Signaling and molecular networks related to development and inflammation involved in CCA initiation and progression

Intrahepatic cholangiocarcinoma (iCCA) is a rare neoplasm of the bile ducts with a low survival rate, whose incidence is continuously increasing and is associated with a rich and varied tumor microenvironment (TME). Although the main mutations characterizing iCCA are known, there are several unresolved issues regarding the processes leading to the accumulation of mutations in the normal cholangiocyte. The inflammatory mediators and the molecular pathways involved in cholangiocarcinogenesis, which regulate the transition from normal to dysplastic cells, resulting in neoplastic cholangiocytes, are poorly understood. Moreover, once the tumor is established, it is unclear which effects of the interaction between the tumor and TME constituent cells, in particular cancer-associated fibroblasts (CAFs), are responsible for stimulating the malignant behavior of iCCA. In this review, we described the main mutations affecting the bile ducts leading to iCCA development as well as the putative inflammatory mediators and morphogenetic pathways involved in the establishment of the malignant transition of the bile ducts. We also described the main signaling pathways involved in TME-tumor cell interactions, with particular emphasis on the effect of CAFs in cancer. Finally, we wanted to analyze possible new therapeutic approaches aimed at modifying the composition of TME and the possible role of immunotherapy in improving the treatment of this cancer.