The role of non-canonical NF-κB signaling in intrahepatic B signaling in intrahepatic cholangiocarcinoma

• Applicant: Privatdozent Dr. Bruno Christian Köhler
• Subject Area: Gastroenterology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 469903177

The proposed project aims at investigating the non-canonical Nuclear Factor kappa B (NF-кB) signaling pathway in intrahepatic cholangiocarcinoma (iCCA).The incidence of iCCA is increasing worldwide. A deeper molecular understanding of iCCA is urgently needed for the development of a more effective and precise therapy.NF-кB signaling comprises a complex network of proteins and is divided in a canonical and a non-canonical pathway. In contrast to the canonical pathway, little is known about the role of the non-canonical pathway in the liver, especially in cholangiocytes. Our previous work identifies an activation of non-canonical NF-кB signaling in the biliary epithelium in human chronic liver diseases and reveals the major transcription factor of the non-canonical signaling pathway, RELB, as responsible driver for biliary fibrosis and ductular reactions in a mouse model. Our experiments emphasize an essential role of Lymphotoxin beta (LTB) as key activating ligand of non-canonical NF-кB signaling in the diseased biliary epithelium. Furthermore, we identified RELB as highly active in a set of murine and human iCCA.Hence, the proposed project aims at a mechanistical investigation of non-canonical NF-кB in iCCA. Therefore, we will utilize a comprehensive platform of in vitro, in vivo and ex vivo strategies as well as multi-omic data. Human cholangiocytes and CCA cells will be investigated for their responsiveness towards non-canonical NF-кB activation. Organoid cultures of biliary epithelial cells and iCCA will dissect the role of non-canonical NF-кB in a purified, tissue-like situation. To assess non-canonical NF-кB in a complex system, liver parenchymal cell (AlbCre) as well as cholangiocyte specific (CK19Cre) RELB knockout mice will be challenged in murine iCCA models. Additionally, well-defined precursor lesions as well as CCA tissue cohorts, which we assess through international collaborations, will be immunohistochemically analyzed. Comprehensive mechanistic studies will reveal protein interactions and identify key players in the signaling pathway. To identify the transcriptional changes directed by RELB, we will apply ChIP-sequencing in the in vitro and in vivo setting.The involvement of non-canonical NF-кB in the process of iCCA spread will be assessed in a cohort of metastasized CCA, comprising tissue as well as RNA - and genome sequencing. In sum, the major goal is to dissect the role of non-canonical NF-кB signaling from the ligand/receptor to the transcriptional level. The comprehensive analyses will add significant knowledge to an incompletely understood disease.

• DFG Programme: Research Grants