Interactions between cancer-associated fibroblasts and T-cells: functional crosstalk with targeting and biomarker potential

Cancer-associated fibroblasts (CAFs) are a heterogeneous cell population recognized as a key component of the tumour microenvironment (TME). Cancer-associated fibroblasts are known to play an important role in maintaining and remodelling the extracellular matrix (ECM) in the tumour stroma, supporting cancer progression and inhibiting the immune system's response against cancer cells. This review aims to summarize the immunomodulatory roles of CAFs, particularly focussing on their T-cell suppressive effects. Cancer-associated fibroblasts have several ways by which they can affect the tumour's immune microenvironment (TIME). For example, their interactions with macrophages and dendritic cells (DCs) create an immunosuppressive milieu that can indirectly affect T-cell anticancer immunity and enable immune evasion. In addition, a number of recent studies have confirmed CAF-mediated direct suppressive effects on T-cell anticancer capacity through ECM remodelling, promoting the expression of immune checkpoints, cytokine secretion and the release of extracellular vesicles. The consequential impact of CAFs on T-cell function is then reflected in affecting T-cell proliferation and apoptosis, migration and infiltration, differentiation and exhaustion. Emerging evidence highlights the existence of specific CAF subsets with distinct capabilities to modulate the immune landscape of TME in various cancers, suggesting the possibility of their exploitation as possible prognostic biomarkers and therapeutic targets.