Targeting glucosylceramide synthase upregulation reverts sorafenib resistance in experimental hepatocellular carcinoma
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Milica Stefanovic1, Anna Tutusaus1, Guillermo A. Martinez-Nieto1, Cristina Bárcena1, Estefania de Gregorio1, Catia Moutinho2, Elisabet Barbero-Camps1, Alberto Villanueva3, Anna Colell1, Montserrat Marí1, Carmen García-Ruiz1,4, Jose C. Fernandez-Checa1,4,5, Albert Morales1
1Department of Cell Death and Proliferation, IIBB-CSIC, IDIBAPS, Barcelona, Catalonia, Spain
2Cancer Epigenetics and Biology Program (PEBC), Bellvitge Biomedical Research Institute, Barcelona, Catalonia, Spain
3Translational Research Laboratory, Catalan Institute of Oncology - Bellvitge Biomedical Research Institute, Barcelona, Catalonia, Spain
4Liver Unit, Hospital Clinic, CIBEREHD, Barcelona, Catalonia, Spain
5Research Center for Alcoholic Liver and Pancreatic Diseases, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
Albert Morales, e-mail: firstname.lastname@example.org
Jose C. Fernandez-Checa, e-mail: email@example.com
Keywords: liver cancer, chemotherapy, mitochondria, ceramide, mouse model
Received: July 27, 2015 Accepted: January 13, 2016 Published: January 22, 2016
Evasive mechanisms triggered by the tyrosine kinase inhibitor sorafenib reduce its efficacy in hepatocellular carcinoma (HCC) treatment. Drug-resistant cancer cells frequently exhibit sphingolipid dysregulation, reducing chemotherapeutic cytotoxicity via the induction of ceramide-degrading enzymes. However, the role of ceramide in sorafenib therapy and resistance in HCC has not been clearly established. Our data reveals that ceramide-modifying enzymes, particularly glucosylceramide synthase (GCS), are upregulated during sorafenib treatment in hepatoma cells (HepG2 and Hep3B), and more importantly, in sorafenib-resistant cell lines. GCS silencing or pharmacological GCS inhibition sensitized hepatoma cells to sorafenib exposure. GCS inhibition, combined with sorafenib, triggered cytochrome c release and ATP depletion in sorafenib-treated hepatoma cells, leading to mitochondrial cell death after energetic collapse. Conversely, genetic GCS overexpression increased sorafenib resistance. Of interest, GCS inhibition improved sorafenib effectiveness in a xenograft mouse model, recovering drug sensitivity of sorafenib-resistant tumors in mice. In conclusion, our results reveal GCS induction as a mechanism of sorafenib resistance, suggesting that GCS targeting may be a novel strategy to increase sorafenib efficacy in HCC management, and point to target the mitochondria as the subcellular location where sorafenib therapy could be potentiated.
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