Cancer Research | LRRC15 in Cancer-Associated Fibroblasts Regulates Extracellular Matrix Remodeling and Enhances Anti-Tumor Immune Responses to Suppress Lung Cancer Progression

This study reveals the critical immunoregulatory function of LRRC15 within the tumor microenvironment, providing a novel intervention node for immunotherapy strategies in non-small cell lung cancer (NSCLC), suggesting that targeting CAF subsets may overcome the resistance bottleneck of current immune checkpoint blockade therapies.

 

Literature Overview

The article titled "Targeting LRRC15 in Cancer-Associated Fibroblasts Modifies the Extracellular Matrix and Enhances Tumor Immune Responses to Suppress Lung Cancer Progression," published in the journal Cancer Research, systematically investigates the specific expression of LRRC15 in lung cancer-associated fibroblasts and its regulatory mechanisms on the immune microenvironment. By integrating single-cell transcriptomic analysis, gene knockout mouse models, and bispecific antibody development, the study uncovers the molecular pathway by which LRRC15+ CAFs promote immunosuppressive macrophage polarization through extracellular matrix (ECM) remodeling, thereby suppressing CD8+ T cell activity. This work not only identifies LRRC15 as a potential therapeutic target but also proposes a novel CAF-directed immunotherapeutic strategy with strong translational potential.

Background Knowledge

1. The NSCLC challenges addressed by this study: Although immune checkpoint blockade (ICB) has shown efficacy in some NSCLC patients, most exhibit primary or acquired resistance, primarily due to a highly immune-excluded tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs), as a major stromal component of the TME, broadly contribute to immune escape by secreting factors, remodeling the matrix, and inhibiting immune cell infiltration, representing a critical barrier for current immunotherapies.
2. Current research bottlenecks regarding LRRC15: Although LRRC15 has been found to be specifically expressed in CAF subsets across multiple solid tumors, its precise function within the TME, regulatory mechanisms, and potential as a therapeutic target remain unclear. Moreover, conventional CAF-targeting strategies often lead to treatment failure or even tumor progression due to disruption of CAF heterogeneity, highlighting the importance of identifying functionally specific CAF subset markers.
3. Research rationale: Leveraging a pan-cancer single-cell atlas, the authors identified LRRC15+ CAFs as a terminally differentiated myofibroblast subset enriched in lung cancer, with high expression correlating with poor prognosis and ICB resistance. Building on this, the study focuses on functional validation and targeted intervention of LRRC15 to elucidate its role in ECM remodeling and immune regulation, providing both theoretical basis and tool antibodies for precise CAF targeting.

 

 

Research Methods and Experiments

The authors first integrated 12 public and in-house single-cell RNA-seq datasets to construct a stromal cell atlas of lung cancer. Through unbiased clustering, nine fibroblast subsets were identified, among which LRRC15+ CAFs (c03) were significantly enriched in tumor tissues and associated with poor patient prognosis. Multiplex immunohistochemistry (mIHC) further validated the specific expression of LRRC15 in CAFs within clinical samples, predominantly localized in αSMA+ fibroblasts, with almost no expression in normal tissues.

To investigate LRRC15 function, the study generated an Lrrc15 gene knockout mouse model and employed multiple lung cancer transplantation models (including TC1-GFP, LLC, and KPS models), demonstrating that LRRC15 deletion significantly suppressed tumor growth and lung metastasis. Single-cell RNA sequencing (scRNA-seq) analysis revealed increased CD8+ T cell infiltration and upregulated expression of activation markers (e.g., IFNγ, perforin) in the TME upon LRRC15 loss, along with a reduced proportion of CD206+ M2-like macrophages, suggesting that LRRC15 modulates antitumor immunity via macrophage polarization.

Mechanistically, in vitro co-culture and extracellular matrix (ECM) transfer experiments demonstrated that ECM secreted by LRRC15-deficient CAFs—particularly type I collagen—was reduced, leading to diminished M2 macrophage polarization. Western blot and collagen detection assays further confirmed that LRRC15 regulates COL1A1 expression and collagen deposition. Additionally, dual neutralization of TGFβ and LRRC15 achieved synergistic tumor suppression, indicating enhanced therapeutic efficacy through combined intervention.

Key Conclusions and Perspectives

• LRRC15+ CAFs are specifically enriched in lung cancer and significantly associated with poor patient outcomes, suggesting their potential as a prognostic biomarker to guide stratified treatment strategies in non-small cell lung cancer
• Deletion of LRRC15 significantly inhibits lung cancer progression without causing notable toxicity, indicating a favorable safety profile and making it an ideal candidate for targeted therapy
• LRRC15 promotes ECM secretion (especially collagen I) by CAFs, inducing CD206+ macrophage polarization and subsequently suppressing CD8+ T cell function, revealing a novel stroma-immune crosstalk mechanism that provides a theoretical foundation for developing interventions targeting the CAF–macrophage–T cell axis
• The developed anti-LRRC15–TGFβ bispecific antibody effectively downregulates LRRC15 expression and enhances antitumor immunity, demonstrating strong translational potential as a novel immunotherapeutic agent, particularly for tumors with high TGFβ expression or abundant stroma

Research Significance and Prospects

This discovery offers new insights for drug development: targeting LRRC15 enables functional reprogramming of CAFs rather than their complete elimination, avoiding the tumor-promoting effects observed with previous CAF-targeting approaches. Moreover, the near-absent expression of LRRC15 in normal tissues makes it an ideal tumor microenvironment-specific target, potentially minimizing off-target toxicity.

In clinical monitoring, the abundance of LRRC15+ CAFs could serve as a potential biomarker to predict patient response to ICB therapy, aiding in the design of personalized treatment regimens. Furthermore, the bispecific antibody strategy proposed in this study sets a precedent for multi-target combination therapies, with future exploration of its synergy with other immunotherapies (e.g., PD-1 inhibitors) warranted.

In disease modeling, the Lrrc15^fl/fl;Col1a2-CreER system utilized in this study provides a reliable tool for conditionally knocking out specific genes in CAFs, facilitating the construction of more precise lung cancer immune microenvironment models and advancing mechanistic studies and drug efficacy evaluation.

 

 

Conclusion

This study systematically elucidates the critical role of LRRC15+ CAFs in non-small cell lung cancer progression, revealing the mechanism by which they shape an immunosuppressive microenvironment through the ECM–macrophage–CD8+ T cell axis. This finding not only deepens our understanding of CAF functional heterogeneity but also introduces a new therapeutic paradigm shifting from "eliminating CAFs" to "reprogramming CAFs." As a highly tumor-specific target, LRRC15 offers excellent safety and therapeutic potential, and the development of its bispecific antibody marks a significant step toward clinical translation of CAF-targeted therapies. In the future, integrating LRRC15 expression levels with immune profiles may enable more precise patient stratification and rational design of combination therapies, providing a new cornerstone for improving long-term survival in NSCLC patients.

 

Lu Qi, Guohui Dang, Xinnan Ling, Zemin Zhang, and Linnan Zhu. Targeting LRRC15 in Cancer-Associated Fibroblasts Modifies the Extracellular Matrix and Enhances Tumor Immune Responses to Suppress Lung Cancer Progression. Cancer Research.