Targeting the IL-17/NGAL/NETs/ITGA5 Axis: A Novel Strategy to Overcome Immunosuppression and Fibroblast Reprogramming in Pancreatic Cancer

Highlight

Neutrophil extracellular traps (NETs), induced by tumour-derived neutrophil gelatinase-associated lipocalin (NGAL), directly interact with integrin α5β1 (ITGA5) on cancer-associated fibroblasts (CAFs), prompting inflammatory CAF differentiation and immunosuppression in pancreatic ductal adenocarcinoma (PDAC). This IL-17/NGAL/NETs/ITGA5 signaling axis fosters tumour growth and CD8+ T-cell exhaustion. Combining IL-17 and ITGA5 blockade with anti-PD-1 immunotherapy shifts CAF phenotypes and enhances antitumour immunity, offering a novel therapeutic approach for PDAC.

Study Background

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest malignancies, largely due to its aggressive nature, late diagnosis, and profound resistance to current therapies including immune checkpoint inhibitors. This resistance is attributed chiefly to its highly immunosuppressive tumour microenvironment (TME), which includes complex interplay between various cellular components and extracellular matrix.

Cancer-associated fibroblasts (CAFs) in PDAC display heterogeneity, with distinct subtypes exerting divergent effects on tumour progression and immune modulation. Specifically, inflammatory CAFs (iCAFs) promote tumour progression and immune evasion by secreting cytokines such as interleukin-6 (IL-6). Neutrophil extracellular traps (NETs), networks of extracellular DNA fibers adorned with proteins, accumulate in PDAC and associate with poor prognosis. However, their role in modulating CAF heterogeneity and the upstream tumour-derived signals driving pathological NETosis have remained poorly characterized.

Study Design

This investigation employed a multifaceted experimental approach integrating quantitative spatial analysis of human PDAC tissue specimens, coculture systems involving NETs and pancreatic stellate cells (an origin of CAFs), patient-derived CAFs, and a spectrum of molecular biology techniques including biotinylated DNA pull-downs combined with mass spectrometry, live-cell integrin inhibition assays, and CUT&RUN sequencing to elucidate gene regulatory mechanisms.

Functional in vivo modelling included orthotopic pancreatic tumour implantation and hepatic colonisation assays in immunocompetent mice to assess tumour progression and metastatic potential. CD8+ T-cell functionality assays and single-cell RNA sequencing were integral to assessing immune modulation and fibroblast subtype dynamics across an eight-arm combinatorial therapeutic study investigating the impact of targeting IL-17, integrin α5β1 (AV3), and PD-1 pathways.

Key Findings

1. NETs Reprogram CAF Phenotypes through ITGA5: The study demonstrated that NETs-derived DNA directly binds integrin α5β1 (ITGA5) on fibroblasts via its N-terminal domain. This interaction activates a signalling cascade involving focal adhesion kinase (FAK), Src family kinase (SRC), Yes-associated protein (YAP), and IL-6-mediated Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3), culminating in specification of iCAF differentiation. These inflammatory CAFs contribute to tumour progression and shape an immunosuppressive microenvironment.

2. Tumour-Derived NGAL Drives NETosis via IL-17: Neutrophil gelatinase-associated lipocalin (NGAL) expression is induced by IL-17 produced in the tumour milieu. NGAL promotes extracellular signal-regulated kinase (ERK) activation and reactive oxygen species (ROS) production, which collectively drive abnormal NET formation (NETosis) in neutrophils. Thus, the tumour microenvironment orchestrates pathological NETosis promoting PDAC progression.

3. NETs-Reprogrammed iCAFs Accelerate Tumour Growth and CD8+ T-Cell Exhaustion: Functionally, iCAFs stimulated by NETs enhance PDAC tumour growth and facilitate hepatic metastatic colonisation. Spatial mapping revealed exhausted CD8+ T cells preferentially localize in iCAF-rich areas, indicating that NETs and iCAFs jointly orchestrate local immunosuppression and T-cell dysfunction, a key barrier to effective immune responses.

4. Clinical Relevance of NETs/ITGA5 Signature: A composite molecular signature combining NETs and ITGA5 expression stratified overall survival in patients with PDAC, emphasizing the prognostic potential of this axis and its value as a biomarker for patient risk assessment.

5. Therapeutic Synergy of Targeting IL-17, ITGA5, and PD-1: Utilising single-cell transcriptomics, the study dissected effects of triple therapy combining anti-IL-17, an integrin α5β1 inhibitor (AV3), and anti-PD-1 checkpoint blockade. This regimen reprogrammed CAF populations by decreasing inflammatory CAFs in favor of myofibroblastic CAFs (myCAFs), restored effector functions of CD8+ T cells, and achieved superior tumour suppression and survival benefits compared to monotherapies or dual combinations.

Expert Commentary

The elucidation of the IL-17/NGAL/NETs/ITGA5 signaling axis offers profound insight into the stromal and immune crosstalk underpinning PDAC progression. By revealing how tumour-intrinsic signals provoke pathological NETosis that in turn sculpt immunosuppressive CAF phenotypes and exhausted T-cell niches, this work advances understanding of tumour ecosystem dynamics that sustain therapeutic resistance.

Importantly, the identification of ITGA5 as a direct receptor for NETs-DNA on fibroblasts bridges innate immune mechanisms with stromal reprogramming, highlighting novel molecular targets. The demonstrated synergy of concomitant blockade of IL-17 and ITGA5 with PD-1 immunotherapy addresses a major unmet need given PDAC’s notorious refractoriness to immune checkpoint inhibitors.

Still, translational hurdles remain, including confirming safety and efficacy in early-phase clinical trials and further dissecting the complex fibroblast heterogeneity and possible compensatory pathways. Future studies might also explore combinatorial regimens incorporating NETs inhibitors or ROS modulators.

Conclusion

This comprehensive study delineates a novel IL-17/NGAL/NETs/ITGA5 axis driving CAF subtype reprogramming toward immunosuppressive inflammatory phenotypes that promote pancreatic cancer progression and immune evasion. It underscores the therapeutic potential of targeting this axis synergistically with immune checkpoint blockade to overcome the immunosuppressive tumour microenvironment and improve patient outcomes in PDAC. These findings pave the way for innovative combinatorial approaches integrating stromal and immune modulation, enthusing new avenues in pancreatic cancer treatment research.

Funding and Trial Registration

No specific funding statement or clinical trial registry information was reported in the original publication.

References

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