Yoshiaki Sunami1,2, Marc Ringelhan3,4,5, Enikö Kokai2, Miao Lu1, Tracy O'Connor4, Anna Lorentzen4, Achim Weber6, Ann-Katrin Rodewald6, Beat Müllhaupt7, Luigi Terracciano8, Sarah Gul2, Sebastian Wissel2, Frank Leithäuser9, Daniel Krappmann10, Petra Riedl11, Daniel Hartmann1, Reinhold Schirmbeck11, Pavel Strnad12, Norbert Hüser1, Jörg Kleeff1, Helmut Friess1, Roland M Schmid3, Fabian Geisler3, Thomas Wirth2, Mathias Heikenwalder4,13. 1. Department of General Surgery, Klinikum rechts der Isar, Technical University Munich, Munich, Germany. 2. Institute of Physiological Chemistry, University of Ulm, Ulm, Germany. 3. Department of Internal Medicine II, Klinikum rechts der Isar, Technical University Munich, Munich, Germany. 4. Institute of Virology, Technical University Munich/Helmholtz Zentrum Munich, Munich, Germany. 5. German Center for Infection research (DZIF), Munich partner site, Munich, Germany. 6. Institute of Surgical Pathology, Zürich, Switzerland. 7. Department of Gastroenterology and Hepatology, University Hospital Zürich, Zürich, Switzerland. 8. Institute of Pathology, University Hospital Basel, Basel, Switzerland. 9. Institute of Pathology, University Medical Center Ulm, Ulm, Germany. 10. Research Unit Cellular Signal Integration, Helmholtz Zentrum Munich, Munich, Germany. 11. Department of Internal Medicine I, University Medical Center Ulm, Ulm, Germany. 12. Department of Medicine III and IZKF, University Hospital Aachen, Aachen, Germany. 13. Division of Chronic Inflammation and Cancer, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Abstract
UNLABELLED: Chronic hepatitis B virus (HBV) infection remains the most common risk factor for hepatocellular carcinoma (HCC). Efficient suppression of HBV viremia and necroinflammation as a result of nucleos(t)ide analogue treatment is able to reduce HCC incidence; nevertheless, hepatocarcinogenesis can occur in the absence of active hepatitis, correlating with high HBV surface antigen (HBsAg) levels. Nuclear factor κB (NF-κB) is a central player in chronic inflammation and HCC development. However, in the absence of severe chronic inflammation, the role of NF-κB signaling in HCC development remains elusive. As a model of hepatocarcinogenesis driven by accumulation of HBV envelope polypeptides, HBsAg transgenic mice, which show no HBV-specific immune response, were crossed to animals with hepatocyte-specific inhibition of canonical NF-κB signaling. We detected prolonged, severe endoplasmic reticulum stress already at 20 weeks of age in NF-κB-deficient hepatocytes of HBsAg-expressing mice. The unfolded protein response regulator binding immunoglobulin protein/78-kDa glucose-regulated protein was down-regulated, activating transcription factor 6, and eIF2α were activated with subsequent overexpression of CCAAT/enhancer binding protein homologous protein. Notably, immune cell infiltrates and liver transaminases were unchanged. However, as a result of this increased cellular stress, insufficient hepatocyte proliferation due to G1 /S-phase cell cycle arrest with overexpression of p27 and emergence of ductular reactions was detected. This culminated in increased DNA damage already at 20 weeks of age and finally led to 100% HCC incidence due to NF-κB inhibition. CONCLUSION: The role of canonical NF-κB signaling in HCC development depends on the mode of liver damage; in the case of HBsAg-driven hepatocarcinogenesis, NF-κB in hepatocytes acts as a critical tumor suppressor by augmenting the endoplasmic reticulum stress response.
UNLABELLED: Chronic hepatitis B virus (HBV) infection remains the most common risk factor for hepatocellular carcinoma (HCC). Efficient suppression of HBV viremia and necroinflammation as a result of nucleos(t)ide analogue treatment is able to reduce HCC incidence; nevertheless, hepatocarcinogenesis can occur in the absence of active hepatitis, correlating with high HBV surface antigen (HBsAg) levels. Nuclear factor κB (NF-κB) is a central player in chronic inflammation and HCC development. However, in the absence of severe chronic inflammation, the role of NF-κB signaling in HCC development remains elusive. As a model of hepatocarcinogenesis driven by accumulation of HBV envelope polypeptides, HBsAg transgenic mice, which show no HBV-specific immune response, were crossed to animals with hepatocyte-specific inhibition of canonical NF-κB signaling. We detected prolonged, severe endoplasmic reticulum stress already at 20 weeks of age in NF-κB-deficient hepatocytes of HBsAg-expressing mice. The unfolded protein response regulator binding immunoglobulin protein/78-kDa glucose-regulated protein was down-regulated, activating transcription factor 6, and eIF2α were activated with subsequent overexpression of CCAAT/enhancer binding protein homologous protein. Notably, immune cell infiltrates and liver transaminases were unchanged. However, as a result of this increased cellular stress, insufficient hepatocyte proliferation due to G1 /S-phase cell cycle arrest with overexpression of p27 and emergence of ductular reactions was detected. This culminated in increased DNA damage already at 20 weeks of age and finally led to 100% HCC incidence due to NF-κB inhibition. CONCLUSION: The role of canonical NF-κB signaling in HCC development depends on the mode of liver damage; in the case of HBsAg-driven hepatocarcinogenesis, NF-κB in hepatocytes acts as a critical tumor suppressor by augmenting the endoplasmic reticulum stress response.