood vessel formation critical for tumor sustenance and expansion. According to Jordi Alcaraz, a professor at the University of Barcelona’s Faculty of Medicine and Health Sciences and the senior author of the study, these fibroblasts do much more than merely inhabit the tumor niche—they actively influence vascular network architecture, oxygen and nutrient availability, and potentially the metastatic potential of lung tumors along with shaping the immune landscape within the tumor milieu.

This international investigation involved multidisciplinary collaboration between prestigious institutions such as the Catalan Institute of Oncology, the Bellvitge Biomedical Research Institute, the Mayo Clinic in the United States, the Francis Crick Institute in the United Kingdom, and the Garvan Institute of Medical Research and the University of New South Wales in Australia. Spearheaded by the University of Barcelona’s researcher Natalia Díaz Valdivia, the team deployed sophisticated experimental approaches to study angiogenesis markers and hypoxia-related pathways in human lung cancer samples and animal models.

Immunotherapy, a therapy that invigorates the patient’s immune system to target cancer cells, has emerged as a promising lung cancer treatment modality. Nonetheless, many patients fail to derive benefit from immunotherapy alone. Combined therapeutic regimens integrating immunotherapy with anti-angiogenic agents have garnered attention due to their ability to normalize abnormal tumor vasculature and potentially alleviate immunosuppressive tumor niches. Despite this, squamous cell carcinoma has consistently underperformed in response to anti-angiogenic therapy, unlike adenocarcinoma where these drugs demonstrate more robust clinical success.

The researchers distinctly observed that adenocarcinomas display vigorous and functionally competent angiogenesis, characterized by elevated oxygen levels and reduced apoptotic cell death within the tumor mass. Conversely, squamous cell carcinomas were marked by poor vascularization, heightened hypoxia, and an acidic microenvironment—conditions that foster tumor survival under nutrient-deprived and oxygen-starved states but also confer resistance to anti-angiogenic treatments. This stark divergence in vascular biology was traced back to the behavior of cancer-associated fibroblasts, which interact differentially with molecular signaling pathways in these histotypes.

A key mechanistic insight uncovered relates to the synergistic interplay between vascular endothelial growth factor (VEGF) and TIMP-1 (tissue inhibitor of metalloproteinases-1), a novel pro-angiogenic factor. In lung adenocarcinoma, fibroblasts actively enhance angiogenesis through this VEGF-TIMP-1 axis alongside SMAD2/3 signaling pathways, thus facilitating the formation of a functional vascular network. On the other hand, fibroblasts in squamous cell carcinoma exhibit altered molecular profiles likely induced by chronic tobacco exposure, resulting in diminished vessel formation capability and exacerbated tumor hypoxia.

These findings not only elucidate the historically observed selective efficacy of anti-angiogenic drugs favoring adenocarcinoma patients but also shed light on the disparate metastatic behavior of these subtypes. Adenocarcinomas, with their extensive and operational blood vessel networks, seem more predisposed to early metastatic spread, leveraging the vasculature to disseminate cancer cells. Squamous tumors, burdened with hypoxia and acidic stress, appear to metastasize less readily, indicating a complex interplay between the tumor microenvironment and cancer progression dynamics.

The study drives home the imperative need for precision medicine strategies that recognize the heterogeneity of lung cancer subtypes. Therapeutic regimens must transcend one-size-fits-all paradigms, instead integrating tumor microenvironment features such as angiogenesis and hypoxia to stratify patients meaningfully. Biomarkers like TIMP-1 emerge as promising candidates for identifying patient subsets who may benefit from targeted anti-angiogenic interventions or tailored immunotherapy combinations.

Importantly, the work spotlights novel therapeutic targets relevant to these tumor microenvironment differences. For example, adenocarcinoma therapies might be optimized by focusing on agents that disrupt the pro-angiogenic TIMP-1 and SMAD3 pathways, while squamous carcinoma treatments may achieve greater efficacy by addressing tumor hypoxia and metabolic acidosis. This nuanced understanding offers a research blueprint for drug development aiming to manipulate the surrounding stroma in addition to the malignant cells themselves.

A significant practical challenge moving forward is the translation of these mechanistic discoveries into clinical practice. Researchers underscore the importance of validating biomarkers like TIMP-1 in prospective clinical trials and demonstrating that targeting stromal components alongside cancer cells genuinely enhances patient outcomes. The identification and development of specific inhibitors against TIMP-1, currently lacking, represent a critical avenue for therapeutic innovation.

The study received funding from prominent sources including the Spanish National Research Council, the European Union’s Horizon 2020 program, and the Spanish Association Against Cancer. As the global burden of lung cancer continues to rise, innovations that dissect and exploit the tumor microenvironment’s complexity may significantly impact therapeutic efficacy and survival rates for patients worldwide.

Overall, this comprehensive research not only deepens the scientific community’s understanding of lung cancer biology but also paves the way for next-generation treatment strategies that are finely tailored to histotype-specific microenvironmental characteristics, heralding a new era of personalized oncology.

Subject of Research: Cells

Article Title: Antagonistic SMAD2/3 control of TIMP-1, VEGF-A, and hypoxia signaling in myofibroblasts shapes histotype-specific angiogenesis in lung cancer

News Publication Date: March 30, 2026

Web References:
https://doi.org/10.1038/s41419-026-08677-2

References:
Published in Cell Death & Disease, 2026

Image Credits: UNIVERSITY OF BARCELONA

Keywords: Lung Cancer, Adenocarcinoma, Squamous Cell Carcinoma, Anti-angiogenic Therapy, Tumor Microenvironment, Fibroblasts, Angiogenesis, TIMP-1, VEGF, Hypoxia, Immunotherapy, Personalized Therapy

At the core of the paradox lies the diverse phenotypic and functional landscape of CAFs. These cells, originating from various sources including resident fibroblasts, mesenchymal stem cells, and possibly endothelial-to-mesenchymal transition, adopt distinct molecular signatures and secretomes depending on tissue context and tumor subtype. This heterogeneity dictates their dualistic influence: some subsets foster immune evasion and metastatic potential, whereas others facilitate immune surveillance and constrain tumor growth. Such dichotomy complicates therapeutic strategies aimed at targeting CAFs, as indiscriminate depletion may paradoxically promote metastasis and worsen patient prognosis.

Mechanistically, CAFs orchestrate immunotherapy resistance through multiple intricate pathways. One prominent mode involves remodeling the extracellular matrix (ECM), where activated CAFs deposit abundant collagen and fibronectin, creating dense physical barriers that impede immune cell infiltration. This stromal fibrosis not only limits access of cytotoxic T lymphocytes but also alters tissue stiffness, which can modulate signaling pathways critical for both tumor and immune cells. Moreover, CAFs actively reprogram the phenotype of tumor-infiltrating immune cells. For example, they secrete cytokines such as transforming growth factor-beta (TGF-β) and interleukin-6 (IL-6), which drive macrophages toward a pro-tumoral M2 phenotype and induce T-cell exhaustion or regulatory T-cell expansion, thereby dampening anti-tumor immunity.

Another layer of complexity emerges from CAF-derived extracellular vesicles, including exosomes enriched with immunosuppressive cargos. These vesicles facilitate horizontal transfer of modulatory RNAs and proteins to immune cells, further subverting immune responses and enhancing tumor survival. Consequently, tumors characterized by high CAF density are frequently refractory to PD-1/PD-L1 checkpoint inhibitors, a cornerstone of modern immunotherapy, illustrating the formidable barrier CAFs pose to effective treatment.

Intriguingly, in cancers such as pancreatic ductal adenocarcinoma and certain subtypes of breast cancer, select CAF populations, notably those expressing alpha-smooth muscle actin (αSMA), exhibit paradoxical anti-tumor activity. These CAFs have been observed to promote infiltration and activation of cytotoxic CD8+ T cells, attenuating tumor progression. Such findings illuminate the nuanced roles of CAF subsets and underscore the danger of broad-spectrum CAF elimination, which risks destroying beneficial fibroblast populations essential for restraining tumor expansion.

Addressing this dilemma, recent preclinical advances focus on selective targeting of deleterious CAF subsets. Fibroblast activation protein (FAP)-positive CAFs have attracted significant attention as viable therapeutic targets due to their robust immunosuppressive capabilities. Innovative approaches, such as the development of FAP-specific chimeric antigen receptor T cells (CAR-T) and peptide-based vaccines, have demonstrated promising potential in selectively ablating these pathogenic fibroblasts, thereby enhancing immunotherapy efficacy in animal models.

Complementing cellular therapies, strategies inhibiting CAF-secreted soluble factors are also under rigorous investigation. Blocking chemokines like CXCL12, which recruits immunosuppressive cells and promotes fibrosis, or antagonizing TGF-β signaling pathways has been shown to normalize the tumor microenvironment. These interventions aim to dismantle the immunosuppressive network orchestrated by CAFs, facilitating deeper penetration and activity of immune effector cells.

Efforts to disrupt CAF-mediated remodeling of the ECM additionally hold promise. Agents targeting enzymes involved in collagen crosslinking or matrix metalloproteinases may alleviate the physical barriers erected by CAFs, potentially restoring immune surveillance and improving drug delivery. Integrating these stromal-targeting modalities with existing immunotherapies represents a frontier in combating resistance and achieving durable anti-cancer responses.

Nevertheless, the pursuit of CAF-directed therapies is fraught with challenges. FAP, although enriched in tumor-associated fibroblasts, is also expressed in certain normal tissues, raising concerns about potential off-target toxicities and adverse effects. Achieving therapeutic precision necessitates comprehensive mapping of CAF heterogeneity at single-cell resolution across diverse cancer types, enabling identification of context-dependent functional subtypes amenable to selective targeting.

Furthermore, the development of reliable biomarkers to stratify patients who would benefit from CAF-modulating treatments remains an urgent clinical need. Such precision oncology tools would not only optimize therapeutic outcomes but also minimize unwarranted toxicity, a critical balance in the translation of these approaches from bench to bedside.

Experts like Dr. Peng Luo and Dr. Jian Zhang emphasize the imperative of embracing the complexity and duality of CAF biology. Their insights advocate for a paradigm shift—from viewing CAFs as universal adversaries to recognizing their contextual roles within the dynamic tumor ecosystem. This nuanced understanding paves the way for designing sophisticated combination therapies that harness the protective CAF functions while neutralizing their tumor-promoting counterparts.

In summary, the emerging narrative of cancer-associated fibroblasts as both friend and foe in tumor immunotherapy highlights the intricate symbiosis between stromal cells, immune components, and cancer cells. Unraveling the molecular mechanisms underpinning this paradox will be instrumental in overcoming therapeutic resistance and advancing personalized oncology. As research progresses, integrating CAF-targeted interventions holds the promise of transforming the immunotherapeutic landscape and improving survival outcomes for patients afflicted with formidable malignancies.

Subject of Research: Not applicable

Article Title: Friend or foe: The paradoxical roles of cancer-associated fibroblasts in tumour immunotherapy.

Web References: http://dx.doi.org/10.1002/ctd2.70056

Keywords: Cancer