Inhibition of the ZEB1-BCL2 axis in cancer-associated fibroblasts as a strategy to improve chemotherapy response in intrahepatic cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (iCCA) is an aggressive tumour from the biliary tree that is characterized by a prominent desmoplastic stroma, mainly composed of cancer-associated fibroblasts (CAF), and a poor prognosis due to its late clinical presentation and the lack of effective non-surgical treatments. Current therapies still include chemotherapeutic combinations of gemcitabine and cisplatin for the majority of the patients showing poor results due the apparition of resistance. This situation led us to interrogate the potential role in the development of chemoresistance of ZEB1, an EMT-inducing transcription factor (EMT-TF) that we previously identified as a pro-tumorigenic factor in tumour cells and CAF of iCCA. By analysing human CCA samples and sc-RNAseq public databases, we show here that ZEB1 is present in the tumour microenvironment of all iCCA patients tested and is prominently expressed by the myofibroblastic CAF subpopulation (myCAF). Using cellular models of CAF, we show that cells depleted for ZEB1 are more sensitive to gemcitabine and cisplatin, via a mechanism involving the direct regulation of the anti-apoptotic gene BCL2. Moreover, ZEB1 expressing CAF protect iCCA tumour cells against the toxicity of the chemotherapeutic drugs through the release of paracrine soluble factors, including CTGF, IL6 and IL8, an event that could be reversed by the BCL2 inhibitor venetoclax. Therefore, our results point to the use of BCL2 inhibitors as a way to improve the efficacy of current chemotherapeutic regimens in iCCA patients.