Identification and functional characterization of cancer cell-derived, stroma-modulating factors in cholangiocarcinoma

• Applicant: Privatdozentin Dr. Anna Lena Saborowski
• Subject Area: Gastroenterology
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325247206

Cholangiocarcinoma (CCA) is a highly aggressive malignancy that displays features of biliary differentiation. While the incidence of CCA has increased worldwide over the last decade, 5 year survival rates stall at less than 10%. Thus, CCA belongs to the most aggressive cancers, and novel therapeutic strategies are urgently needed. A typical histological finding in CCAs and other ductal neoplasias (e.g. pancreatic ductal adenocarcinoma (PDAC)) is the dense desmoplastic stroma that surrounds the cancer cells. The stroma is increasingly recognized as a therapeutic target; however, modification of the tumor microenvironment can have both tumor suppressive- and tumor promoting effects. In CCA, the molecular mechanisms that shape the tumor reactive stroma are thus far insufficiently investigated. Assuming that paracrine signaling from cancer cells is crucial for the tumor-reactive environment, we aim to functionally characterize factors that mediate the cross talk between tumor cells and stroma cells. We will initially characterize two designated stroma-modulating factors, PDGF-D and SHH, in cholangiocarcinogenesis. To annotate the pathobiological relevance of candidate secreted factors in an in-vivo system, we will utilize a genetically tractable, transplantation based murine CCA model we recently developed. Importantly, tumors in this model exhibit a prominent desmoplasia and histologically closely resemble the human disease. Additionally, to enable acute tumor cell specific RNAi-mediated loss-of-function experiments in an established cancer we will adapt a genetically flexible embryonic stem cell based platform (GEMM-ESCs) that we originally developed for PDAC. The GEMM-ESC technology facilitates drug target validation experiments in an autochthonous and immune-competent adult organism. Importantly, multi-allelic CCA-prone shRNA-transgenic mice will be made directly from ESCs by blastocyst injection, circumventing the need for time consuming breeding. Importantly, instead of random integration into the genome, regulatable shRNAs, cDNAs or CRISPRs are expressed from a defined chromosomal locus that has been thoroughly tested for superior expression efficiency with minimal leakiness. Finally, we aim to identify novel cholangiocarcinoma-relevant secreted proteins using murine organoid systems and human primary tissues. In this regard, we will comparatively analyze the supernatant of biliary organoids in direct dependence on the presence or absence of cholangiocarcinoma-initiating lesions. In parallel, we will analyze expression data of laser-capture microdissected cholangiocarcinoma tissue (stroma versus epithelial tumor compartment ) and normal biliary cells to identify cancer cell-derived secreted factors that segregate with abundant stromal desmoplasia.

• DFG Programme: Research Grants