Project description:Cholangiocarcinoma (CCA) is a devastating liver cancer characterized by high aggressiveness and resistance to therapy, which results to poor prognosis. Signals imposed by oncogenic pathways, such as transforming growth factor β (TGFβ) frequently contribute to CCA development. In this study, we explored novel effectors of the TGFβ pathway in CCA by gene expression profiling. We identified the long non-coding RNA LINC00313 as a novel target gene of TGFβ signalling in CCA cells. TGFβ induced LINC00313 expression in a TβRI/Smad-dependent manner. Subcellular fractionation showed that LINC00313 is a predominantly nuclear lncRNA. By integrating RNA-seq and ATAC-seq data from LINC00313 over-expressing cells, we observed that LINC00313 regulates the expression of several genes involved in the Wnt signalling pathway. As a proof of concept, we focused on the gene encoding transcription factor 7 (TCF7), a major effector that drives transcription of Wnt-target genes. LINC00313 gain of function resulted in increased TCF7 expression, while its loss of function diminished basal or TGFβ-induced TCF7 expression levels. Interestingly, LINC00313 enhanced basal or chemically induced TCF/LEF-dependent transcriptional responses, promoted colony-forming capacities of CCA cells in vitro and accelerated tumor growth in vivo. We also report that genes associated with LINC00313 over-expression recapitulate poor prognosis human CCA associated with a reduced overall survival and KRAS mutations. To decipher the underlying molecular functions of LINC00313, we identified its interacting proteins by performing an unbiased RNA pull-down assay followed by mass spectrometry. We demonstrated that actin-like 6A (ACTL6A), a subunit of the SWI/SNF chromatin remodelling complex specifically binds to LINC00313 and impacts TCF7 expression and TCF/LEF signalling output. Thus, we propose a model whereby TGFβ induces LINC00313, in order to regulate the expression of a subset of target genes, such as TCF7 possibly in co-operation with the SWI/SNF chromatin remodelling complex, via establishing direct interaction with ACTL6A. By regulating key genes of the Wnt pathway, LINC00313 fine-tunes Wnt/TCF/LEF-dependent transcriptional responses and boosts cholangiocarcinogenesis.

Project description:ObjectivesThe relative contributions of inflammatory signalling and sequential oncogenic dysregulation driving liver cancer pathogenesis remain incompletely understood. Lymphotoxin-β receptor (LTβR) signalling is critically involved in hepatitis and liver tumorigenesis. Therefore, we explored the interdependence of inflammatory lymphotoxin signalling and specific oncogenic pathways in the progression of hepatic cancer.DesignPathologically distinct liver tumours were initiated by hydrodynamic transfection of oncogenic V-Akt Murine Thymoma Viral Oncogene Homolog 1 (AKT)/β-catenin or AKT/Notch expressing plasmids. To investigate the relationship of LTβR signalling and specific oncogenic pathways, LTβR antagonist (LTβR-Fc) or agonist (anti-LTβR) were administered post oncogene transfection. Initiated livers/tumours were investigated for changes in oncogene expression, tumour proliferation, progression, latency and pathology. Moreover, specific LTβR-mediated molecular events were investigated in human liver cancer cell lines and through transcriptional analyses of samples from patients with intrahepatic cholangiocarcinoma (ICC).ResultsAKT/β-catenin-transfected livers displayed increased expression of LTβ and LTβR, with antagonism of LTβR signalling reducing tumour progression and enhancing survival. Conversely, enforced LTβR-activation of AKT/β-catenin-initiated tumours induced robust increases in proliferation and progression of hepatic tumour phenotypes in an AKT-dependent manner. LTβR-activation also rapidly accelerated ICC progression initiated by AKT/Notch, but not Notch alone. Moreover, LTβR-accelerated development coincides with increases of Notch, Hes1, c-MYC, pAKT and β-catenin. We further demonstrate LTβR signalling in human liver cancer cell lines to be a regulator of Notch, pAKTser473 and β-catenin. Transcriptome analysis of samples from patients with ICC links increased LTβR network expression with poor patient survival, increased Notch1 expression and Notch and AKT/PI3K signalling.ConclusionsOur findings link LTβR and oncogenic AKT signalling in the development of ICC.

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Inhibition of LTβR signalling activates WNT-induced regeneration in lung.

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