Transcriptional Regulation and Signaling Pathways in Hepatocytes and Liver Cancer Cells

With more than 700.000 new cases each year, hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death. Its risk factors are well defined (e.g., chronic viral hepatitis, alcoholic and non-alcoholic steatohepatitis) and are detectable in up to 90% of all cases. However, genetic heterogeneity of HCC severely complicates the development of effective drugs, which is reflected by the current lack of therapeutic options.

The multi-step process of hepatocarcinogenesis.

Different aetiologies lead to chronic hepatitis characterized by continued cycles of hepatocyte necrosis and regeneration. Stellate cell activation and production of extracellular material mark progressed liver disease with fibrosis and cirrhosis. During ongoing proliferation, hepatocytes acquire somatic mutations and copy-number alterations that promote the formation of early HCC. Additional acquisition of epigenetic changes and alterations in molecular signalling pathways characterize HCC progression.

 

Transcriptional regulators (TRs) such as transcription factors or transcriptional co-activators represent cellular bottlenecks in the process of signal transduction. In carcinogenesis, many TRs as well as upstream regulators have been described as deregulated, which is leading to tumor cell proliferation and apoptosis resistance. Therefore, TRs are discussed as promising target structures for the development of innovative therapeutic strategies. In our group, we are focusing on the regulation and function of different TRs involved in regenerative processes as well as HCC development and progression. We want to understand how TRs support tumorigenesis and if they could serve as biomarkers for patient stratification. For our interdisciplinary approaches, we utilize techniques ranging from cell and molecular biology to bioinformatic methods. We investigate suitable in vitro model systems, in vivo models, and confirm findings in well-characterized human patient cohorts.

The Hippo signaling pathway is a sensor for cell density and negatively regulates its transcriptional coactivator yes-associated protein (YAP). In case of hepatocarcinogenesis, YAP is a very aggressive oncogene since inactivation of Hippo pathway constituents (e.g. Mst1/2) or overexpression of YAP rapidly induce liver tumor formation in mice. We showed that YAP is overexpressed in a subgroup of human HCCs and that this factor supports tumor cell proliferation and invasion. Using cross-species comparison, the Notch receptor ligand Jagged-1 (Jag-1) was identified as central downstream target gene not only in HCC, but also in other gastrointestinal tumor types. In addition, YAP induces a gene signature that characterizes HCC patients with chromosomal instability (CIN).

Scheme of Hippo signaling pathway.
The Hippo kinase cassette consists of kinases (MST1/2, LATS1/2) and scaffold proteins (e.g., SAV1, NF2). Kinase-dependent YAP/TAZ phosphorylation is associated with their cytoplasmic retention and degradation (black arrows). Pathway inactivation leads to nuclear translocation of both transcriptional co-activators, where they interact with different TFs (e.g., TEAD1-4; red arrows).  Binding of YAP/TF or TAZ/TF complexes in gene promoter regions stimulates the expression of factors controlling cell cycle and chromosomal segregation (blue arrow). Due to the negative impact of the kinase cassette on nuclear YAP/TAZ enrichment, the Hippo pathway is considered as tumor-suppressive, while its downstream effectors YAP/TAZ act as oncogenes in different model systems.

 

Moreover, recent studies illustrate that YAP not only supports carcinogenesis via tumor cell-endogenous mechanisms but also via the regulation of inter-cellular communication networks. For example, overexpression of YAP in HCC cells induces the expression of specific receptors on non-tumorous blood vessel cells, which sensitize them to paracrine-acting growth factors and cytokines (e.g., c-MET expression is induced on liver sinusoidal endothelial cells of the liver by YAP-dependent osteopontin production in HCC cells).
In addition, we aim to implement methods from systems biology to better understand the Hippo pathway in tumorous and non-tumorous liver cell. For example, we recently showed that the painkiller acetaminophen controls the dynamic shuttling process of YAP via nuclear phosphorylation processes. This was possible by using sensitive live-cell imaging technology in combination with mathematical pathway modeling (manuscript submitted).
Ongoing projects are focusing on molecular 'upstream' mechanisms leading to an aberrant enrichment of YAP in hepatocytes and HCC cells. On the other hand, we aim to identify cancer patients, who may benefit from future Hippo/YAP-directed therapies.

 

Own Publications (related to Hippo/YAP signaling and liver cancer)

Tóth M, ... Breuhahn K. Co-expression of YAP and TAZ associates with chromosomal instability in human cholangiocarcinoma.  BMC Cancer. 2021 Oct 6;21(1):1079. (IF: 4.64)
Thomann S, ... Breuhahn K. YAP-induced Ccl2 expression is associated with a switch in hepatic macrophage identity and vascular remodelling in liver cancer. Liver Int. 2021 Dec;41(12):3011-3023. (IF: 8.75)
Marquard S, ... Breuhahn K. Yes-associated protein (YAP) induces a secretome phenotype and transcriptionally regulates plasminogen activator Inhibitor-1 (PAI-1) expression in hepatocarcinogenesis. Cell Commun Signal. 2020 Oct 23;18(1):166. (IF: 5.71)
Thomann S, ... Breuhahn K. YAP Orchestrates Heterotypic Endothelial Cell Communication via HGF/c-MET Signaling in Liver Tumorigenesis. Cancer Res. 2020 Dec 15;80(24):5502-5514.  (IF: 12.70)
Weiler SME, ... Breuhahn K. TAZ target gene ITGAV regulates invasion and feeds back positively on YAP and TAZ in liver cancer cells. Cancer Lett. 2020 Mar 31;473:164-175. (IF: 8.68)
Wei T, ... Breuhahn K. YAP-dependent induction of UHMK1 supports nuclear enrichment of the oncogene MYBL2 and proliferation in liver cancer cells. Oncogene. 2019 Jul;38(27):5541-5550. (IF: 6.6)
Pinna F, ... Breuhahn K. A20/TNFAIP3 Discriminates Tumor Necrosis Factor (TNF)-Induced NF-κB from JNK Pathway Activation in Hepatocytes. Front Physiol. 2017 Aug 23;8:610. (IF: 3.2)
Wan S, ... Breuhahn K. Cytoplasmic localization of the cell polarity factor scribble supports liver tumor formation and tumor cell invasiveness. Hepatology. 2018 May;67(5):1842-1856. (IF: 15.0)
Weiler SME, ... Breuhahn K. Induction of Chromosome Instability by Activation of Yes-Associated Protein and Forkhead Box M1 in Liver Cancer. Gastroenterology. 2017Jun;152(8):2037-2051. (IF: 20.8)
Beuke K, ... Breuhahn K^*, Sahle S^*. Quantitative and integrative analysis of paracrine hepatocyte activation by nonparenchymal cells upon lipopolysaccharide induction. FEBS J. 2017 Mar;284(5):796-813. (*shared senior authorship) (IF: 4.2)
Tschaharganeh DF, ... Breuhahn K. Yes-Associated Protein Up-regulates Jagged-1 and Activates the NOTCH Pathway in Human Hepatocellular Carcinoma. Gastroenterology. 2013 Jun;144(7):1530-1542. (IF: 13.9)
Pinna F, ... Kummer U, Breuhahn K. A Systems Biology Study on NFκB Signaling in Primary Mouse Hepatocytes. Front Physiol. 2012;3:466. (IF: 3.6)
Straßburger K, ... Breuhahn K, Teleman AA. Insulin/IGF signaling drives cell proliferation in part via Yorkie/YAP. Dev Biol. 2012 Jul 15;367(2):187-96. (IF: 3.2)
Breuhahn K, Schirmacher P. A cellular view of Nf2 in liver homeostasis and tumorigenesis. Dev Cell. 2010 Sep 14;19(3):363-4. (IF: 9.3)

Group members

Lena Thiess (lena.thiess(at)med.uni-heidelberg.de)
Fabian Rose (fabian.rose(at)med.uni-heidelberg.de)
Yingyue Tang (yingyue.tang(at)med.uni-heidelberg.de)
Michaela Bissinger (michaela.bissinger(at)med.uni-heidelberg.de)
Patrizia Birner (patrizia.birner(at)med.uni-heidelberg.de)

Currently not in the lab

Dr. Sofia Weiler sofia.weiler(at)med.uni-heidelberg.de
Dr. Lilija Wehling geb. Aprupe; lilija.aprupe(at)bioquant.uni-heidelberg.de
Dr. Marcell Tóth marcell.toth(at)med.uni-heidelberg.de
Jennifer Schmitt jennifer.schmitt(at)med.uni-heidelberg.de

Active collaborations

Prof. Arndt Vogel (MHH, Medizinische Hochschule Hannover)
PD Dr. Anna Saborowski (MHH, Medizinische Hochschule Hannover)
Prof. Heike Bantel (MHH, Medizinische Hochschule Hannover)
PD Dr. Katja Breitkopf-Heinlein (UMM, University Hospital Mannheim)
Prof. Jan Hengstler (IfADo, Dortmund)
Dr. Nachiket Vartak (IfADo, Dortmund)
Prof. Ahmed Abdelaziz Fahmy (NewGiza University, Cairo, Egypt)
Prof. Peter Angel (Deutsches Krebsforschungszentrum, DKFZ)
Prof. Mathias Heikenwälder (Deutsches Krebsforschungszentrum, DKFZ)
Prof. U. Kummer (COS, Bioquant, Heidelberg)

Our work is currently supported by

• Deutsche Forschungsgemeinschaft (DFG)
• Deutsche Krebshilfe
• The China Scholarship Council (CSC) for Higher Education Exhibition

Open positions

We continuously welcome applications from persons with external funding sources.
For ambitious medical students we offer experimental projects that require two semesters full-time commitment.
We offer the possibility to perform the experimental part of Master's Thesis in our group. Supervision by experienced scientists or PhD students is guaranteed.

Former group members

Dr. Stefan Thomann (PhD student, scientist)
Dr. Margarita González-Vallinas Garrachón (scientist)
Dr. Federico Pinna (scientist)
Dr. Jana Samarin (diploma student, scientist)
Dr. Mona Malz (PhD student, scientist)
Dr. Sabrina Schmitt (scientist)
Dr. Maria Knaub (PhD student)
Dr. Shan Wan (PhD student)
Dr. Benedikt Müller (PhD student)
Dr. Antje Brauckhoff (PhD student)
Dr. Tanja Nussbaum (PhD student)
Dr. Stephanie Schnickman (PhD student)
Dr. Sebastian Vreden (PhD student)
Dr. Teng Wei (Dr. sc. hum. student)
Dr. Kaijing Liu (medical student)
Dr. Simone Marquard (medical student)
Dr. Charlotte Jankovitz (medical student)
Dr. Teresa Lutz (medical student)
Dr. Philipp Latzko (medical student)
Dr. Michael Bovet (medical student)
Dr. Pia Moinzadeh (medical student)
Anne-Sophie Meyer (physician)
Dr. Christian Rupp (physician)
Dr. Darjus Tschaharganeh (physician)
Prof. Stephan Singer (physician)
Vera Riehmer (diploma student)
Yelena Burda (diploma student)
Ute Müller (technician)
Petra Hubbe (technician)
Martina Keith (technician)

Our nationalities

Contact

Prof. Dr. Kai Breuhahn
University Hospital Heidelberg
Institute of Pathology
Im Neuenheimer Feld 224
69120 Heidelberg
+49-6221-56-4675
kai.breuhahn(at)med.uni-heidelberg.de

Last update: July 2022