Cancer-associated fibroblasts in intrahepatic cholangiocarcinoma progression and therapeutic resistance

Cancer-associated fibroblasts (CAFs) are one of the most abundant stromal cell type in the tumor microenvironment (TME) of intrahepatic cholangiocarcinoma (iCCA), where they are actively involved in cancer progression through a complex network of interactions with other stromal cells. The majority of the studies investigating CAFs in iCCA have focused their attention on CAF tumor-promoting roles, remarking their potential as therapeutic targets. However, indiscriminate targeting of CAFs in other desmoplastic tumors has ended in failure with no effects or even accelerated cancer progression and reduced survival, indicating the urgent need to better understand the nuances and functions of CAFs to avoid deleterious effects. Indeed, recent single cell RNA sequencing studies have shown that heterogeneous CAF subpopulations coexist in the same tumor, some promoting- and other restricting- tumor growth. Moreover, recent studies have shown that in iCCA, diverse CAF subtypes interact differently with the cells of the TME, suggesting that CAFs may dynamically change their phenotypes during tumor progression, a field that remains uninvestigated. The characterization of heterogenous CAF subpopulations and their functionality, will provide a feasible and safer approach to facilitate the development of new therapeutic approaches aimed at targeting CAFs and their interactions with other stromal cells in the TME rather than solely tumor cells in iCCA. Here, we discuss the origin of CAFs, as well as their heterogeneity, plasticity, mechanisms and targeting strategies to provide a brief snapshot of the current knowledge in iCCA.