Cancer-associated fibroblast heterogeneity and immune cell interaction in pancreatic ductal adenocarcinoma

Zayou, Fouzia (2025). Cancer-associated fibroblast heterogeneity and immune cell interaction in pancreatic ductal adenocarcinoma. University of Birmingham. Ph.D.

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Abstract

Pancreatic ductal adenocarcinoma (PDAC) represents one of the greatest unmet needs in oncology with suboptimal clinical outcome for most patients. An important factor is the complex tumour microenvironment (TME) in PDAC that serves to support tumour growth whilst suppressing potential immune control. Cancer-associated fibroblasts (CAFs) play a pivotal role within the TME and may represent an important target for future immune therapies.

This thesis investigates the diversity of fibroblast populations within PDAC tumours, comparing them to adjacent normal fibroblasts (ANFs), with a focus on the predominant subtypes: myofibroblasts (myCAFs) and inflammatory fibroblasts (iCAFs). Flow cytometry identified iCAFs as the dominant CAF subtype within the tumour stroma, in contrast to their lower prevalence in ANFs. Functional assays demonstrated that co-culturing patient-derived fibroblasts with healthy donor NK and T cells led to distinct effects on T cell phenotype. Specifically, CAF co-culture selectively induced proliferation in unstimulated NK and T cells, along with increased expression of activation markers CD69 and NKG2D, and the checkpoint inhibitor PD- 1 on T cells, suggesting a role in either T cell activation or exhaustion and immune evasion within the tumour microenvironment.

Furthermore, unstimulated CAFs enhanced lymphocyte adhesion and migration, while an inhibitory effect was observed on activated cells. Stimulation of CAFs with the inflammatory cytokines TNF-α/IFN-γ, which elicits an iCAF phenotype, further promoted lymphocyte migration. In contrast, incubation with TGF-β, which develops a myCAF profile, suppressed migration, indicating opposing effects of cytokine polarization on lymphocyte dynamics. Co-culture of cytokine-polarised CAF populations revealed that TGF-β incubation led to decrease in CD56bright NK cell adhesion and an increase in CD56dim stimulated NK cell migration. CAFs also upregulated KIRs and NKp46 on NK cells, indicating potential alterations in NK cell activation and recognition capabilities.

Spatial analysis revealed that tumour-proximal fibroblasts have a myCAF phenotype and express markers that form barriers to lymphocyte migration, while distal fibroblasts display characteristics of iCAF and likely contribute to an inflammatory environment through cytokine secretion.

My findings contribute to studies showing the profound diversity of the CAF population in PDAC. Together, the findings indicate that the PDAC environment is enriched with the presence of inflammatory CAF that are located relatively distant from the tumour, most likely in the lymphoid follicles and tertiary lymphoid structures that develop during PDAC development. These populations appear to support the transmigration of lymphoid cells and may help to support the recruitment of populations that initiate a tumour-specific immune response. In contrast, the myofibroblast populations encase the tumour, and my work indicates that these are also likely to suppress the migration of lymphoid cells into the tumour bed.

These findings highlight the significant heterogeneity and functional diversity of CAFs in PDAC, underscoring their critical roles in modulating immune cell behaviour and suggesting potential targets for enhancing immune surveillance and improving therapeutic outcomes in pancreatic cancer.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):