Fibrosis-Driven Activation of Schwann Cells in Pancreatic Cancer: Unraveling the Nuclear Mechanosensing Pathway

Highlight

• Fibrosis in pancreatic ductal adenocarcinoma (PDAC) stiffens the tumor microenvironment, activating Schwann cells (SCs) through mechanical forces.
• Activated SCs demonstrate increased c-Jun phosphorylation via a non-canonical nuclear mechanosensing mechanism involving phospholipase A2.
• Pancreatic fibrosis alone, without malignant cells, is sufficient to trigger SC activation, implicating roles in non-malignant pancreatic diseases.
• SCs are more mechanically sensitive than PDAC cells, revealing a critical interaction that may be targeted in future microenvironment-focused therapies.

Study Background

Pancreatic ductal adenocarcinoma (PDAC) remains among the deadliest cancers worldwide, largely due to its aggressive nature and resistance to conventional therapies. Two hallmark features within the tumor microenvironment (TME) that facilitate PDAC progression are fibrosis and tumor innervation.

Fibrosis, characterized by excessive deposition of extracellular matrix components, leads to tissue stiffness, influencing cellular behavior and tumor aggressiveness. Simultaneously, tumor innervation—nerve infiltration within the cancer milieu—has been implicated in cancer progression through neurotrophic signaling and modulation of cellular crosstalk.

Although both fibrosis and innervation contribute to PDAC lethality, their interrelationship remains poorly understood. Schwann cells (SCs), glial cells of the peripheral nervous system, are known to support neural integrity but also actively participate in tumor biology. Prior studies identified that SC activation promotes pancreatic cancer invasion; however, the upstream mechanisms activating SCs within the fibrotic microenvironment have not been elucidated.

Study Design

This study integrated analyses of human PDAC patient samples with murine models to investigate the relationship between fibrosis-induced mechanical stress and SC activation. The investigators used immunohistochemistry to detect c-Jun phosphorylation—a marker of SC activation—in nerves surrounded by fibrotic stroma.

Atomic force microscopy (AFM) quantified mechanical stiffness, and multiphoton live imaging enabled real-time visualization of SC dynamics within the fibrotic TME. In vitro models applied controlled mechanical forces to cultured SCs expressing a reporter for c-Jun activation, coupled with RNA sequencing to delineate molecular pathways involved.

Key Findings

The study demonstrated a positive correlation between stromal stiffness and SC activation. Nerves embedded in a stiff fibrotic matrix exhibited significantly higher levels of phosphorylated c-Jun, indicative of activated SCs. Intravital imaging confirmed that SC activation was dynamically dependent on the mechanical properties of the surrounding matrix.

Mechanistically, mechanical forces induced c-Jun phosphorylation in SCs through a non-canonical pathway involving nuclear mechanosensing. Specifically, nuclear compression activated the AP-1 transcription factor complex without relying on traditional upstream signaling but instead required phospholipase A2 (PLA2), a pro-inflammatory enzyme localized in the nucleus.

Remarkably, fibrosis alone—absent of cancer cells—was sufficient to trigger SC activation, proposing that mechanical stress from extracellular matrix remodeling can prime SCs toward a protumorigenic phenotype. Furthermore, SCs displayed a higher sensitivity to mechanical activation than PDAC cells, underscoring their crucial role as mechanotransducers in the pancreatic TME.

Expert Commentary

This study elucidates a novel mechanotransductive pathway by which pancreatic fibrosis recruits SCs toward a protumorigenic state, revealing a previously underappreciated nuclear mechanosensing mechanism. The identification of phospholipase A2 as a key mediator introduces potential therapeutic targets to modulate SC activation.

Clinically, targeting the fibrotic stroma or the activated SCs themselves could disrupt critical crosstalk facilitating tumor progression and invasion. Given that fibrosis precedes malignant transformation in some pancreatic diseases, these findings might also inform early intervention strategies.

Limitations include the challenge of translating findings from murine and in vitro models to human PDAC pathology and the complex interplay between multiple TME components not fully addressed here. Nevertheless, the comprehensive methodological approach strengthens the study’s validity.

Conclusion

This investigation provides substantial evidence that pancreatic fibrosis mechanically activates Schwann cells through a nuclear mechanosensing mechanism involving phospholipase A2 and AP-1 transcriptional activation. By promoting a protumorigenic SC phenotype, fibrosis not only alters the tumor microenvironment but actively contributes to PDAC aggressiveness.

These insights emphasize the importance of understanding TME biophysical properties and their cellular consequences, opening avenues for innovative therapies focusing on microenvironment modulation rather than solely on cancer cells. Future research should explore pharmacologic inhibition of this pathway and evaluate its impact on PDAC progression and patient outcomes.

Funding and Clinical Trials

The original study was funded by research grants supporting translational cancer biology. No specific clinical trials were referenced in the publication.

References

• Stupakov P, Sadatrezaei G, Velazquez Quesada I, et al. Pancreatic cancer fibrosis activates protumorigenic Schwann cells through a nuclear mechanosensing mechanism. Gut. 2026 Jun 23;doi:10.1136/gutjnl-2026-XXX.
• Neuzillet C, Tijeras-Raballand A, Ragulan C, et al. Inter- and intra-tumoural heterogeneity in cancer-associated fibroblasts of human pancreatic ductal adenocarcinoma. J Pathol. 2019;248(1):51-65.
• Koikawa K, Steimle CN, Ishihara R, et al. Cancer-associated fibroblasts promote pancreatic tumor progression through IGF-1R signaling. Cancer Res. 2020;80(12):2503-2517.